Semiconductor mode-locked lasers: Modeling, characterization and applications.

摘要

This thesis describes the modeling and characterization of mode-locked semiconductor lasers and a number of new applications.; An enhanced dynamic model is developed to describe the startup and steady-state behavior of mode-locked lasers. The combined time and frequency-domain model includes both linear mode-coupling effects through carrier density modulation as well as nonlinear effects like gain saturation and additional mode-coupling through four wave mixing. The effects of spontaneous emission and its cause of timing and amplitude jitter on the mode-locked pulse train is studied.; The potential of a semiconductor mode-locked laser with a dense mode spacing (∼25 GHz) as an optical source for wavelength division multiplexing is studied. First, one of the locked modes is filtered out by a narrow band fiber Bragg grating and its use as a single wavelength source is examined. Next, when the semiconductor laser is used in an external fiber grating feedback configuration, lasing only occurs when the fiber grating is tuned to one of the monolithic cavity modes leading to a discretely tunable single wavelength source whose channel spacing is determined by the mode spacing of the semiconductor laser.; As another new application, the use of semiconductor mode-locked lasers in a photonic analog to digital (A/D) converter is proposed. The method uses wavelength multiplicity to increase the sampling rate of A/D converters. The optical outputs of a number of semiconductor lasers each mode-locked at a different center wavelength are spectrally stitched and time-interleaved into a high repetition rate multi-wavelength sampling pulse train which can be used in a photonic A/D converter to sample a high-end microwave signal.; Finally, a new method for the characterization of ultrashort pulses called time resolved optical gating based on dispersive propagation is introduced. This method does not require an optical gating pulse. An algorithm is developed for the full reconstruction of the pulse from the measurements. The pulse train emitted from a mode-locked semiconductor laser at 1.5μm is characterized using this new technique.