Double acceptor doped Ge: A new medium for inter-valence-band lasers

Abstract

We report on intervalence-band laser emission from Be- and Zn-doped germanium crystals. The duty cycle of 10−3 at a repetition rate of 1 kHz is one order of magnitude larger than the highest duty cycle reported for p-Ge lasers doped by group II acceptors. This improvement is due to the much larger hole binding energy of double acceptors Be and Zn which results in a strong reduction of the internal absorption of the generated far-infrared radiation. Laser action has been achieved with crystal volumes as small as 0.04 cm−3, and a laser pulse length of 25 μs has been reached. Germanium crystals doped with these acceptors may offer an opportunity for achieving the ultimate goal of continuous wave operation.