1.8 mJ高倍率Nd:YAG板条皮秒激光放大器

设计了一种高倍率的固体皮秒脉冲激光放大器,采用Nd:YAG板条作为激光增益介质。借助板条结构的角度选通结构,搭建了板条五通放大系统,实现了对注入皮秒脉冲激光的高倍率放大。种子源工作在脉冲模式,放大器泵浦源在连续模式工作。皮秒光纤激光器可以在不同的重复频率下工作,脉冲宽度为13.4 ps。种子光经过隔离和耦合系统之后,注入板条的单脉冲能量为25 nJ。当种子源工作重复频率为24.46 MHz时,板条放大器输出平均功率377 W,单脉冲能量15.5 μJ;当种子源工作重复频率为49.8 kHz时,板条放大器输出平均功率89 W,单脉冲能量1.8 mJ,峰值功率为134 MW,放大倍率达到7.2×104。     

皮秒激光泵浦的亚10fs钛宝石激光器

研制了高稳定Nd∶YVO_4皮秒激光振荡器,并在15 W、808nm激光泵浦下得到6 W的连续锁模皮秒激光输出,光-光效率为40%.对该皮秒激光进行单通放大后得到14 W的基频光输出,倍频后可以得到7 W的532nm皮秒激光,用作钛宝石振荡器的泵浦源.在4.5 W的皮秒532nm激光泵浦下,结合腔外压缩,得到了脉宽为9.4fs、平均功率为150mW的脉冲序列输出.调节钛宝石振荡器的腔长使其与皮秒振荡器的腔长一致时,可实现自触发克尔透镜锁模.实验结果表明皮秒激光泵浦可以有效地触发钛宝石激光器的自动锁模,输出飞秒脉冲序列.     

泵浦匀化对Innoslab激光放大器光束质量的改善

针对结构紧凑的部分端面泵浦混合腔板条激光放大器，研究了泵浦匀化对其输出激光光束质量的改善作用。基于ZEMAX仿真软件，设计并对比分析了直接成像和波导匀化后再成像两种泵浦耦合方式对激光二极管阵列慢轴（晶体宽度）方向光强分布均匀性的影响，发现波导匀化后泵浦均匀性得到明显提升且激光二极管阵列发光坏点对泵浦成像的影响得以弱化。进一步实验验证了泵浦匀化对Innoslab激光放大器性能的改善作用:波导匀化后慢轴方向泵浦均匀度从90.6%提高到95.4%，进而使3通放大后输出激光光束质量因子M2从2.41提升到1.55，并且有效抑制了多通放大腔内的自激振荡。     

LD泵浦全固态355nm紫外皮秒脉冲激光器

利用激光二极管（LD）端面抽运Nd∶YVO4激光晶体皮秒三倍频355nm全固态紫外激光器,采用半导体可饱和吸收镜（SESAM）锁模技术及皮秒再生放大技术,对1 064 nm基波采用Ⅰ类相位匹配Li3B3O5（LBO）晶体二倍频和Ⅱ类相位匹配LBO晶体三倍频,获得了稳定性好、倍频效率较高的355 nm紫外激光输出。当二极管泵浦功率为5 W时,获得了脉宽为17 ps、重复频率为1 Hz、单脉冲能量为129.6 J的稳定三倍频紫外激光输出,基频光到二倍频光和三倍频光的转换效率分别达到60.3%和16.6%,3 h输出单脉冲能量的抖动在0.58%以下。     

LD泵浦Er,Yb∶glass板条多程放大器设计及热效应分析

设计了一种LD阵列泵浦的铒镱共掺磷酸盐玻璃(Er, Yb∶glass)板条放大器，通过多次折叠反射结构来提高能量提取效率，实现1.5μm波段较大能量的激光输出，激光放大增益可达35.29倍。基于稳态热传导理论，对所设计的Er, Yb∶glass板条放大器进行了热效应分析，建立了热力耦合模型，采用有限元方法比较不同参数条件下板条介质的热力学特性。结果表明通过提高板条宽厚比和减小泵浦光功率密度可以有效缓解热效应，在此基础上提出了一种补偿波前畸变的方法。     

包层泵浦fs光纤放大器的实验研究

 在实验上对双包层光纤放大器进行了研究。采用新型内包层为六边形的铒镱共掺双包层光纤作为放大介质,用带尾纤的半导体激光器进行泵浦,对fs光脉冲进行放大。当用2.5 W的入纤功率泵浦50 cm长的双包层铒镱光纤时,把平均功率为10.8 mW、重复频率20.84 MHz的激光放大到176 mW,增益为12.2 dB,相应的单脉冲能量为8.1 nJ,放大后脉冲宽度为480 fs,峰值功率为16 kW。     

掺钕保偏光纤放大器的研究

对掺钕双包层光纤放大器中抽运光和信号光沿光纤传播的功率分布进行了数值模拟,以808nm半导体激光器为抽运源,掺钕双包层保偏光纤为增益介质,对种子注入主振荡光纤放大器进行了理论分析和实验研究.利用实验室自制的皮秒锁模激光器为种子源,注入1064nm皮秒锁模脉冲,获得了稳定的放大脉冲.小信号时的放大倍数为300（增益为25dB）,获得了平均功率5W的皮秒脉冲.同时利用TDS5104型示波器探测信号光放大前后的波形,并用光谱分析仪得到输出脉冲激光的光谱图. 关键词： 光纤放大器 掺钕保偏光纤 种子注入 反向抽运     

高效率Nd:YVO4/LBO临界相位匹配脉冲绿光激光器

报道了一种利用激光二极管（LD）端面泵浦Nd:YVO4晶体,声光调Q,LBO临界相位匹配腔内倍频的高效率、小体积、风冷绿光激光器。分析了不同偏振光泵浦的情况下,激光晶体对泵浦光的吸收特性。由分析得出,采用部分偏振光泵浦,可以提高激光晶体对泵浦光吸收均匀性,改善基波畸变,获得高转换效率激光输出。实验中,在泵浦光功率为33 W、声光调Q重复频率为20 kHz时,得到脉宽为23.96 ns、平均功率为15 W的1064 nm基频光输出。经倍频后,得到平均功率为11.2 W的绿光输出,倍频效率为74.6%,总体光-光转换效率为34%。在输出功率为10 W时,测得1 h内输出功率不稳定度为0.512 2%,水平方向和竖直方向的光束质量因子M2分别为1.2和1.1。     

基于MOPA结构的1120nm掺Yb光纤放大器

基于主振荡功率放大器,采用1120nm光纤激光器作为种子激光,将其注入20m大模场面积单模双包层掺Yb光纤放大器,并用976nm半导体激光器泵浦实现了1 120nm信号光输出.实验中将注入种子激光功率预设为10mW,当半导体激光器泵浦功率增大至1.5 W时,放大器系统开始输出1 120nm信号光.当泵浦功率低于3.4W时,信号光功率随泵浦功率缓慢增长,系统斜率效率较低;而当泵浦功率高于3.4W时,信号光功率随泵浦功率线性增长,斜率效率明显增大,达到48.5%.限于最大注入泵浦功率为6.8W,放大器输出最高1 120nm信号光功率为1.97W,总的光-光转化效率为29%.输出信号光中心波长为1 120.89nm,线宽为0.02nm,极好地保持了种子激光的特性.结合实验情况,利用双包层光纤放大器的稳态理论模型,采用有限差分方法模拟了放大器输出信号光功率随泵浦光功率的变化曲线,结果显示理论模拟所得变化趋势与实验结果吻合良好,系统将在泵浦功率达到200W左右时达到饱和状态,说明目前光纤放大器系统具有很大的功率提升空间.     

掠入射板条放大器链的热效应模拟分析

对LD泵浦的掠入射板条放大器链系统激光介质的热效应进行研究。针对掠入射放大器结构建立了相应的热力学模型,对激光介质的温度场分布、热致波前畸变和热透镜效应进行了详细的理论分析。利用有限元分析软件COMSOL模拟了晶体内部的温度、应力及应变的分布情况,并进一步讨论了板条厚度、泵浦尺寸以及种子光入射角对光程差和热透镜造成的影响。结果表明,随着泵浦光斑尺寸和种子光入射角的增大,光程差变小,热透镜效应减弱;板条厚度对光程差和热透镜的影响较小。模拟计算结果对于预测板条热效应的强弱、热效应的补偿,以及放大器链结构参数的设计提供了依据。     

105 W, <10 ps, TEM(00) laser output based on an in-band pumped Nd:YVO4 Innoslab amplifier

We reported on a compact and efficient in-band pumped Nd:YVO4 partially pumped slab (Innoslab) picosecond amplifier. A new method for mode-matching was demonstrated to simplify the amplifier design. Integrating the benefits of the in-band pumping technique and the excellent thermal management of the Innoslab amplifier design, a 105 W, 8.4 ps laser output was achieved with near-diffraction limited beam quality of M(x)(2)=1.12 and M(y)(2)=1.09 in the orthogonal directions.     

Highly efficient CW intracavity frequency-doubled Yb:YAG-LBO laser at 515 nm under 968 nm diode laser pumping

We describe the output performances of the 1030 nm transition in Yb:YAG under in-band pumping with diode laser at the 968 nm wavelength. An end-pumped Yb:YAG crystal yielded 1.93 W of continuous-wave (CW) output power for 9.1 W of absorbed pump power. The slope efficiency with respect to the absorbed pump power was 23.6%. Furthermore, 205 mW 515 nm green light was acquired by frequency doubling, resulting in an optical-to-optical efficiency with respect to the absorbed pump power of 2.7%. Comparative results obtained for the pump with diode laser at 940 nm are given in order to prove the advantages of the in-band pumping.     

Efficient CW Yb:YAG laser at 1048 nm under 968 nm diode laser pumping

We describe the output performances of the 1048 nm transition in Yb:YAG under in-band pumping with diode laser at the 968 nm wavelength. An end-pumped Yb:YAG crystal yielded 787 mW of continuous-wave (CW) output power for 9.1 W of absorbed pump power. Furthermore, 104 mW 524 nm green light was acquired by frequency doubling. Comparative results obtained for the pump with diode laser at 940 nm are given in order to prove the advantages of the in-band pumping.     

Efficient Nd:YVO_4 laser in-band pumped by wavelength-locked 913.9-nm laser diode and Q-switch operation

An efficient 1064-nm Nd:YVO_4laser in-band pumped by a wavelength-locked laser diode(LD) at 913.9 nm was demonstrated. The maximum continuous wave(CW) output power of 23.4 W at 1064 nm was realized with the incident pump power of 40 W, corresponding to a total optical-to-optical efficiency of 58.5%. This is to the best of our knowledge the highest total optical-to-optical efficiency and output power of Nd:YVO_4laser in-band pumped by a 913.9-nm laser diode.The Q-switched operation of this laser was also investigated. Through a contrast experiment of pumping at 808 nm, the experimental results showed that an Nd:YVO_4laser in-band pumped by a wavelength-locked LD at 913.9 nm had excellent pulse stability and beam quality for high repetition rate Q-switching operation.     

Efficient, resonantly pumped, room-temperature Er3+:GdVO4 laser

We report an efficient room-temperature operation of a resonantly pumped Er3+:GdVO4 laser at 1598.5 nm. The maximum continuous wave (CW) output power of 3.5 W with slope efficiency of 56% was achieved with resonant pumping by an Er-fiber laser at 1538.6 nm. With pumping by a commercial laser diode bar stack, a quasi-CW (QCW) output of 7.7 W and maximum slope efficiency of ~53% versus absorbed pump power were obtained. This is believed to be the first resonantly (in-band) pumped, room-temperature Er3+:GdVO4 laser.     

Diode-pumped continuous-wave eye-safe Nd:YAG laser at 1415 nm

We describe the output performance of the 1415 nm emission in Nd:YAG in a plane-concave cavity under traditional pumping into the 4F5/2 level (808 nm) and direct in-band pumping into the 4F3/2 level (885 nm). An end-pumped Nd:YAG laser yielded maximum cw output power of 6.3 W and 4.2 W at 885 nm and 808 nm laser diode (LD) pumping, respectively. To the best of our knowledge, this is the highest output power of a LD-pumped 1415 nm laser.     

High-power Tm-doped fiber distributed-feedback laser at 1943 nm

We report on high-power operation of a fiber distributed-feedback (DFB) laser fabricated from Tm-doped photosensitive alumino-silicate fiber and in-band pumped by an Er/Yb fiber laser at 1565 nm. The fiber DFB laser yielded up to 875 mW of single-ended output at 1943 nm on two orthogonally polarized modes for 3.5 W of absorbed pump power. Further scaling of the DFB laser output power was achieved with the aid of a simple Tm-doped fiber amplifier stage spliced directly to the DFB fiber without the need of an optical isolator. The maximum output power from the DFB laser and fiber amplifier was >3 W for a combined absorbed pump power of 8.1 W. The influence of thermal loading, owing to quantum defect heating in the Tm-doped core, on the output power and longitudinal mode behavior is discussed, and the prospects for further improvement in performance are considered.     

2μm single-frequency master-oscillator fiber power amplifier

We report a single frequency laser source consisting of a Tm:YAP coupled-cavity master-oscillator and a Tm-doped fiber power amplifier. The MOFPA yielded 4.55 W of single frequency output at 1990 nm when the input signal was 270 mW and the pumping power was 35.2 W. A strong amplification of spontaneous emission (ASE) was observed when higher pumping power was applied. Therefore, the output power of the single frequency fiber power amplifier was limited by the input power of seed laser.     

Modeling and Investigation of High-Power Optical-Fiber Transmitters for Lidar Applications

In this work, we develop a high-power optical-fiber transmitter for lidar applications. The device can be utilized for measurements of the methane concentration and determination of the parameters of methane absorption line at wavelengths near 1,650 nm. The transmitter is based on a fiber Raman amplifier with an active fiber length converting the pumping radiation with a wavelength of 1,540 nm to the desired wavelength region of about 1,650 nm. We conduct the theoretical modeling of the Raman amplifier operation and demonstrate the advantage of the two-stage amplifier design over the single-stage design. In the modeling, the total power of a single Raman amplifier in the twostage design is 4.5 W with a pumping power of 5 W and an active fiber length of 1,000 m. Then we experimentally investigate the developed single Raman amplifier and demonstrate a satisfactory agreement between its parameters and the results of the theoretical modeling. The achieved average power of the transmitter at the output stage is over 7 W with two single Raman amplifiers joined in parallel. The distributed-feedback (DFB) master laser utilized in the transmitter is modulated by a linear-frequency signal with simultaneous application of a nonsynchronous high-frequency signal to eliminate the noise due to stimulated Brillouin scattering.     

An efficient continuous-wave YVO_4/Nd:YVO_4/YVO_4 self-Raman laser pumped by a wavelength-locked 878.9 nm laser diode

We report an efficient continuous-wave self-Raman laser at 1176 nm based on a 20-mm-long composite YVO_4/Nd:YVO_4/YVO_4 crystal and pumped by a wavelength-locked 878.9 nm diode laser.A maximum output power of 5.3 W is achieved at a pump power of 26 W,corresponding to an optical conversion efficiency of 20%and a slope efficiency of 21%.The Raman threshold for the diode pump power was only 0.92 W.The results reveal that in-band pumping by a wavelength-locked diode laser significantly enhances output power and efficiency of self-Raman lasers by virtue of improved pump absorption and relieved thermal loading.