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Title: Investigating the ultra-fast dynamics of semiconductor lasers by optical pulse injection techniques
Author: Gordon, R.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2002
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Resonant injection of sub-picosecond optical pulses were explored as an ultra-fast analogue to injection locking, to influence the phase of the semiconductor laser on short time-scales. This allowed for efficiently altering the absolute phase of the lasing modes (without exciting new modes to lase) and produced mode interference beating; both demonstrated in vertical cavity surface emitting lasers (VCSELs). The ultra-fast optical sampling was extended to resolve polarization degrees of freedom, showing the nonlinear coupling between transverse modes through the charge carriers. Phase-sensitive double-pulse injection, commonly used for coherent control, was applied to VCSELs to introduce a field component into a specifically selected subset of the transverse lasing modes. The self-organization between transverse modes in VCSELs was investigated with resonant pulse injection and optical sampling. At different bias currents, mode-locking was observed to produce both a train of 2 ps pulses with an 11 ps repetition period, and self-organization of the laser mode resonances to tones within the Fibonacci sequence (with a 19 GHz fundamental tone). It was demonstrated that the nonlinear optical sampling technique could be used to measure the coherence length and type of fluctuations within the VCSEL. While the pulsed mode-locking showed the expected shot-noise fluctuations from spontaneous emission, the Fibonacci-type mode-locking was more stable and showed popcorn noise. The emergence of the Fibonacci-type mode-locking was explained by a spatio-temporal theory of the symmetry-breaking interaction between nearly degenerate modes and the carrier density. Edge-emitting semiconductor laser structures, with and without an optical grating, were also investigated. Resonant and non-resonant optical pulses were used to free laser light from a trapped defect state within an optical grating, and create carrier-heating relaxation oscillations. These effects were reproduced with a spatio-temporal model. Double pulse injection was used to measure the separate effects of group-velocity dispersion and gain curvature on pulse propagation within a Fabry-Pérot laser.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available