实验室天体物理学简介

超短脉冲强激光与因体靶相互作用产生的高温高压、高密、高磁场、大加速度等性质与太阳及其他许多恒星中的物理条件非常相似,通过实验室 里模拟研究这种等离子体中的辐射输运、大尺度流体不稳定性、热核反应等过程,对于天体物理学家了解太阳和其他恒 中的物理过程提供了极好的实验手段。     

User Workshop on High-Power Lasers at the Linac Coherent Light Source

A two-day international workshop on the physics and integration of high-power lasers with the Linac Coherent Light Source was held in Stanford, California, USA, on October 1–2, 2013. The workshop was co-organized by UC Berkeley, Lawrence Berkeley, Lawrence Livermore, and SLAC National Accelerator Laboratories. More than 150 scientists, including 30 students and postdocs who are working in high-intensity laser-matter interactions, fusion research, and dynamic high-pressure science, came together from North America, Europe, and Asia. The group discussed the most promising and important new physics experiments that will be enabled by the unique combination of high-power lasers and the world-class LCLS free-electron laser X-ray beam.     

大功率半导体激光器发展及相关技术概述

激光被称为"最快的刀"、"最准的尺"、"最亮的光",与原子能、计算机、半导体并称为20世纪新四大发明。大功率半导体激光器在工业加工、医疗美容、光纤通信、无人驾驶、智能机器人等方面有着广泛的应用。如何实现大功率半导体激光光源,一直以来都是国际的研究前沿和学科热点。为此,简述了大功率半导体激光器的发展历史,综述了大功率半导体激光器的共用技术,包括大功率芯片技术和大功率合束技术,并对大功率半导体激光的发展方向进行了展望。     

High power laser operation with crystal fibers

We present the very last results on the development of high-power lasers with crystal fibers in Nd:YAG and in Yb:YAG grown by the Micro-Pulling Down technique. An overview of the main optical properties of the grown crystal fibers is given as well as the principles of the diode-pumped systems are developed. The average output power obtained with those materials reaches now several tens of watts in the CW regime and in high repetition rate Q-switched operation. Pulses with an energy of several millijoules have been obtained with pulse durations from 10 to 20 ns and peak powers from 100 kW to 350 kW. In each case, the measured M ² quality factors remained in the range 2.5 to 5. In addition, the first demonstration of high-power laser emission with an Yb:YAG crystal fiber of 0.4 mm in diameter is reported. In this case, we obtained an output power of 27 W at 1030 nm under 100 W of pump power at 940 nm in CW regime. To our knowledge, those results represent the highest powers ever generated with crystal fibers obtained directly from the growth. We finally conclude this work by exposing the potential of crystal fiber lasers for a new generation of high-power laser systems.     

On the possible production and detection of coherent low-energy neutrino beams

Seminal experiments are discussed to prove or disprove the possibility of producing and detecting collimated coherent beams of low-energy neutrinos with the assistance of lasers. Expressions are given for the relative probability that a laser-beam-aligned co- or counter-propagating neutrino-antineutrino pair is emitted instead of a laser photon, during stimulated de-excitations of lasable excited states inside a lasing medium. For a neodymium laser this probability is approximately 10^?7. To detect coherent beams of epithermal neutrinos and antineutrinos emitted from a pulsed high-power laser, it is anticipated that resonant non-absorptive stimulated de-excitations of lasing levels by neutrinos can be exploited to register their fly-through in a second near-threshold laser.     

用于激光二极管抽运固体激光器热畸变补偿的微变形镜特性研究

在很多高功率的激光器中,由于热效应的缘故会导致激光器的光束质量大幅下降。为了改善激光光束的动态畸变,自适应光学是一种有效的方法。作为自适应光学系统的核心部件,设计了一种可用于大功率激光二极管抽运固体激光器(DPL)热畸变补偿的新型可变形反射镜,并且通过工艺流片实际制造出有效反射面积为30 mm×30 mm,拥有49个静电驱动单元的可变形反射镜。对该微机电系统(MEMS)微变形镜的变形特性进行了详细的理论分析和模拟研究,并和实际测量结果进行了比较,得到了满意的结果。为了实现闭环控制,对微变形反射镜的光学影响函数矩阵进行了全面测量,并用得到的电压矩阵对畸变激光光束的波前进行了校正。实验结果表明,微变形反射镜可以有效地改善激光光束质量。     

高功率掺镱双包层光纤激光器中光纤损伤及其理论分析

针对高功率掺镱双包层光纤激光器热效应引起的光纤损伤情况,由热传导方程,结合边界条件推导了两端泵浦情况下双包层光纤激光器光纤内的温度分布及热效应引起的应力分布,并对光纤内的温度分布和应力分布进行了数值模拟.结合模拟结果,对光纤的损伤进行了解释,分析了引起光纤热效应的主要因素.对两端泵浦情况的模拟与分析符合高功率光纤激光器的实际工作情况,这对优化高功率光纤激光器的设计有一定的参考价值.     

二极管泵浦高能激光研究进展和展望

高能激光广泛应用于材料加工、科学研究、空间碎片清除、军事应用等领域。二极管泵浦高能激光具有结构紧凑,系统简单、全电驱无限弹仓的特点,近年来,各类二极管泵浦高能激光围绕着同时实现高功率、高效率、高光束质量这一总目标发展迅速。详细综述了国内外高平均功率块状固体激光、高功率可见光波段激光、高峰值功率激光、高功率光纤激光、碱金属蒸气激光等二极管泵浦高能激光的研究进展,并对其发展趋势进行了展望。     

薄片激光介质分区域主动冷却方法

针对高功率、大口径薄片激光器,提出了采用半导体制冷片阵列对薄片激光介质进行分区域主动冷却的方法,通过调节各单元半导体制冷片的工作电压,改变阵列的冷却效率分布,实现了对薄片激光介质的局部温度的控制,进而使得薄片介质的横向温度分布均匀,降低了热效应的影响,为薄片激光器的冷却设计提供了新思路,并通过实验验证了该方法的可行性。     

高功率皮秒紫外激光器新进展

高功率皮秒紫外激光器在高精密加工、激光医疗、光电对抗和光伏产业等领域有重要应用,近年来成为固体激光新光源研究热点。本文对国内外基于和频技术的高功率皮秒紫外激光器研究新进展进行了归纳和总结。首先,阐述了和频工作原理,介绍了和频产生皮秒紫外激光的非线性晶体;然后,介绍了国内外高功率皮秒紫外激光器的新进展,包括:高功率皮秒紫外激光器、高峰值功率皮秒紫外激光器、高功率和高峰值功率皮秒紫外激光器。最后,展望了高功率皮秒紫外激光器的进一步发展及应用。归纳和总结表明:高功率皮秒紫外激光器在国外较成熟,国内在该领域的研究刚刚起步。光子晶体光纤和碟片激光器输出基频光的皮秒紫外激光器有突出的优势,已成为皮秒紫外激光产业的主力军。     

Gravitational limitation on the verification of special relativity in the laboratory

We analyze the Michelson type experiment performed by Brillet and Hall. The order of magnitude of the gravitational effect (a beating frequency between two lasers) is calculated. We prove that Newtonian tidal forces could be observed when they originate from the oblateness of the Earth, from its rotation, from local masses, from the Moon or the Sun but not from the Galaxy (contrary to what has been recently claimed). We conclude that it is important to build a new parametrized theoretical framework for the analysis of high-precision experiments.     

Present status of research into the electron-beali-controlled discharge excitation method

The present status of research into electron-beam-controlled discharge (EB) lasers is considered briefly, and the main trends in the development of the investigations in this field are indicated. A concise review is given of the latest results on the development of pulsed and cw high-power EB CO₂ lasers, on the improvement of the design systems and optimization of the pumping regimes of such lasers, on the development of the theory of EB lasers, on the construction and investigation of EB lasers using, new active media, studies of the stability of nonautonomous discharge excited by the EB method, and the use of EB discharge to stimulate chemical reactions.Translated from Trudy Ordena Lenina Fizicheskogo Instituta im. P. N. Lebedeva, Akademii Nauk SSSR, Vol. 116, pp. 3–6, 1980.     

高功率双包层光纤激光器

介绍了高功率双包层光纤激光器的结构和工作原理，综述这种新型光纤激光器的主要特点及其在国内外的最新进展状况，展望了双包层光纤激光器的应用前景。     

Theoretical and experimental study on rare-eath element-doped silicon single-mode fiber laser with two different structures of resonators

Abstract: Laser resonator is very important in the study and fabrication of lasers. The work conditions and work parameters of rare-earth element-doped optical fiber lasers with two different structures of laser resonators, i. e., the fiber ring resonator and Fabry-Perot resonator are studied. The fineness, laser resonant conditions, laser oscillation conditions and threshold inversion of these two different cavity are deduced. A series of experiments are also given. The result is very valuable to evaluate the output of optical fiber laser and can be a foundation of device fabrication. The Nd~(3 )-doped silica single-mode fiber laser pumped by Ar~ laser with a low threshold of 1.02 mW and a maximum output of more than 1 mW are presented in this paper.     

Method for determination of co-spectral gain and absorption coefficients in high-power lasers

A new method is described for determining the small-signal gain and non-saturable absorption coefficients over the same spectral region for high-power lasers. Preliminary tests of this method on the discharge-pumped XeCl excimer laser have yielded B²σ→X²σ gain coefficients which are comparable to those observed in other experiments under similar excitation conditions. However, the absorption coefficient is found to be a high and nearly constant fraction (~$\text{1}\text{4}$) of the gain. This result suggests that all of the absorption processes are due to excited species, including XeCl B²σ.     

Thermal lensing and spherical aberration in high-power transversally pumped laser rods

A precise knowledge of the thermal effects in laser crystals is very important for high-power laser design, but some relevant parameters are most often neglected in their calculation. In this paper, with the example of transversally pumped, high-power Nd:YAG lasers, we show the importance of the thermal dependence of the gain medium’s physical properties such as the thermal conductivity, the dn/dT and the expansion coefficient on the thermal aberration and thermal lensing values; we also prove that the choice of the resonator can influence the amount of spherical aberration. Finally, analytically calculated values are confronted to experimental values, and show a very good agreement.     

高功率垂直腔面发射激光器的湿法腐蚀工艺

为提高高功率垂直腔面发射激光器(VCSEL)光电性能,对氧化限制型高功率VCSEL湿法腐蚀工艺进行了实验研究。实验中采用H₃PO₄系溶液替代以往制备此类器件常用的H₂SO₄系溶液作为高功率VCSEL外延片的腐蚀液,利用扫描电镜(SEM)研究了腐蚀后外延片氧化窗口的腐蚀形貌变化与腐蚀液浓度的关系,消除了以往采用H₂SO₄系溶液腐蚀时,高功率VCSEL氧化层侧壁出现的"燕尾"结构;通过改变湿法腐蚀工艺的外部温度条件和腐蚀液的浓度配比,实验研究了高功率VCSEL湿法腐蚀速率规律,最后得出了制备高功率VCSEL时湿法腐蚀工艺的最佳外部温度条件与腐蚀液的最佳浓度配比。     

连续/脉冲复合体制高功率固体激光技术研究

常规高功率激光器以连续或者长脉冲方式工作,与物质作用主要是依靠单一“加热”模式,针对其对复杂目标作用能力有限的问题, 提出一种连续和脉冲激光同时输出,脉宽、重频可调的新体制高功率激光技术,激光放大链路以特殊时域模式工作,即高重频脉冲与连续运转同时输出,在重频10 kHz时,实现输出功率4800 W,其中连续激光功率3600 W,脉冲激光功率1200 W,脉冲宽度为3.6 ns;在重频100 kHz时,实现输出功率4920 W,其中连续激光功率3100 W,脉冲激光功率1820 W,脉冲宽度为7 ns,光束质量4.8倍衍射极限 。     

0.9~1.0μm近红外连续光纤激光器的研究进展

波长为0.9~1.0μm的近红外连续光纤激光器在高功率蓝光和紫外激光产生、高功率单模泵浦源、生物医学以及激光雷达等领域具有重要的应用前景,成为近年来的一个研究热点。目前,0.9~1.0μm光纤激光器的增益机制主要有稀土离子增益和非线性效应增益,本文详细梳理了基于这两类增益机制的0.9~1.0μm连续光纤激光器的研究进展,并深入分析了各类激光器存在的技术瓶颈及解决途径,最后对0.9~1.0μm光纤激光器的发展趋势和应用前景进行了展望。