Modulation Response of Superluminescent Lasers

Abstract

The superluminescent diode is one possible alternative to the well-established injection lasers and LEDs as light sources for fiber-optic communications. A superluminescent diode is basically a laser diode without mirrors. The first investigation of the superluminescent diode was carried out by Kurbatov et al. [176], its static properties were evaluated in detail by Lee et al. [177] and Amann et al. [178, 179]. Superluminescent diodes have also been integrated monolithically with detectors for optical memory readout, their fabrication being (possibly) simpler than that involved in laser-detector integration since a mirror facet is not required within the integrated device [180]. (However, given the high optical gain inside the device, it is not trivial how to eliminate even the minute amount of optical feedback to prevent lasing from occurring.) It has also been observed that [181, 182] the optical modulation bandwidth increases substantially as light-emitting diodes enter the superluminescent regime. This regime is characterized by a rapid increase in the optical power output and a narrowing of the emission spectrum. This increase in modulation speed was attributed to the shortening of the carrier lifetime due to stimulated emission.