Abstract

The operation of the p-Ge hot hole laser is based on the acceleration of holes in $\overrightarrow{E}\perp \overrightarrow{B}$ fields at T≤20 K¹. The heavy holes (hh) are scattered by optical phonons - partially into the light hole band - whereas the light holes (lh) are accumulated on closed trajectories below the optical phonon energy. The resulting population inversion between the lh- and hh-band leads to emission in the 1.5- 4.2 THz range. An electric field || $\overrightarrow{B}$ causes an acceleration of the holes || $\overrightarrow{B}$, leading also to lh-optical phonon scattering, resulting in a decrease of the population inversion. Gain modulation at the roundtrip frequency (=772 MHz for the 49.5 mm long crystal used) and possible mode locking can thus be achieved by applying an rf electric field || $\overrightarrow{B}$ at half this frequency. Recently we reported on the first experimental observation of mode locked operation in the Voigt configuration (optical axis $\perp \overrightarrow{E},\overrightarrow{B}$)². Now we present results on optical output in two different wavelength regions, as studied with a Schottky diode detector and a 6 GHz bandwidth real-time oscilloscope.

© 1998 IEEE