Analytical Modeling of the Transistor Laser

We derive analytic expressions for the small-signal modulation response of the transistor laser (TL) operating in the common-emitter (CE) and common-base (CB) configurations. We compare the performance (current gain and small-signal modulation bandwidth) of the TL in these two modes of operation. The CE operation results in a small-signal modulation response with the same relaxation oscillation limitations as conventional lasers. The CB configuration shows a bandwidth enhancement due to a bandwidth equalization together with a suppression of the relaxation oscillations. Finally, we show that the small-signal responses of the CB and CE can be approximated by a third-order transfer function.