Stephen Elsmere

Ultrafast optical Stark mode-locked semiconductor laser

We report on 260 fs transform-limited pulses generated directly by an optical Stark passively mode-locked semiconductor disk laser at a 1 GHz repetition rate. A surface recombination semiconductor saturable absorber mirror and a step-index gain structure are used. Numerical propagation modeling of the optical Stark effect confirms that this mechanism is able to form the pulses that we observe.

All-semiconductor room-temperature terahertz time domain spectrometer

We report what we believe to be the first demonstration of an all-semiconductor room-temperature terahertz time domain spectrometer. An optical Stark mode-locked vertical-external-cavity surface-emitting laser with 480 fs pulses at 1044 nm was used to illuminate low-temperature-grown photoconductive antennae with 5 mum-gap bow-tie-shaped electrodes. The coherently detected spectrum has a bandwidth close to 1 THz, in which water absorption lines at 0.555 and 0.751 THz can be resolved.

High-Repetition-Rate Subpicosecond Source of Fiber-Amplified Vertical-External-Cavity Surface-Emitting Semiconductor Laser Pulses

We report a 6-GHz fundamental repetition-rate source of 545-fs pulses with 1.5-W average power at 1042.6 nm, based on ytterbium-doped fiber amplification of a Stark mode-locked vertical-external-cavity surface-emitting semiconductor laser.

70-fs Transform-Limited Pulses Emitted by InGaAs/GaAs Quantum Well Laser

We observe near-transform-limited 70-fs pulses, stable over ~1010round trips, and stable 260-fs transform-limited pulse trains from an optical Stark mode-locked vertical-external-cavity surface-emitting InGaAs/GaAs quantum well laser operating at 1040 nm.

Characterization of pulse timing jitter of actively stabilised 1-GHz vertical-external-cavity surface-emitting semiconductor laser producing 500-fs pulses

The rms timing jitter of 500-fs optical pulses from a passively mode-locked, actively stabilised vertical-external-cavity surface-emitting laser was determined by the Von der Linde method to be 350 fs over 500 Hz - 500 KHz.

Spectrotemporal gain bandwidth measurement in an InGaAs/GaAsP quantum well vertical-external-cavity surface-emitting semiconductor laser

Analysis of spectral condensation in a VECSEL with a near-antiresonant gain structure incorporating InGaAs/GaAsP quantum wells emitting around 1030 nm shows the effective FWHM gain bandwidth of this laser to be 32 nm.

High repetition-rate sub-picosecond source of fibre-amplified vertical-external-cavity surface-emitting semiconductor laser pulses

In this work we used a V-cavity VECSEL with InGaAs quantum-well-based gain and semiconductor saturable absorber mirror structures as described in S. Hoogland et al.(2005): an overall cavity length of 25 mm conferred a fundamental pulse repetition frequency of 5.9908 GHz, and the VECSEL emitted 1-ps pulses in a stable passively mode-locked train with 40 mW average power. Pulses from the VECSEL were then launched through a free space optical isolator into 2 m of Yb-doped fiber with an octagonal core and outer cladding diameters of 20 mum and 125 mum respectively (Liekki Yb 1200-20/125DC). The fiber was cladding-pumped by a 5-W fibre-coupled diode at 915 nm.

Passively mode-locked 832-nm vertical-external-cavity surface-emitting semiconductor laser producing 15.3-ps pulses at 1.9-GHz repetition rate

The authors report the first passively mode-locked 830- nm vertical-external-cavity surface-emitting laser. A semiconductor saturable absorber mirror with carrier recovery time governed by surface recombination was used to demonstrate pulses of 15.3 ps duration.

First Demonstration of an All-Semiconductor Room-Temperature Terahertz Time-Domain Spectrometer

We report the first demonstration of an all-semiconductor, room temperature terahertz time-domain spectrometer using a femtosecond mode-locked Vertical-External-Cavity Surface-Emitting Laser at 1040 nm and photoconductive antennae.