Tunable Far Infrared Semiconductor Lasers

A review of recent investigations on tunable far infrared semiconductor lasers on hot holes in Ge are given. This laser operates due to inverted hot hole distributions caused by the accumulation of carriers in crossed E and B fields in special regions of the momentum space. A radiative transition responsible for the simulated emission is the transition between subbands of light and heavy holes or between light hole Landau levels. Some additional possibilities to obtain inverted distributions are discussed.