Passive FM locking in InGaAsP semiconductor lasers

Abstract

Passive FM locking of the longitudinal modes in MOVPE (metalorganic vapor-phase epitaxy)-grown InGaAsP semiconductor lasers due to four-wave mixing is discussed. Due to the locking, the lasing field closely resembles a single-frequency modulated wave with a modulation frequency equal to the cavity mode spacing of about 160 GHz, when the lasers are well above threshold. The existence of this FM wave is demonstrated by comparing the fundamental and the second-harmonic spectrum. A simplified analysis of the FM operation which explains the experimental data rather well is presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>