On the various time constants of wavelength changes of a DFB laserunder direct modulation

摘要

The temporal behavior of the optical frequency emitted by severalnDFB lasers under direct square wave modulation was measured using annall-fiber implementation of a Mach-Zender interferometer with annimbalance of 30 ps. The impulse response of the optical frequency toninjection current modulation was found to contain a time constant asnshort as 10-20 ns, together with a few longer ones. The existence ofnsuch a short time constant is consistent with a thermal analysis of anlaser structure with finite thermal impedance of the active region andnshould be taken into consideration in various wide bandwidthnapplications of direct modulated semiconductor lasers