Barry J. S. Gale

Composite frequency comb spanning 0.4-2.4 μm from a phase-controlled femtosecond Ti: sapphire laser and synchronously pumped optical parametric oscillator

A repetition-rate-stabilized frequency comb ranging from the violet to the mid-infrared (0.4-2.4 microm) is obtained by phase locking a femtosecond Ti:sapphire laser and a synchronously pumped optical parametric oscillator to a common supercontinuum reference. The locking results have bandwidths lower than 3 kHz. By changing the locking frequencies, different relative and absolute offsets of the constituent frequency combs are achievable.

Dual-color operation of a femtosecond optical parametric oscillator exhibiting stable relative carrier-envelope phase-slip frequencies

A femtosecond optical parametric oscillator is demonstrated that can operate in a regime where two signal pulses with well-separated center wavelengths are simultaneously resonant. Measurements show that the oscillator output contains a stable modulation at a frequency corresponding to the difference in the carrier-envelope phase-slip frequencies of the co-resonant pulses. The physical origin of this internal beat signal is attributed to second-order mixing effects, and its frequency is shown to be consistent with theory.

Frequency comb generation and carrier-envelope phase control in femtosecond optical parametric oscillators

We describe progress in the measurement and control of the carrier-envelope phase-slip frequencies of pulses generated by a femtosecond optical parametric oscillator. Example applications of such control are presented and include the generation of a frequency comb spanning nearly three optical octaves, and the creation of a train of 30-fs pulses via coherent pulse synthesis. Future prospects for frequency combs based on femtosecond optical parametric oscillators are discussed.

Coherent synthesis using carrier-envelope phase-controlled pulses from a dual-color femtosecond optical parametric oscillator

A coherent waveform is synthesized from two co-resonant optical parametric signal pulses with different center wavelengths and independent carrier-envelope phase-slip frequencies. XFROG measurements confirm the synthesized waveform is a train of high-contrast 30 femtosecond pulses.

Testing the parametric energy conservation law in a femtosecond optical parametric oscillator

An experimental verification of energy conservation in a parametric oscillator is reported with an optical frequency precision of approximately 200 kHz (< 10(-6) nm). This high precision is made possible by simultaneously measuring the frequency offsets of the pump, signal and idler frequency combs in a singly-resonant femtosecond optical parametric oscillator system.

Towards versatile coherent pulse synthesis using femtosecond laser and optical parametric oscillators.

Pulses from a tunable near-infrared femtosecond optical parametric oscillator and its Ti:sapphire pump laser were phase-locked by matching their carrier-envelope phase-slip frequencies to one quarter of their common pulse repetition frequency. Interferometric second-order cross-correlation and spectral interferometry traces demonstrated their mutual coherence for periods of at least 20 ms, compared with individual coherence times of 0.1 ms estimated from their phase-noise power spectra. This result is a prerequisite for versatile coherent pulse synthesis. Implications for the synthesis of arbitrary waveforms from multi-colour pulses are discussed.

Towards Versatile Coherent Pulse Synthesis using a Femtosecond Laser and Synchronously Pumped Optical Parametric Oscillator

Pulses from a femtosecond optical parametric oscillator and its Ti:sapphire pump laser were phase-locked as a prerequisite to coherent synthesis from different wavelengths.Mutual coherence was demonstrated using spectral interferometry and cross-correlation.

Towards coherent pulse synthesis using independently tunable femtosecond oscillators

Pulses at 780 nm from a femtosecond optical parametric oscillator and its Ti:sapphire pump laser were phase-locked as a prerequisite to coherent synthesis at different wavelengths. Coherence was demonstrated using spectral interferometry and interferometric cross-correlation.

Composite frequency comb spanning 0.4-2.4 μm from a femtosecond Ti:sapphire laser and synchronously pumped optical parametric oscillator

In this paper, we present the composite comb spectrum comprising the Ti:sapphire laser pulses and OPO signal and idler pulses with various SFM outputs. Comb offsets of the pump and OPO red (signal second-harmonic generation, SHG) and yellow (pump-idler SFM output) were determined by beating against a supercontinuum spectrum generated from the pump. We stabilised the entire spectrum by locking the laser repetition frequency (comb interval) to a 200 MHz clock and the comb offsets of the pump and one OPO output (red) to sub-harmonics of the same frequency. Feedback control over the pump offset was achieved by modulating the input power to the Ti:sapphire laser using an acousto-optic modulator, and over the OPO offset by fine-tuning the cavity length via a moveable end mirror mounted on a piezo-electric transducer.

Direct Carrier-Envelope Phase Control for Coherent Synthesis with a Dual-Color Femtosecond Optical Parametric Oscillator

Coherent synthesis offers a route to sub-femtosecond laser pulses but generally requires a spectral bandwidth wider than the emission from a single laser. A direct way to realize this is to combine outputs from several independent lasers coherently by controlling their relative phases and pulse repetition frequencies. Using outputs from a synchronously pumped ultrafast optical parametric oscillator for coherent synthesis passively ensures that the pulses have perfectly matched repetition frequencies, relaxing the technical constraints on achieving coherent synthesis.