Electro-optic frequency shifts in a Q-switched CO₂laser

Abstract

Measurements are described of intrapulse frequency shifts in an electro-optically Q-switched CO2 laser. These can be identified with the electro-optically induced refractive index changes in the modulator crystal. These refractive index changes, which play a fundamental role in the Q-switching process, can be exploited to provide either positive or negative frequency excursions. The frequency shift can be controlled between two extremes by the appropriate orientation of polarising elements. The effect may be eliminated to a high degree using an arrangement which provides maximum Q-switched power, or alternatively a large frequency shift (typically a quarter of the laser axial mode separation) may be produced with minimal Q modulation. This second mode of operation offers a valuable method of chirp correction in hybrid CO2 lasers.

Electro-optic refractive index compensation applied to the intrapulse frequency stabilisation of a carbon dioxide TEA laser

“…Transversely excited single-mode carbon dioxide lasers are prime candidates for this role due to their high output power and compactness. In a previous series of studies (Willetts and Harris 1982, 1983. 1984.…”