RESUMEN
We demonstrate longwave infrared (LWIR) generation with an optical parametric oscillator (OPO) based on quasi-phasematched orientation-patterned gallium arsenide (OPGaAs). The OPGaAs OPO was directly pumped with a Q-switched λ = 2.054 µm Tm,Ho:YLF laser. OPGaAs samples representing three different grating periods were used to explore the LWIR OPO performance yielding outputs ranging from λ = 2.5-2.7 µm (signal) and λ = 8.8-11.5 µm (idler). Slope efficiencies for the combined signal and idler outputs reach as high as 26% while slope efficiencies for only the idler reached 8%. Spectral measurements of OPO output confirm good agreement with theoretical calculations.
RESUMEN
A simple difference frequency generation (DFG) scheme based on two seeded optical parametric generators is presented as a tunable terahertz (THz) source. Using the nonlinear optical crystal 4-dimethylamino-N-methyl-4-stilbazolium-tosylate (DAST) as the DFG crystal, our system has demonstrated continuous and seamless tunable operation from 1.6 to 4.5 THz. The output bandwidth of the THz source is 2.4 GHz. The utility of the source over this spectral range is demonstrated by measuring a high-resolution transmission spectrum of water vapor in air.
RESUMEN
For what is believed to be the first time, a single-longitudinal-mode passively Q-switched Nd:YAG microlaser is used to pump a narrow-bandwidth periodically poled lithium niobate (PPLN) optical parametric generator-optical parametric amplifier (OPG-OPA). Before amplification in the OPA, the output of the OPG stage was spectrally filtered with an air-spaced etalon, resulting in spectroscopically useful radiation (bandwidth, ~0.05 cm(-1) FWHM) that was tunable in 15-cm(-1) segments anywhere in the signal range 6820-6220 cm(-1) and the idler range 2580-3180 cm(-1). The ability to pump an OPG-OPA with compact, high-repetition-rate, intrinsically narrow-bandwidth microlasers is made possible by the high gain of PPLN. The result is a tunable light source that is well suited for use in portable spectroscopic gas sensors.
RESUMEN
Backscatter absorption gas imaging (BAGI) is a technique that uses infrared active imaging to generate real-time video imagery of gas plumes. We describe a method that employs imaging at two wavelengths (absorbed and not absorbed by the gas to be detected) to allow wavelength-differential BAGI. From the frames collected at each wavelength, an absorbance image is created that displays the differential absorbance of the atmosphere between the imager and the backscatter surface. This is analogous to a two-dimensional topographic differential absorption lidar or differential optical absorption spectroscopy measurement. Gas plumes are displayed, but the topographic scene image is removed. This allows a more effective display of the plume image, thus ensuring detection under a wide variety of conditions. The instrument used to generate differential BAGI is described. Data generated by the instrument are presented and analyzed to estimate sensitivity.
RESUMEN
We fabricated and characterized periodically poled lithium niobate monolithic optical parametric oscillators (OPO's) and generators. The compact monolithic devices were trivial to align and operate and provided widely tunable, nearly diffraction-limited, stable output pulses. Low thresholds and high conversion efficiencies were obtained when the devices were pumped with 3.5-ns 1.064-mum pulses. In addition, the monolithic OPO devices exhibited broad tuning by crystal rotation through noncollinear phase matching. The bandwidth-broadening effects exhibited in the noncollinear phase-matching geometry were measured and explained.
RESUMEN
We report on a new periodically poled lithium niobate grating design with a continuous grating-period change (fan-out). We observed 350cm(-1) (80 nm at 1.5microm) of complete spectral coverage at a constant temperature in a cw optical parametric oscillator. Complete spectral coverage is demonstrated by measurement of an absorption band of CO(2) .
RESUMEN
The results of a simple scheme to generate continuously tunable pulsed narrow-bandwidth (less than 0.1 cm (-1)) light in the infrared are presented. A periodically poled lithium niobate (PPLN) optical parametric amplifier is seeded with the filtered output of a PPLN optical parametric generator. A high-finesse Fabry-Perot etalon is used as the filtering element, giving bandwidths as narrow as 0.08 cm (-1) and tunable over 18 cm (-1) without any adjustments to the PPLN crystals. High efficiency is obtained with a 15-ns 1-kHz Nd:YAG laser, giving energies of up to 180 microJ of signal at 1.6 microm and 60 microJ of idler at 3.3 microm .
RESUMEN
One can apply two-tone frequency modulation spectroscopy techniques to the detection of gas-phase species by using laser light scattered from hard targets. High sensitivities are demonstrated, with a minimum detectable absorption of 10(-4) possible with a simple apparatus. The effects of laser speckle on the FM signal are described, and we show that the detection signal-to-noise ratio can be improved by collecting an increased number of speckle cells.
RESUMEN
A high-repetition-rate Ti:sapphire-pumped optical parametric oscillator based on the new nonlinear optical crystal CsTiOAsO(4) is described. The operation of this optical parametric oscillator is characterized for a 90 degrees -cut crystal by use of a type II interaction. Tuning from 1.46 to 1.74 microm is demonstrated, and there is the potential for tuning from 0.9 to 5 microm with angle tuning. Powers of 100 mW in the signal and the idler branches are obtained. Pulse widths as short as 64 fs are generated with and without prisms in the cavity.
RESUMEN
A high-repetition-rate Ti:sapphire-pumped femtosecond optical parametric oscillator based on the new nonlinear-optical crystal RbTiOAsO(4) is described. Tuning from 1.03 to 1.3 microm in the signal branch and from 2.15 to 3.65 microm in the idler branch with powers as high as 250 mW in the signal and 200 mW in the idler is presented. The possibility of extending the tuning range beyond 3.65 microm is discussed.
RESUMEN
A broadly tunable femtosecond optical parametric oscillator (OPO) based on KTiOPO(4) that is externally pumped by a self-mode-locked Ti:sapphire laser is described. Continuous tuning is demonstrated from 1.22 to 1.37 microm in the signal branch and from 1.82 to 2.15 microm in the idler branch by using one set of OPO optics. The potential tuning range of the OPO is from 1.0 to 2.75 microm and requires three sets of mirrors and two crystals. Without prisms in the OPO cavity, 340 mW (475 mW) of chirped-pulse power is generated in the signal (idler) branch for 2.5 W of pump power. The total conversion efficiency as measured by the pump depletion is 55%. With prisms in the cavity, pulses of 135 fs are generated, which can be shortened to 75 fs by increasing the output coupling.
RESUMEN
A self-mode-locked ring-cavity Ti:sapphire laser is described that is self-starting within milliseconds and completely unperturbed by the self-starting mechanism while mode locked. This technique makes use of a position-modulated mirror in an external cavity in which the cavity length and alignment are noncritical. Other benefits of the ring cavity over the linear cavity configuration are described.