Abstract

The subject of coupled-cavity semiconductor lasers (e.g., C³,¹ GRECC²) has experienced renewed interest as a means of achieving superior modal selectivity. Aside from studies of modal switching, however, little effort has been directed toward fundamental understanding of the modulation dynamics and quantum noise properties of these devices. We derive the modulation and noise properties (e.g., modulation bandwidth,³ modal linewidth,^4–7) of an active cavity/passive cavity compound semiconductor laser. We show that because of physical effects unique to lasing action in a semiconductor (a detuned gain spectrum leading to amplitude phase coupling of the lasing field⁸) several dramatic improvements in modulation and noise performance can be expected to result in a coupled-cavity laser. These include the following simultaneous improvements over conventional (uncoupled) lasers; first, enhancement of the direct-modulation corner frequency by nearly 2X; second, suppression of the FM component of modulation with respect to the AM component⁹; third, lasing linewidth reduction (i.e., phase noise reduction) exceeding an order of magnitude.

© 1984 Optical Society of America