This PDF file contains the front matter associated with SPIE Proceedings Volume 6824, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

High power semiconductor lasers have broad applications in the fields of military and industry. Recent advances in high power semiconductor lasers are reviewed mainly in two aspects: improvements of diode lasers performance and optimization of packaging architectures of diode laser bars. Factors which determine the performance of diode lasers, such as power conversion efficiency, temperature of operation, reliability, wavelength stabilization etc., result from a combination of new semiconductor materials, new diode structures, careful material processing of bars. The latest progress of today's high-power diode lasers at home and abroad is briefly discussed and typical data are presented. The packaging process is of decisive importance for the applicability of high-power diode laser bars, not only technically but also economically. The packaging techniques include the material choosing and the structure optimizing of heat-sinks, the bonding between the array and the heat-sink, the cooling and the fiber coupling, etc. The status of packaging techniques is stressed. There are basically three different diode package architectural options according to the integration grade. Since the package design is dominated by the cooling aspect, different effective cooling techniques are promoted by different package architectures and specific demands. The benefit and utility of each package are strongly dependent upon the fundamental optoelectronic properties of the individual diode laser bars. Factors which influence these properties are outlined and comparisons of packaging approaches for these materials are made. Modularity of package for special application requirements is an important developing tendency for high power diode lasers.

Ultra-high-brightness diode lasers open new applications in material processing. LIMO introduces flexible and compact laser tools, including application specific beam shaping and optimised intensity profiles for economical processes. The benefits of micro-optics beam shaping, like compactness and the maintenance-free use of diode lasers, enable a growing number of industrial applications.

In the previous study, we have obtained the spontaneous emission spectra for a quantum well embedded in planar microcavity laser by the numerical integration. Although the numerical integration in the spherical coordinate can given the spontaneous emission for the QW in any microcavity lasers, one would be like to obtain the analytic expression. A new analytic expression for the TM mode spontaneous emission spectra in the planar microcavity laser typically consisting of half a wavelength λ_ο is given in this paper. The results show that TM mode spontaneous emission spectrum by the new analytic expression agrees well with that in the numerical integral in planar semiconductor microcavity laser. The main part to control the TM mode spontaneous emission spectrum is found in the analytic expression. The new analytic expression can be used to study the TM mode spontaneous emission spectra with a quantum well in the microcavity laser.

We investigate the nonlinear dynamics of a pulse injected semiconductor laser that a laser is optically injected by repetitive pulses. Rich dynamics, including both oscillation and pulsation states, are found by varying the intensity and repetition rate of the injection pulses. The laser enters into chaotic pulsation (CP) and chaotic oscillation (CO) states through individual period-double routes. Under proper injection, frequency-locked states with different winding numbers, the ratio of the oscillation relaxation frequency and the repetition frequency of the injection pulses, are observed. The winding numbers reveal a Devil's staircase structure, where a Farey tree showing the relation between the neighboring states is presented. Moreover, the bandwidth enhancement phenomenon of the chaotic states under repetitive pulse injection is also discussed.

The measurement and analysis of the microwave frequency response of semiconductor optical amplifiers (SOAs) are proposed in this paper. The response is measured using a vector network analyzer. Then with the direct-subtracting method, which is based on the definition of scattering parameters of optoelectronic devices, the responses of both the optical signal source and the photodetector are eliminated, and the response of only the SOA is extracted. Some characteristics of the responses can be observed: the responses are quasi-highpass; the gain increases with the bias current; and the response becomes more gradient while the bias current is increasing. The multisectional model of an SOA is then used to analyze the response theoretically. By deducing from the carrier rate equation of one section under the steady state and the small-signal state, the expression of the frequency response is obtained. Then by iterating the expression, the response of the whole SOA is simulated. The simulated results are in good agreement with the measured on the three main characteristics, which are also explained by the deduced results. This proves the validity of the theoretical analysis.

Various high-speed laser modules are fabricated by TO-Packaged processes, such as FP laser modules, DFB laser modules, and VCSEL modules. Furthermore, the resonance among the circuit elements provides an approach to compensating the TO packaging parasitics, and improving the frequency response of the devices. The detailed equivalent circuit model is established to investigate both the laser diode and packaging comprehensively. The small-signal modulation bandwidths of the TO packaged FP laser, DFB laser and the VCSEL modules are more than 10, 9.7 and 8 GHz, respectively.

A laser diode transmitter packaged in a butterfly module is coupled into a single mode fiber using double small ball lenses. The process of alignment and fixing of all the components inside the module is performed in an active alignment procedure, where the laser diode is powered and the output power is continuously measured during the alignment process of all coupling components to determine the optimum positions for maximum coupling efficiency and then fixed in their holders and to the main substrate by laser welding technique using dual beam Nd:YAG laser welding. The double ball lenses coupling scheme found to be very effective in mode matching between laser diode and single mode fiber. The axial, lateral and angular 1dB misalignment tolerances are enhanced for the transformed laser mode field radii in both X and Y directions. The experimentally measured coupling efficiency of the proposed coupling system was around 75% with a relaxed working distance (separation of the coupling system from the fiber tip) in the range of (2-4mm) by optimizing the separation between the two lenses as well as the separation between the first lens and the facet of the laser diode. The experimental results match very well with those obtained theoretically by employing ABCD ray tracing matrix.

Diode lasers develop very fast and are widely used in various optical equipment. Diode laser sources produce fields that show fundamental variations with respect to the canonical Gaussian beam. A partially coherent Lorentz model is employed to describe the far field of a single mode diode laser beam. This paper is concerned with laser junctions significantly narrower than the wavelength. Two lenses system are placed in front of the laser diode, so that the diverging beam is transformed into a converging beam. The across spectral density function in the plane perpendicular to the diode junction is considered in detail, and subsequently employed to predict the light intensity at various beam cross sections near the focus by using the generalized Huygens diffraction integral. The intensity profile at a focused spot produced by a partially coherent Lorentz beam is investigated and compared with that of Gaussian Schell-model beam. It is shown that it has a simple form but fairly describes the optical field in the focal region. The theoretical results are well fit to the practical results in this model and the variations between theory and the experiments are quite less than that of in Gaussian beams. Since Gaussian beams have a minimum uncertainty field, i.e. it possesses the minimum achievable angular spreading once the spatial extension is fixed. Since diode lasers produce highly diverging fields, a Gaussian description for the transverse fields fails. In this case, our results show that partially coherent Lorentz model is a better approximation, and the numerical simulation and discussions are given in detail.

A detailed kinetic Monte Carlo simulation (KMC) is developed to investigate the temperature dependence of semiconductor quantum dot (QD) grown by molecular beam epitaxy syetem. We find that growth temperature plays an important role in determining the size of the QD. The simulation results are compared with the experiment and the agreement between them indicates that this KMC simulation is useful to study the growth mode and the atomic kinetics during the growth of the semiconductor QDs.

The problems and fabrication difficulties for the conventional semiconductor LDs (laser diodes), VCSELs (vertical cavity surface emitting lasers) and LEDs (light emitting diodes) were analyzed. The high quantum efficiency transverse optical coupled LDs, longitudinal optical coupled VCSELs with multi-active region structure and high internal and external quantum efficiency high brightness LEDs with small size were proposed and fabricated; they have showed the excellence performance. The external and differential quantum efficiency are 3.3 and 3.8 W/A, and the output light power is as high as ~ 6.6W when the injecting current equals 2A for the four active regions 980nm strained InGaAs/GaAs QW lasers; the highest pulse and CW light power output are 13.1mW and 9mW of the 980nm longitudinal optical coupled VCSELs; the on-axis luminous intensity of the tunneling regenerated multi-active region LEDs will increase linearly with the number of active regions approximately. The on-axis luminous intensity for the high external quantum efficiency 622nm LEDs with small size 8milx×8mil is as high as 150-200mcd at 20mA injecting current.

A 16×10Gbit/s multiplexer basing on the combination of fiber and space structure method is manufactured. The time-delay error of the multiplexer is only 0.007ps, and this accuracy meets the demand of 160Gbit/s transmission. It differs from the structure of general Mach-Zehnder interferometer. It has the structure of Michelson interferometer. The low insertion loss provides maximum transmission power. It also has such features: high time-delay accuracy, polarization insensitivity, broadband, very short coherence length, high time-delay accuracy, and excellent temperature stability.

A new method of detecting target is presented based on vibration and polarization and a series of experiments have been done. The frequency difference is modulated by vibration displacement signal. A computer is used to adopt and analyze the vibration signal. The method has a good potential prospective to be applied in high resolution, low and middle frequency vibration measurement or random vibration measurement. Vibration imagery offers new possibilities for target classification, and for investigating and monitoring vibration behavior of large scale structures. Experimental and theoretical comparisons of laser detecting techniques with and without spatial resolution capability will be presented. The polarizing characteristics of laser reflected from targets are studied, and some physical parameters of the laser are given, such as backward reflection energy and polarization degree. In order to discriminate the original polarization radiation and non-polarization radiation, the emission system of laser and the detection system of both vertical polarization and parallel polarization are discussed. Analysis of the measured relative polarization and reflectance consists of single wavelength and multi-wavelength comparisons with man-made and background items. A direct comparison is made between natural and man-made materials and different wavelengths of light.

Aiming at the limitations of the existing measuring technology, the paper presents a novel method for inclination angle measurement of inertial platform based on LD-PSD. The proposed scheme adopts autocollimation principle, using a laser diode(LD) as the light source and a two-dimensional position sensitive detector(PSD) for laser spot sensing. The light from LD is first converted to parallel light, and then projected onto a reflector on the inertial platform. The returned light falls on PSD at last. When the inclination angle of inertial platform moves, the laser spot on PSD changes correspondingly, providing 2-D inclination angle information of inertial platform. According to its working principle, a mathematical model of inclination angle measurement is established. High accuracy and long stable working time are the key indexes to implement the measurement system. Considering several main factors including the uniformity and size of laser beam, laser beam excursion, temperature and laser interference etc, which influence the precision and stability, improving methods are put forward. The measurement system, consisting of optical structure, PSD signal processing and inclination angle calculation, is introduced in detail. Finally, calibration and experiment are carried out to verify its performance. The result of the experiment shows that the resolution of the measurement system reaches 0.05" with a working rang of ±600" and the indication error is less than ±0.5" within 24 hours. The measurement system can exactly and reliably measure the inclination angle of inertial platform and monitor the drift of inclination angle for a long time.

High-stability output's system of laser diode is introduced in this paper. The system which is based on the MCU of MSP430 has been designed light power feedback loop and coller of TEC. It includes stable current, protecting circuit, light power feedback loop, temperature controlling, power display and so on. It is also able to control and show the power at the real time. The power could be set by botton too. The software of slow start up, slow close and the protecting relay are adopted by MCU. DRV592 is introduced as PWM driver to control the current of TEC. The duty cycle is generate by MCU. In order to control temperature, it is changed to influence the current of TEC. The power that is sampled by photodiode which is integrated in the laser diode is controlled by the micro-processing. The laser is monitored by voltage control circuit and current control circuit at the real time.

Wavelength tunable electro-absorption modulated distributed Bragg reflector lasers (TEMLs) are promising light source in dense wavelength division multiplexing (DWDM) optical fiber communication system due to high modulation speed, small chirp, low drive voltage, compactness and fast wavelength tuning ability. Thus, increased the transmission capacity, the functionality and the flexibility are provided. Materials with bandgap difference as large as 250nm have been integrated on the same wafer by a combined technique of selective area growth (SAG) and quantum well intermixing (QWI), which supplies a flexible and controllable platform for the need of photonic integrated circuits (PIC). A TEML has been fabricated by this technique for the first time. The component has superior characteristics as following: threshold current of 37mA, output power of 3.5mW at 100mA injection and 0V modulator bias voltage, extinction ratio of more than 20 dB with modulator reverse voltage from 0V to 2V when coupled into a single mode fiber, and wavelength tuning range of 4.4nm covering 6 100-GHz WDM channels. A clearly open eye diagram is observed when the integrated EAM is driven with a 10-Gb/s electrical NRZ signal. A good transmission characteristic is exhibited with power penalties less than 2.2 dB at a bit error ratio (BER) of 10^-10 after 44.4 km standard fiber transmission.

Laser Raman Spectroscopy (LRS) is a proven and powerful technique in geochemical analyses, especially in the study of seawater and seafloor hydrothermal minerals anions, such as SO ₄^2-,CO₃^2-,HCO₃^-, etc. In our lab we have used LD pumped Nd:YAG Laser operating at 532 nm which is selected for its relatively efficient propagation through seawater to investigate the LRS of seawater, Na₂SO_4-NaHCO₃ and Na₂SO_4-Na₂CO₃ aqueous mixed solutions of different established concentrations. The sample is interrogated by a 532 nm laser and the Raman backscattering radiation passes through grating and is recorded on a CCD camera. In the Raman spectrum of seawater near Qingdao sea area, we find SO₄^2- symmetric stretching band centered at ~981 cm^-1 but neither CO₃^2- nor HCO₃^- signal could be observed . We have detected Raman spectra of mixed solutions and separated the Raman shift of anions from mixed Raman spectra, fitted the peak area and center with the method of the multi-peaks Gaussian Fit, then, used the ratios of the fitted areas (the ~981cm^-1 band in SO₄^2-, the ~1066cm^-1 band in CO₃^2- and ~1016cm^-1 band in HCO₃^-) and established concentrations to estimate the Raman cross-section rations. The results show Gaussian Fit can effectively separate the Raman shifts of anions in mixed solution which close to each other and conform to the single solution's in the released papers. And we obtain relative Raman cross-sections ratios [SEE MANUSCRIPT FOR EQUATION] are 2.52 and 3.88 respectively at excitation wavelength 532nm.

Narrow-linewidth tunable diode lasers have been widely used in the field of research, but the output power of such lasers is generally low. This paper deals with a low-cost and easily constructed diode laser amplifier. With the technique of laser injection, the output of an external cavity diode laser (ECDL), which is locked onto the D₂ line of ⁸⁷Rb, is injected into a common commercial 784nm laser diode and the injection locking is achieved. This yields a 120mW single mode laser of which the line width is less than 1MHz, which is to be used in laser trapping of ⁸⁷Rb atom. Furthermore, the influences of the parameters, including the seed light power, the injection current and the temperature, on the operating characteristics of the injection locked laser diode is investigated. The threshold over which the locking would be interrupted due to the variation of the current and the temperature is also derived, which leads to the optimized operating parameters of injection locking.

This paper gives an overview of recent product development and advanced engineering of diode laser technology at Spectra-Physics. Focused development of device design, heat-sinking and beam-conditioning has yielded significant improvement in both power conversion efficiency (PCE) and reliable power, leading to a family of new products. CW PCEs of 60% to 70% have been delivered for the 880 to 980 nm wavelength range. For 780 to 810 nm, PCE are typically between 50% and 56%. Comprehensive life-testing indicates that the reliable powers of devices based on the new developments exceed those of established, highly reliable, production designs. For the progress of ultra-high power bars, CW output power in excess of 1000 W and 640 W have been demonstrated from single laser bars with doubled-side and single-side cooling, respectively. Spatial power density of greater than 2.8 kW/cm² and FWHM spectral widths of 3.5 nm have been obtained from laser stacks.

InGaN/GaN multiple quantum well samples were grown by metal organic chemical vapor deposition with thinner low-temperature GaN buffers than that in the conventional structure. It was found that the absorption recovery times of the InGaN/GaN quantum wells can be controlled by varying the thickness of the low-temperature GaN buffers. Transmission electron microscopy results showed that increased dislocations were introduced in the quantum well region with decreased low-temperature GaN buffer thickness. The degraded crystalline quality of the absorbing regions caused an increased density of nonradiative recombination centers, which were responsible for the fast recovery of the absorption.

A strain analysis model in the pseudomorphically grown epitaxial multilayer system is investigated. Analytical formulas of strain parameters in each epitaxial layer are derived as the following assumptions: (1) the substrate thickness is finite, (2) the in-plane lattice constant is the same for all epitaxial layers for dislocation free growth, (3) the stress along the crystal growth direction is constant, but not necessary zero, (4) the in-plane lattice constant is determined such that the total strain energy. We find the residual stress affect the electronic properties of epitaxially grown multilayer system even though in-plane lattice constant is unchangeable compare with no stress along the crystal growth direction.

The edge emitting PL spectrum of semiconductor gain chip used in vertical external cavity surface emitting lasers was theoretically calculated by using Lorenz linear function when considering of the intraband relaxation and the valence band coupling. A model of laser output which considered of thermal effect was used to simulate our VECSELs' output power. The theoretical results were in good agreement with the experimental results. The factors which influence the output wavelength were discussed too.

An atmospheric aerosol lidar is introduced and its measuring experiment in Beijing is discussed in the paper. The vertical distribution of aerosol extinction coefficients and the relativity between aerosol and Black Carbon within summer planetary boundary layer over the observation site are shown in this paper. The experimental data indicates that the aerosol is almost trapped within PBL and troposphere layer is rather stable and BC is a important composition of aerosol in Beijing. The multi-layer structure of the aerosol distribution is obvious.

Retrieval method for aerosol mass concentration vertical distribution with Lidar is the one of research contents in environment monitoring fields, but little headway has been made. Making use of the extinction coefficients on ground gained by Lidar and corresponding mass concentrations gotten by TEOM, the relationship between extinction coefficient and mass concentration can be disclosed, then the mass concentration vertical distribution can be retrieved through the extinction coefficient vertical distribution. Based on it, two models are developed, and confirmed by some experiments. It is indicated that the aerosol mass concentration vertical distribution retrieved by both the models are consistent with each other, and consistent with fact. The models are maneuverable and simple, and can monitor online and real-time.

In this paper, the influences of the external light injection on the chaotic carrier fundamental frequency of vertical-cavity surface-emitting lasers (VCSELs) with optical feedback have been investigated. The results show that, for the fixed frequency detuning between the master laser diode and the slave VCSEL, the chaotic carrier fundamental frequency can be increased generally with the increase of injected strength; the chaotic carrier fundamental frequency can be improved significantly by adjusting frequency offset and injected strength. For the normalized injected parameter K is 330 and frequency detuning is 42GHz, chaotic output with 47.3GHz fundamental frequency can be obtained.

Based on the theoretical model of the synchronization system with incoherent optical feedback, message encoding and decoding of the chaotic system have been investigated. The results show that message can be hidden efficiently in the chaotic signal during the transmission with three encryption schemes (i.e., chaos shift keying (CSK), chaos masking (CMS) and additive chaos modulation (ACM)); the message of 250Mb/s can be decoded in the receiver with CSK and CMS; when the bit rate increases to 2.5Gb/s, the message can not be decoded with CSK and the quality of message decoded with CMS becomes bad; and when the bit rate increases to 12.5Gb/s, the message can not be decoded with CSK and CMS, however the message can be decoded perfectly by adopting ACM.

We present an extension of an early work on external optical feedback in semiconductor lasers. A more general formalism has been developed, which takes into consideration the anisotropy properties of an external cavity. The expressions are derived for description of the feedback phenomena in a system composed of a laser diode and a Fabry-Perot cavity which is optically birefringent. We show that the emission behavior of such a system can be strongly affected by the polarization states of the feedback waves, and that therefore multiple solutions become possible for stabilization of a composite mode. Particular attention is paid to the angle-dependent phase condition. Examples are given for a laser emitting at the wavelength of 1.54 μm and for an external cavity made of a quartz crystal.

The research on beam shaping of stack pulse laser diodes (LDs), which have little emitter interval and bigger discreteness, by means of the technology of photolithography, filming, precision position adjusting and fiber cylindrical lens array, and on relative technologies are introduced in this paper. To obtain high peak power, which is in need of application fields such as laser ranging, laser fuse, laser guidance, gate imaging and laser radar, direct stacking pulse LDs are widely adopted, but the research on the relative beam shaping technology is done seldom. Owing to the micro-lens is processed once only during the fabrication and the range interval of it is fixed, technologies now available is difficult to take account of beam shaping and the interval discreteness of stack pulse LDs. The most advantageous of fiber cylindrical lens array introduced in this paper is that it can adjust precisely every unit in the array respectively according to the real emitting interval of stack pulse laser diodes, and carry out beam shaping effectively. After that the high effectively coupling of multi-mode fiber can be realized. Thus the practical effect of stack pulse LDs is improved in a large degree.

Accurate and rapid analyses and simulation of semiconductor laser performance, such as small-signal modulation bandwidth, dynamic impedance and large-signal nonlinear distortion etc., are required for the optimal design of an optical communication system. In this paper, by introducing a novel normalized transformation for rate equations of semiconductor lasers, a compact rate-equation-based circuit model is presented and implemented in Agilent's advanced design system. Furthermore, the model is enhanced by including the current-voltage characteristics, and can be directly cascaded with extrinsic parasitic circuits for circuit- or system-level simulation. Thus, the model is applicable for optical transmission system performance evaluation and network characterization in both time and frequency domains. The steady-state and small-signal characteristics, such as current-photon density curve, current-voltage curve and input impedance, are predicted by this model. Two important dynamic characteristics of second-order harmonic distortion and two-tone third-order intermodulation products are simulated under different driving conditions. Fundamental sinusoidal signals at 1 GHz and 2GHz with peak-to-peak modulation current of 11.2mA and 18mA are used to investigate second-order harmonic distortion of semiconductor lasers. For the two-tone third-order intermodulation, two equal-amplitude sinusoidal signals at 4 GHz and 4.04 GHz, each with peak-to-peak modulation current of 11.2 mA, are used to examine the products at 3.96 and 4.08 GHz. The simulated results are compared to the published measurements results. Experiments show that the measured results agree well with the published data.

According to the principle of carrier diffusion within injection stripe, we fabricated a new type of high power single quantum well broad area semiconductor laser. The designed device has a special current injection stripe which results in a Gaussian-like photon gain laterally. The output power is up to 3.75 watt when the beam quality factor M² is 10.6 in continuous-wave operation, and the beam quality factor M² is 5.4 when the output power is 2.5 watt at the same operation condition. The beam quality of broad area semiconductor single quantum well laser has been improved obviously by the designed device

Semiconductor laser is paid more attention and widely used in laser range finder, laser fuse and laser guidance due to its monochromaticity, coherence and high density, as well as small volume and low power consumption. The principle of laser encoding and emitting system is set forth. Based on the principle of spatial frequency-encoding, a laser encoding-emitting system is developed; a new laser encoding mode is designed, which can transfer continuous laser into pulse laser with different frequencies, they represent different position. The mathematic model to calculate the deviation from center is obtained. A new encoding pattern is designed, which is composed of two light paths crossed 90°. Azimuth information of target is given in orthogonal coordinate system and deviation from center is linearity. As well as, characteristic distribution of spatial laser field is analyzed and irradiance distribution is homogeneous. Laser diode is directly applied as guidance source and information carrier in place of solid-state laser. Output power of a single laser diode can reach 3w. Two laser diodes are installed in series for increasing output power in the system. Tested in 2 kilometers outdoor; experimental results prove that: the receiver can receive correctly the signal emitted by system. The laser encoding mode can satisfy guidance precision demand.

With the development of semiconductor laser technology, laser proximity fuzes have been widely used in various kinds of guided missiles and routine ammunitions. An approach to pulsed laser fuze based on pseudorandom code is presented in this paper. Based on the principle of laser fuze using pseudorandom code, the system has been divided into emitting module, receiving module, optical system and information processing module. The different modules have been analyzed in details and principles for selecting the parameters of the modules are given. The testing shows that laser fuze based on pseudorandom code has a better ability of detection and a higher resistance to interference. The theoretic foundation is provided for scientifically designing pulsed laser fuze of pseudorandom code.

The experiment result of semi-insulating GaAs photoconductive semiconductor switch (PCSS) with different electrode gaps triggered by semiconductor laser is reported. With the biased voltage of 500V, the semi-insulating GaAs PCSS with 2mm electrode gap is triggered by laser pulse with 5ns pulse width and repetition rate of 15 kHz, then two groups of electrical pulse samples indicate that laser pulse is instable when laser energy is very low. With the biased voltage of 210V, the GaAs PCSS with 0.5mm electrode gap is triggered by the laser pulse in several dozens nanoseconds at 905nm with a repetition rate of 2 kHz. A stable linear electrical pulse is observed. When the energy of the laser increases, the amplitude and the width of the electrical pulse also increase. It indicates that a stable electrical pulse is obtained while laser energy is high. With the biased voltage of 2400V, the GaAs PCSS with 1mm electrode gap is triggered by laser pulse about 100nJ in 40ns at 904nm. The GaAs PCSS switches a electrical pulse with a voltage up to 1700V. Carriers accumulation effect is discussed and the critical value of carriers accumulation effect is given. The relation of the biased voltage, electrode gap and carriers accumulation effect is also discussed. The concentration of deep EL₂ traps in GaAs has a certain effect on nonlinear mode of GaAs PCSS.

Laser diode (LD) pumped slab laser, as an important high average power solid-state laser, is a promising laser source in military and industrial fields. The different laser diode pumping structures lead to different thermal effect in the slab gain medium. The thermal and stress analysis of slab laser with different pumping structure are performed by finite element analysis (FEA) with the software program ANSYS. The calculation results show that the face pumped and cooled laser results in a near one-dimension temperature distribution and eliminates thermal stress induced depolarization. But the structure is low pump efficiency due to the small thickness of slabs and the requirement to cool and pump through the same faces. End-pumped slab laser is high pump efficiency and excellent mode match, but its pumping arrangement is fairly complicated. The edge-pumped face-cooling slab laser's pump efficiency is better than face-pumping, and its pumping structure is simpler than end-pumped laser, but the tensile stress on surfaces may initiate failure of the gain medium so it is important to design so that the stress is well below the stress fracture limit. The comparison of the thermal effects with different pumping structure shows that, the edge-pumped slab laser has engineering advantages in high power slab laser's application. Furthermore, the end-pumped slab laser tends to get the best beam quality, so it is fit for the application which has a special requirement on laser beam quality.

By using oxidation confinement technology high power vertical-cavity surface-emitting lasers are fabricated in experiment. The electrical and optical performance characteristics such as threshold current, efficiency, emission wavelength, and output power are measured under continuous wave (CW) condition at room temperature. The maximum output power is up to watt regime at wavelength of about 980nm. The temperature characteristics of the device are investigated experimentally in detail. The variation in lasing threshold current with temperature is studied. The characteristic temperature T₀ of the device is derived, and the value is about 211K. Such a high characteristic temperature T₀ of threshold current can lead to good temperature sensitivity of the device. At the same time, the lasing spectrum characteristics with temperature are also measured. The wavelength shift with temperature is just about 0.06nm/K. From the measured results, it is shown that the device can still operate at high temperature condition.

In this paper, we will present the new structure of the concavity heat sink with flower water in the pipe for semiconductor laser array. In the CW operation, the main equations of controlling temperature and boundary conditions are described in the concavity heat sink. The static thermal conduction equation that govern heat flow in the high power laser array and the heat sink is given. The variational equation integral of equation has been described according the boundary conditions based on Finite Element Method. The process of solving the equation is included and the distribution of temperature in the concavity heat sink is studied. The virtues of concavity heat sink comparing with the rectangle heat sink are showed. We also design the thickness of the concavity heat sink. The difference of the concavity heat sink and the rectangle heat sink will be presented. The result shows that the maximum temperature in the heat sink and the temperature grads especially in the corner of heat sink are dropped and this heat sink is best fit for the heat leaving off the laser array.

A novel fabrication method and process of Au(80wt.%)-Sn(20wt.%) eutectic alloys solder with excellent thermal, electrical and mechanical properties and relatively low melting and reflow temperature was presented, the characteristic of gold-tin alloy solder and the key technique to realize highly reliable bonding were discussed.

Laser diode bar (LDB) are used increasingly often for many applications, but spectral bandwidth of LDB are generally approximately 2-4nm, far too wide for many demanding applications, e.g. spin-exchange optical pumping, terahertz generation, and lidar. External-cavity feedback can improve the spectral properties of LD or LDB. However, spectrum narrowing of LDB is more difficult than that of LD. Bar curvature (i.e. "smile") produced in the manufacturing process affects the spectrum narrowing greatly. By geometrical optics approach and ORIGIN software, smile which can be corrected by plano-convex cylindrical lens is simulated and the result is in good agreement with experiment. The selection of grating which is also a critical factor of spectrum narrowing will be stated. Finally, an external cavity consisting of fast axis collimator, two plano-convex cylindrical lens and a diffraction grating is used. The scheme is implemented on a 19-element LDB and yields 3-fold reduction in spectral linewidth under the situation that all optical elements in the system which are not optimized. Further, we use a slit in the experiment and analyze the spectrum narrowing of each element in LDB.

The AlGaAs/GaAs double quantum well semiconductor lasers grown by molecular beam epitaxy show high external quantum efficiency and high power conversion efficiency at continuous-wave power output using an asymmetric structure. The threshold current density and slope efficiency of the device are 200A/cm² and 1.25W/A, respectively. The high external quantum efficiency and maximum conversion efficiency are 81% and 66%, respectively.

Laser diodes are widely used in many fields, but the poor beam quality is an obvious deficiency. The intensity distribution of a beam from a laser diode in the slow axis is so complex that it is difficult to be described by a Gaussian distribution of a certain order. The beam qualities of a certain type of laser diode in the directions of perpendicular and parallel to junction are evaluated in this paper. The intensity distributions in two directions are described respectively by fundamental mode Gaussian distribution and multi-mode Hermite-Gaussian distribution. The computed data is basically in accord with the experimental data. The mathematical model may provide some suggestions for the designing of optical system with laser diodes and related simulations.

A novel chaotic lidar with high resolution is proposed and studied theoretically. In chaotic lidar system, the chaotic laser emitted from chaotic laser diode is split into two beams: the probe and the reference light. The ranging is achieved by correlating the reference waveform with the delayed probe waveform backscattered from the target. In chaotic lidar systems presented previously, the chaotic signal source is laser diode with optical feedback or with optical injection by another one. The ranging resolution is limited by the bandwidth of chaotic laser which determined by the configuration of chaotic signal source. We proposed a novel chaotic lidar which ranging resolution is enhanced significantly by external optical injected chaotic laser diode. With the bandwidth-enhanced chaotic laser, the range resolution of the chaotic lidar system with optical injection is roughly two times compared with that of without optical injection. The resolution increases with injection strength increasing in a certain frequency detuning range.

Circuit model is presented by considering carriers transportation behavior in SCH region and analyzing rate-equations of vertical-cavity surface emitting lasers. The frequency response characteristics are given by circuit simulation and we discuss and compare the result with practical device.

We investigate the feasibility of multi-target ranging using broad-band chaotic laser numerically and experimentally. Chaotic laser generated by semiconductor laser with optical feedback can be utilized as chaotic signal source for target ranging and detection. Chaotic laser is split into reference beam and signal beam, the ranging is realized by correlating the reference waveform with the time-delayed signal waveform reflected back from the target. Simulation results indicate that the signal beam can be divided into several portions, by correlating the reference waveform with several time-delayed signal waveforms backscattered from multi-targets, the range measurements of multi-targets are achieved in real time. We design a proof-of-concept experiment to confirm the simulation results and realize the range measurements of two targets simultaneously.

The effects of dispersion on optical fiber chaotic secure communication are numerically investigated. A theoretical model for fiber chaotic secure communication system which is consisted of a pair of synchronized chaotic lasers and an optical fiber channel is presented. Chaotic secure communication for a 1-GHz sinusoidal message after propagating several hundred kilometers is numerically analyzed. By numerically studying the effects of dispersion on the system's performance, we show that the synchronization progressively degrades and the signal-to-noise ratio of the recovered message decreases as the fiber length increases. We also find that the signal-to-noise ratio descends when the modulation frequency of the encoding message increases. We propose a dispersion management scheme to compensate the dispersion in fiber chaotic secure communication system. The proposed dispersion management map is consisted of a segment of 5-km dispersion-compensating fiber with value of dispersion β₂=-49ps²/km, a segment of 245-km nonzero dispersion-shifted fiber with value of dispersion β₂=1ps²/km and optical amplifiers. The results show that the signal-to-noise ratio of the extracted 1-GHz sinusoidal message increases from 2.75dB to 14.02dB when the length of fiber is set to 500km.

We experimentally investigated the wavelength matching between the probe light and injection-locked modes of FP-LD (Fabry-Perot laser diode) for wavelength conversion configuration. Wavelength conversion from 1552.9nm to 1548.5nm was obtained experimentally based on cross-gain modulation with the 10GHz repetition rate optical pulse train in a FP-LD. Our results indicate that there always exists a selected longitudinal mode of the probe light in the FP-LD to maximize the extinction ratio of the conversion signal. Moreover, there also exists an optimum injection signal pulse power to improve the conversion signal further under the same matching mode of probe light wavelength with the constant input power, and the constant detuning between the probe light and signal pulse wavelengths and the locked modes of FP-LD with a certain bias current range.

We numerically study the message filtering characteristics of semiconductor laser as a receiver in optical chaos communication. The transmitter is an external-cavity laser subjecting to optical feedback that operates in a chaotic regime. The receiver can operate at a chaotic regime either similar to the transmitter (closed-loop scheme) or without optical feedback (open-loop scheme). We study the effects of frequency detuning and parameters mismatch between transmitter and receiver on quality of the recovered signal in both open and closed loop schemes. We find that the closed-loop scheme has, in general, a higher quality of recovered signal compared with the open-loop. We also study the effects of message frequency on quality of the recovered signal in the two types of schemes. The results demonstrate that the filtering effect of semiconductor laser receiver is larger for low frequency message and decreases as the message frequency approaches the relaxation oscillation frequency of semiconductor laser. The SNR of the recovered signal of the open-loop scheme remains higher than that of the closed-loop scheme when the message frequency is in high frequency region.

Extensive experiment studies are performed in the evolved process from low-frequency fluctuations to chaos. The low-frequency fluctuations and high dimension chaos with 12.2 correlation dimension are generated experimentally by a DFB semiconductor laser with optical feedback. Meanwhile, the effects of pumping current and feedback strength on the average duration and the peak-peak value of low-frequency fluctuations are experimentally analyzed. Our results show that there exists an obvious critical point for the bias current of the semiconductor laser. When the bias current I_b is set below 1.03I_th, the peak-peak value of the low-frequency fluctuations is increasing at first and then decreasing with the feedback strength decreasing, while its average duration is decreasing but chaos don't appear in the whole performance. However, when the bias current I_b is set above 1.03I_th, the output of the laser can evolutes from low-frequency fluctuations chaos with the feedback strength decrease. Moreover the peak-peak value of the low-frequency fluctuation is increasing continually and its average periodic time is decreasing with the decrease of the feedback strength.

Acousto-optic modulator (AOM) and electro-optic modulator (EOM) drived by voltage controlled oscillator (VCO) are widely used to control and modulate laser, especially semiconductor lasers. We designed a frequency generator based on direct digital synthesizer (DDS) technology which can be used to replace VCO. The frequency generator with high frequency stability can reach 160 MHz bandwidth and frequency resolution up to 1 Hz. The output frequency is programmable and controlled by input TTL edge. These advantages are not available with VCO. We obtain a output radio frequency (RF) power as high as 1W with a power amplifier in order to drive an AOM. This device has been used to scan the wavelength of external cavity laser diode (ECLD) in our laser cooling experiments.

We propose and experimentally demonstrate a novel technique that uses a single Fabry-Perot laser diode (FP-LD) to perform simultaneous all-optical clock division and wavelength conversion. Utilizing the period-two oscillations characteristics in an optically injected semiconductor laser and the cross-gain modulation effect of the injection locked semiconductor laser, we achieve the simultaneous all optical clock division and wavelength conversion in a single FP-LD. Clock frequency division of 12.8 GHz to 6.4 GHz with simultaneous wavelength conversion from 1550.24 nm to 1545.91 nm is obtained. The experimental results indicate there is a certain injection signal power to obtain stable clock frequency division in an optimum wavelength detuning. It was empirically found that the best clock division and wavelength conversion occurred when the injected signal power was approximately 2~2.5 times as the injected probe light power, and the range of optimum wavelength detuning was about from -0.01 nm to 0.06 nm. Moreover, the FP-LD's bias current also influence the clock frequency divisions, we demonstrate that the most effective conversion can be obtain when bias current is located in the range of 1.6Ith~2.3Ith. The experimental investigations further show that there is an optimum matching mode between the FP-LD and the probe light for obtaining the largest extinction ratio in wavelength conversion.

Laser diodes are efficient, compact, and inexpensive light sources and are already part of our modern life. However, their use for spectroscopy has been limited due to the intrinsic problem of reliably controling output frequency and power. In application where linewidth, stability or tunable narrow-band frequency output is required, free-running laser diodes are from satisfactory. The problem can be overcome with External-Cavity Diode Lasers (ECDL). The obvious features of my working are the optimization of the spatial mode and the design of the direction of light. We design the optical trace, and having a well result. In the process of the experiment using grating for the modulation of external-cavity and geometry optimization for maintaining the fixed direction of output beam. So when declining the grating for tuning the frequency of laser, you have not the demand of changing the rest part in experiment. In the system, I utilized a feedback to obtain a good precision of the controlling of the temperature and current.

A novel and compact near-infrared (NIR) Raman system is developed using 785-nm diode laser, volume-phase technology holographic system, and NIR intensified charge-coupled device (CCD). Raman spectra and first derivative spectra of Rhizoma Dioscoreae are obtained. Raman spectra of Rhizoma Dioscoreae showed three strong characteristic peaks at 477.4cm^-1, 863.9cm^-1, and 936.0cm^-1. The major ingredients are protein, amino acid, starch, polysaccharides and so on, matched with the known basic biochemical composition of Rhizoma Dioscoreae. In the first derivative spectra of Rhizoma Dioscoreae, distinguishing characteristic peaks appeared at 467.674cm^-1, 484.603cm^-1, 870.37cm^-1, 943.368cm^-1. Contrasted with Rhizoma Dioscoreae Raman spectra, in 600cm^-1 to 800cm^-1, 1000cm^-1 to 1400cm^-1 regions, changes in Rhizoma Dioscoreae Raman first derivative spectra are represented more clearly than Rhizoma Dioscoreae Raman spectra. So Rhizoma Dioscoreae raman first derivative spectra can be an accurate supplementary analysis method to Rhizoma Dioscoreae Raman spectra.