W. E. Sleat

Light-emitting diodes as measurement devices for femtosecond laser pulses

We present results showing that, when it is used as a photodetector, a light-emitting diode (LED) has a power-dependent response that can be used for sensitive detection and characterization of picosecond and femtosecond laser pulses. A characterization of a typical LED is presented at 800 nm, and we demonstrate how this effect can be used to construct an extremely compact novel autocorrelator based on a Wollaston prism.

Regeneratively initiated self-mode-locked Ti:sapphire laser.

It is demonstrated that the incorporation of an acousto-optic modulator within the cavity of a self-mode-locked Ti:sapphire laser can lead to self-starting and stable generation of pulses that have durations of 60 fs when the acousto-optic device is driven regeneratively from the laser output. Data are also presented that show that the application of cavity-frequency locking techniques dramatically improves the phase noise characteristics of the mode-locked laser.

Reduction of phase noise in passively mode-locked lasers

The phase noise of a colliding-pulse mode-locked ring dye laser and a coupled-cavity mode-locked color-center laser has been reduced by up to two orders of magnitude in the 50-500 Hz range by referencing the cavity frequency of the optical resonators to that of an electronic oscillator. Using this technique a common reference is available to provide a direct electronic signal to the deflection electronics of a synchroscan streak camera so that real-time phase error detection can be achieved. >

Time synchronisation measurements between two self-modelocked Ti:sapphire lasers

Abstract The pulses from two self-modelocked titanium:sapphire lasers have been time synchronised by locking their repetition frequencies to an electronic crystal oscillator and a relative timing jitter between the lasers of 1–2 ps has been recorded. Somewhat better jitter figures of

Pulse Asymmetry in the Colliding-pulse Mode-locked Dye Laser

Abstract The design and performance characteristics of a group velocity dispersion-compensated colliding-pulse passively mode-locked ring dye laser are discussed. Pulses as short as 19 fs have been observed and analyses of experimental autocorrelations—both intensity and interferometric—together with spectral data that show evidence of pulse asymmetry are presented.

Compact, efficient 344-MHz repetition-rate femtosecond optical parametric oscillator.

We describe configurations of a novel synchronously pumped femtosecond optical parametric oscillator based on the crystal RbTiOAsO(4) and operating with a signal-pulse-repetition frequency as high as 344 MHz. Average signal powers as high as 600 mW and pulse durations of 78 fs are demonstrated at a wavelength of 1.25 microm, and a characterization of the signal output using frequency-resolved optical gating implies asymmetric near-sech(2)(t) intensity-profile pulses with significant amounts of spectral cubic phase.

Noise characterization of a mode-locked InGaAsP semiconductor diode laser

Noise measurements were made on an InGaAsP semiconductor diode laser by monitoring and analyzing the mode-locked pulse train power spectrum. The noise content of the mode-locking RF source was observed to be transferred directly to the laser pulse train and, thus, careful selection of the drive oscillator is essential. Amplification of the laser pulses by an erbium-fiber amplifier did not lead to any increase in timing jitter and the additional amplitude noise present could be removed by using a more compatible pump source such as a diode laser operating at either 980 or 1490 nm. >

Subpicosecond synchroscan operation of a Photochron IV streak camera

The electronic drive circuitry employed in the operation of a synchroscan Photochron IV streak camera is described. The experimental performance of two synchronization systems, a passive configuration (whereby the deflection signal is derived directly from a mode‐locked pulse source) and an active system (incorporating a tunnel‐diode oscillator phase locked to the laser), have been compared. A semiquantitative assessment of phase noise in the deflection signal and its effects on achievable temporal resolution is detailed and tested experimentally. On the basis of this analysis it has been possible to optimize the streak circuitry and thereby demonstrate a limiting instrumental resolution of 930 fs.

Amplitude noise reduction of a coupled-cavity mode-locked NaCl:OH- color-center laser by active synchronization.

Stable noise-free operation of a coupled-cavity mode-locked NaCl:OH− color-center laser was obtained by synchronizing it to the mode-locked Nd:YAG pump laser. This stabilization technique, based on active cavity-length control of the color-center laser, eliminated the amplitude modulation of the output power arising from the beating of the pump laser pulse train with the color-center laser pulse train.

A Real-time FROG-trace Acquisition System for Non-amplified Femtosecond Oscillators

Details are presented of an implementation of second-harmonic generation frequency-resolved optical gating (SHG FROG), which allows real-time acquisition of the FROG trace from a femtosecond oscillator. A spinning mirror phase-locked to an autocorrelator is used to scan line-spectra of the correlation function across a CCD camera. The FROG trace is updated at around 20 Hz and displayed on a video monitor.