Transverse mode propagation and gain coefficients in a planarwaveguide CO2 laser amplifier

摘要

The transverse mode propagation and amplification characteristicsnof a large electrode area, planar waveguide carbon dioxide lasernamplifier have been investigated. Amplification of an imperfectlynmode-matched input produces varying output beam quality with changingndischarge conditions, through the modification of the propagationnconstants of the waveguide modes by the gas thermal lens. For improvednmode-matching to the amplifier, a near ideal TE1 output isnobtained without discharge-induced variations. The maximum gainncoefficient for propagation in the fundamental mode is shown to bendependent on the radio frequency discharge conditions through thenfrequency dependence of the minimum stable power density. At 81 MHz, angain coefficient of 0.65 m-1 at 50 torr pressure is obtained