Towards a solid state far infrared laser: Designs kinetics and problems

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Description/Abstract

Current far infrared sources of significant average output power are extremely inefficient, bulb gas lasers which are only line tunable, or require liquid helium cooling and high magnetic fields, for example the p-Ge laser. There is increasing interest in this spectral region for possible security, quality control and gas sensing applications. Electrically pumped multiple quantum well structures would be attractive, but suffer from problems of poor mode overlap with the gain region and free carrier loss from mode overlap with carrier injection and extraction regions. We consider the design of an optically pumped multiple quantum well far infrared laser designed to emit in the one hundred micron region. The spectroscopy and kinetics of these structures, measured on the FELIX free electron laser with picosecond time resolution at the pump wavelength near ten microns using pump/probe techniques will be discussed. Strong two photon ahorption, leading to long lived free carrie
r absorption was observed, and represents a potential difficulty for these lasers, although fortunately should be avoidable with suitable designs. Preliminary attempts at laser action are reported.