The frequency of a CO2 laser for sub-mm laser pumping has been stabilized by the use of a Stark modulated Lamb dip signal of CH3OH. Systematic investigation has been made to obtain a signal-to-noise ratio of the Lamb dip signal as high as possible. A frequency stability better than ±0.5 MHz has been achieved for the 9P(34) and 9P(36) lines of a CO2 laser. As a result, the output power of the optically pumped sub-mm laser also became stable. Power stabilities of ±4% and ±2.5% for about 1 hour have been obtained for the 70.5um line of CH3OH pumped by 9P(34) line and for the 119μm line of CH3OH pumped by 9P(36) line of a CO2 laser, respectively.
The present paper considers the rigorous solutions for electromagnetic waves transmitted and reflected by a medium of finite length with time-space periodic fluctuation, loaded in a rectangular waveguide, When an electromagnetic wave is incident upon the medium mod-ulated in a travelling wave fashion by a pump wave, the reflected and transmitted waves are shifted in frequency by +nω1, (where n is an integer, ω1 is the angular frequency of fluctuation). The harmonic level of the reflected waves is much increased as the frequency of the incident wave approaches the cutoff-frequency of TE10 mode of the rectangular waveguide. Measurement of the spectrum of the reflected waves can be utilized as a diagnosis of even a very slightly fluctuating medium. The theoretical results have been verified on examining experimentally the harmonic level of the microwave reflected by a plasma, weakly modulated (about 10-4) by RF signal and loaded in the WRJ-10 waveguide.
The energy transfer mechanism of the mixed-dye laser using 9-methylanthracene-perylene system is discussed from the exper-imental results on the time-resolved fluores-cence characteristics of the acceptor dye. The fluorescence lifetime of the acceptor dye is elongated when a dye mixture solution is excited by the energy transfer process whose duration is longer than the excitation pulse. Rate constants of the energy transfer are estimated from the fluorescence intensity ex-pressed by a convolution integral. The energy transfer mechanism of this mixture is discuss-ed from the computed results.
For the preparation of SiC film, powder and whisker by the CVD method, tetrame-thyldisilane (TMDS) was used as a starting material. This paper is mainly devoted to the discussion of the formation of ultra-fine particles of SiC. By changing the pyrolytic conditions, the particle size of the β-type SiC can be controlled in the range of 5_??_200nm with a high degree of homogeneity. The present SiC powders could be useful as a raw material for the ceramics.