This PDF file contains the front matter associated with SPIE Proceedings Volume 8551 including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

Excimer Pumped Alkali Laser (XPAL) is a hopeful choice to solve Diode Pumped Alkali Laser (DPAL)’s disadvantages. Theoretical and experimental investigations of Rb-Ar XPAL were carried out in this paper. Time dependent rate equation model illustrated that extreme pump strength was needed to exceed threshold and to assure efficient cw running. 780nm lasing of four level Rb-Ar excimer was realized with a surrogate 15 ns pulsed optical parametric oscillator (OPO). Possible resonator configuration may increase pumping strength was proposed.

In this paper, a simple one dimensional heated flow analysis model and 3-D finite volume method (FVM) is set to discuss the real gas dynamic effect in FDPAL. We found that huge amount of waste heat deposited in extreme compact volume size will notably affect active medium’s local velocity, temperature and the density distribution along flow direction, and would accordingly affect pump beam’s absorption and change optimized lasing conditions, hence, a comprehensive model incorporate gas dynamic effect should be built for DPAL’s next stage development. We further proposed that expanding fluid channel may be a choice to increase optical thickness along pumping direction and alleviate this effect.

Photo-ionization probability is an important factor in the practical use of resonance enhanced multiphoton ionization (REMPI). To a certain experimental condition, it depends on the competition between spontaneous radiation and ionization of the excited particles. In this work, we investigate the influence of laser resonance detuning, Rabi frequency and ionization rate on spontaneous radiation and ionization in the process of REMPI with the theory of density matrix equation. A model of three energy level system is adopted. It is found that the spontaneous radiation and ionization probability increase with the decrease of laser resonance detuning. They get to the maximum when resonance detuning equals zero. The line width of spontaneous emission will decrease with the increase of ionization rate due to the competition between spontaneous radiation and ionization. In addition, the spontaneous radiation and ionization probability increase with Rabi frequency until gets to saturation. Laser resonance detuning has no influence on the saturation value. It only influences the Rabi frequency for saturation. If Rabi frequency increases further after saturation, the spontaneous radiation will decrease because of the phenomena of energy level splitting in strong laser field. Now that resonant absorption and large laser intensity can increase the ionization probability greatly, so we must select suitable laser frequency and large laser intensity in the practical use of REMPI, in order to get optimum detection result.

We investigate the thermal lensing along the direction of heat removal in a zigzag slab laser by numerically computing its temperature distribution, the OPD profile and the focal length of the thermal lens. Particular attention is paid to the dependence of the curvature type of the thermal lens on the number of bounces. As the number of bounces increases consecutively, the curvature type of the thermal lens in the slab thickness direction oscillates between the concave lens and the convex one, but not in an alternate manner. The reason is disclosed that for the convex lens case, the average temperature along the route, through which the ray on the edge of the main lobe aperture travels, is much lower than that at the center. The formation of the concave lens can be well explained in a similar way. In addition, we conclude that the beamlet with a larger number of bounces experiences weaker thermal lensing but more serious wavefront deformation due to the large side lobe portion in the curve of optical path difference. The analysis and the discussion provide a good reference for the design of slab parameters and the selection of the number of bounces. Furthermore, multiple zigzag slabs with different curvature types of thermal lenses can be placed in a cavity or lined up as a multi-stage amplifier, which may compensate the thermal lensing and the wavefront deformation, thus improving the beam quality.

Based on the optical path model for nonlinear imaging, we systematically investigated the propagation of flat-topped Gaussian beam which is modulated by two parallel gain-typed wirelike scatterers through computer simulation. It is found that hot image for each scatterer can be formed, with the hot image plane several centimeters behind the predicted conjugated plane obtained by the approximate theory for attenuation-typed scatterers. It is found that the object distance, i.e. the distance from the scatterer plane to the incident surface of the Kerr medium slab, has an important influence on the propagation properties and results in a new phenomenon. Under certain object distances, the evolution of the maximum intensity of the beam has one prominent peak before that for hot image, where the on-axis location is dozens of centimeters ahead of the hot image plane. As the size of the scatterers increases, the value of this peak increases at first and then decreases. As the object distance increases, the value of this peak decreases. The intensity distribution corresponding to this peak shows that, there is an intense fringe, which is the most intense fringe in the plane, at the middle point of the line connecting the two scatterers, indicating that it is a unique result of the interaction of the two scatterers. Besides, the influences of the object distance and the scatterer size on hot image intensity are discussed.

Based on prior calibration with analogist samples, a system, consisting of a CCD camera, a frame grabber and a computer, is developed to in-situ measure the molten pool parameters during laser cladding. The signals captured by CCD vary with change in substrate or clad material, so that, in order to gain the true data of the molten pool parameters, calibration of the instrument must be performed for every set of substrate and clad materials. In this study, a new strategy for on-line acquisition of molten pool parameters is presented. Before measurement of the objective molten pool, cladding is performed to get some analogist samples of the same materials as those used to generate the objective molten pool. The width of a certain segment of the clad bead on the analogist sample is gauged to calibrate the CCD camera-grabbed image of the molten pool which has solidified to this segment of the clad bead. The pool width in the grabbed image can be confirmed to the gauged bead width times the scaling because the width of the clad bead segment must be equal to the width of the related pool. It is assured which type of area in the grabbed image is located on by the pool, and the CCD is calibrated for this set of substrate and clad materials. After calibration, the CCD system is applied to in-situ measure the molten pool parameters during laser cladding. In the presented experiments, the measured values agree well with the actual ones.

By changing pumping light for cholesteric liquid crystal based laser, the laser efficiency measurement of laser is done. To gain laser of high power and high efficiency, some improvement measures are proposed and tested, such as align treatment and temperature condition which also affects the wavelength of exit light. For the helical structures of cholesteric liquid crystal and its temperature-tunable characteristics, the impact of temperature is also discussed.

Thermal recovery uniformity is key factor on high energy laser device. Based on the principle of statistics, combined with the amplifier glass neodymium thermal recovery research results, we put forward degree of uniformity as evaluation index for Nd-glass laser slab on multi-segment amplifier. The simulation results show that the heat transfer coefficient of the Nd:glass laser slab on the amplifier is affected by number, pitch and diameter of the inlet jet. The heat transfer coefficient and temperature contour of Nd:glass laser slab are obtained based on numerical simulation. Moreover, the degree of uniformity of Nd-glass laser slab is on the base of simulation results. The more the degree of uniformity is close to 1, the better thermal recovery of Nd:glass laser slab.

We present a theoretical and experimental study on PM ultra-short fiber laser cavities operating at low repetition rate. The mode-locking operation in this study always relies on SEmicondutor Saturable Absorber Mirror (SESAM) and intracavity spectral filtering. Several experimental configurations have been tested and modeled. Repetition rates as low as 7.7 MHz with sub-picosecond pulse duration have been obtained. A longer cavity has also been modeled in order to determine if stable ultra-short pulsed operation would also possible at lower repetition rates.

A 100 W-class all-fiber linearly-polarized single-mode fiber laser at 1120 nm with an optical pump efficiency of 50% was demonstrated. Linearly polarized output with a polarization extinction ratio of 15 dB is achieved by a cavity that selects both wavelength and polarization. Macro pulse operations with square shaped pulses from 100 μs to 1 ms are achieved without relaxation oscillation. The exact wavelength of pump diode is found to be crucial for amplified spontaneous emission and parasitic oscillation in high power 1120 nm fiber laser. Effects of inhomogeneous spectral broadening and temperature dependent absorption are proposed to explain experimental observations.

Femtosecond fiber lasers are becoming an enabling technology for biomedical imaging and diagnostics from the bench to the bedside. Techniques used for achieving mode locked fiber lasers are discussed. These techniques include polarization shaping, pulse shaping, and spectral shaping. Mode locked fiber lasers operating at 1 μm, 1.55 μm, 2 μm and their harmonic generations (780-800 nm, 515-532 nm, 344-355 nm, 257-266 nm) are discussed. By using dispersion managed amplifiers, amplification and compression of 100 fs femtosecond pulses to 10 watts were demonstrated. These femtosecond fiber lasers are packaged in compact and robust modules and passed long term operation test without any degradation, and proved to be reliable light sources for clinic applications.

We report a novel design of solid-state laser amplifier chain based on Nd:YAG gain mediums, by lining up multiple single-side-pumped slabs in a special manner. The scheme takes advantage of the excellent power scalability of the sidepumping configuration, and allows a reduction in cost and complexity comparing to the conventional way, by decoupling the cooling and pumping interfaces and thus avoiding water sealing application and water contamination to the crystal. Specifically, influences of ASE effects on the amplifier performance (power scaling, beam quality and transverse mode profile) are described in detail, considering the re-amplification of ASE along the slab chain. A point design at 10 kW power level including the ASE effect is also described.

According to saturable absorber function of two-level system and theoretical model of Q-switched mode locking, and combining with all-solid-state Yb:YAG laser, the characteristics of the saturable absorption of graphene which is varied with layers and the critical pump power of Q-switched mode locking have been studied numerically. It can be seen that the saturable fluence and modulation depth are proportional to the graphene layers. The critical pump power will decrease when the graphene layers, transmittance of output mirror, beam radius on graphene and cavity length decrease, and Q-switched mode locking becomes easier. The resonant beam radius and laser crystal length have an optimal value each, which can obtain minimum critical pump power.

We demonstrated a passive phase locking of a seven-element 352 W all-fiber polarization-maintaining amplifiers array using an all-optical feedback loop. Every single channel has four-stage amplifiers and is seeded by a broadband master oscillator for stimulated Brillouin scattering free. The seven laser beams are tiled side by side into a hexagonal laser array with a high space duty ratio of 65% in the near field. When system is in closed-loop, a visibility more than 90% of coherent pattern in the far field is obtained. By using the all-optical feedback loop and more pump power, higher power scaling with high beam quality appears to be achievable in a coherent beam combination system.

Because of the limited optical element aperture, damage threshold, gain bandwidth, and so on, the output capability of a single laser beam is limited seriously. The coherent laser beam combining offers an excellent method to improve the peak intensity which could be gotten greatly. Aiming at getting the general requirements of the coherent beam combining for large aperture laser facilities, this work devotes to modeling the influences of the phase factors and spectrum factors on the combine results. The effects of the phase factors, including the piston error and tip/tilt error, are studied analytically and numerically. It is found that the expressions of the intensity in the focal plane can be written as three parts, the scale factor, a point spread function (PSF), and a grid function (GF), for the ideal beam combining and beam combining with piston error. Every part has its special physical meaning, and decides different characteristics of the combined focus. For the beam combining with tip/tilt error, though the expression of focal spot intensity can not be separated like the above situations, every part still has obvious physical meanings. The results show that the beam configuration can not affect the Strehl ratio of the combined beam, but it influences the FWHM of the main peak and the ratio of the main peak and the side peak. The piston error affects the grid function greatly, including its maximum value, transverse translation, and shape. For the two beam combining, a piston error less than 2π/5 rad is suitable. For multibeam combining, the standard deviation of the piston error should be no more than 2π/10 rad. The tip/tilt error affects the superposition degree of the focal spots of the combined elements directly. A requirement of 0.5~1μrad for the standard deviation of the tip/tilt error is adequate. The effects of the spectrum factors, including the longitudinal chromatism, high order dispersion, and residual chirp, are studied analyzed. Results show that the above spectrum factors have significant influences on the short pulse coherent beam combining, and must be controlled carefully when the pulse is shorter than 1ps.

In the past decade of development in fiber laser technology, the market share of high power full fiber lasers has expanded tremendously to replace traditional gas and solid laser systems. While fiber lasers offer advantages of compact dimensions, high conversion efficiency, and full fiber integration, cost is still a major challenge for fiber laser manufacturing. With an increasing power rating, high power diode pump lasers become the most critical component to control the cost margin of fiber laser. Oclaro offers the most complete solution of fiber coupled diode lasers for fiber laser customers with platforms of multi-mode single emitter, multi emitters and mini-bar fiber coupled, with the benefit of competitive $/W margin and Telcodia standard high reliability performance .

A novel external cavity with double volume Bragg gratings is approved in this paper. The linewidth of the LDA with the external cavity can be tunable through controlling the temperature differences of the two VBGs, while the output power changed no more than 4%.

We report external cavity Raman lasers using a 9.5-mm-long low-loss CVD diamond pumped by a 35 W q-switched Nd:YVO₄ laser with approximately 22 ns pulses at 36 kHz pulse repetition frequency. Two systems were investigated. The first demonstrated first and second Stokes simultaneously with more than 14.5 W of combined optical power. For an output coupler optimized for second Stokes only output (1485 nm), 11.1 W at 38% conversion efficiency was obtained. This output power is comparable to the maximum output powers reported for competing pulsed eye-safe technologies such as optical parametric oscillators and Er:YAG lasers.

We put forward a quasi-concentric laser resonator configuration employing a line-shaped end-pumping profile (QRLE). A thermal lensing modeling of the QRLE is developed, including the quartic phase deformation and the dependence of the thermal focal power on the TEM₀₀ mode size at the thermal lens. Based on the calculation, we found that the dynamic operating point of the QRLE depends on both the resonator condition and the thermal effect condition. Furthermore, we predicted that the operating point in the subcritical region is insensitive to power fluctuation, i.e., the QRLE with extremely short cavity length is capable of stable operation. The validity of our prediction was well confirmed by theoretical modeling and experimental realization. Compared to conventional resonator designs, the QRLE resonator design produces the fundamental mode output with an LD bar instead of the fiber-coupled pump source and realizes good stability with short cavity length, demonstrating a clear advantage of both low cost and compactness. Based on the QRLE configuration, we produced >12 W pulsed TEM₀₀ output, with the repetition rate of 30 kHz and optical-optical efficiency of 27%. The laser output mode is elaborately symmetrized in two directions in terms of beam quality, waist radius, and waist position.

A novel distributed-side-pumped configuration is presented for power scaling of solid-state slab lasers, which combines the advantages of both end-pumped and side-pumped geometries, realizing large absorption length and large pump area at the same time. In the distributed-side-pumped slab laser, the long gain medium can be divided into multiple segments (slab units), each of which adopts an end-pumped like geometry, thus the pump uniformity and the utilization ratio of the whole slab are greatly improved comparing to the end-pumped scheme. Furthermore, this configuration decouples the pump windows from the cooling areas, avoiding the necessity of water sealing the optical surfaces. The parameters of gain medium and pumping system are carefully optimized, while numerical calculation of thermal effects for composite slab and homogeneous slab are compared. An oscillator based the Nd:YAG slab that includes 5 slab units, is expected to produce CW output at 1 kW level, with the optical-optical efficiency of 52.6%. By adding more slab units, the distributed-side-pumped slab laser can be enhanced easily and efficiently.

Previous experiments in both the lab and field have verified that the Fourier Telescopy (FT) technique to imaging geostationary targets is both viable and robust. By theory analysis and numerical calculation of power dispersal and atmosphere’s affection, it is proved that the Adaptive Optical(AO) System for the transmitter subsystem of FT is necessary. A special AO system is designed for FT. The AO systemp includes two wavefront sensors (WFS), a deformable mirror(DM) and an actuator command computer. The AO system can use laser guide stars , GEO itself or star as reference star. Two wavefront sensors have different functions. One WFS is used to measure the wavefront of the reference star’s wavefront after it’s broadcast through the atmosphere, the other WFS is used to measure the transmitted laser’s wavefront before it leave the telescope. The actuator command computer syn-calculate the DM’s distortion value according to two waveront sensors’ measure results and figure out the drive voltage of every actuator. The AO system of Fourier Telescopy will realize two functions. On the one hand，it will improve the transmitted beam’s quality，decrease the laser ‘s size formed at the side of the GEO object and increase the centralization of the transmitted beam. On the other hand, the AO system will decrease effect of atmospheric scintillation and beam-wander on the uplink beams and increase the possibility of the interferometry on GEO targets, so the AO system will decrease the infection to the uplink beam caused by atmosphere turbulence.

Gamma-gamma distribution model was widely used in numerical simulations of the free-space optical communication system. The simulations are often interrupted by numerical overflow exception due to excessive parameters. Based on former researches, two modified models are presented using mathematical calculation software and computer program. By means of substitution and recurrence, factors of the original model are transformed into corresponding logarithmic formats, and potential overflow in calculation is eliminated. By numerical verification, the practicability and accuracy of the modified models are proved and the advantages and disadvantages are listed. The proper model should be selected according to practical conditions. The two models are also applicable to other numerical simulations based on gamma gamma distribution such as outrage probability and mean fade time of the free-space optical communication.

In a high-energy laser, the thermal aberrations degrade the beam quality and reduce the laser’s output power. Adaptive optics (AO) technique based on a stochastic parallel gradient (SPGD) algorithm can be used to compensate for the distortions in real time to clean up the laser beam. Such a beam clean-up system was simulated and experiments were conducted to study the optimization of the parameters of the gain coefficient and the amplitude of the perturbation. The results show that the convergence property of the SPGD algorithm is improved after the parameters being optimized.

According to the heat features of LD with high power and the different patterns of heat dissipation , the cooling module of MMR has been put forward ,refering to heat dissipation modes and theory of steam cooling. Data analysis has been shown in the paper according to the temperature distribution of the steam cooling module.

We demonstrate a Q-switched Ytterbium-doped double-cladding fiber laser based on single-walled carbon nanotubes as saturable absorbers. The pure single-walled carbon nanotubes were directly deposited on the one end of the Ytterbium-doped double-cladding fiber by optically driven deposition method. A linear-cavity was employed and a 1.5m long Ytterbium-doped double-cladding fiber played as the gain fiber. The Ytterbium-doped double-cladding fiber was pumped by a 976-nm fiber coupled diode laser. The maximum output power of 1.3W was obtained at the wavelength of 1070nm. The pulse-repetition rates were tuned from 9.1 KHz to 60 KHz when the pump powers were changed from 1.85W to 10W and the shortest pulse duration was around 600ns.

In this study, LD end-pumped Nd:YAG/LBO solid state blue laser is realized by even hollow cavity. A thermal distribution model of Nd:YAG crystal is established. Based on the calculation, the temperature distribution of laser crystal is obtained. The results show that the temperature decreases from the pump end to the launch end exponentially. When the pumping power is 10 W and the radius of pumping beams is 240μm, a biggest output power 1.06 W of blue light is achieved, giving an optical conversion efficiency of 10.6%.

The amorphous oxide semiconductors (AOSs) are promising for emerging large-area optoelectronic applications because of capability of large-area, uniform deposition at low temperatures such as room temperature (RT). Indium–gallium–zinc oxide (InGaZnO) thin film is a promising amorphous semiconductors material in thin film transistors (TFT) for its excellent electrical properties. In our work, the InGaZnO thin films are fabricated on the SiO2 glass using pulsed laser deposition (PLD) in the oxygen partial pressure altered from 1 to 10 Pa at RT. The targets were prepared by mixing Ga₂O₃, In₂O₃, and ZnO powder at a mol ratio of 1: 7: 2 before the solid-state reactions in a tube furnace at the atmospheric pressure. The targets were irradiated by an Nd:YAG laser(355nm). Finally, we have three films of 270nm, 230nm, 190nm thick for 1Pa, 5Pa, 10Pa oxygen partial pressure. The product thin films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), Hall-effect investigation. The comparative study demonstrated the character changes of the structure and electronic transport properties, which is probably occurred as a fact of the different oxygen partial pressure used in the PLD.

A passively Single-walled carbon nanotube is a new material as a saturable absorber to obtain a Q-switched laser or a mode-locked laser because of it’s broadband absorption wavelength and cheaper price comparing with SESAM. Here, by using a single-walled carbon nanotube as saturable absorber (SWCNT-SA), a passively Q-switched Nd:YCOB (Nd³⁺:YCa₄O(BO₃)₃)laser was realized at 1085.3nm pumped by a 808 nm diode laser .The fluorescence spectrum of Nd:YCOB crystal near 1.06 μm. The output power of the Q-switched laser of 175 mW were obtained at the pump power of 9W in a V-type cavity. The range of the repetition rate was from 35 kHz to 62.5 kHz and pulse width was 1.6μs (FWHM) at 62.5 kHz.

The single-walled carbon nanotubes (SWCNT) could be used as saturable absorber in Q-Switched and mode-locked lasers. In this paper, the influence of the concentration and the ultrasound time on the absorption coefficient of the single-walled carbon nanotubes was discussed. The structure and morphology of the single-walled carbon nanotubes were investigated by the atomic force microscope（AFM）and the scanning electron microscopy(SEM). When the single-walled carbon nanotube saturable absorbers (SWCNT-SAs) were used in both the Yb-doped double cladding fiber laser and the solid state lasers, the Q-switched pulses were obtained. And we use the single-walled carbon nanotubes saturable absorber (SWCNTs) in the passively Q-switched Nd:YCOB (Nd3+:(Nd³⁺:YCa₄O(BO₃)₃) laser, a duration of 1.6μs pulses were obtained at the center wavelength of 1085.3 nm, a 175 mW output power were obtained at the pump power of 9W.

numerical simulation model for coherent combination of multiple rectangular beams, square beams and circular beams has been developed. The beam quality factor β of wavelet and its combination was obtained by numerical calculation through fast Fourier transform (FFT) when each wavelet has Zernike aberrations with twenty-one polynomials. The influence of piston on coherent beam combination was analyzed too. It’s demonstrated that the influence of piston on CBC(coherent beam combination) was small if each wavelet has many other higher order aberrations. The relationship between the averaged beam quality factor β of all wavelets and beam quality factor β of CBC based on these wavelets was also obtained by numerical calculation. A fitting formula was used to fit the discrete data. By this way, an expression of the relationship was acquired. Fitting coefficients between numerical calculation and theoretical result were compared and the affecting factor of the difference was analyzed. We concluded that fitting coefficients of numerical calculation result was smaller than theoretical result because of wavelet arrangement and filling ratio.

In this paper, we demonstrate the output characteristics of a kind of all-fiber optical source based on Er³⁺/Yb³⁺ co-doped double-clad fiber (EY-DCF) in a master oscillator-power amplifier (MOPA) configuration. The amplifier is composed of a 10m long EYDCF, two isolators at both input and output terminals, and a 976nm pump diode connecting with the EYDCF via a side-pump fiber coupler. A DFB diode laser operating at 1547.8nm serves as the master oscillator. A maximum output power of 1.16W is obtained. The gain of the fiber amplifiers is up to 30.7dB. The wavelength centered at 1547.8nm with a spectral width no more than 0.02nm shows longtime stability.

A high power diode-pumped composite YVO₄/Nd:YVO₄/YVO₄ actively Q-switched and mode-locked laser with ring resonator is demonstrated. For mode-locking operation, the maximum average output power at 1064 nm was up to 14.4 W at a pulse repetition frequency (PRF) of 85 kHz and at the incident pump power of 40 W, with the corresponding optical conversion efficiency of 36%. The shortest mode-locked pulse width was obtained to be 117.1 picosecond (ps) at the incident pump power of 26 W and PRF of 55 kHz, with the corresponding average output power of 7.37 W and the linewidth of 0.0436 nm. The highest pulse energy and peak power were obtained to be 93.5 μJ and 0.362 MW at PRF of 5 kHz and incident pump power of 40W, respectively.

A novel method for rapidly synthesized Au colloidal under microwave irradiation was present in this paper. Size of the Au nanoparticles varied from 10 nm to 60 nm along with varying mol fractions by chloroauric acid solution reduced with sodium citrate. The prepared Au nanoparticles were characterized by transmission electron microscope (TEM) and ultraviolet-visible (UV-Vis) spectrophotometer. It is found that the nanoparticle size and shape are highly dependent on the reaction time and the molar ratios of the reducing agent. By the SERS measurements of R6G, 4-MBA and Crystal violet, this Au colloid is shown to be an excellent SERS substrate with good stability. As the fabrication process of this SERS substrate is simple and inexpensive, this method may be used in large-scale preparation of substrates that can serve as an ideal SERS substrate in biomedical application.

The damage threshold and morphology of optical material have been investigated by 800nm, 75MHz, 30fs laser pulses, in 40 magnification and 0.65 numerical aperture (NA) objective in the Z-LiNbO₃ crystals. The influence of several experimental parameters, for example energy per pulse, a ser scanning speed, or repeat time on writing quality and the characters of relative microstructures has been analyzed and studied in theory. The damage structural change, from small refractive index changes to micro explosion structure in LiNbO₃ induced by high intensity nanosecond laser is studied. Nonlinear interactions of nanosecond laser and transparent material are discussed. The subsurface morphology of the processed structures inside the LiNbO₃ was obtained by a Nikon optical microscope. Particularly, we find that the wider width of the buried channel with the increase of energy per pluse, repeat time and the reduce of scanning speed. It was caused by the avalanche ionization and multi-photon absorption of lithium on the processed area, and which is also lead to the refractive index change rang by the writing conditions. The result shows that the propagation of optical waveguide could achieve ideal effect when the energy per pluse is under 300mW, the scanning speed is from 0.05mm/s to 0.2mm/s, and the focus depth is from 350μm to 400μm.At last, in this approach, the insertion loss of 1×4 optical splitter is less than 1dB/cm.

Electrical effect induced by laser plasma in air is measured using a tiny probe placed in close to a metal target. Analysis shows that the resulting signal wave varies with detection distance. Based on the testing system, an equivalent circuit model was proposed to analyze the formation mechanism and evolution of the electrical signal and its dependence on the probe distance. The observed signal peak polarity overturn was also analyzed and explained. Finally, our method provides an explanation for the effects of the testing angle on the probe signals according to the time and space evolution of the laser plasma.