侧面抽运国产Nd∶YAG陶瓷棒的激光特性

实验研究了激光二极管阵列(LDA)侧向抽运国产Nd∶YAG陶瓷棒的准连续及被动调Q激光输出特性。该陶瓷激光器采用LDA侧面紧密环绕均匀排布的抽运结构,陶瓷棒抽运区域长度为20 mm,其总尺寸为3 mm×35 mm,掺杂原子数分数为~1%。在千赫兹准连续运转条件下,当平-平谐振腔的输出耦合镜透过率为47.3%时,获得最大平均功率23 W的1064 nm激光输出,光束发散角为4.5 mrad,斜率效率达12%。在谐振腔内插入Cr4+∶YAG晶体作为被动调Q开关,成功地实现了陶瓷激光器千赫兹重复频率调Q激光脉冲输出,当Cr4+∶YAG晶体初始透过率为60%时,输出激光脉冲宽度(半峰全宽)可窄至14.5 ns,调Q动静比约为40%。

高重复频率、窄脉宽全固态光纤放大器种子源

高重复频率、窄脉宽的全固态激光器种子源级联光纤放大器是获得高功率脉冲激光输出的有效手段.短上能态寿命的Nd∶YVO4晶体在连续抽运、高重复频率Q开关工作时容易得到接近连续性能的平均输出功率.理论分析了声光(AO)调Q器件中影响输出能量和脉宽大小的主要因素,优化配置了腔型参数.利用激光二极管(LD)光纤耦合模块端面抽运Nd∶YVO4晶体,实现了声-光调Q重复频率100 kHz以上,脉宽20 ns以下,波长1064 nm的激光输出.在抽运功率5.7 W时,得到了脉宽15.3 ns,重复频率150 kHz的种子光输出,在级联单级光纤放大器后,得到了20 W的输出.

All solid-state, injection-seeded Ti:sapphire ring laser

In this letter, we present an all solid-state, injection-seeded Ti:sapphire laser. The laser is pumped by a laser diode pumped frequency-doubled Nd:YAG laser, and injection-seeded by an external cavity laser diode with the wavelength between 770 and 780 nm. The single longitude mode and the doubling efficiency of the laser are obtained after injection seeding. The experimental setup and relative results are reported. It is a good candidate laser source for mobile differential absorption lidar (DIAL) system.

A Q-swicthed all-solid-state single-longitudinal-mode laser with adjustable pulse-width and high repetition rate

A single-longitudinal-mode (SLM) laser-diode pumped Nd: YAG laser with adjustable pulse width is developed by using the techniques of pre-lasing and changing polarization of birefingent crystal. The Q-switching voltage is triggered by the peak of the pre-lasing pulse to achieve the higher stability of output pulse energy. The output energy of more than 1 mJ is obtained with output energy stability of 3% (rms) at 100 Hz. The pulse-width can be adjusted from 30 ns to 300 ns by changing the Q-switching voltage. The probability of putting out single-longitudinal-mode pulses is almost 100%. The laser can be run over four hours continually without mode hopping.

Depolarization loss compensated resonator for electro-optic Q-switched solid-state laser

A novel laser resonator for compensating depolarization loss that is due to thermally induced birefringence in active rod is reported. As this new structure being applied to an electro-optic Q-switched LIDA side-pumped Nd:YAG laser operating at a repetition rate of 1000 Hz, substantial reduction in depolarization loss has been observed, the output pulse energy is improved about 56% from that of a traditional resonator without compensation structure. With incident pump energy of 450 mJ per pulse, linearly polarized output energy of 30 mJ per pulse is achieved, the pulse duration is less than 15 ns, and the peak power of pulse is about 2 MW. The extinction ratio of laser beam is better than 10:1, and the beam divergence is 1.3 mrad with beam diameter of around 2.5 mm. (c) 2006 Published by Elsevier B.V.

20-W average power, high repetition rate, nanosecond pulse with diffraction limit from an all-fiber MOPA system

In this article, we report an all-fiber master oscillator power amplifier (MOPA) system, which can provide high repetition rate and nanosecond pulse with diffraction-limit. The system was constructed using a (2 + 1) X 1 multimode combiner. The Q-Switched, LD pumped Nd:YVO4 solid-state laser wets used (is master oscillator. The 976-nm fiber-coupled module is used as pump source. A 10-m long China-made Yb3+-doped D-shape double-clad large-mode-area fiber was used as amplifier fiber. The MOPA produced as much as 20-W average power with nanosecond pulse and near diffraction limited. The pulse duration is maintained at about 15 its during 50-175 kHz. The system employs a simple and compact architecture and is therefore suitable for the use in practical applications such as scientific and military airborne LIDAR and imaging. Based oil this system. the amplification performances of. the all fiber amplifier is investigated. (C) 2008 Wiley Periodicals, Inc.

Numerical and experimental analysis on green laser crystallization of amorphous silicon thin films

The effect of laser fluence on the crystallization of amorphous silicon irradiated by a frequency-doubled Nd:YAG laser is studied both theoretically and experimentally. An effective numerical model is set up to predict the melting threshold and the optimized laser fluence for the crystallization of 200-nm-thick amorphous silicon. The variation of the temperature distribution with time and the melt depth is analyzed. Besides the model, the Raman spectra of thin films treated with different fluences are measured to confirm the phase transition and to determine the optimized fluence. The calculating results accord well with those obtained from the experimental data in this research. (C) 2008 Elsevier Ltd. All rights reserved.

Nd：YAG透明陶瓷的制备与激光输出

成功制备了高质量的Nd：YAG透明陶瓷，激光测试样品的尺寸为3mm×3mm×3mm,双面抛光、未镀膜，最高连续输出能量为1003mW，斜率效率为14％．

A comparison between TGT and Cz grown Nd : YAG

Large sized neodymium-doped Y3Al5O12 (Nd:YAG) laser crystals have been grown by temperature gradient technique (TGT) method and compared with Czochralski (Cz) method. The comparison of these two crystal growth methods has been listed. The results showed that the TGT method has many advantages over the Cz method. The concentration distribution of Nd ions in the crystals was determined and the absorption spectra of these crystals have been investigated and compared. The TGT grown highly doped Nd:YAG crystal has a larger absorption FWHM than that of Cz grown Nd:YAG crysral. Highly doped Nd:YAG (similar to 2.8 at. pct) crystals could be obtained by TGT.

Deposition of Au/TiO2 film by pulsed laser

Au nanoparticles, which were photoreduced by a Nd:YAG laser in HAuCl4 solution containing TiO2 colloid and accompanied by the TiO2 particles, were deposited on the substrate surface. The film consisting of Au/TiO2 particles was characterized by the absorption spectra, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The adhesion between the film and substrate was evaluated by using adhesive tape test. It was found that the presence of TiO2 dramatically enhanced the adhesion strength between the film and the substrate, as well as the deposition rate of film. The mechanism for the deposition of Au/TiO2 film was also discussed. (c) 2005 Elsevier B.V. All rights reserved.

Stress, absorptance and laser-induced damage threshold properties of 355-nm HR coatings

A number of 355-nm Al2O3/MgF2 high-reflectance (HR) coatings were prepared by electron-beam evaporation. The influences of the number of coating layers and deposition temperature on the 355-nm Al2O3/MgF2 HR coatings were investigated. The stress was measured by viewing the substrate deformation before and after coating deposition using an optical interferometer. The laser-induced damage threshold (LIDT) of the samples was measured by a 355-nm Nd:YAG laser with a pulse width of 8 ns. Transmittance and reflectance of the samples were measured by a Lambda 900 spectrometer. It was found that absorptance was the main reason to result in a low LIDT of 355-nm Al2O3/MgF2 HR coatings. The stress in Al2O3/MgF2 HR coatings played an unimportant role in the LIDT, although MgF2 is known to have high tensile stress.

Overcoat dependence of laser-induced damage threshold of 355 nm HR coatings

A series of HR coatings, with and without overcoat, were prepared by electron beam evaporation using the same deposition process. The laser-induced damage threshold (LIDT) was measured by a 355 nm Nd:YAG laser with a pulse width of 8 ns. Damage morphologies of samples were observed by Leica-DMRXE Microscope. The stress was measured by viewing the substrate deformation before and after coatings deposition using an optical interferometer. Reflectance of the samples was measured by Lambda 900 Spectrometer. The theoretical results of electric field distributions of the samples were calculate by thin film design software (TFCalc). It was found that SiO2 overcoat had improved the LIDT greatly, while MgF2 overcoat had little effect on the LIDT because of its high stress in the HR coatings. The damage morphologies were different among HR coatings with and without overcoats. (c) 2005 Elsevier B.V. All rights reserved.

Nd：YAG激光器光栅式扫描预处理的计算模拟与优化分析

采用计算模拟的方法．研究了光栅式扫描预处理的扫描方式以及脉冲能量波动、定位误差对预处理效率的影响。研究发现。脉冲能量波动及其定位误差使预处理效率降低，同时其影响与扫描方式之间存在相互调制作用．因此可以通过选择合适的扫描方式以及扫描间隔来优化预处理流程，提高预处理效率。此外发现，光斑呈等边三角形排列时的预处理效率优于正方形。

Influence of SiO2 additional layers on the laser induced damage threshold of Ta2O5 films

A series or Ta2O5 films with different SiO2 additional layers including overcoat, undercoat and interlayer was prepared by electron beam evaporation under the same deposition process. Absorption of samples was measured using the surface thermal lensing (STL) technique. The electric field distributions of the samples were theoretical predicted using thin film design software (TFCalc). The laser induced damage threshold (LIDT) was assessed using an Nd:YAG laser operating at 1064 nm with a pulse length of 12 ns. It was found that SiO2 additional layers resulted in a slight increase of the absorption, whereas they exerted little influence on the microdefects. The electric field distribution among the samples was unchanged by adding an SiO2 overcoat and undercoat, yet was changed by adding an interlayer. SiO2 undercoat. The interlayer improved the LIDT greatly, whereas the SiO2 overcoat had little effect on the LIDT. (C) 2007 Elsevier Ltd. All rights reserved.

Influence of oxygen post-treatment on laser-induced damage of antireflection coatings prepared by electron-beam evaporation and ion beam assisted deposition

Antireflection coatings at the center wavelength of 1053 nm were prepared on BK7 glasses by electron-beam evaporation deposition (EBD) and ion beam assisted deposition (IBAD). Parts of the two kinds of samples were post-treated with oxygen plasma at the environment temperature after deposition. Absorption at 1064 nm was characterized based on surface thermal lensing (STL) technique. The laser-induced damage threshold (LIDT) was measured by a 1064-nm Nd:YAG laser with a pulse width of 38 ps. Leica-DMRXE Microscope was applied to gain damage morphologies of samples. The results revealed that oxygen post-treatment could lower the absorption and increase the damage thresholds for both kinds of as-grown samples. However, the improving effects are not the same. (c) 2008 Elsevier B.V. All rights reserved.