Dispersion Effects in a High Gain 3.39 Micrometer He-Ne Laser: Application to the Laser Heterodyne Measurement of Plasma Density

摘要

A He-Ne laser heterodyne system was utilized to evaluate the dispersive effect at 3.39 micrometer in a He-Ne laser. The dispersion introduced by lasering atoms at 3.39 micrometer was measured as a function of cavity loss, excitation level and deviation of the laser frequency from line center. Theoretical and experimental results were compared, and close agreement was obtained if the natural line width was taken to be 115 MHz and the Doppler line width was taken to be 315 MHz for the 3.39 micrometer transition. The evaluation of the dispersive effect at 3.39 micrometer was then used in the laser heterodyne measurement of plasma density using a three-wavelength He-Ne laser. Temporally and spatially resolved electron number densities in the range from 2 x 10 to the 11th power to 3 x 10 to the 12th power per cu. cm. were measured in the afterglow of an argon plasma. The spatially resolved laser measurements involving the 3.39 micrometer transition compared wuite favorably with the measurements using only the .6328 micrometer and 1.15 micrometer transitions and were also comparable to the integrated electron density measurements made with a microwave cavity operating in the TM010 mode at 5.0 GHz. (Author)