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We demonstrated a narrow pulse-width long-wave infrared ZnGeP2 (ZGP) optical parametric oscillator (OPO) pumped by a 2.1 μm Ho:YAG master oscillator power-amplifier (MOPA). By short-cavity structure, a minimum pulse width of ∼12 ns was achieved at 1kHz, 2kHz and 3kHz in Ho:YAG oscillator. By employing a three-stage amplifier, a maximum average output power of 73.1 W with pulse width of ∼17 ns at the pulse repetition frequency of 3 kHz was obtained. Then a ZGP OPO pumped by the Ho:YAG MOPA was demonstrated. The maximum average output powers of 5.48 W at 8.2 μm and 22.4 W at 2.8 μm were obtained, corresponding to the pulse width of

Taking a comprehensive consideration of related excited state absorption, upconversion emission, and cross relaxation processes, a theoretical model concerning a pulsed Yb-Tm fiber laser is established. The criterion for stable Q-switching is derived with both excited state absorption processes and mode field area mismatch taken into account. And, detailed population transitions of major energy levels are illustrated. Impacts of pump power, mode field area ratio and saturable absorber length on the output characteristics of the pulsed laser system are investigated and analyzed. Simulations show that the excited state absorption transition 3F4→3F2,3 is the predominant factor supporting the passive Q-switching of Yb-Tm fiber lasers. Besides the pump power, the mode field area ratio and the length of the saturable absorber are also important factors affecting the output characteristics of the pulsed laser system. Proper choice of these parameters not only brings significant improvements to the pulse performance, with regards to both the pulse energy and the pulse duration, but also expands the stable operation range of the laser system. And, in practice, an effective mode field area ratio bigger than 1.65 should be exploited for the stable Q-switching operation of a pulsed Yb-Tm fiber laser.

The continuous wave laser characteristics of a Tm:GdScO3 laser were researched in this work. Under the absorbed pump power of 19.11 W, a maximum output power of 4.41 W was obtained at 1978 nm, corresponding to the slope efficiency of 28.25%. With a quartz birefringent filter (BF), a broad wavelength tunable range from 1845 nm to 2006 nm was obtained, for the first time. Then, a long-pass filter was used to replace the quartz BF. A maximum output power of 3.21 W was obtained at 2002 nm, with the slope efficiency of 21.98%. The beam quality factors M 2 for horizontal and vertical directions were 1.14 and 1.11, respectively.

We report a 2 μm band high power pulsed all-polarization maintaining (PM) thulium-doped fiber laser based on the acousto-optic q-switching technique. It is constructed in a two-stage master-oscillator power amplifier (MOPA) configuration. A Q-switched seed laser was composed of a homemade 1559 nm fiber laser, a pair of fiber Bragg gratings (FBGs) with central wavelength at 2009 nm, a piece of single-cladding thulium-doped fiber (TDF) and an acoustic-optical modulator (AOM). Using a two-stage amplifier seeded by an acousto-optic modulator modulated pulsed laser, We achieved the laser with a central wavelength of 2009.71 nm, and the laser has a 3 dB linewidth of 0.09nm and output power of approximately 2.04 W. Based on the acousto-optic switch, the pulse width of 97 ns at a repetition rate of 20 kHz was obtained. The maximum peak-power of the fiber power amplifier is 2.1 kW and pulse energy is more than 204 μJ. This high power thulium-doped fiber laser has an all-fiber based configuration. We used a cladding power stripper (CPS) with matched passive fiber to remove residual pump light that leaked into cladding. The slope efficiency of the thulium-doped fiber power amplifier was 22.7%.

We demonstrated a stable fiber laser setup for real-time monitoring of Tm-doped gain fibers while being exposed to gamma-rays. The output power is about 10W, and the power stability of the system is ±0.25% based on the 12-hour continuous measurement. By using this laser setup and 60Co gamma-ray irradiation source, the dose rate effect and total dose effect on the typical Tm-doped fiber specimens under water-cooling condition were experimentally studied. According to the obtained experimental results on five kinds of Tm-doped gain fiber from different R and D institutions and batches at home and abroad, the output power declines monotonously with the total irradiation dose increasing. During a dose rate range of 0.05 to 0.5 rad(Si)/s, the dose rate effects of Tm-doped gain fiber samples basically disappear, which means the differences of power degradation under different dose rate are almost invisible.

Most of the FBGs used in continues-wave thulium-doped fiber lasers are made in foreign companies. So we built up a fiber Bragg grating (FBG) writing platform to produce different parameter FBG for research, and a homemade FBG-based thulium-doped fiber laser testing system was experimentally demonstrated in this paper. Here homemade uniform FBGbased thulium fiber laser output characteristic was explored. The thulium-doped fiber laser was built up with two 793nm laser diodes as pump source, a thulium-doped fiber, a combiner and a pair of homemade FBGs. A 1916 nm thulium-doped fiber laser with output power of 20.87 W and slope efficiency of 41.29% and a 1917 nm thulium-doped fiber laser with output power of 19.53 W and slope efficiency of 38.56% were obtained by optimizing the thulium-doped fiber length, the operation temperature of the grating and the center wavelength of the grating.

Yb3+/Al3+-doped and Yb3+/Al3+/P5+-doped silica fibers with almost identical Yb3+ doping concentrations were prepared using modified chemical vapor deposition methods. A harsh experimental environment for simultaneous photo-darkening (PD) and radio-darkening (RD) of an ytterbium-doped silica fiber (YDF) was established. The RD, PD, and photo-radio-darkening (PRD) of the YDF were characterized at two dose rates of 0.1 rad(Si)/s and 1 rad(Si)/s. The laser performances before and after the darkening process were tested under 974-nm pumping. The results demonstrated that the PD largely dominated the PRD kinetics of the YDF at a low dose rate (e.g., that in space) and that the PRD was not a superposition of RD and PD owing to the pump light bleaching if the induced loss was larger than the PD equilibrium level. The induced loss and defect types were investigated through absorption spectra and electron paramagnetic resonance. The results revealed that the P doping could enhance the PD, RD, and PRD resistances by inhibiting the formation of aluminum–oxygen hole centers.

Impacts of Tm ion concentration and Ho ion concentration on the saturable behaviors of Tm-Ho codoped fiber saturable absorbers and the output characteristics of the passively Q-switched laser systems are investigated and analyzed both at the initial lasing state and the stable passive Q-switching state. Simulations show that, varying concentrations of Tm and Ho ions have different impacts on the temporal evolution processes but similar effects on the macroscopic characteristics of the laser system. The root for the impacts of dopant concentrations is the population of the 3H6 energy level and the cavity loss it induces. For Tm ions, the rise of the Tm concentration improves the population of the 3H6 energy level directly, while, for Ho ions, higher Ho concentration leads to larger recovery rate of the 3H6 energy level, thus increasing the population of the 3H6 energy level indirectly. As for limited total dopant concentration, the Tm:Ho concentration ratio can be optimized for different applications.

A theoretical model concerning FSA-based active Q-switching is developed. And, characteristics of the active Q-switching operation are investigated and compared with the traditional passive Q-switching operation. Numerical results demonstrate that the active control of the repetition rate of FSA-based Q-switching is attainable. And, stable active Q-switching could be obtained from both no lasing state and stable passive Q-switching state.

We build a Tm-doped fiber amplifier based on a gain-switched seed laser. At Er-doped fiber-laser pumping, the maximum peak power of the gain-switched seed pulse is 227.7 W with a pulse duration of 48.3 ns. In the amplifier, peak power of the amplified pulse reaches 1.1 kW with a 3 dB linewidth of 0.06 nm. Supercontinuum generation is observed when this amplified pulsed laser source is injected into a section of 7 m long Tm-doped double-clad fiber.

With both radiation effects and thermal effects taken into consideration, a multiphysics thermal model concerning high-power Yb-doped fiber lasers operated with post-irradiated active fibers is established. Radiation-related parameters, including propagation losses, refractive indexes and lifetime, are considered. And, with the temperature profile of the active fiber, temperature-dependent parameters, including absorption and emission cross-sections, refractive indexes and lifetime, are updated every loop to simulate the output parameters. Simulation results show that radiation induces great changes to the thermal profiles of the active fiber. And severe performance degradation of high-power Yb-doped fiber lasers are recorded, featuring a remarkable drop in output power and an even steeper decline in the transverse mode instability threshold, which is a predominant limitation at high radiation doses. With a deposited radiation of 100 Gy, an output decline of about 50% and a mode instability threshold drop over 85% are observed. And it’s shown that, with the exploited active fiber, it’s hardly possible for the investigated fiber laser to generate stable single-mode output at kilowatt levels with accumulated radiation doses beyond 50 Gy. At low radiation doses within 20 Gy, to maintain safe and stable single-mode operation of the laser system, longer active fibers with lower absorption coefficients are preferred despite a small rollover of the output power.

We build an all-optical, all-fiber actively Q-switched Er-doped fiber laser with a simple ring cavity. Active Q-switching is attained by saturating a section of 34 cm Tm–Ho co-doped fiber saturable absorber with a 1550 nm pulsed fiber laser. The repetition rate of the pulsed output is 30 kHz determined by that of the subsidiary pump. The maximum pulse energy generated is about 80 nJ with a pulse duration of 2.07 μs. The line width of the pulsed output is only 0.054 nm limited by the resolution capability of the spectrum analyzer.

The multi-tone amplification for the purpose of mitigating stimulated Brillouin scattering (SBS) effect is investigated. Different wavelengths and power ratio are considered in the simulation model to achieve optimal results. The numerical simulation results indicate that SBS is effectively suppressed in a fiber amplifier with an output from 53.7W to 96.9W by utilizing this approach.

The high power infrared 2μm lasers have been extensively investigated for a number of commercial, scientific and engineering applications, such as remote chemical sensing, medical diagnostics, eye-safe laser radar, and environmental monitoring. Furthermore, high-power 2μm lasers are effective pump sources of optical parametrical oscillators and optical parametrical amplifications to generate mid-infrared 3-5μm laser. In recent years, Ho:YAlO3(Ho:YAP) crystal has drawn great attention as a promising efficient laser material for its long emission wavelength at 2118nm. An acoustic-optical Q-switched Ho:YAP laser pumped by an all fiber thulium-doped fiber laser is demonstrated. The all fiber thulium-doped fiber laser can emit 80W output power, and the output laser wavelength is 1915nm. By using this 1915nm laser to end pump the AO Q-switched Ho:YAP laser system, 2118nm laser with 30W average power and 45ns pulse width at 20kHz repetition rates was obtained.

A theoretical model concerning the 3 H 6 → 3 F 4 transition of Tm ions for passive Q-switching of an Er-doped fiber laser is built. Related population transitions of the passive Q-switching mechanism are simulated and described. Effects of pump power, output reflectivity and cavity length on the laser performance are investigated and analyzed. Numerical results indicate that pump power and output reflectivity are major factors affecting the laser output, while the cavity length mainly determines the pulse duration. Besides, high repetition rate operation is achievable with 3 H 6 → 3 F 4 transition of Tm ions at the expense of the output pulse energy.

It is generally accepted that increasing the object distance can decrease the radiation influence of the self-luminous object in a schlieren system. This paper shows that a larger object distance results in a brighter image that exerts a greater influence on schlieren imaging because of overwhelming. To decrease the radiation influence, we propose to put the self-luminous object nearer to the second schlieren mirror, e.g. in the front focal plane, and spatially filter the radiation at the back focal plane of the second schlieren mirror by a diaphragm. An experiment was carried out, showing that the image irradiance contributed by self-luminescence can be reduced by several orders by this scheme.

Determination of parameters is presented in the modeling of Tm-doped fiber lasers. The thesis chooses parameters, numerical simulation to examine the performance of the laser system for different pump schemes and cavity parameters. Their impacts on the laser performance are discussed.

Super-flat supercontinua are generated from a double clad Tm-doped fiber amplifier. Two different laser configurations are investigated and compared. In the direct-output configuration, the long-wavelength edge of the supercontinuum spectra is extended to beyond 2.65 μm with a 10 dB bandwidth of 740 nm. In the passive pigtail configuration, the generated supercontinuum features excellent flatness with an intensity difference smaller than 1 dB in the wide central spectral range from 1.98 μm to 2.41 μm.

A Tm–Ho codoped fiber amplifier system is built. And, amplification of a gain-switched Tm–Ho codoped fiber laser is investigated. Average output of 300 mW is obtained at repetition rate of tens of kHz with an amplification gain bigger than 11 dB. And, pulse amplification efficiency of resonantly pumped Tm–Ho codoped single clad fiber is comparable with 793 nm pumped Tm-doped double clad fiber. The maximal pulse energy generated is about 13.1 μJ, corresponding to a peak power of 282 W at 20 kHz. During the amplification process, gain-switching, partially modulated gain-switched mode-locking and 100% modulated gain-switched mode-locking are observed sequentially. At gain-switching mode, the laser output enjoys a narrow linewidth of 0.31 nm, while at gain-switched mode-locking mode, the spectral linewidth broadens to 0.6 nm.

Two possible methods for repetition rate improvement of Tm-doped fiber saturable absorber based passively Q-switched Er-doped fiber lasers are reviewed. Simulations show that both methods are effective.

The investigations of the XeF laser bumped by ultraviolet radiation have been studied for more than 20 years in Northwest Institute of Nuclear Technology (NINT Xi’an China). Up to now, several XeF laser devices were developed and an integrative experimental system has been set up which is comprised of a laser device, an electrical power supply, a high voltage trigger generator and a mixture gas supply device. Many key technologies were studied in detail and have been applied now. These technologies include section surface discharge, XeF2 photodissociation, synchronal trigger generating, double-sides optical pumping from opposite directions, active mixture gases supplying in real time, gases circulation, and so on. The XeF laser system operating on pulse repetition frequency (PRF) is up to 10 Hz. Two kinds of operating modes were applied. For the open gas flowing mode, the pulse energy of 3.2 J and the average power of 32 W at 10Hz is obtained. For the gases circumrotate mode, the average energy of 20 laser pulses is more than 0.5J.

The output power of a narrow line-width laser is usually limited by the Stimulated Brillouin Scattering effect. In Master Oscillator Power Amplifier structures, multi-point pump could rearrange the gain distribution along the fiber, leading to the suppression of the Stimulated Brillouin Scattering effect with maintained amplification efficiency. A theoretical model concerning 100W-level fiber amplifiers is proposed. Stimulation is performed to analyze the amplification process of the laser signal and Stimulated Brillouin Scattering. The results demonstrate that the power of scattering light decreases from 3.2W to 6.8mW (with two-point pump) indicating the effectiveness of this new technology in Stimulated Brillouin Scattering suppression.

In this article, an overview of laser dazzling effect to buried channel CCD camera is given. The CCDs are sorted into staring and scanning types. The former includes the frame transfer and interline transfer types. The latter includes linear and time delay integration types. All CCDs must perform four primary tasks in generating an image, which are called charge generation, charge collection, charge transfer and charge measurement. In camera, the lenses are needed to input the optical signal to the CCD sensors, in which the techniques for erasing stray light are used. And the electron circuits are needed to process the output signal of CCD, in which many electronic techniques are used. The dazzling effects are the conjunct result of light distribution distortion and charge distribution distortion, which respectively derive from the lens and the sensor. Strictly speaking, in lens, the light distribution is not distorted. In general, the lens are so well designed and fabricated that its stray light can be neglected. But the laser is of much enough intensity to make its stray light obvious. In CCD image sensors, laser can induce a so large electrons generation. Charges transfer inefficiency and charges blooming will cause the distortion of the charge distribution. Commonly, the largest signal outputted from CCD sensor is restricted by capability of the collection well of CCD, and can’t go beyond the dynamic range for the subsequent electron circuits maintaining normal work. So the signal is not distorted in the post-processing circuits. But some techniques in the circuit can make some dazzling effects present different phenomenon in final image.

A pulsed Er 3+ -doped ZBLAN fiber laser at 2.8 μm in fundamental-transverse-mode operation is reported. Stable gainswitching is achieved with the repetition rate range from 0.5 to 10 kHz. The maximum laser pulse energy of up to 4.2 μJ and pulse duration of 1.18 μs at a repetition rate of 10 kHz, yielding the maximum peak power of 3.5 W, has been obtained. The maximum slope efficiency with respect to the launched pump power at 975 nm is determined to be 12.2%. Pulse spikes occur by increasing the pump energy of larger than 75 μJ.

A Tm-doped double-clad fiber MOPA system is built. Amplification characteristics of a Tm-doped double-clad narrow linewidth fiber master oscillator (MO) are investigated both experimentally and numerically. Linewidth of the fiber MO is only 112 pm at 3 W output. The output and efficiency of the MOPA system increase with the injected seed power. When the seed power is increased to 2 W, a maximum output of 10.5 W is obtained with a slope efficiency of 41.5%. Spectral center of the output lies at 1996.7 nm with the linewidth no bigger than 120 pm throughout the experiment.

开展了1 915 nm高功率、高效率、窄谱宽输出的掺铥光纤激光器（TDFL）研究。基于全光纤主振荡功率放大（MOPA）结构，采用40 W的793 nm半导体激光器泵浦纤芯直径25 m的双包层大模场面积（LMA）掺铥光纤，获得了最高功率12.1 W的1 915 nm窄谱宽连续种子激光输出。将8 W种子光注入掺铥光纤放大器，在793 nm激光泵浦功率为142.9 W时，获得了平均功率90 W的激光输出，其中心波长为1 915.051 nm，3 dB谱宽仅为94 pm，斜率效率为60.2%，光-光转换效率达63.0%。该系统在40 min运行考核时间内输出激光稳定性良好。

This paper describes systematically the properties of the surface discharge pumping source. The pre-ionization technology was investigated. The characteristics of the surface discharge and the photodissociation wave of exciting media have been studied. The temporal and Spatial Stability of discharge were measured and analyzed. The discharge spectral and ablation rate of three different materials were obtained.

The design and performance of a closed cycle, repetitively pulsed HF/DF laser is described. For obtained higher stable laser pulse energy and running frequency, discharge stability with different electrode profile and different gas circulation structure are researched. The functional relations of laser pulse energy with electric field strength (E) and gas mixture pressure (P) for various gas flow velocity are studied. It is shown that with preliminary optimized of the gas injection segment structure before pump region and optimal E/P conditions, maximal running frequency of 100Hz is obtained and operating stability keeps well. Under these conditions, the laser average power is 40W and peak power is 4MW.

Modeling of Tm-doped fiber lasers pumped with 793 nm, 1.6 μm and 1.9 μm is presented and compared. Output performance of three different pump schemes with active fiber length, pump power and output reflectivity is investigated. Numerical simulation shows that, with 793 nm pump, the cross relaxation process is of vital importance for high efficient operation of Tm-doped fiber laser. And, 1.9 μm pump scheme is more likely to offer even higher output compared with 793 nm pump and 1.6 μm pump.

The hyperspectral absorption spectroscopy is attracting more and more attention as this technique enables continuous wavelength sweep over a whole absorption band, rather than one or several discrete absorption lines. Owing to the H2O possesses much stronger and more abundant absorption lines in the 2μm region, this work develop a widely tunable, narrow linewidth Tm-doped fiber laser around 1.87μm for the application of combustion diagnostics. The laser wavelength tuning range is designed from 1850 nm to 1890 nm to overlap the strong absorption band of H2O, and the laser linewidth is further narrowed to 0.04 nm by a fiber saturable absorber. With this laser system, demonstration experiments are implemented for the continuous detection of H2O absorption lines. Detailed absorption peaks of H2O from 1866 nm to 1879 nm are detected and well-resolved. The measured absorption spectrum agree well with the theoretical computation derived from HITRAN2012 database quantitatively, verifying this laser system ready for hyperspectral absorption applications.

In this work, the nanostructured rutile-phase titania with mean grain size of 8.5 nm was synthesized by PEPVD (plasma-enhanced physical vapor deposition) method, the measurements on frequency spectra of capacities and dielectric loss for corresponding bulk and film specimens have been conducted by using ac LRC method, and the conductivity and the polarization relaxation time have also been calculated from the frequency spectra of real and imaginary parts of the dielectric constants. It has been found that there exist abnormal dielectric behaviors in the bulk and film specimens. In low-frequency range, the dielectric constants of nanostructured specimens increase dramatically with decreasing frequency and are 10∼102 times higher than that of the corresponding coarse-grained counterpart. The aforementioned anomalous dielectric behaviors imply the existence of new polarization mechanism caused by the defects and the dangling bonds within the numerous interfaces.

The spectra of the dielectrical constant and dielectrical loss in three nanostructured α-Fin23 samples at different annealed temperatures are measured by using ac LRC method. The relaxation times of polarization and the conductance are calculated by means of the Debye mechanism and the interface effects in two kinds of polarization processes with two different relaxation times are proposed.

The measurements of electric capacities and dielectric loss angles for nanocrystalline γ-Fe2O3, under air and vacuum atmospheres have been conducted by using ac LRC method, and the conductivity and the polarization relaxation time have also been calculated from the frequency spectra of real and imaginary parts of the dielectric constants. The anomalous dielectric behavior implies the existence of two kinds of polarization mechanisms with different relaxation times, which are caused by the defects and the dangling bonds in the interfaces, respectively. The experimental and calculated results indicated that the polarization loss and the conductance loss are dominant in air atmosphere and vacuum, respectively.

Nanocrystalline maghemite O was prepared by a wet chemical method. The thermal stability of this material has been investigated by using differential thermal analysis (DTA) measurements and x-ray diffraction analyses. One exothermic peak without weight loss appears irreversibly on the DTA curve. It was confirmed for the first time that this exothermic peak corresponds completely to the maghemite-to-hematite (-to-) structural phase transition. The nanocrystalline maghemite O particles grow very slowly when the temperature is lower than the range of the exothermic peak; whereas, during and after the transition, the nanocrystalline hematite O particles grow rapidly with increasing temperature. Moreover, the transition temperature of nanocrystalline maghemite O is higher than that of the coarse-grained counterpart. In this paper, the authors have also suggested some preliminary physical interpretations of the experimental results.

A superconducting joint between Bi(2223)/Ag-sheathed tapes has been fabricated with approximately 90% of the current capacity of the tape itself. The silver sheath was mechanically or chemically removed from one side of each tape without disturbing the superconducting core. The exposed superconducting cores of the two tapes are brought into contact, wrapped up with a thin silver foil, and pressed so as to again seal the superconductor in a silver sheath. Then a series of different reaction anneal and mechanical treatments were performed on the joined tapes to obtain an optimum heat-treatment condition. The optical micrographs of a longitudinal section of the entire joint shows that there is no constriction of the superconducting core throughout the joint.

From the results of Fourier Transform Infrared (FTIR) spectra and X-ray Diffraction (XRD), we found that there exists size effect on the structure and infrared behavior in nanocrystalline MgO. When the grain size decreases, the crystal lattice dilates anisotropically, and the red shift of stretching vibrational mode coexists with the blue shift of the bending vibrational mode. We give a preliminary interpretation to the above abnormal phenomena.

Using differential-thermoanalytical (TG-DTA) measurement and X-ray diffraction (XRD) analysis, the characteristics of nanocrystalline brookite-based TiO 2 with a certain amount of anatase and rutile have been studied. There are two irreversible endothermic peaks on the DTA curve. The first peak (with weight loss on thermal-gravity TG and differential thermalgravity DTG curves) corresponds to the desorption of physical or chemical species, while the second one (without weight loss on TG and DTG curves) is related to the structural phase transition from brookite to anatase then to rutile, and the structural phase transitions are beneficial to the grain growth. In this paper, the grain size and the content of each individual phase in specimens at different temperatures are also reported.

We have found that there is an exothermal peak on the DTA curve of nanostructured γ-Fe2O3 sample and that this peak is not repeatable. The XRD microstructure analysis confirms for the first time that this exothermal peak corresponds to the structural phase transition from γ-Fe2O3 to α-Fe2O3. After this transition, the nanostructured Fe2O3 crystalline grains grow continuously with increasing temperature.

The magnetization hysteresis loop and magnetic relaxation of YBa2Cu3O7-delta + x MgO samples with x = 0 and 0.1 were systematically measured over a wide range of temperature (10-80 K) and magnetic field (0-7 T). Through the analysis of the J(c)(B, T) behavior, it is found that the addition of nanometer-sized MgO particles will enhance the critical current density and the fishtail effect in the low- and intermediate-temperature regions, but will lower the critical current density in the high-temperature region. The effective pinning energy extracted form the magnetic relaxation data is found to increase with the MgO particle addition. A preliminary explanation to the observed experimental results is proposed.

The theoretical analysis and experimental research of the optical parametric oscillator (OPO) based on periodically poled LiNbO 3 (PPLN) crystal are presented. The wavelength tuning curves of PPLN-OPO are calculated through the coupling equations of the three-wave mixing. An optical parametric oscillator with the output signal at 1.49μm and idler at 3.8μm, which is pumped by a Nd:YAG laser at 1.064μm, is obtained based on PPLN of length 20mm and thickness 0.5mm. When the pump power of the Nd:YAG laser is 5.2W with a repetition rate of 5kHz, the output of the idler at 3.8μm reaches 307mW.