Numerical modelling of optical Stark effect saturable absorbers in mode-locked femtosecond VECSELs

Adrian H. Quarterman, Geoff J. Daniell, Stewart Carswell, Keith G. Wilcox, Zakaria Mihoubi, Aaron L. Chung, Vasilis Apostolopoulos, Anne C. Tropper

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Quasi-soliton modelocking has been identified as the mechanism responsible for the formation of picosecond pulses in passively mode-locked VECSELs, but neither this mechanism nor Kerr lens modelocking can account for the formation of sub-picosecond pulses from these lasers. Numerical simulations have shown that the optical Stark effect is capable of shortening pulses in the absence of bleaching, but to date no studies have been performed under realistic operating conditions. We model the interaction of an optical pulse with an absorbing quantum well using a semi-classical two level atom approximation. As the bandwidth of a VECSEL pulse is small compared to the spread of energies within a semiconductor band the population of two level atoms is divided into "live" atoms which interact with the optical field, and "dead" atoms which do not. Live and dead states are coupled by carrier-carrier scattering. Results from this model show an increase in pulse shortening above that due to saturable absorber bleaching at pulse durations below one picosecond, implying that an additional effect is responsible for the formation of femtosecond pulses. At these pulse durations the model predicts that the absorbing resonance broadens and decreases in amplitude. This is recognisable as a result of the optical Stark effect. The predictions of this model are compared to experimental results from several femtosecond VECSELs. For some modelocked VECSELs an excellent match between simulation and experiment is found, but in other cases the model cannot reproduce experimental results. We conclude that while the optical Stark effect may be the dominant pulse shaping mechanism in some modelocked VECSELs, others appear to be dominated by other effects.

Original languageEnglish
Title of host publicationVertical External Cavity Surface Emitting Lasers, VECSELs
EditorsUrsula Keller
PublisherSPIE-International Society for Optical Engineering
Number of pages7
ISBN (Print)9780819484567
DOIs
Publication statusPublished - 21 Feb 2011
EventVertical External Cavity Surface Emitting Lasers, VECSELs - San Francisco, CA, United States
Duration: 24 Jan 201125 Jan 2011

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
Volume7919
ISSN (Print)0277-786X

Conference

ConferenceVertical External Cavity Surface Emitting Lasers, VECSELs
CountryUnited States
CitySan Francisco, CA
Period24/01/1125/01/11

Fingerprint Dive into the research topics of 'Numerical modelling of optical Stark effect saturable absorbers in mode-locked femtosecond VECSELs'. Together they form a unique fingerprint.

Cite this