Abstract

A convenient method to generate short optical pulses from laser diodes is by electronic gain switching. As the series resistance of the diodes is usually a few ohms, the optimization of power transfer from the external circuits to the optical devices becomes a critical issue. By investigating the spectral content of the broadband input source and the measured diode impedance, we have designed a quarter-wave transformer for efficient coupling of the signal. The results are compared to those of a conventional broadband matching technique using a chip resistor. For all bias level below threshold, the former technique yields approximately a two-fold improvement in the output optical power. The results are attributed to higher ac power coupling due to the elimination of electrical loss in the resistor. The increase in optical pulse width as a result of narrow band matching in the transformer circuit is also studied. Minimal width of 51 ps is observed, as compared to 39 ps in the case of a chip resistor. The compensation in bandwidth is relatively small. We will also present computer simulated results on the power and bandwidth of the driving electrical signals. A good qualitative match with our experimental observations is obtained.

© 1993 Optical Society of America