Abstract

The practical direct-modulation bandwidth of semiconductor lasers is commonly believed to be in the lower gigahertz range (below 2 GHz). Recent experimental work¹ has shown that a modulation bandwidth of 4-5 GHz is possible in a number of laser structures. However, achieving that kind of modulation bandwidth requires that the laser be biased at a level well above their nominal ratings, dangerously close to the point of castatrophic damage. Previous work placed greater emphasis on investigating modulation characteristics of existing lasers than on developing lasers with parameters optimized for high-speed modulation. We describe recent developments on the latter. Following a theoretical re-evaluation of the relevant physics, a direct-modulation bandwidth of beyond 10 GHz has recently been achieved. The theoretical background and special laser designs used for achieving such high-modulation bandwidths are discussed. The effect of parasitic elements and mirror reflectivity on the modulation bandwidth and characteristics are also described.

© 1984 Optical Society of America