Abstract

Slab waveguide resonators provide mode volume scaling for gain media which have limitations on thickness, but which can be scaled in area to increase laser power. The broad junction diode laser is an example in solid state lasers, whilst for gases, hollow slab waveguides with RF or microwave discharge excitation give operation of CO₂ and CO lasers with high power density. In considering the properties of the resonator modes, diode lasers have mode confinement highly dependent on fabrication, and non-uniformity of injection current and non-linear interaction of optical fields and carrier density both make mode control difficult. In contrast the mid-infrared gas lasers have well defined confinement at the physical boundaries of macroscopic structures, and the discharge can be made very uniform. Refractive index variations, and coupling between power deposition, refractive index and in-cavity optical flux, are relatively weak. The gas lasers thus provide an ideal vehicle for the study of slab waveguide resonators, and emphasis can be placed on the development of new resonator concepts, free of the restrictions of micro-fabrication and non-linear interactions in diode lasers.

© 1992 IQEC