Dynamic instabilities in the power spectrum of deeply modulated semiconductor lasers

Igor Vurgaftman, Jasprit Singh
1994 Journal of Applied Physics  
Semiconductor lasers under large-signal direct modulation by a square waveform are found to exhibit a transition from a power spectrum characterized by a fundamental frequency and FM sidebands to a continuous spectrum with a catastrophically broadened linewidth of the order of several GHz. The interesting feature of the phenomenon is that the photon output remains periodic apart from noise-induced fluctuations, and the broadening of the power spectrum is attributed to the sensitivity of the
more » ... e of the optical field to a large difference in the relaxation oscillation frequencies in the ON and OFF states as well as the coupling between motions at the intrinsic resonance frequency of the system and the externally-imposed modulation frequency. It is shown that under deep modulation by a periodic injection current, the optical phase becomes aperiodic generating a wide range of new frequencies in the power spectrum. It is also demonstrated that by confining the excursions of the injection current to the region of almost-linear optical response, linewidth broadening may be avoided. Qpantitative criteria for determining the boundary of the broadened-linewidth region are presented for several modulation frequencies.
doi:10.1063/1.357346 fatcat:uksddpfkazhb7jsav4av53je74