Temperature-dependent etalon effects in laser systems

This paper deals theoretically with the variety of temperature-dependent extracavity and intracavity etalon effects that must be considered in the design of laser systems. All examples refer to carbon dioxide lasers and materials appropriate for use with carbon dioxide lasers, although the analyses and results are valid for other lasers as well. Etalon effects in extracavity flats and lenses are examined, and the temperature-dependent transmittance is calculated. It is shown that the transmission of a ten-surface optical system, assumed to be uniform in temperature with 1% antireflectance coatings on each surface, can vary 18% as the system temperature varies. Temperature-dependent variations in the performance of a carbon dioxide laser are analyzed with respect to etalon effects of the laser resonator and with respect to etalon-within-an-etalon effects due to intracavity elements, e.g., an electrooptic modulator crystal. It is shown that etalon effects can produce line hopping that cannot be prevented by tuning of the laser.