Numerical simulation of optical Stark effect saturable absorbers in mode-locked femtosecond VECSELs using a modified two-level atom model

School of Physics and Astronomy, University of Southampton, Southampton, UK.
Optics Express (Impact Factor: 3.49). 12/2011; 19(27):26783-95. DOI: 10.1364/OE.19.026783
Source: PubMed


The interaction of an optical pulse with a quantum well saturable absorber is simulated using a semi-classical two-level-atom model which has been modified to approximate spectral hole burning in the carrier distribution. Saturable absorption behaviour is examined in the limit where pulse duration approaches the carrier-carrier scattering time. For long pulses bleaching dominates the absorber response but as the pulse duration approaches the carrier-carrier scattering timescale an additional pulse shaping mechanism becomes active, allowing the absorber to continue to shorten pulses beyond the limit set by bleaching. Examination of the spectral and temporal absorption profiles suggests that intense pulses experience additional pulse shortening from the optical Stark effect.

Download full-text


Available from: K.G. Wilcox
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We report a repetition frequency tunable, passively mode-locked vertical-external-cavity surface-emitting semiconductor laser (VECSEL) with continuous repetition frequency tuning between 2.78 and 7.87 GHz using mechanical tuning of the laser cavity length. The laser emits near-transform-limited, sub-500-fs pulses over almost an octave tuning range between 2.78 and 5 GHz. At repetition rates above 6 GHz the pulse duration increases to ~2.5 ps. Over the entire tuning range the laser emits an average output power of 40 ± 5 mW in a fundamental transverse mode. The change in pulse duration highlights a change in the dominant modelocking mechanism which forms the pulses. At high repetition frequencies the pulse duration is set by the saturable absorber recovery time. At low repetition frequencies the fluence and peak intensity on the SESAM increases to a point where the fast pulse shaping mechanisms of the optical Stark effect and carrier thermalization dominate the pulse shortening.
    Full-text · Article · Nov 2011 · Optics Express
  • [Show abstract] [Hide abstract]
    ABSTRACT: We describe recent advances in the development of optically pumped passively mode-locked semiconductor lasers; ultrashort pulse sources that begin to offer levels of pulse duration, beam quality, and average power that formerly belonged only to diode-pumped solid-state lasers (DPSSLs) based on impurity-doped dielectric gain media. Unlike dielectric gain media, however, III-V semiconductors exhibit immense spectral versatility, with alloy compositions allowing emission wavelengths spanning the spectrum from visible through to the mid-infrared. Within the past few years, it has been shown that strained InGaAs/GaAs quantum well lasers operating around 1. μm are capable of generating transform-limited pulse durations of 100. fs or less; and moreover, that sub-400-fs pulses with >. 300. W peak power, and 1.5-ps pulses with ~. 500. W peak power can be generated. Very recently, material systems other than InGaAs quantum wells have been used to demonstrate femtosecond mode locking, with results reported for a self-assembled quantum dot laser, a 2-μm antimonide laser and a 1.5-μm indium phosphide device.The vertical-external-cavity surface-emitting semiconductor laser, or VECSEL, mode-locked under the influence of a semiconductor saturable absorber mirror in the external cavity, is thus capable of bridging the gap in performance between mode-locked edge-emitting diodes and DPSSLs. A particular advantage of VECSELs is that they operate easily at repetition frequencies in the 1-20. GHz range, where dielectric lasers tend toward Q-switching instability, whereas monolithic diodes become inconveniently large - the range addressed both by electronics, and by the optical resolution of simple grating devices.
    No preview · Chapter · Dec 2012
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The performance of ultrafast semiconductor disk lasers has rapidly advanced in recent decades. The strong interest from industry for inexpensive, compact, and reliable ultrafast laser sources in the picosecond and femtosecond domains has driven this technology toward commercial products. Frequency metrology and biomedical applications would benefit from sub-200-femtosecond pulse durations with peak powers in the kilowatt range. The aim of this review is to briefly describe the market potential and give an overview of the current status of mode-locked semiconductor disk lasers. Particular focus is placed on the ongoing efforts to achieve shorter pulses with higher peak powers.
    Full-text · Article · Jul 2015 · Light: Science & Applications