Control of frequency chirp in nanosecond-pulsed laser spectroscopy 1 Optical-heterodyne chirp analysis techniques

A narrow-band injection-seeded pulsed titanium:sapphire oscillator-amplifier system with on-line chirp analysis for high-resolution spectroscopy

“…They preprogrammed pulse envelopes, in the range of durations between 10 ns and 1 s, by acoustooptical modulator ͑AOM͒ intensity modulating the output of a cw Ti:sapphire laser and subsequently amplifying these in a series of multipass amplifiers; this led to XUV pulses at bandwidths as low as 55 MHz. 10 Dupré and Miller extended the development of injection-seeded pulsed Ti:sapphire lasers, focusing on methods to optimize cavity stabilization, to achieve pulse energies of 100 mJ at bandwidths as low as [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] MHz ͓full width at half maximum ͑FWHM͔͒ for use in high-resolution spectroscopy. 11 When using injection-seeded pulsed laser systems in high-resolution spectroscopic applications, either at the fundamental wavelength or at generated harmonics, effects of time-dependent gain in the amplifier will give rise to phase excursions deviating from the carrier wave.…”

“…Such phenomena have been studied in alexandrite lasers 19 as well as in optical parametric oscillator devices. 20,21 In this paper, we describe the operation of a pulsed Ti:sapphire laser system consisting of an injection-seeded oscillator and a bow-tie amplifier. In the characterization, the frequency-pulling and chirp effects are measured and quantified, while methods to reduce these disturbing effects for high-resolution spectroscopic applications of the system are discussed as well.…”

A near Fourier-transform limited optical parametric oscillator/amplifier system as a pulsed source for high resolution spectroscopy

“…1. Optical heterodyne techniques [3] have been used to control the OPO's output frequency chirp and to optimize its SLM operation. Investigation of the longpulsed system [2] shows that at low pump energies (<2.5 times the free-running threshold), the narrowband tunable OPO output is SLM and its frequency chirp can be <10 MHz, much less than the transform-limited optical bandwidth (~17.5 MHz).…”

“…2 shows that the chirp (variation of the instantaneous frequency f inst during each OPO pulse) can be minimized by matching the output wavelength of the injection-seeded OPO to that of a free-running (unseeded) OPO with a given PPKTP crystal temperature. More recently, we have amplified the OPO output using an optical parametric amplifier (OPA) based on birefringently phase-matched LiNbO 3 .…”

“…However, the chirp can easily be controlled to be very close to zero simply by matching the seed laser wavelength to the free-running OPO wavelength [1][2][3][4]. Therefore, this system has great potential for applications that require very high resolution, near FT-limited pulsed laser spectroscopy.…”