Method for frequency-selective coupling of radiation out of the resonator for selection of lines of a Q-switched CO laser

Vibrational-rotational lines of Q-switched pulsed CO lasers can be selected by a method in which only one line is coupled out through the resonator mirrors and all the other lines are reflected totally by the mirrors. It is shown theoretically that in the limiting case of instantaneous Q switching and the absence of vibrational exchange, a laser providing selection by this method and operating as a result of a cascade of n transitions can develop a pulsed power which is n²/2 times greater than that obtainable from the same laser by selection with a diffraction grating. The energy in a pulse then increases at least n-fold and the pulse duration decreases by a factor n/2.