Self-injected semiconductor distributed feedback lasers for frequency chirp stabilization

Abstract

It is well known that semiconductor distributed feedback lasers (DFB) are key devices for optical communications. However direct modulation applications are limited by the frequency chirp induced by current modulation. We demonstrate that a proper external control laser operation leads to chirp-to-power ratio (CPR) stabilization over a wide range of modulation frequencies as compared to the free-running case. Under experimentally selected optical feedback conditions, the CPR decreases significantly in the adiabatic regime from about 650 MHz/mW in the solitary case down to 65 MHz/mW. Experimental results are also confirmed by numerical investigations based on the transfer matrix method. Simulations point out the possible optimization of the CPR in the adiabatic regime by considering a judicious cavity design in conjunction with a proper external control. These results demonstrate important routes for improving the transmission performance in optical telecommunication systems.

Analysis of frequency chirp of self‐injected nanostructure semiconductor lasers

“…For instance, at a 0.1 GHz modulation frequency, the latter is lowered from 0.5 GHz/mW in the free-running case down to 0.1 GHz/mW ( f ext = 10 −3 ). These numerical results are actually in agreement with the recent experimental observations conducted on a QW distributed feedback laser in which the CPR was decreased in the adiabatic regime with a proper external control [31]. On the contrary, when the modulation frequency approaches the laser's relaxation frequency, the magnitude of the peaks is progressively enhanced especially under strong feedback rates.…”

“…The CPR is a convenient way to quantify the chirping properties as already demonstrated both theoretically and experimentally [30,31]. In the following section, we investigate the effects of the feedback parameters on the modulation response and on the CPR properties both for the short and the long external cavity configurations.…”

“…It is known that under a direct modulation, the strong non‐linear photon–carrier coupling in a semiconductor laser cavity gives rise to both amplitude and frequency modulation responses. Thus, from (11), the amplitude modulation transfer function for the QD lasers subjected to external optical feedback can be extracted as The frequency response (frequency chirp) is evaluated via the chirp‐to‐power ratio (CPR) given by the expression The CPR is a convenient way to quantify the chirping properties as already demonstrated both theoretically and experimentally [30, 31]. In the following section, we investigate the effects of the feedback parameters on the modulation response and on the CPR properties both for the short and the long external cavity configurations.…”

Influence of external optical feedback on the alpha factor of semiconductor lasers

“…We noticed a recent report [11] showing that the alpha value for a solitary QW laser decreases when the laser is subject to certain EOF, indicating that EOF does influence the alpha. However, to the best of our knowledge, there is not yet a report in literature investigating how the alpha changes with the EOF.…”

Linewidth enhancement factor in semiconductor lasers subject to various external optical feedback conditions

“…With optical feedback, α has been shown to increase with the feedback strength in the long cavity regime [14]. With a relatively weak feedback, reduction in α from its free-running value has also been observed [15]. While the effects from the external feedback are determined not only by the feedback strength but also by the external cavity length and the feedback phase, it is of great interest to study the α of semiconductor laser subject to various external optical feedback conditions.…”