The Studies on the Raman Scattering Processes in Potassium Vapor and the Applications of AgGaSe2 Crystal in Infrared Up-conversion
|關鍵字:||拉曼散射;鉀蒸氣, 四波混合;放大自發輻射;雙晶體上轉換器;銀鎵硒晶體;偏硼酸鋇晶體;薛米爾方程, 折射率;相匹配, 和頻;stimulated Raman scattering;potassium vapor, four-wave mixing;amplified spontaneous emission;two-stage up-convertor;AgGaSe2 crystal;beta-BBO crystal;Sellmeier equation, Refractive index;phase-matching, sum-frequency|
In this thesis some nonlinear optical phenomena in atomic vapor and optical crystal are discussed. Firstly, the competition of stimulated Raman scattering (SRS) between 4S-(5P)-5S and 4S-(5P)-3D channels has been observed as laser is tuned near 4S-5P resonance in potassium vapor. The experimental results show that the SRS only occur in the 4S-(5P)-5S channel. In this Raman scattering, the suppression of the amplified spontaneous emission (ASE) (5S-4P) has been observed. The influence of the four-wave mixing (FWM) processes on the SRS is discussed. In the 4S-(5P)-3D channel, in the backward direction no detectable emission corresponding to the SRS (4S-(5P)-3D) has been observed, so the forward (5P)-3D emission should be the FWM, not the SRS. The ASE (3D-4P) arises from the ASE (5P-3D), which can be observed in the backward direction. Secondly, a two-stage infrared up-convertor made of the AgGaSe2 and beta-BBO crystals has been built up, that can up-convert the middle infrared radiation of 11 - 16 microns range into the 0.8 microns range where the sensitive photomultiplier can be used. This up-convertor is pumped with a near infrared radiation of 1.7 - 1.8 microns wavelength range generated by a beta-BBO optical parametric oscillator. Finally, the refractive indices of AgGaSe2 for ordinary and extraordinary rays in the 11-16 microns mid-infrared range were measured and the improved Sellmeier equations from 0.85 microns to the 16 microns wavelength range were proposed. In this experiment, the mid-infrared radiations of the 11-16 microns wavelength range were mixed with a near-infrared radiation of the 1.7-1.8 microns wavelength range in AgGaSe2 crystal. With the measurement of phase-matching angles the refractive indices for ordinary and extraordinary rays were calculated. The near-infrared radiation was produced by a beta-BBO optical parametric oscillator.