Parasitic amplitude modulation of stabilized CO2 lasers

An experimental investigation was made of parasitic amplitude modulation in a CO₂ laser with intracavity frequency modulation. This effect was due to periodic misalignment of the laser cavity during operation of a piezoelectric ceramic modulator. A method for controlling and minimizing the parasitic modulation was developed. Relationships were derived for the shift of the stabilized frequency due to such parasitic amplitude modulation and estimates were obtained for the case of a stabilized CO₂/OsO₄ laser. It was found that the parasitic modulation could give rise to a dependence of the stabilized frequency on the phase relationships in the case of phase-sensitive detection in an automatic frequency control system of the laser.