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The thermodynamic limits of optical pumping - Investigation of a novel, intra-cavity pumped thin disk laser

光泵浦的热力学极限 - 新型腔内泵浦薄盘激光器的研究

基本信息

批准号：
232615474
负责人：
Professor Dr. Ulrich Wittrock
金额：
--
依托单位：
Fachbereich Physikingenieurwesen
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2012
资助国家：
德国
起止时间：
2011-12-31 至 2016-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/232615474?language=en
关键词：
thermodynamic limits optical pumping Investigation

项目摘要

The fundamental thermodynamic limits of optical pumping of lasers shall be investigated. The performance that has been achieved over the past years by fiber lasers and thin disk lasers was made possible by replacing the incoherent pumping of classical rod lasers using gas discharge lamps by pumping the fibers and disks using spectrally and spatially partially coherent pump light from semiconductor lasers. The light from the semiconductor lasers only has a small quantum defect with respect to the laser wavelength. If the wavelength difference between pump light and laser light can be reduced even further, another increase of the brightness of fiber lasers and thin disk lasers can in principle be expected. However, in doing so, one is approaching a two-level laser system which is forbidden by the second law of thermodynamics. Technologically, this shows up in the form of two problems: On one hand, the absorption of the pump light is becoming increasingly weaker, while on the other hand the increasing thermal population of the lower laser level demands ever higher pump power densities in order to reach inversion. However, if the laser medium that is to be pumped is placed inside the resonator of the pump laser, both problems can be solved in an elegant way. This shall be realized for a high power laser for the first time. Looking at it from a thermodynamic viewpoint, we want to reduce the entropy in a two-step process: First, a conventional thin disk laser will be pumped by diode lasers. This laser will operate in a high transverse multi-mode and thus produces fairly coherent but not totally coherent light. This laser has no output coupler, it experiences losses only by the second laser disk which resides inside its resonator. This disk represents an impedance-matched coherent perfect absorber and shall produce spatially fully coherent laser light in the fundamental transverse mode at a wavelength that is just slightly longer.

应研究激光光泵的基本热力学极限。光纤激光器和薄盘激光器在过去几年中取得的性能是通过使用半导体激光器的光谱和空间部分相干泵浦光来泵浦光纤和圆盘来取代使用气体放电灯的经典棒状激光器的非相干泵浦而实现的。半导体激光器发出的光相对于激光波长只有一个很小的量子缺陷。如果泵浦光和激光之间的波长差能够进一步缩小，则原则上可以预期光纤激光器和薄片激光器的亮度将再次提高。然而，在这样做时，人们正在接近热力学第二定律所禁止的二能级激光系统。在技术上，这表现为两个问题：一方面，泵浦光的吸收变得越来越弱，另一方面，较低激光能级的热布居要求越来越高的泵浦功率密度才能达到反转。然而，如果要泵浦的激光介质放在泵浦激光器的谐振腔内，这两个问题都可以很好地解决。这将首次在高功率激光器中实现。从热力学的角度来看，我们希望通过两个步骤来降低熵：首先，传统的薄片激光器将由半导体激光器泵浦。这种激光器将工作在高横向多模模式下，从而产生相当相干但不完全相干的光。这种激光器没有输出耦合器，它只受到位于其谐振器内部的第二个激光盘片的损耗。这个圆盘代表了一个阻抗匹配的相干完美吸收体，并将在基本横模下产生波长略长的空间完全相干激光。