This PDF file contains the front matter associated with SPIE Proceedings Volume 11437, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists.

We report a high-power 10 ps level ultrashort pulsed polarization maintaining (PM) supercontinuum source (SCS) fiber amplifier based on a typical Master Oscillator Pulse Amplification (MOPA) configuration. At the pulse width of 12.1 ps, an average output power of 35.45 W is achieved with the single pulse energy of 2.2 μJ. The output wide spectrum ranging from 1020 nm to 1700 nm has been obtained directly from the Yb-doped fiber amplification (YDFA). But the nonlinear effects in this amplification system are too strong to enhance the average power due to the high peak power of 184 kW. Thus an improved high-power picosecond pulsed PM fiber amplifier is achieved based on a chirped pulse amplification (CPA) configuration. The pulse width is stretched to hundred picosecond scale to reduce the high nonlinear effects and the high peak power by a PM single mode fiber (SMF) stretcher. Only 0.9 m-long PM highly Yb-doped fiber is used in the main-stage amplifier. High average output power of 100.8 W is achieved with repetition rate of 16.68 MHz and pulse width of 280 ps. The central wavelength of the output laser is 1064 nm with 3 dB bandwidth of 2.32 nm. The peak power is 21.58 kW and the single pulse energy is 6.04 μJ, respectively. In addition, the pulse trains are stable without serious distortion and pulse splitting which ensure that the high power PM pulse laser can be used in both fundamental research and industrial fields.

In this paper, an experimental investigation of monolithic diffusion-bonded nonplanar Ho:YAG ring oscillator(NPRO) operated at 2.09μm was presented. A theoretical thermal model for the diffusion-bonded NPRO was established, the thermal effect of the diffusion-bonded Ho:YAG NPRO and un-bonded NPRO were calculated and compared in detail. A diode-pumped Tm-YLF solid-state laser was used to pump the diffusion-bonded Ho:YAG NPRO, a stable singlefrequency output power of up to 12.5W was obtained at 2.09μm with a slope efficiency of 46.3%. The beam quality M²- factors were less than 1.3 in both x- and y- directions.

A novel approach based on the isomerous structure is proposed to improve the performances of liquid crystal optical phased array. Inspired by a space-variant structure, a series of kinoforms are sent to the spatial light modulator to produce space-variant beam steering. The mathematical model of the proposed is deduced and the key parameters are studied. Simulations and experiments are carried out to test the models. Simulations agree well with the experiments, which shows the correctness of the theory. The results are of interested to the integrated, low-cost, and stable beam steering system.

This paper presented a near diffraction limit output of YDFL employing 20/400 μm gain fiber. By coiling the fiber at different radius, different beam quality output was obtained. Combined with the BPM analysis, including the impact of fiber bending and the eccentric core loss induced by fusion splicing on beam quality, the bending radius was optimized to be 4.5 cm. Then, two optimized bending fiber parts were added in our FL system. Accordingly, an excellent beam quality output of M² = 1.06 under the output power of 50 W was achieved successfully.

In this paper, a mode-locked Ytterbium-doped fiber laser based on nonlinear optical loop mirror (NOLM) is proposed. The laser generates a wide-spectrum dissipative soliton resonance mode-locked pulse with strong stimulated Raman scattering. The fiber laser is pumped forward, and the fiber ring cavity contains double-cladding Yb-doped fiber, output coupler, polarization controller, polarization independent isolator and other elements. NOLM is connected with the ring cavity by through a 3dB beam splitter and 25m single-mode fiber. The total length of the eight-shape cavity laser is about 60meters. By adjusting the intra-cavity polarization controller, a stable dissipative soliton resonance mode-locked spike pulse can be achieved. The repetition frequency of the pulse train is 3.44MHz, which is consistent with the cavity length. The 3dB bandwidth of the spectrum reaches 70.6nm, and the 10dB bandwidth is close to 147.11nm. In this experiment, dissipative soliton resonance mode-locked pulses with wide spectrum and high pulse energy are realized by a traditional mode-locking method, which has wide application in many fields such as laser spectral detection and terahertz wave generation.

Long-range wind sensing using coherent Doppler lidar is attractive in many fields such as wind shear warning, aerosol detection and aircraft wake vortex detection. Recently, single frequency, all-solid-state laser around 1.6 μm has caused great interests for its eye-safety and high pulse energy. Velocity accuracy which is one of the key factors of wind lidar systems needs to be calibrated. The 1645 nm eye-safe coherent Doppler wind lidar based on injection-seeded technique consists of laser systems, transceiver optics, and data processing systems is developed. The average power of the laser pulses is 2.6 W with a pulse width of 190 ns at a repetition rate of 300 Hz. The accuracy of velocity measured by the lidar system is calibrated with a velocity calibrator based on a servo motor with a maximum speed of 3000 r/min and a rotating disk with a diameter of 300 mm. A real-time display software based on the LabVIEW platform is designed to get the velocity results and signal to noise ratio (SNR) from the FPGA acquisition module, and the central frequency correction algorithm is used to eliminate frequency jitter of the laser. To calibrate the wind velocity near 0 m/s, a nonmoving hard target at the range of 1.2 km with an elevation angle of about 0.5 deg is measured. Results show that a velocity accuracy (standard deviation of the measurement errors) of 0.38 m/s in the range ±40 m/s and the accuracy of zero velocity is 0.16 m/s.

A1645nm injection-seeded Q-switched Er:YAG ceramic laser pumped by a 1532 nm fiber laser with changeable pulse repetition frequency (PRF) used for Coherent wind measurement Lidar is demonstrated. Single-frequency operation of Er:YAG laser is achieved by injection seeding technique. A ‘M-shape’ ring cavity is utilized to eliminate the effects of spatial hole burning. The laser delivered single-frequency pulses with energy ranging from 6.6 to 10.2 mJ. The corresponding pulse width and PRF varied between 179 ns-271 ns and 300 Hz-1 kHz, respectively. And the line width at 300 Hz is measured to be 2.82 MHz. The measured M2 factors are 1.51 and 1.54 in x and y directions, respectively.

The temperature and thermal stress distributions of end-pumped Er: YAG rod and slab are analyzed by using the finite element method. A thermal-structural coupling model is established for the thermal effects analysis of the crystal based on the steady heat conduction theory. The influences of the crystal structure parameters on the thermal effects inside the Er:YAG slabs and rods are discussed. The analysis results show that the slab structure can effectively improve the thermal distribution performance of the laser medium under the same clear aperture and pumping conditions, compared with the rod crystal. In addition, the thermal effects can be further reduced by increasing the width-to-thickness ratio of the slab. It is also found that a well-designed gradient doping technology can efficiently reduce thermal effects, resulting in the higher output power and beam quality than that in the uniform doping Er: YAG crystal.

Dispersive interferometry ranging with optical frequency comb (OFC) has shown great advantages in distance metrology for its simple structure, high accuracy and the ability to resist disturbance. In this paper, the principle of optical frequency comb dispersive interferometry ranging is analyzed theoretically, and various data processing methods or system improvements proposed by researchers are summarized. The resolution, precision, none-ambiguity range and other parameters of dispersion interference ranging systems are analyzed quantitatively and qualitatively. According to the analysis, the shortcomings of current methods are pointed out and the possible solutions are provided. At last, the prospects of instrumentation and application in the future are also given.

It is indispensable to obtain more information such as the 3D structure of the space target by detecting and identifying the target, when complete the on-orbit servicing and on-orbit control tasks. Both lidar and binocular stereo vision can provide three dimensional information of the environment. But it is very sensitive to the illuminance of environment and difficult to image registration at weak texture region, when we are using the binocular stereo vision in space. And lidar also has some defects such as the lidar data is sparse and the scanning frequency is low. So lidar and binocular stereo vision should be used together. The data of the lidar and binocular stereo vision are fused to make up for each others flaws.

In this paper, uniform point drift registration method is used in the fusion of point cloud which is sampled by lidar and binocular stereo vision. In this method, the two groups of point cloud are considered as one which submit to mixed probability distribution and the other one which is sampled from the points submit to mixed probability distribution. The transformation estimation between the two groups of the point cloud is maximum likelihood estimation. The transformation is required to take overall smoothness. In other words, the point clouds should be uniformed. The uniform point drift method can solve the registration problem efficiently for 3D reconstruction. Usually the time can be compressed by 10%.

It has always been difficult to process a metal film with high reflectivity in the field of manufacture, industry, medicine, and military, etc. Since much of the laser energy can be reflected especially when the reflectance of the target film surface is high, it is hard to process such a metallic film by laser radiation as the energy absorbed by the film material is very little. In this paper, we used a nanosecond pulsed laser to scribe some patterns on a smooth titanium (Ti) film, and investigated the surface morphology of a Ti film ablated by different laser spot sizes and laser energy. In our experiments, it has been found that the Ti film can be efficiently processed although the surface reflectance of the Ti film is about 57% at the wavelength of 532 nm. We also see that the processing range of the Ti film will decrease when the diameter of a laser beam increases. The experimental results show that the ablated status of the surface of a Ti film for a just-focus beam is much better than that for a defocus beam under the same laser power. Furthermore, the higher the laser power, the larger the processed area. By using the optimal parameters we obtained, we also produced some hole matrices and line patterns on a glass-based Ti film by employing a short pulsed laser. The processed samples were observed with a reflecting microscope and a transmitting microscope, respectively. Our research results can play an important role in the selection of laser parameters for laser processing of some materials with a high reflectivity.

A multiple mode rate equations model of the dual-cavity solid-state vortex laser has been established and used to investigate the dynamic process of the Laguerre-Gaussian (LG) modes competition. We calculated the dynamic processes of the modes LG01, LG02 and LG03. The results show that the laser exhibits a complex cross-spiking and cross-relaxation characteristic during the early stage of mode competition. The later start of a mode would cause the cross-spiking and cross-relaxation process, and ultimately the mode started firstly may even not be the one that can be sustained at steady state. To ensure the successful mode selection, the reflectivity of the secondary cavity should be larger than that of the primary cavity, but a too large one would decrease the stable output power of the mode LG01, even to its suppression. The pumping beam distribution has a great influence on the dynamic process and the stable output power of the modes, so the radius and the order of the pumping beam should be optimized. In our case, the optimized beam radius is 0.4 mm, slightly larger than the beam radius of the mode LG00, i.e.0.3 mm, and the optimized order is 4. Moreover, if the laser do not have proper reflectivities of output couplers and pumping beam distribution, the mode selection may not be demonstrated only by optimization of the aperture radius, which would only delay the crossspiking.

LD-side-pumping schemes for a solid-state laser offer the advantages of both high pump efficiency and high output power. However, thermally-induced lens has been known to severely affect the performance of high-powered solid-state lasers. To solve the problem, a systematic simulation model was developed by combining two procedures of ray tracing and finite element method (FEM) together to explore the thermal lens characteristics of a high-powered Nd:YAG laser. The relationship between the spatial heat density distribution and thermally-induced refractive index distribution was investigated by taking an inhomogeneous pentagonal pumping into account. The influence of a pentagonal pumping on the characteristics of the thermal lens focal length of a laser rod was studied afterwards. According to the results, if the volume average heat density of a laser rod is kept as a constant, the focal lengths of a thermally-induced lens in the pentagonal pumped laser rods will be shorter than those of the homogeneously pumped laser rods with different rod diameters. It has also been demonstrated that the focal lengths of both pumping cases are not sensitive to the variation of the rod diameter. The study is thought to be helpful for the design of a high-powered solid-state laser.

Laser screen velocity measurement system is widely used due to its real-time, non-contact, repeatability and high-precision measurement. This paper proposes a circular arc cylinder reflective laser screen velocity measuring method. The first step is to build and deduce the mathematical model of circular cylindrical reflective laser screen velocity measurement system, on this basis, the aberration formula of the optical system is calculated; and the mathematical expression of the theoretical light power density distribution in the effective laser screen area is obtained; optical simulation of the system is performed with Zemax, the photoelectric detection receives a narrow light spot with a diameter of 1.22mm , the result is similar to the theoretical aberration formula; the 7.62mm projectile is respectively passed through different areas of the light screen, calculating the difference value between that’s light power and the light power of the detector when no projectile passes through the light screen, obtaining the system signal sensitivity distribution, the results show that the light power density of the central superimposed region is higher than that of the two sides and decreases with the increase of the y coordinate, moreover, it jumps at the intersection of regions; the maximum variation of light power is 0.19mW , and the minimum is 9.9μW , the effective target surface utilization rate is 93.75% . The construction of the system provides a reliable basis for the design of velocity measurement target for large caliber projectile and another method for realizing velocity measurement of large range trajectory dispersion.

Laser processing plays a key role in treating a lot of materials. The visible nanosecond laser processing based on a tripartite-interaction system has been proved to be an effective method of processing materials with high optical transparency, which has the advantages of low cost, high efficiency, and simplicity over the direct processing by using a femtosecond laser. However, further studies on the theoretical mechanism and parameter optimization keep to be rear for the hybrid tripartite-interaction laser processing. In this study, we have carried out the confirmatory experiment and numerical simulation of laser processing with a tripartite-interaction system, which includes a visible nanosecond laser (19 ns@532 nm), a piece of transparent glass, and a copper foil. The experiment indicates that drilled holes can be obtained on the glass sheets by using the visible nanosecond laser. The numerical results, which have been obtained by an approach named as constrained interpolation profile, reveal that the processing mechanism is based on the heat conduction, generation of stress and ablation between the glass and the copper foil. Our results could to be useful for the development of visible nanosecond laser processing in industrial applications.

We demonstrate a wavelength tunable continuous wave single-frequency Cr:ZnSe laser based on a self-seeded ring cavity configuration in this paper. The laser system is based on anti-coated Cr:ZnSe crystal which has a length of 6 mm and a low signal transmission of 15% (at 1908nm). Unidirectional operation of Cr:ZnSe laser is obtained by using a retro-reflecting device which can retro reflect a self-seed laser back into the ring cavity. The transmission of the output coupler is also optimized to get unidirectional operation. With three different birefringent filters inserting in the cavity, single-frequency operation with narrow linewidth is obtained. By rotating the angle of the birefringent filters, the laser’s wavelength under single-frequency operation could be continuously tuned from 2338 nm to 2572 nm. The tuning range is over 200 nm. The maximum single-frequency output power is 0.92 W at wavelength of 2357 nm.

Linear cavity optical fiber lasers have the advantages of small size, light weight, stable mode, and easy large-scale multiplexing. However, due to the spatial hole burning effect in linear cavity lasers, the long linear cavity fiber lasers have the problem of multi-mode oscillation. In this paper, the quarter-wave plate made by polarization-maintaining fiber and the special combination of fiber grating are used to control the polarization of light transmitted in different directions, which reduces the hole burning effect and realizes the laser few-mode output. The laser performance test results showed that the structure have obvious effect of eliminating space burning holes,which played an important role in eliminating the space burning hole of the line cavity laser and narrowing the laser line width.

We report a new method to prepare active silica fiber preform at low temperature, not exceeding 1300℃ through the whole process. We prefabricated glass parts with nano-porous structure by UV cure equipment and debinded, the average pore diameter is about 46 nm. To prepare the active fiber preform, several different concentrations of Yb³⁺ ions were impregnated with solution doping method and further sintering under flowed O₂. After several hours vitrification, the Yb³⁺- doped silica fiber preform with 0.05 wt%, 0.1 wt% and 0.2 wt% doping concentration were produced, and the size of the final fiber preform is φ3×39 mm. Then the fiber owning an Yb³⁺ concentration of 0.1 wt% was drawn by rod-in-tube, the measurements show that Yb³⁺ ions are homogeneous, central wavelength is 1030 nm, the 3 dB linewidth is about 38 nm, fluorescent lifetime is 1 ms, the fiber has absorption from Yb³⁺ 7 dB/m at 976 nm. To best of our knowledge, it is first time that active fiber preform is produced by this approach.

We report a dispersion-management mode-locked Yb-doped fiber laser utilizing all-polarization-maintaining (PM) components and cross-splicing method, which, to the best of our knowledge, is the first report about dispersion management mode-locking with this approach. The compact linear cavity is constructed with a chirped fiber Bragg grating for dispersion-management, and nonlinear polarization evolution based on all PM fiber structured artificial saturable absorber as nonlinear mode-locking mechanism, delivering 1.855 mW average power output pulses with 3dB spectral bandwidth of 25.18 nm centered at 1031 nm. The stable pulse train had a repetition rate of 6.14 MHz and pulse duration was 7.01 ps which could be further compressed to 179.6 fs. The net dispersion of the cavity is adjusted by changing lengths of the single mode fiber in the cavity from anomalous dispersion to normal dispersion. We have obtained different features of pulses, which distinguished in spectral shapes and time traces. In the meantime, we discuss the nonlinear characteristics of this saturable absorbers theoretically and provide a theoretical basis for further improving the mode-locked fiber lasers.

We report on an all-polarization-maintaining mode-locked fiber with a nonlinear amplifying loop mirror. The repetition rate of the laser varying from 100 kHz to 21 MHz by adjusting the length of passive fiber at the proper position of the cavity. The pulse energy up to 0.1 μJ is realized in case of 100 kHz, and the compressed pulse duration of 177 fs is demonstrated in the case of 5.92 MHz. It’s noticeable that almost all the pulses can be compressed to hundreds of femtosecond level.

PM2.5 and PM10 are important indexes reflecting air quality. Based on the MIE angular scattering principle, a PM2.5 and PM10 detector arraywasdesigned,which was miniaturized and all fiber structures. Theoretical deduction and Matlab program simulation were given to illustrate the basic principle of the system. The influence of system parameters on measurement accuracywere discussed, such aslaser wavelength, scattering angle and receiving range parameters. Using optical fiber spherical end face instead of discrete lens group, miniaturization of probe structure was realized. The introduction of frequency modulated continuous wave (FMCW) technology, realization of multi-element frequency division multiplexing. At the same time, the influence of stray light is eliminated and the signal to noise ratio is improved effectively. The system can simultaneously measure the concentration of PM2.5 and PM10 at multiple locations.

We demonstrated a multi-dark soliton train generated from self-mode-locking ultra-long ring cavity fiber laser. The fiber laser used 10m double-clad Yb-doped fiber as gain medium, and used a polarization independent isolator to ensure the light propagation in one direction. The ring cavity of the laser was designed without any intra-cavity polarization controlling component. The cavity length is 1300 meters by insetting single mode fiber. When the pump power was increased to 2.75W, the multi-dark soliton trains were obtained. The stable pulse train has a repetition rate of 153.9 kHz corresponding to the cavity length. The number of sub-pulse continues to decrease during the increase of the incident pumping power until 3.39W. Stable three peaks appear in the spectra of our fiber laser due to the absence of the polarization controller in the cavity. The maximum peak wavelength locates around 1083.9nm with the 3dB bandwidth of 1.4nm. There are two sidebands with the central wavelength of 1086.3nm and 1090.1nm with a lower intensity. The occurrence of multi-dark soliton pulses train is relevant to the self-mode-locked operation at the cavity with a large amount of normal dispersion and accumulated nonlinearity.

Lightning causes great property losses to human beings every year, therefore how to control lightning and reduce its harm has always been one of the hotspots of the scientific community. In recent years, with the development of high energy ultra-fast laser technology, the peak power of ultrafast laser has been able to reach the GW, TW and even PW. Under the support of such high peak power laser technology, a new type of lightning triggering and guiding technology -- lasertriggered lightning has gradually attracted researchers’ attention. When the laser power intensity reaches TW, Kerr selffocusing effect and plasma defocusing effect will reach dynamic equilibrium. At this time, a light filament with a diameter of a few millimeters and a length of several hundred meters will be formed in the atmosphere, and a low-density plasma channel will be generated in the path. Then a leader is formed through the plasma channel which can trigger and guide discharge from the thunderstorm cloud. Compared with the traditional triggering and guiding of lightning technology, triggering and guiding of lightning by ultrafast Laser has the advantages of flexibility, pollution-free, no consumable consumption, flexible initiative, etc. It will be an important lightning triggering and guiding technology in the future, and it has gradually attracted the attention of scholars from various countries and has obtained a lot of research results. This paper mainly introduces the basic principles of laser-triggered-and-guided lightning, including the laser filament formation mechanism, the basic principle of laser-triggered-and-guided lightning and its history and recent research progress. Moreover, the scientific difficult problems and possible solutions for laser-triggered-and-guided lightning are also discussed, which can be a reference for future development of laser-triggered-and-guided lightning technology.

The dimensioning of a passively q-switched solid state laser can be seen as an interplay between gain on the active medium, the losses caused by the saturable absorber and the optical power within the cavity. This is typically represented by a system of coupled ordinary differential equations. Other rate equation models based on population densities and fluence in the laser cavity are also well known. In previous work we presented a first implementation of one such model that exploited the equivalence between rate equations based on versus a similar model and some preliminary laboratory results for the Q-Switched Microchip Laser that we are developing for range finding applications in space. The current work presents our efforts in bridging the gap between numerical simulation predictions and experimental results. By fitting our laboratory results to our rate equations, we endeavor to obtain the cavity specification values that better represent the physical behavior of our prototype.

We report a high-power chirped pulse amplification (CPA) based on nonlinear amplifying loop mirror (NALM) oscillator and Yb-doped rod-type photonic crystal fiber (PCF). An all-polarization-maintaining NALM mode-locked fiber oscillator was used providing an average power of 9.4 mW, a pulse duration of 5.3 ps at the repetition rate of 21 MHz. After pulse stretching, selection and amplification, an average power of 120 W with the pulse duration of 145 ps at repetition rate of 4.2 MHz has been achieved. The pulse duration is compressed to 14 ps using a pair of reflective gratings coated by gold film. In order to prevent the damage of the gratings, the compressed average power is limited to 51 W. The compressed pulse average power can be further improved by using transmissive gratings coated by dielectric film.

Frequency-sweeping lasers have drawn considerable attentions, especially in FMCW LIDAR. The frequency sweeping single-frequency PM fiber laser is respectively realized by piezoelectric (PZT) modulation and pump modulation, which using the same Er-doped distributed Bragg reflection (DBR) fiber cavity. The central wavelength is 1552.49 nm with the extinction ratio of above 20 dB. The frequency sweeping range of PZT modulation is seen to be up to 745 MHz under the modulation repetition rate of 1Hz, and the modulation repetition rate of the pump can be tuned from 1Hz to 20 kHz. However, the frequency sweeping range and tunable range of pump modulation is 635 MHz and from 1Hz to 10 kHz, respectively. Comparing with both methods, the PZT modulation has wider sweeping range and tunable range, however, the mechanical resonance will be occurred. The pump modulation indicates virtually linearly frequency modulation. Future works to achieve more characteristic of two modulation methods are undergoing.

Employing double wall carbon nanotube (DWCNT) grown by vertical growth method as saturable absorbe（SA）r, and we realize a watt-level Q-switched mode-locking operation in an all-solid-state Tm,Ho:LiLuF₄ (Tm,Ho:LLF) laser with high power. When the pump power is greater than 7.76 W, the laser operation enters a stable Q-switched mode-locking state. When the pump power is increased to 20 W, the maximum output power is 1480 mW under 9% output coupled mirror. In this case, the central wavelength is 1882 nm and the repetition frequency is 55.55MHz, corresponding a maximum single pulse energy of 2.88 nJ, and modulation depth in Q-switching envelopes is close to 100%.

We report an injection-locked single-frequency fiber laser with widely tunable repetition rate. A distributed Bragg reflection (DBR) fiber laser with a central wavelength of 1.063μm and a single frequency continuous-wave (CW) output is used as the master laser. A Fabry–Pérot (F-P) laser diode (LD) with wavelength range of 1.050μm to 1.067μm is used as the slave laser. The single-frequency pulsed laser output is achieved at 1.063μm by controlling pulse, amplitude, temperature of F-P LD and adjusting injection power of DBR fiber laser. The pulse duration can be adjusted between 0.6ns and 40ns. The repetition rate of the laser output can be tuned between 100kHz and 2MHz by tuning the electronic trigger signal. The linewidth is 14MHz when pulse duration is 11ns with repetition rate of 100kHz. The laser with local-oscillator (LO) output shows important value for the applications in the field of coherent LIDAR (Light Detection And Ranging).

With the development of lasers, laser sources have been well adopted in spectrophotometry and optical material measurement. Especially in the ultraviolet range, ultraviolet laser has broad application prospects in the fields of optical data storage, lithography, micromachining, photobiology and medical treatment. The previously used xenon lamps have limited reliability, high energy consumption, and poor beam direction stability. NIM's new facility uses Ti: sapphire lasers as a source of monochromatic beams. Femtosecond pulse lasers can be tuned in a wide spectral range via parametric oscillation and high efficiency frequency conversions. For (280-340) nm femtosecond pulses generated via two nonlinear conversion of a (680-1080) nm Ti:Sapphire laser, the average power can be well controlled from 1 mW to sub-nW level using a polarizer-based attenuator. The laser beam quality was significantly improved using a spatial filter consists of an objective lens, a silica optical fiber, and an off-axis parabolic reflective collimator. The spatial filter was mounted on a two-dimension linear stage to accommodate the spatial beam shift. A spatially stabilized, quality beam over (280-340) nm spectral range was obtained and suitable for free-space optical materials measurements.

Femtosecond pulses tunable in (280-540) nm were generated via second and third harmonic generation processes from a Ti:Sapphire femtosecond laser with a 80 MHz pulse repetition rate. The temporal widths of the pulses are ~200 fs and the spectral bandwidths are <10 nm. These pulses can be used for spectral transmittance measurement using an integrating sphere photodetector with less than 0.1% fluorescence effect. The spectral transmittance measurement nonlinearity of the femtosecond pulse laser spectrophotometer was characterized using a double-path scheme for the incident power level from 1 mW to 10 μW. The nonlinearity results were compared with those obtained using a 532 nm continuous wave laser at similar power levels. The spectrophotometer can be well applied for the spectral transmittance measurement of a wide variety of neutral optical materials after nonlinearity corrections.

Fiber coupled diode laser source is one of the important applications of diode laser. Aimed at a multi-mode fiber of 105μm core diameter and 0.15 numerical aperture, a fiber coupled diode laser system based on a novel reflected aspherical beam shaping component which combines the beam collimating and re-orienting is designed, and a single polarization model is used to validate the design. The simulation and experiment all show that: the system can couple 16 single emitter diode lasers into the multi-mode fiber of 105μm core diameter and 0.15 numerical aperture. In the principle validate experiment of 8 emitters, when the operation current is 10.5A, the output power can achieve 62W, the brightness is 10MW（cm²·sr）, and the E-O efficiency is 52%, separately. In this design, the ratio of the system length and width can be adjusted by changing the offset of the reflected aspherical beam shaping component, so that the system can satisfy different structure demands. Moreover, the novel beam shaping component will effectively conduce to reducing the components amount in the system, which can improve the system integration and reliability. This fiber coupled diode laser can be applied in fiber pumping, material processing and many other areas after being engineered.