Femtosecond dynamics of active semiconductor waveguides: microscopic analysis and experimental investigations

Abstract

We present theoretical and experimental results of nonlinear amplification and propagation of short optical pulses in Fabry-Perot semiconductor lasers. The theoretical description is based on spatially resolved Maxwell-Bloch-Langevin equations that take into account the spatially varying light-field dynamics including counterpropagation, diffraction, self-focusing, and the microscopic carrier dynamics including carrier heating and carrier relaxation. Femtosecond pump-probe measurements using upconversion and femtosecondresolved pump-probe measurements and frequency-resolved optical gating on a Fabry-Perot laser allow a combined analysis of the transmitted pulses in real time and the spectral domain. The experimental results are compared with the microscopically calculated gain and index distributions, pulse shapes, and optical spectra. In order to assess the full potential of semiconductor lasers and amplifiers, a quantitative measurement and understanding of amplitude and phase dynamics is required. The computer simulations of the ultrashort dynamics of semiconductor waveguides with optical injection of light pulses provide insight into the dynamic spectral gain and index changes responsible for frequency drifts and self-phase modulation, visualization of propagation effects, and a time-and frequency-resolved analysis of the amplified light pulses.

Nonlinear pulse-shaping phenomena of semiconductor saturable absorber mirror

“…In fact, the excitation induced absorption and refractive index changes in GaAs-based materials have been studied experimentally and theoretically. [16][17][18][19] In general, the linewidth enhancement factor should be considered as a function and not a constant, as reported by many previous studies. [20][21][22][23][24] A question is thus raised about how the observed pulse-shaping effects of SESAM influence soliton mode locking.…”

Diode laser MOPA system for the generation of 920 nm femtosecond pulses with 65 W peak power

“…The key concept of the MOPA system is to generate and amplify chirped pulses with durations exceeding the amplifiers gain recovery time (~500 fs [1]) and to compress the amplified pulses to durations in the range of fs. If the pulse duration is shorter than the gain recovery time, gain saturation causes spectral and temporal pulse distortions [1][2][3]. These distortions can be prevented by the "chirped pulse amplification" (CPA) technique [4].…”

Spatially Resolved Femtosecond Pump–Probe Spectroscopy in Broad-Area Semiconductor Lasers

“…In addition, these processes are regarded of high practical relevance for future applications in optical communication and optical signal processing with semiconductor optoelectronic devices. On the one hand, they can generate complicated temporal and spectral distortions in propagating ultrafast optical pulses [3]- [8]. On the other hand, however, they can also enable the realization of devices for subpicosecond all-optical signal pro-cessing such as wavelength converters, switches, or demultiplexers which are based on ultrafast cross gain modulation or four-wave mixing [9].…”