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

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 accepters. This improvement is due to the much larger hole binding energy of double accepters 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 df 25 mu s has been reached. Germanium crystals doped with these accepters may offer an opportunity for achieving the ultimate goal of continuous wave operation. (C) 1996 American Institute of Physics.