Title :
Theoretical study on enhanced differential gain and extremely reduced linewidth enhancement factor in quantum-well lasers
Author :
Yamanaka, Takayuki ; Yoshikuni, Yuzo ; Yokoyama, Kiyoyuki ; Lui, Wayne ; Seki, Shunji
Author_Institution :
Opto-electronics Labs., NTT, Kanagawa, Japan
fDate :
6/1/1993 12:00:00 AM
Abstract :
Low-chirp lasing operation in semiconductor lasers is addressed in a theoretical investigation of the possibility of reducing the linewidth enhancement factor (α factor) in quantum-well (QW) lasers to zero. It is shown that in reducing the α factor it is essential that lasing oscillation be around the peak of the differential gain spectrum, not in the vicinity of the gain peak. The condition for such lasing oscillation is analytically derived. The wavelength dependence of the material gain, the differential gain, and the α factor are calculated in detail taking into account the effects of compressive strain and band mixing on the valence subband structure. The effect of p-type modulation doping in compressively strained QWs is discussed. It is shown that the α factor, the anomalous dispersion part in the spectrum, crosses zero in the region of positive material gain, which makes is possible to attain virtual chirpless operation by detuning
Keywords :
laser theory; laser tuning; optical dispersion; oscillations; semiconductor lasers; spectral line breadth; α factor; anomalous dispersion; band mixing; chirpless operation; compressive strain; compressively strained QWs; detuning; differential gain spectrum; enhanced differential gain; extremely reduced linewidth enhancement factor; lasing operation; lasing oscillation; low-chip lasing; material gain; p-type modulation doping; quantum-well lasers; semiconductor lasers; valence subband structure; wavelength dependence; Chirp; Effective mass; Epitaxial layers; High speed optical techniques; Laser theory; Optical mixing; Optical refraction; Optical variables control; Quantum well lasers; Semiconductor lasers;
Journal_Title :
Quantum Electronics, IEEE Journal of
