Invited: Novel Optical Methods for High Speed Direct Modulation of Semiconductor Lasers

Abstract

In high speed direct modulation of semiconductor lasers, serious drawbacks arise from relaxation oscillation in the light output. Several possible schemes have been examined to attain the high speed direct pulse modulation. Electronic band reduction in the detection system improves the waveform distortion caused by the relaxation oscillation at modulation rates up to about 400 Mb/sec in practice. Novel optical methods are proposed to overcome the limit of the modulation rates. Feedback of light from a laser into itself with a time delay (optical feedback) and injection of external radiation into laser modes (optical injection) have been found theoretically and experimentally to be quite effective for reducing the waveform distortion. These methods are expected to extend the direct modulation capability of semiconductor lasers.