Franz–Keldysh Photon-Assisted Voltage-Operated Switching of a Transistor Laser

Data are presented on the transistor laser light-output (L
_I-V
) as a function of base current and the collector-to-emitter voltage (V
_CE
) revealing sensitive fine structure that can, with suitable bias, be exploited for signal switching and mixing. The output light intensity versus current-voltage characteristics (L
_I-V
) and the fine structure in the L
_I-V
characteristics are related to the change in laser operation from the ground state to the first excited state of the quantum well incorporated in the transistor base, laser mode changes, or shift from spontaneous to stimulated emission (or the reverse). The region of stimulated recombination and its boundary are or particular interest. The concept of the voltage-driven switching of a transistor laser employing the Franz-Keldysh photon-assisted process to shift the operation from stimulated (high coherent optical field) to spontaneous (lower incoherent field) is demonstrated