Experimental Study Of A Discharge Driveing Continuous Wave Hydrogen Fluoride Overtone Chemical Laser

Starting with the basic theories of HF chemical laser, the difference of overtone lasing and fundamental lasing has been compared and analyzed. The difficult of HF overtone lasing, which is the fundamental gain suppression, has been pointed out, and the key is the choosing of cavity parameters, which should highly reflect the overtone wavelengths (1.3-1.5μm) and transmit the fundamental wavelengths (2.5-3.1μm). On a discharge-driving CW HF chemical laser, the gain has been computed with the data of fundamental laser, and the range of fundamental gain is 0.04cm-1~0.055cm-1.Base on the relationship of overtone gain and fundamental gain, the range of overtone gain is 0.04%cm-1~0.55%cm-1. Considering with the lasing threshold and the data of overseas'HF overtone chemical laser, those parameters have been chosen to made some cavity mirrors: the reflectance of high reflector with overtone band is R1>99% and fundamental band R1′<2%; the reflectance of out coupler with overtone band is R2≈98% and fundamental band R2′<2%.3.5 Watts of overtone power have been obtained on 1mm station. The dimension of beam with distance of 60 cm is about 10mm×7mm, the overtone efficiency is 10%, and the overtone spectra contains lines P20(6) and P20(7). 0.7 Watts of fundamental power has been obtained with the overtone lasing. When studying this experiment again, the laser only obtains many Watts of fundamental power, the spectra contains lines P2(4) and P2(5). When the cavity axis sets at 0.5mm and 2mm downstream of hydrogen injecting, many watts of fundamental power has been obtained. On the station of 0.5mm downstream of hydrogen injecting, 2 Watts of fundamental power has been obtained and the spectra contains lines P2(4) and P2(5); On the station of 2mm downstream of hydrogen injecting, 4 Watts of fundamental power has been obtained and the spectra contains lines P2(4) or P2(5). No laser has been obtained when changing NF3 to SF6. The mostly possibility reasons, why the overtone laser can't been obtained repeatedly, are optical coating degradation of resonator mirrors.