Development of a Very Widely Tunable Laser Source for Spectroscopy

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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.