Intervalence Band THz Laser in p/p+ Ge Heterostructure

In this STTR phase I project, a new THz laser mechanism based on p/p+ periodically doped Ge heterostructures will be studied. The intent is to eliminate the optical phonon scattering required in traditional bulk p-Ge lasers, which causes overheating andlimits their duty and gain. A CW laser with 1-4 THz tunability and picosecond pulse capability is anticipated. The new mechanism is based on selective scattering of light and heavy holes on the periodic p+ layers, leading to light-hole accumulation andamplification of THz emission on direct light- to heavy-hole transitions. The average hole concentration will be increased by several orders, giving a proportional increase in gain. A candidate structure will be selected from results of Monte Carlosimulations of hole dynamics in crossed electric and magnetic fields for various delta-, square-, and sinusoidally-modulated doping profiles. A contract manufacturer will grow the structure. The doping profile will be verified by the electron beaminduced current technique, and far-infrared gain will be measured. A new laser with novel application opportunities in communications (space, air, ground), chemical sensing (upper atmosphere, bio/chem agents), and non-destructive evaluation.