Development of a Very Widely Tunable Laser Source for Spectroscopy

1.本项目的目标是利用高功率短脉冲染料激光器泵浦氢的高阶斯托克斯和反斯托克斯拉曼激光器，开发一种在真空紫外到红外的宽光谱范围内连续可调谐的相干光源。高阶受激拉曼发射的使用使得染料激光器在有限的可调谐范围内覆盖宽的光谱区域成为可能。研究结果（1）利用纳秒准分子泵浦染料激光（2.5 MW，2 nsFWHM）激发高压氢拉曼池，研制了一种波长可达209 nm的可调谐光源。反斯托克斯辐射高达6度。秩序得到遵守。(2)用准分子激光（1MW，25ns半高宽）抽运的商用染料激光器作了类似的实验。在这种情况下，调谐范围扩展到真空紫外区，最低可达175nm，具有7阶反斯托克斯线。(3)为了进一步扩展可调谐区域，需要通过缩短脉冲来增加染料激光器的峰值功率。为此，我们尝试用30 ps的KrF激光产生皮秒范围的受激拉曼散射，并获得了低至128 nm的非常宽的光谱范围内的拉曼发射。

1. Objective of Project The objective of the project is to develop a coherent light source continuously tunable over a wide spectral region form the vacuum ultraviolet to the infrared, using higher-order Stokes and anti-Stokes Raman liser with hydrogen pumped by a high-power short-pulse dye laser. The use of higher-order stimulated Raman emission makes it possible to cover a wide spectral region with a limited tunable range of the dye laser.2. Results of Project (1) A tunable source which can cover down to 209 nm is developed by using a high-pressure hydrogen Raman cell excited by a nanosecond exciser-pumped dye laser ( 2.5 MW, 2 nsFWHM ). Anti-Stokes radiation up to 6th. order was observed. (2) Similar experiment was made by using a commercial dye laser pumped by an exciser laser ( 1 MW, 25 nsFWHM In this case, the tunable range was extended to the vacuum ultraviolet region down to 175 nm with the 7th Anti-Stokes line. (3) In order to extend the tunable region further, increase in the peak power of the dye laser by pulse shortening is required. For this purpose, we tried the generation of stimulated Raman scattering in the picosecond region with a 30 ps KrF laser, and obtained Raman emission over a very wide spectral range down to 128 nm.