In this paper, a highly dispersive pure silica photonic crystal fiber is designed and fabricated with maximum chromatic dispersion value of about -600 ps/(nm·km) around 1.55 μm wavelength region. This kind of a photonic crystal fiber structure is suitable for high dispersion application in photonic crystal fiber array based phased array antenna systems. A four-element true-time delay module is constructed using the fabricated highly dispersive photonic crystal fibers. The true time delay value of 10.5m PCF is characterized to provide maximum delay of 31.3ps with 32nm optical wavelength tuning range, which is sufficient to scan from -45° to 45° for a 4-element PAA subarray having 1.3cm spacing. A multiple-beam optical beamformer is designed based on the fabricated highly dispersive photonic crystal fibers. The true-time delay beamformer can be programmed to continuously sweep the antenna aperture independently for multiple RF beams. Since the dispersion of the fabricated photonic crystal fibers is as high as -600 ps/nm•km at 1550 nm, compared to telecom SMF-28 that has a dispersion parameter of 18 ps/nm•km, the length of delay line is reduced by a factor of 33.

Detection of biological samples in low concentration is of great significance to the basic research in science, the development of medical technology and many other fields related to our lives. Surface-Enhanced Raman Scattering (SERS), well-known as a powerful analytical tool with high sensitivity, is especially suitable for biomolecule detection as it enables near infrared (NIR) excitation and label-free detection. SERS probe made of conventional optical fiber provides better flexibility in detection; however, it requires a complicated fabrication process and doesn't serve as a well-set detecting platform. In this talk we propose and demonstrate a photonic crystal fiber (PCF) based SERS probe, which has the new advantages of simplicity in fabrication, better light confinement and increased light-analyte interaction volume. The PCF-based SERS probes are prepared in three different ways: mixed solution of sample and gold nanoparticles filled in air holes of PCF, sample solution dried in gold coated air holes and sample solution filled in gold coated air holes, respectively. Sample solution of adenine is in concentration of about 10^-6M. Almost every characteristic peak of adenine can be observed in the spectra detected by each of the three probes.

A Fabry-Perot interferometer (FPI) constructed in a two-dimensional photonic crystal (2D PhC) has been proposed and demonstrated theoretically. The perfect 2D PhC consists of square-lattice cylindric air holes in silicon. Two same line defects with spacing of d = 16a, which is the physical length of the FP resonant cavity, are introduced in the PhC to form the FPI. The two line defects have high reflectivity and low transmission. Their transmission is between 4.81% and 11.1% for the self-collimated lights with frequencies from 0.275c/ato 0.295c/a and thus they form the two partial reflectors. Lights propagate in the FPI employing self-collimation effect. The transmission spectrum of the FPI has been investigated with the finite-difference time-domain method. The calculation results show that peaks have nearly equal frequency spacing 0.0078c/a. Even slight increases of d can cause peaks shift left to lower frequencies. As a result, the peak spacing decreases nonlinearly from 0.0142c/a to 0.0041c/a when dis increased from 9a to 30a. Through changing the configuration of the reflectors which results in transmission between 4.18% and 7.73%, the varieties of the sharpness of peaks and the degree of extinction of the frequencies between the peaks are obviously observed.

A segmented-cladding fiber (SCF) has a uniform core of high refractive index and a cladding consisting of alternating high and low refractive-index angular segments. It is known that such a fiber can be designed to provide effective single-mode operation with an ultra-large core size. In this paper, we analyze a SCF that is doped with erbium ions in its high-index regions (i.e., the core and the high-index cladding segments). The core of the fiber has a diameter of 20 &mgr;m and the cladding consists of 8 segments of equal size. The concentration of the erbium ions is 1×10²⁶. We calculate the mode-field distributions in the fiber at the signal (1530 nm) and the pump (980 nm) wavelength with the finite-element method. We obtain the gain characteristics and the pump efficiency of the fiber by solving the propagation rate equations. Assuming an initial signal power of 1 μW, the threshold pump power required is 102 mW for a 30-cm long fiber. The optimal gain of the fiber is 25 dB, which can be achieved with a fiber length of 26 cm and a pump power of 150 mW. Our results confirm that a properly designed SCF can provide highly efficient optical amplification with a short length.

In this paper, we report the experimental study of erbium-doped mode-locked fiber laser using semiconductor saturable absorber mirror (SESAM). Two configuration erbium-doped mode-locked fiber lasers, single wavelength operation and multi-wavelength operation, are study systematically. In single wavelength operating configuration, the fiber laser can operate harmonic mode-locking of 31 MHz repetition rate, which is two times of the fundamental repetition rate in our setup. In multi-wavelength operation, the output spectrum range from 1550 nm to 1556 nm with interval of 0.8 nm. The self-starting passive mode-locked laser is constructed in a Fabry-Perot configuration using the saturable absorber mirror as the back reflector of the cavity. Fiber Bragg grating and Chirped Bragg grating are used as the other reflector. Both of our mode-locked lasers are very compact, the output pulse train is stable, which has potential applications in high speed optical communication and optical sensor.

In this paper, we report the gain-switching operation in Yb³⁺-doped DFB fiber laser. Our DFB fiber laser operates with single longitudinal mode and single polarization state under cw pump, however, the DFB fiber laser will operate with gain-switching mode if it is pump by pulse of certain duration. Detail experimental results are given in the paper. We believe this king of pulse source is useful in optical sensor.

We present a two-stage dual-forward pumped configuration to achieve a wavelength stable L-band amplified spontaneous emission (ASE) source. The effects of EDF length and pump power arrangements on the characteristics of L-band ASE spectrum, output power, and mean wavelength are investigated. The results show that not only the pumping conversion efficiency can be improved largely but also the pump power independent mean wavelength operation can be achieved by optimizing the fiber length ratio and pump ratio of the dual-forward pumped configuration as comparing to that of the conventional double-pass forward configuration.

This paper provides research progress in the development of fast electro-optic gratings for laser beam attenuations and in free space optical (FSO) communications involving mobile terminals. The electro-optic phase grating is formed by the phase separation of ~100nm liquid crystals droplets from a polymerizing organic matrix using holographic interference technique. The formed grating separates the incident laser beam into the output beams: the transmitted and diffracted beam, whose intensities can be electrically adjusted through electro-optic effect. The fast electro-optic gratings have a very fast electro-optic response time of 50 μs with diffraction efficiency above 99.8%. Optical receivers used in FSO have a limited dynamic range and there is a need for in-line variable attenuators to keep the signal levels from overloading the receiver. These attenuators should be continuous, provide sufficient attenuation, and also provide a low insertion loss for weak signal reception. The use of electro-optic phase gratings is one solution to meet the requirements for an in-line attenuator for FSO.

In this paper, the design and fabrication for a high speed, low crosstalk 12 channels monolithic integrated CMOS optoelectronic integrated circuit (OEIC) receiver module is reported. The module consists of a Si-based photodetector array and front-end circuit integrated receiving chip; printed circuit board (PCB); fiber array; package and shield components. The structure of Si-based double photodiode (DPD) can speed up the receiver but at the same time make the deterioration of responsivity. The adoption of active inductors in TIA circuit can extend the -3dB bandwidth to a higher level. In particular, the design method of low crosstalk is discussed in detail. Instead of conventional isolation methods used to reduce inter-channel crosstalk, we find a novel way to cancel it by study crosstalk issues from a circuit design perspective. The chip fabricated by CSMC (a foundry in WuXi, China) 0.6μm standard CMOS process without any modification to the process or additional post-process steps. This extremely reduced chip fabrication costs. The module has the merit of high speed, low crosstalk and low cost spontaneously. The measured results show that every single channel of the receiver is able to work at bit rates about 1Gb/s. In total the monolithic integrated 12-channel OEIC receiver module can be operated at 12 Gb/s. The module can be used in ultra high speed optical interconnection system.

A novel 3D modeling of a lateral PIN photodiode (LPP) is presented utilizing In_0.53Ga_0.47As as the absorbing layer. The LPP has profound advantages compared to the vertical PIN photodiode (VPD) mainly due to the ease of fabrication where diffusion or ion implantation can be used to form the p+ and n+ wells in the absorbing layer. The device has an interdigitated electrode structure to maximize optical absorption. At a wavelength of 1550 nm, optical power of 5 Wcm^-2 and 5 V reverse bias voltage, the device achieved responsivity of 0.5 A/W. The -3dB frequency response of the device was at 14 GHz and it is able to cater for 10 Gbit/s optical communication networks.

We have developed a novel InP-based, ridge-waveguide photonic integrated circuit (PIC), which consists of a 1.1-um wavelength Y-branch optical waveguide with low loss and improved far field pattern and a 1.3-um wavelength strained InGaAsP-InP multiple quantum-well superluminescent diode, with bundle integrated guide (BIG) as the scheme for monolithic integration. The simulations of BIG and Y-branches show low losses and improved far-field patterns, based on the beam propagation method (BPM). The amplified spontaneous emission of the device is up to 10 mW at 120 mA with no threshold and saturation. Spectral characteristics of about 30 nm width and less than 1 dB modulation are achieved using the built-in anti-lasing ability of Y-branch. The beam divergence angles in horizontal and vertical directions are optimized to as small as 12°×8°, resulting in good fiber coupling. The compactness, simplicity in fabrication, good superluminescent performance, low transmission loss and estimated low coupling loss prove the BIG and Y-branch method to be a feasible way for integration and make the photonic integrated circuit of Y-branch and superluminescent diode an promising candidate for transmitter and transceiver used in fiber optic gyroscope.

A novel in-fiber optical switch based on two-core optical fiber is demonstrated. A Mach-Zehnder intereferometer was integrated into a single optical fiber of 125 μm diameter using a novel coupling connection technology. Then embedding the single optical fiber into a universal optical fiber transmission line, the novel in-fiber optical switch is formed. It can make microscale and integrated optical fiber elements into a complex function system, which greatly improve the performance of in-fiber elements and can develop and manufacture fiber optical sensors acceptable for various special situation. The reference and sensing arms of the intereferometer of the perfect in-fiber optical switch based on two-core optical fiber is integrated into a single fiber, which makes the structure more simple and the optical paths relatively stable, so it can effectively avoid the influence of enviroment factors such as vibration, temperature and greatly improve the performance of in-fiber optical swiches.

By using overlapping-imaging characteristic of the multimode interference (MMI) and the area modulation method, this paper presents a three-wavelength 3×3 rearrangeable switch, which consists of the two cascaded building blocks: a 2×2 tunable splitter and a full shuffle 1×3 switch with only one compound modulation region. Its operation characteristics are analyzed by utilizing 2-D BPM simulation. The simulated extinction ratio is higher than 30dB for all operating wavelengths 1545 nm, 1550 nm and 1555 nm. Good 3-D performances can be expected after optimization and improved fabrication.

For the high absorption loss of the Electro-optic (EO) polymers, there are only a few reports on polymeric EO switches. This paper presents a new design and fabrication method of the polymer 1×2 Mach-Zehnder Interference (MZI) switch operating at 1550nm. The switch is consists of two vertically coupled waveguides located at different levels. And it will be easier to fabricate by traditional technology. The finite difference Beam Propagation Method (BPM) has been used to analyze the device propagation characteristics. The result indicated that the propagation loss of this Three-dimensional (3-D) switch is decreased 2dB by that of the ordinary two-dimensional (2-D) switch. And this kind of structure has high potential for the application of low-loss optical modulator and attenuator.

Several pulse response property of Avalanche photodiode (APD) were discussed in the paper, including the amplitude nonlinearity of large optical power signal input due to space-charge-effects, the reshape property and time domain property from the nonlinearity model of APD. In the pulse response measurement experiment, the APD was illuminated with a pulsed laser diode whose impulse width is several decades nanosecond with peak power up to decade watt. The experiment results showed the nonlinearity pulse response was well matched with the model numerical simulate result. The affect to the APD based range finder and Ladar was discussed and useful correction solution from the model was made especially for pulse TOF range finder.

A high quality (Q) factor microring resonator in silicon-on-insulator rib waveguides was fabricated by electron beam lithography, followed by inductively coupled plasma etching. The waveguide dimensions were scaled down to submicron, for a low bending loss and compactness. Experimentally, the resonator has been realized with a quality factor as high as 21,200, as well as a large extinction ratio 12.5dB at telecommunication wavelength near 1550nm. From the measured results, propagation loss in the rib waveguide is determined as low as 6.90dB/cm. This high Q microring resonator is expected to lead to high speed optical modulators and bio-sensing devices.

Guiding modes and field distribution are calculated by finite element method. For three kinds of etched cross-section waveguide (rectangle, trapezoid, upside-down trapezoid) with 0.5μm and 1.0μm film thickness, mode characteristic, percentage of core power at wavelength of 1.53μm and 0.98μm and overlap factor between signal and pump are contrastively studied. For the same etched depth and mask width, trapezoid waveguide is superior to rectangle and then upside-down trapezoid in the view of field confinement and overlap factor. Whereas rectangle waveguide is optimum and upside-down trapezoid is the worst for the same core cross-section area. The gain of different etched cross-section waveguide amplifier is numerically calculated by multi-theoretical model, which is founded by rate equations pumped at 0.98μm, two-dimension waveguide finite element model, propagation equations with forward and backward direction amplified spontaneous emission. Results also show rectangle waveguide is optimum for the same core cross-section area. The gain of 1μm film thickness waveguide amplifier increases by more than 20% compared with 0.5μm thickness waveguide. These simulation results provide a theoretical basis for the design of Yb-Er co-doped Al₂O₃ waveguide amplifiers.

Submicrometer channel and rib waveguides based on SOI (Silicon-On-Insulator) have been designed and fabricated with electron-beam lithography and inductively coupled plasma dry etching. Propagation loss of 8.39dB/mm was measured using the cut-back method. Based on these so-called nanowire waveguides, we have also demonstrated some functional components with small dimensions, including sharp 90° bends with radius of a few micrometers, T-branches, directional couplers and multimode interferometer couplers.

A chlorination surface treatment was used to reduce the surface states of an n-type GaN surface, which improves the Schottky performances of the resultant metal-semiconductor contact. At a reverse bias of 10V, the dark current of the GaN-based UV-PDs with and without chlorinated surface treated were 28.1nA and 0.59μA, respectively. The dark current of chlorine-treated Schottky UV-PDs was 21 times of magnitude smaller than that of those without chlorination treatment. The product of quantum efficiency and internal gain of the GaN Schottky UV-PDs without and with chlorination treatment under a reverse voltage of 10V at a wavelength of 330nm was 650% and 100%, respectively. The internal gain of chlorine-treated GaN UV-PDs can be reduced due to the improvement of surface state density.

We demonstrate an all-optical continuously tunable delay line based on wavelength conversion in semiconductor optical amplifier (SOA), and group-velocity dispersion (GVD) in dispersion-compensating fiber (DCF). The system operates, near 1550 nm, with a nonreturn-to-zero (NRZ) pattern at 10 Gb/s. The maximal delay up to 2700 ps is observed. The scheme achieves continuous control of a wide range of delays, wide signal bandwidth, nearly no pulse broadening and very little spectral distortion.

The experiment result of series photoconductive switches triggered by ns laser pulse is reported. The series switches is composed by two semi-insulating GaAs photoconductive switches with 3mm electrode gap and the electrodes at two sides. Both electrodes touch each other. When it is triggered by ns laser pulse about 2mJ at 532nm, with the biased voltage of 1200V, linear mode of the series switches is observed. Then, laser energy and the biased voltage add to 5mJ and 4000V, the series switches still works in linear mode. When it is triggered by ns laser pulse about 6mJ at 1064nm, with the biased voltage of 3500V, the series switches works in linear mode. When laser energy and the biased voltage are 10mJ and 4000V, the series switches gives a double wave crest waveform. However, with the biased voltage of 6700V and laser energy of 15mJ, series switches gives trend of nonlinear mode. When laser energy rises to 20mJ, nonlinear mode is clearer. Even at 5000V and 30mJ, trend of nonlinear mode is observed. The results indicate that double wave crest appears while series switches works from linear mode to nonlinear mode. Capacitance effect caused by electrodes of switches touch is discussed. And explanation is given that double wave crest is attributed to surge caused by capacitance. When biased voltage and laser energy are enough, high gain of carries is very obvious. Effect of capacitance decreases and double wave crest disappears. Then the series switches is going to nonlinear mode. This explanation matches experiment result.

In this paper, we presents the characterization technique of high-speed optoelectronics devices based electrical and optical spectra, which is as important access to the devices performance as the prevalent vector network analyzer (VNA) sweeping method. The measurement of additional modulation of laser and frequency response of photodetector from electrical spectra, and the estimation of the modulation indexes and the chirp parameters of directly modulated lasers based on optical spectra analysis, are given as examples.

The semiconductor optical amplifiers (SOAs) are employed in all optical networking and all optical signal processing due to the excellent nonlinearity and high speed. The gain recovery time is the key parameter to describe the response speed of the SOA. The relationship between the gain dynamics and a few operation parameters is obtained in this article. A few simple formula and some simulations are demonstrated, from which, a few methods to improve the response speed of the SOA can be concluded as following, lengthening the active area, or lessening the cross area, increasing the injection current, increasing the probe power, operating with a CW holding beam.

The nondestructive photoluminescence technology has been introduced to test and evaluate the growth of InGaAs/GaAs Single-Quantum Well (SQW) by using Molecular Beam Epitaxy (MBE) technology. The experiments are carried out at different temperature in order to test the effect of variation of gap energy. When temperature varied, the lineshape of spectra changed, particular in the short wavelength part. The wavelength of emit light peak blue shift as well. We indicate that the main mechanism of the radiative recombination at high temperature is of band-to-band origin. However, at low temperature, exciton recombination is prevailing.

We demonstrate the high power low RIN Brillouin fiber laser source with stimulated Brillouin scattering. Brillouin fiber laser and high quality RF are generated simultaneously in Brillouin optoelectronic oscillator. Brillouin fiber laser with 104mW power and -154dB/Hz RIN is generated. RIN of Brillouin fiber laser is 8dB lower than RIN of EDFA-amplified DFB.

In this paper, a novel double-pass bidirectional pump broadband L-band erbium-doped superfluorescent fiber source (SFS) is demonstrated for the first time. In this fiber source, the EDF is divided into two segments, one of which (EDF2) is bidirectional pumped by a 980nm laser diode through two wavelength division multiplexers (WDM), and the other one (EDF1) is arranged between the reflector and the first WDM. EDF1 is unpumped. The fiber length ratio of the EDF1 length to the total length is defined as R_L=L_EDF1/(L_EDF1+ L_EDF2). The pump power ratio of forward to total pump power of EDF2 is defined as K=P_forward/P_total. The effects of the fiber length and pump power arrangement on the output characteristics of the L-band fiber source are simulated. With an appropriate pump power ratio K and an optimal fiber length ratio R_L, broadband L-band erbium-doped SFS with flat output spectrum can be obtained. Additionally, the optimal fiber length ratio R_L is also depended on the pump power ratio K. When K>0.4, the optimal R_L tends to be changeless. When K=0.1, the optimal R_L is 0 and widest flat spectrum is achieved with a 3-dB bandwidth of 63 nm (1540nm-1603nm).

A dynamic depolarized light based on the polarization chaos is generated from a SOA-based fiber ring laser experimentally. And also a theoretical model is developed to analyze the experiment phenomenon. By simulation, it is revealed that the polarization dependency in the fiber cavity can cause polarization chaos just as the anisotropy within SOA does, and the numerical results consist well with the experiment results. With the polarization chaos, we have obtained a dynamically depolarized light with a low dynamical DOP less than 3% and with polarization changing rate as high as about several million Hertz.

Compact plasma Pockel's cells (PPC) with 70mm aperture driven by one-pulse process have been constructed for technical integration line (TIL) of SGIII laser facility. The experimental results indicate that the working range of gas pressure is wide, and the delay of gas breakdown is steady. Measurements of the optical performance show static transmittance of 93.1%, static extinction ratio of 3900, and average switching efficiency of 99.7%. Eight compact PPCs are used for the second-stage integrating experiments of TIL. By using of parallel driving technology, one driver can work for four PPCs. An analyzer of optical switch is replaced with Brewster-angle Nd-glass slabs in amplifier. Two years application results show that the PPCs can effectively minimize the growth of parasitic-oscillation, and have a high reliability.

It is the closest technology to practice in the quantum communication at present to apply single-photon scheme to implement the quantum key distribution (QKD), and may achieve the absolute security in principle. Because of the limit of the response speed of the present single-photon detector, the code rate is still too low to come into practical use. The paper has put up a new idea to design a quick single-photon detector with a multi-port optic-fiber splitter or an optical switch array and many avalanche photo diodes (APD). All of the ports with APD work on time division and cooperate with the logic discrimination and deciding unit by the clock signal, thus the quick detection can come true to high repetition-rate pulses with a single photon. The multiple of the detection rate is decided by the number of the port. The optoelectronic integration can be adopted for the reliable detector. The applying of this detector will largely raise the code rate of the QKD, and stimulate the commercial use.

A novel rapidly tunable, low loss, low crosstalk, polarization-independent, four-port reconfigurable optical add/drop multiplexer (OADM) is designed in this article. Electrooptic effect is used in two directions on waveguides which are fabricated on a LiNbO₃ substrate by Ti diffusion in order to convert the polarization between TE and TM mode at the download or upload wavelength. Particularly, voltages applied along propagation direction are separated and can be well programmed to suppress the sidelobe and drop multiple channels.

Carbon nanotubes (CNTs) are of great interests for a wide range of applications because of their unique structural, mechanical, electrical, optical, thermal, and chemical properties. Particularly, CNT thin films can be used as mechanically flexible, electrically conductive, and broadband optically transparent electrodes in various optoelectronic devices. However, one crucial obstacle to implementing CNT-based applications has been the unavailability of pure CNTs suitable for direct industrial use. The as-produced CNTs are very fluffy soot, and thus extremely difficult to be handled in the device fabrication process. Although CNTs can be grown directly on a substrate from the catalyst deposited on the substrate surface, the growing temperature is very high, typically > 900°C, which represents a big challenge to device fabrication and integration. Another issue is that the catalyst on the substrate surface must be removed without affecting the grown CNTs. In the raw CNT soot, there is always a considerable amount of impurities, including metallic particles from the catalyst and carbonaceous impurities from the chemical reaction by-products. Such impurities can greatly degrade the properties of CNT thin films. The production of electronic-grade CNT aqueous solutions, which contain only individually suspended pure CNTs without any kind of surfactant, is a critical milestone for implementing CNT-based applications. By using such solutions, pure CNT thin films of various densities can be formed through common solution-casting processes, such as spin coating, spray coating, micro-dispensing, and ink-jet printing. The properties of these pure CNT thin films will be discussed in this paper.

Gradient-index lens arrays are important elements for many optical systems. In some systems, the higher space factor is needed. That is to say, the area of receiving light should be enhanced and the loss of light information be decreased. However, this can be realized by changing the shape of lens. In this work, thermal ion-exchanging technology was introduced as a method to generate gradient refractive-index distributions of hexagonal aperture microlens arrays. As important elements for many optical systems, this irregular microlens arrays can provide very high filling factor which is more than 95 percent and deduce the loss of optical information. We apply the ion-exchanged technique and photolithography to fabricate this irregular microlens arrays, for the first time to our knowledge. The aim of the research is to fabricate this irregular microlens arrays. Fabrication process includes three steps: first, mask with irregular figure is programmed and fabricated; then with photolithographic technology, the figure of mask is transferred to the glass substrate; At last, ion-exchanged process is needed. The experimental results show that good performance can be obtained through this new type lens and the high filling factor is satisfied. Moreover, the experimental index distribution of hexagonal aperture lens is gradient distribution. Therefore, the research on the irregular microlens arrays has an important meaning in application, and this new type microlens array is useful for some systems in which the loss of light information need to be reduced.

The paper presents a method with the technique of combination filtering of spectrum and the technique of DSP control for the simulation and recognition of the spontaneously lightening object and stellar map in the universe. The magnitude and the spectrum of a star can be simulated in a wide dynamic range. We established the mathematical models of the Vega's visible light spectrum and luminous flux density. Tungsten-halogen lamp as a light source is used to fit the linear light of the spontaneously lightening object in the universe. Through the experiment, it shows that the more sub-channels there are while filtering spectrum in the visible spectrum, and the more degrees the variable neutral density filters and the narrow-band attenuators have, more close to the actual spectrum the simulated spectrum is. It is proved that using the PID technique is beneficial to the output of the accurate and steady radiation from the light sources. The experiment shows that the using of this method can get perfect result in fitting and simulating the spectrum, magnitude and the stellar map of the spontaneously lightening object . The analysis of the consistent result and the experimental error is also discussed in detail in this paper.

Exciton saturation and optical nonlinearities in multiple quantum wells due to many body interactions consisting of phase-space filling and Coulomb screening are investigated. We have made a theoretical model to compare the different effects induced by the two many-body interactions. We focus our calculations on the shift of the exciton absorption resonance at highly excited carrier densities in MQW which can be obtained through femtosecond pump-probe technique. We find that the blue shift of the exciton absorption resonance wavelength caused by the phase-space filling effects is about equivalent to the red shift of Coulomb screening effects in same circular polarization, while in contrary the red shift is much lager than the blue shift in opposite circular polarization. This phenomenon happens within optical switching timescale.

The optical and electrical characteristics from filamentary discharge to pseudo-glow discharge are investigated by a specially designed optical detection systems. The discharges are initiated in mixture of air and argon at atmospheric pressure in a dielectric barrier discharge setup composed of two parallel planar electrodes separated by two layers of dielectric. The optical and electrical characteristics are displayed by the waveforms of the applied voltage, the discharge current and the emission spectral intensity. The waveforms of the applied voltage and the discharge current of two discharge modes have been recorded by oscilloscope. The emission spectra from the discharges are obtained through a spectrometer. When the other conditions are fixed the spectral intensity increases with the increase of voltage and driven frequency. The ratio of spectral intensity to the voltage in the filament discharge is smaller than that in the pseudo-glow discharge.

The paper presents a novel optical approach to realize tracking on glass based on speckle effect produced by vertical-cavity surface-emitting laser (VCSEL). The range of incident angle has been investigated which shows incident angle in the range of 75 to 90 degrees is favorable to acquire a pure speckle field with purity better than 90%. In the system, nearly grazing angle of incidence 85 degrees is introduced, and big operating current of VCSEL and high gain of CCD are adopted to ensure signal detected. We analyze the cause of background contained in the image and remove them by placing a barrier between the laser diode and charge coupled device (CCD) and an infrared filter in front of CCD. After above-mentioned improvement of the system, a good linear dependence between displacement of speckle images and amount of glass translation is proved by experiment and the slope of the fitted line agrees well with theoretical predictions, the accuracy of tracking system is better than 4%.

We propose a compact variable optical attenuator (VOA) based on the W type five-layer symmetric slab waveguide. Simulation result shows that: for the attenuator based on GaAlAs/GaAs epitaxial layers, with a refractive index change of -0.01 in the current injection region of 1000 &mgr;m long (corresponding to injected current of about 80mA), an attenuation of more than 30dB is achieved. The attenuation range can be scaled to fit the requirements by varying the electrode length.

A passive polarization beam splitter in silicon-on-insulator (SOI) waveguides, which consists of two 3-dB multimode interference (MMI) couplers and two Mach-Zehnder interferometer (MZI) arms with the same length but different rib widths, has been proposed recently and a numerical method of design is needed because the analytical solution for this 3-dimensional (3D) SOI waveguides is difficult to achieve. The scalar finite difference beam propagation method (FD-BPM) is used to design the 3-dB MMI couplers and the positions of the input or output waveguides and the length of multimode waveguide are determined. In our design, the length of MMI couplers is 1228 micron when the width of rib is 36 micron. The propagation constants of TE-polarized and TM-polarized mode supported by 3D rib waveguides on SOI are calculated by the Semi-vector FD-BPM which is polarization related. From these data obtained for different rib widths (from 2.0 micron to 4.0 micron), the appropriate length of MZI arms is selected. In our example, the widths of two arms are 3.4 micron and 2.0 micron respectively and the length of arms is 1506 micron. The TE-polarized light and TM-polarized light are input to the splitter separately and the Semi-vector FD-BPM is used to check the design.

Coupled fibers are successfully fabricated by injecting hydrogen flow at 1bar and fused slightly by unstable torch flame in the range of 800-1350°C. Optical parameters may vary significantly over wide range physical properties. Coupling coefficient and refractive index are estimated from the experimental result of the coupling ratio distribution from 1% to 75%. The change of structural and geometrical fiber affects the normalized frequency (V) even for single mode fibers. Coupling ratio as a function of coupling coefficient and separation of fiber axis changes with respect to V at coupling region. V is derived from radius, wavelength and refractive index parameters. Parametric variations are performed on the left and right hand side of the coupling region. At the center of the coupling region V is assumed constant. A partial power is modeled and derived using V, normalized lateral phase constant (u), and normalized lateral attenuation constant, (w) through the second kind of modified Bessel function of the l order, which obeys the normal mode, LP₀₁ and normalized propagation constant (b). Total power is maintained constant in order to comply with the energy conservation law. The power is integrated through V, u and w over the pulling length range of 7500-9500 μm for 1-D where radial and angle directions are ignored. The core radius of fiber significantly affects V and power partially at coupling region rather than wavelength and refractive index of core and cladding. This model has power phenomena in transmission and reflection for industrial application of coupled fibers.

Electro-optical modulator with dual capacitors is designed and based on this design basic configuration of device is realized in laboratory. Exceeding GHz switching speed and high phase modulation efficiency can be expected with this device.

Feedback characteristics in single planar waveguide-coupled square microcavity are investigated by using the two-dimensional finite-difference time-domain method. A square microcavity with refractive index of 3.5 and side length of 2.2μm plays as a wavelength selective feedback element, and a single planar waveguide with width of 0.2μm is used to input and output light in the simulation. Simulation results show that most of the on-resonance extinction in transmitted optical power through the planar waveguide can be reflected. The highest reflection observed is more than 92% of the incident power at the resonance wavelength. For better understanding the high reflection phenomenon, the steady field patterns of single waveguide coupled square microcavity has also been obtained. The influence of coupling gap between the cavity and waveguide, on the resonance wavelength, reflection efficiency and the linewidth of reflection peak has been studied. With increasing gap, the resonance position shifts to the longer wavelength, and the linewidth narrows. The results also show that an optimized gap exits for the highest optical power reflection.

A strengthened acousto-optic (AO) coefficient of piezoelectric crystal is defined. AO coupled-wave equations of surface acoustic wave (SAW) to plane guide optic wave (PGOW) and to fiber guide optic wave (FGOW) are given respectively. A diffractive efficiency formula of SAW PGOW AO interaction and a back-wave efficiency formula of SAW FGOW AO interaction are given. The formulas indicate that under condition of weak AO interaction intensities of the diffractive wave and the back-wave are proportional to ultrasonic powers. Lithium Niobate (LN) is optimum crystal of SAW PGOW AO device, quartz is optimum crystal of SAW FGOW AO device. A SAW PGOW AO modulator using LN and a SAW FGOW AO modulator using quartz are designed and manufactured. Some curves of the diffractive wave power and the back-wave power vs. electric powers of signals driving the modulators are measured. SAW AO modulators have many advantages, for example small volume, good stability, low energy consumption and it is easy to integrate. The modulators can be used as intensity modulators. The modulators have applications in optic communication and real time signal processing.

Silicon-based optical interconnection can solve the problem in interconnection of ULSI, can be used in optical communication and can be used in optical calculation in future. A complete Silicon base interconnection optoelectronic system is achieved, which is composed of light emitting diode (LED), driver, detector, and amplifier. Main attention is to prove the feasibility to fulfill optical transmission and detection in using Silicon material, and obtains enhancement of optoelectronic conversion efficiency at the same time. The phenomenon of electro-luminescence of Silicon positive intrinsic negative (pin) structure diode is investigated. The optical spectral response of the system at 700nm indicates that the emitting light source has low optical loss in Silicon. So the LED is suitable for Silicon optoelectronic interconnection system. The detector is constructed with the same pin structure, the responsivity spectrum of the detector has a lot of overlapping area with the spectrum of the LED. So, high transmission efficiency can be achieved in such a system. Moreover, the driver and the amplifier circuit are all realized with Silicon material. The performance of that system was tested in ordinary condition. The EL response time achieves to 100ns and EL quantum efficiency achieves to 0.05%, which is a high level in Silicon optical interconnection. This system is completely compatible with silicon on isolator (SOI) technique and can serve as a foundamental basis of the research in the field of optical connection. Possible improvements for the optical connection system have been discussed.

As the length scale of the devices decreases, electrons will spend increasingly more of their time in the connections between components; this interconnectivity problem could restrict further increases in computer chip processing power and speed. Considerable effort is therefore being expended on the development of efficient silicon light-emitting devices compatible with silicon based integrated circuit technology. Here, we describe the electrical and optical properties of Silicon positive intrinsic negative (pin) structure diode that operates at room temperature. The voltage-current and electroluminescence (EL) property are measured at room temperature for a silicon pin diode under forward biased current. The optical spectral response of the system at 700nm indicates that the emitting light source has low optical loss in Silicon. So the LED is suitable for Silicon optoelectronic interconnection system.[1][2] The rate-equation model for free carriers on light-emitting pin structure and the equivalent circuit model based on it have been presented. We have developed a way to calculate the model parameters by comparison with experimental results. This parameter extraction way can be fully accomplished automatically by using MATHCAD program and the equivalent circuit model is simulated by using HSPICE program respectively. The results of both experiment and simulation results are good agreement with each other.

The traditional way to measure an electric field electrically disturbs the original field, so that can cause a number of measuring problems. Using a Pockels' crystal to measure an electric field has several advantages over electrical methods, such as interference from electromagnetic radiation, high sensitivity and wide frequency bandwidth. This paper presents a kind of new optical method for measuring electric current, this new method makes the Sensing Technology on Pockels effect, Faraday effect and optical Technology together. The sensor combines a Rogowski coil with a passive integrator located in the high-voltage environment. Test results from 20 A to 1.5 kA show the sensor to be highly linear, exceeding 0.2% linearity standards.

Using negative refractive material slow-wave waveguide, a compact and integrated optical modulator is proposed for the first time to our knowledge. The slow group velocities of light, which are readily achievable in negative refractive material waveguide, can dramatically increase the induced phase shifts caused by small changes in the refractive index. This slow propagation is illustrated with a finite-difference time-domain simulation. Modulation operation was demonstrated by using a 40 μm-long negative refractive material slow-wave waveguide of a Mach-Zehnder interferometer (MZI) structure. The modulation depth is 98%.The size of the novel optical modulator is 100 times shorter than that of conventional MZI optical modulator.

Sm(DBM)₃phen-doped polymer optical fibers were prepared by thermal polymerization. The cross relaxation model of clustering Sm³⁺ ions was described, and the cluster in this kind of fibers was studied based on the above model. The percentages of clustering ions in different fibers were obtained by the rate equation combining with fiber transmission experiment. While rare-earth-doped concentrations in these fibers are 1000 ppm, 2000 ppm, 3000 ppm, 4000 ppm, 5000 ppm and 10000 ppm, the percentages of clustering ions are 0.05, 0.05, 0.05, 0.05, 0.06, and 0.07, respectively. The result shows that this kind of fibers has low percentage of clustering ions. With the increasing of Sm³⁺ concentration, the percentage of clustering ions hardly increases, the clustering of Sm³⁺ ions is not obvious.

Antiresonant guiding microstructured optical fiber (MOF), a new kind of photonic band gap fiber, has several attractive applications including tunable filters, optical modulators and sensors. This new kind of photonic bandgap fiber with low refractive index core surrounded by a finite lattice of high refractive index inclusions reveals several intriguing properties, which are mainly determined by the individual properties of high refractive index inclusions rather than their positions and number. In this paper the dispersion properties of these fibers with hexagonal lattice of cylindrical high refractive index inclusions are discussed based on a full vector multipole method. The influences of inclusion space, inclusion rings number and core size on dispersion properties are investigated with photonic band gap location almost unchanged by keeping the diameter and refractive index of the high refractive index inclusions fixed. In order to evaluate the dispersion property dependence on high refractive index inclusions, the comparisons between fibers with different diameters or refractive indexes inclusions are also done. Numerical results show that the waveguide dispersion can be adjusted in a wide range for individual band with the bandgap location almost unchanged. It is confirmed that the dispersion is more susceptive to inclusion space and fiber core size than inclusion rings number. Individual properties of high refractive index inclusions can affect not only the location of band gaps but also the dispersion properties remarkably. This research is useful to optical fiber communication, fiber nonlinear applications and tunable device designs.

A novel all-optical high speed sampling method using nonlinear polarization rotation (NPR) in a semiconductor optical amplifier (SOA) is proposed in this paper. Using the carrier rate equation in a SOA for the propagation of an optical pulse, a model is proposed to describe the relationship between the polarization rotating angles of probe light and the pump light power. Meantime, affection introduced by the initial polarization of the probe light, as well as the injected current of the SOA is studied. The numerical results indicated that the initial polarization of the probe light affects the transfer curve between the output light power of probe light and the pump light power, and the injected current of SOA could affect the linearly dynamic range and the rise slope of the transfer curve. In order to obtain suitable slope and larger linear dynamic range, the parameters are optimized. The primarily simulated results indicated that the pump light power is not more than 1mW. It is also shown that the all-optical sampling mentioned in this paper has promoting potential to improve the sampling rate at hundreds GS/s and needs considerable lower optical power than others.

The paper proposes a small modulation and high precision laser range finder using the self-mixing effect in a single-mode vertical-cavity surface-emitting laser (VCSEL). According to the characteristic curve of single-mode VCSEL, the nonlinear distortion of Δλ/ΔI is severe and related with the modulation current ΔI, which worsens the system ranging accuracy obviously. In this paper, by applying small current to modulate single-mode VCSEL and specific circuits to process photoelectric signal, the system ranging accuracy is improved obviously. The experiment results show that, using small modulation current ΔI= 0.28 mA_p-p, modulation frequency f_m = 500 Hz to modulate single-mode VCSEL, and applying difference frequency analog phase-locked loop (APLL) to process the self-mixing beat frequency signals that exist phase abrupt changes, when the sampling time is 0.1 s, the measurement dynamic range is as large as 50 ~ 500 mm, and the ranging accuracy is better than 2 mm.

Single mode propagation is an important requirement for optical waveguide devices for use with single-mode fiber, it can reduce the coupling loss. In this paper, a technique is used for calculating the field distribution of the polymeric Y-junction rib waveguide. The technique is based on the combination of the effective index method(EIM) and the variational method(VM). It is mixed between the advantages of each method and avoided their disadvantages, where EIM can make the calculations procedures simple but it has some difficult to find the field distribution, other wise, VM can be used with very good accuracy to find the field distribution. An algorithm is implemented to study the effect of the structure parameters on the field distribution of the polymeric Y-junction rib waveguide. In our simulation, the core layer is PU-FTC (n=1.65@1.3μm),the cladding layers were NOA73 (n=1.54@1.3μm) and Epoxylite9653 (n=1.54@1.3μm). The obtained single mode rid waveguide structure parameters are: the core thickness is 1.5μm, the rib height is 0.2μm, the rib width is 5μm.

Three kinds of structure photodetectors, N⁺/N-Well/P-Substrate, P⁺/N-Well/P-Substrate and finger N⁺/N-Well/P-Substrate, have been fabricated in CSMC 0.5μm CMOS process. The characteristics of different photodetectors are comparatively tested. The N⁺/N-Well/P-Substrate photodetector is choosed for construction of novel Spice model and fabrication of OEIC chip, considered about both high responsivity and good response speed. A novel Spice model of photodetector is introduced for compatible-design of OEIC. At 780nm and 2.5V reverse bias, the simulated responsivity based on the Spice model is 0.251A/W, close to the measured value 0.253A/W. Finally, a full CMOS monolithic OEIC is successfully accomplished with a gain of 38.1mV/μW in 780nm for optical-disc signal pickup.

There should be flaws and defects on the inner surface during the producing period of a pipe, as well as contaminations and corrosions during the using period of it. A corresponding panoramic optical annular staring inspection system has been developed. It requires no rotating mechanism to exam the whole circumference of a cross section of the inner pipe surface at once, which results high speed inspection. There are two main subsystems in this inspection system, the panoramic optical annular staring imaging subsystem and driving robot subsystem. The Flat Cylinder Perspective (FCP) is the principle to image a panoramic annular view to a flat imagery, i.e. a cylinder of vision imaged is flat. Our imaging subsystem includes a panoramic annular lens (PAL), which is critical and used to implement the FCP, a series of image rotation lenses, a charge-coupled device (CCD) camera, and an illuminating light-emitting diode (LED) ring. The CCD camera sending the signal to a personal computer (PC) via VGA signal results a real time inspection. The driving robot subsystem is a fine designed complicated mechanism including a subassembly of stepper motor. It can drive the inspection system forward and backward continuously in the pipe along the axial direction. The experimental system reported in this paper has the following specifications: average detection resolution of 0.5 mm at the circumference direction and 1.0 mm at the axial direction of a pipe, and inspection speed of 15 mm/s.

The influence of the air-concentration on the characteristic of the square super-lattice pattern in dielectric barrier discharge is investigated. The square super-lattice pattern is obtained in the mixture of air and argon at atmosphere pressure, and the air-concentration is changed from 0.1% to 5%. The patterns follow as the square pattern, quasi-crystal state, square super-lattice pattern, stripe pattern and hexagonal pattern when the applied voltage increases. The bifurcation scenario of the patterns dose not changes as the air-concentration changes. But the voltages of the patterns increase as the air-concentration increases. In addition, the influence of the air-concentration on the electron excited of the square super-lattice pattern is studied by using a monochromator with a CCD. The electron excited temperature T_e is estimated by using spectral lines intensity ratio method. It is found that the electron excited temperature of both the small spot channels and the large spot channels composing of the square super-lattice pattern increases as the air-concentration increases. In addition, the electron excited temperature of the large spot channels is higher than that of small spot channels. The difference of the electron excited temperature between small spot channels and large spot channels becomes more obvious as the air-concentration increases.

Thermal stress effects on the mode field characteristics of arrayed waveguides are studied precisely by finite element method (FEM) with plain strain model. The amplitudes of E_x and E_y are comparable for the E^x₁₁ mode and the E^y₁₁ mode in a homogeneous and isotropic optical channel waveguide. Considering the elasto-optic effect, the refractive indices are inhomogeneous and anisotropic. It is shown that the amplitude of E_y for the E^x₁₁ mode and that of E_x for the E^y₁₁ mode are much smaller than the other electric field components. The simplest method to apply thermal stress is to place a stress plate on the arrayed waveguides. It is shown that the effective indices of the two modes, especially the E^y₁₁ mode, can be tuned by stress plates with different thickness. The order of magnitude of tune range is 10^-4 whereas the material of plate is aluminum. The effective indices can be increased by attaching an aluminum plate with appropriate thickness under arrayed waveguides, and will be decreased whatever the thickness of the plate is set if attached over arrayed waveguides. However, the stress plate has small effect on the optical mode fields.

Platinum was deposited on unintentionally doped n-Al_xGa_1-xN films grown by metal-organic chemical vapor deposition (MOCVD) to form MSM ultraviolet photodetectors. All devices were annealed for 10 min at different temperature in N₂ ambient. Results indicate that the generation of hillocks on the surface of Pt thin-film electrodes at the elevated temperatures due to relieving compressive stress affects the dark current directly. Dark current less than 10pA in the (-10V,10V) range was obtained from a device after annealing at 900°C. Both detectors show sharp spectral responsivity cutoff of about three orders of magnitude by 325nm and 315nm respectively.

The all optical pulses replicating technique to measure single-shot or low repetition optical pulses and pulses with poor stability based on optical pulse active replicator (OPAR) is present. The OPAR can provide an identical pulse sequence for equivalent-time sampling method. The analysis show replication error of OPAR caused by nonlinear gain and amplified spontaneous emission (ASE) of semiconductor optical amplifier (SOA) could be reduced by pumping light injecting. Bias current of SOA should choose an intermediate value to confine nonlinear gain and ASE simultaneously. This result is validated by experiment. The stability of OPAR and baseline shift in output pulses sequence are discussed too. The results show that OPAR is suitable to generate low-distortion pulses sequence for equivalent-time sampling with high replicating stability.

A double-time model software correlator with 5ns time resolution was presented. This correlator includes 12 independent linear correlators. A simple algorithm used for counting the number of photon signals and computing the correlation function on line, was complied by using the graphical programming language Labview8.2. By using of a photomultiplier tube (PMT), a National Instruments Model PXI-5152 high-speed acquisition board, a National Instruments Model PXI-8105 control system, correlation functions can be worked out in real time over time scales of 5μs and processing in blocks down to time scales of ~10ms. Its performances were tested by using polystyrene spheres and silicon dioxide spheres diluted in water. These two kinds of nanoparticles are in different sizes. The correlation functions computed indicate that our correlator is feasible to compute the correlation functions in photon correlation spectroscopy (PCS).

A tunable thin-film filter of multi-channel based on thermo-optic is designed. The filer is made of amorphous silicon and silicon nitride layers grown by PECVD. Multiple-channel filer is obtained by designing the structure of the cavity. Due to the excellent thermo-optical property of a-Si, the refractive index of the cavity will be changed by heating; the filter's peaks wavelength and the width between adjacent routeways will therefore shift substantially. The tuning range is >17nm and the tuning coefficient (dλ/dT) is 0.085nm/K.

A novel polymer distributed feedback (DFB) gratings are developed via UV photopolymerization in order to lower lasing threshold to realize electrically driven polymer lasers. A photopolymer formulation sensitive to 355 nm ultraviolet light is proposed for the fabrication of polymer gratings can be used to form polymer films by spin-coating process. Polymer gratings with periods ranging from 200 to 1000 nm were fabricated based on photopolymerization-induced internal diffusion process. A very low surface relief depth ranging from 12.5 to about 1.0 nm has been demonstrated with a refractive index modulation Δn of about 0.012. Results of theoretical analysis indicate that the quality of the polymer film should be improved in order to improve the refractive index modulation of short-period DFB gratings. Such polymer gratings show promising potentials for the fabrication of low-order DFB organic semiconductor lasers.

In this paper, we present a new theoretical model for the design of acoustical waveguides in the guided acousto-optic devices. The electromechanical coupling coefficient and the velocity in the acoustical in the acoustical waveguide are analyzed for different waveguide thicknesses. Some valuable results for the design of acousto-optic devices are obtained.

A dual-wavelength narrow line width laser system, with ultra-narrow wavelength spacing, is proposed and demonstrated. The operation principle of the laser system is based on the pumped-induced thermal effects of the Er-Yb-doped fiber DBR laser. We designed and constructed a common Er-Yb-doped DBR fiber laser with proper parameters. With the pump power of the DBR laser increasing, the Bragg wavelengths and the bandwidths of the two gratings will change unequally. When pumped with 45mW, we obtain a stable dual wavelength lasing with the bandwidth of 0.014nm and the wavelength spacing of 0.055nm.

The experimental results of the nonlinear photoconductive semiconductor switches triggered by laser diode were reported. A new phenomenon of carrier accumulation effect in the nonlinear PCSS was found. The roles of bias voltage and laser pulse on carrier accumulation have been studied. The results indicate that the number of carriers can be controlled by adjusting the bias voltage, optical pulse or using the other methods. Therefore, the nonlinear PCSS can be controlled.

Optical plane waveguide is wildly used in optical communications and sensors. There are many methods to fabricate the optical plane waveguide. The sol-gel coating method is one of the easiest ways. TiO₂ plane waveguides were fabricated on glass substrates in experiments. The fabrication methods are investigated under different conditions. There are many factors can influence the quality of the plane waveguide, such as the concentrations of sol-gel solutions, the pH value of the solutions, the dripping speed of the sol-gel drop, the heating process and so on. The characteristics of plane waveguides under different operating conditions are tested. The factors affecting the quality of the plane waveguide are analyzed. The experimental results show that the sol-gel coating method is a simple way to fabricate high quality plane waveguide under carefully controlling of the conditions.

A novel variable optical attenuator (VOA) based on fiber Sagnac interferometer is proposed and demonstrated. This VOA is constructed with a 3dB coupler and a polarization controller. By tuning the polarization controller, the output power can be adjusted easily. With the advantage of all fiber design, simple structure and essentially polarization independent, The VOA has an attenuation range more than 20dB, a wavelength ripple of 0.07 and its insertion loss is lees than 0.7dB.

A broadband travelling-wave electro-optical modulator based on teflon substrate is proposed. Finite element method is employed to analyze the performance of the proposed modulator. The relations between the structure parameters and the properties of the modulator have been investigated. The optimized structure parameters of the modulator are obtained. The results show that the modulator has wide modulation bandwidth, low half-wave voltage, and perfect impedance match.

A kind of new light emitting diode (LED) based on Si p-n junction forward injection mechanism completely compatible with standard Si-CMOS technology is designed and analyzed, which has higher efficiency than LED based on Si pn junction in reverse bias breakdown mode. At same time according to reversibility of optoelectronic conversion, the same Si-LED can be used as a photodetector (PD). The photoelectric characteristics of this device as both LED and PD are simulated by the commercial software SILVACO. This device is expected to have wide application in next generation optoelectronic integrated circuit (OEIC).

We present a promising integrated single photon receiver module based on an electro-optic waveguide polarization decoder and a TM pass polarizer. Linear and circular detection bases can be selected with a low control voltage of ~1.5V. A TM pass waveguide polarizer was fabricated with an extinction ratio of greater than 40dB. Low quantum key error rate can be expected due to the reduced optical background scattering noise using the index-matched integration approach. The proposed receiver module is promising for free space quantum key distribution.

The influences of polymer optical fiber (POF) on self-mixing signals in laser Doppler velocimetry are investigated in detail. The waveform distortion and Doppler frequency broadening of self-mixing signal have been observed for the first time. It indicates theoretically and experimentally that the large acceptance angle of POF facet is the major reason for this phenomenon. The other characteristics of POF, such as bend radius over 7.5mm and thermal effect at room temperature, don't cause significant signal distortion. Lastly, we demonstrated a compact fiber-optic self-mixing laser Doppler vibrometer with high accuracy of half optical wavelength and long working distance between fiber facet and diffusing target adopting a single-longitudinal mode vertical-cavity surface-emitting laser (VCSEL).

Coupled 1X2 Single Mode Fiber (SMF-28e®) is successfully fabricated using a slightly unstable torch flame at a temperature range 800°C to 1350°C by injecting hydrogen gas flowing at pressure of 1 bar. The fiber structure and geometry are investigated for both core and cladding before and after fusion. Coupled fiber is studied using Field Emission Scanning Electron Microscopy (FESEM) and Electron Dispersive X-Ray (EDX) System. The pulling length speed, coupling time, coupling coefficient and evolution of coupling ratio from 1% until 75% are examined to study the heating effects at the coupling region. The result shows that the core and cladding geometry of fiber are reduced 80-92%. Their structures are changed which are shown by the changes in the refractive indices. These phenomena have wide applications in industrial communications and sensors such as for optical switching and tunable filtering.

This PDF file contains the front matter associated with SPIE Proceedings Volume 6838, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.