S. Haidar

Mid-infrared (5–12-µm) and limited (5.5–8.5-µm) single-knob tuning generated by difference-frequency mixing in single-crystal AgGaS 2

We describe tunable 5-12-microm mid-infrared generation in single-crystal silver gallium sulfide (AgGaS(2)), from nonlinear optical difference-frequency generation. Signal and idler waves obtained from a Nd:YAG laser-pumped LiNbO(3) optical parametric oscillator (OPO) were mixed in AgGaS(2) crystal to yield difference-frequency waves. For the efficient generation of difference frequency, an unstable resonator was employed as the OPO to reduce output beam divergence. A maximum difference-frequency power of 95 microJ/pulse was obtained near 7.5 microm for a 1-cm-long AgGaS(2) crystal. Spectral noncritical phase matching within a specific tuning range was also investigated that permitted limited single-knob tuning (5.5-8.5 microm) of the difference-frequency generator.

Nd:YAG-pumped periodically poled LiNbO3 optical parametric generator seeded with the narrowband output of a 532-nm pumped optical parametric generator

We present a simple scheme to generate a continuously tunable pulsed narrow-bandwidth infrared wave. An Nd:YAG-pumped periodically poled lithium niobate optical parametric generator (OPG) is seeded with the output of another OPG pumped by the second harmonic (0.532 microm) of the Nd:YAG laser. A tunable idler wave from the 0.532-microm pumped OPG, operated away from the degenerate point, provides a narrow linewidth seed source for the 1.064-microm pumped broadband OPG. Seeding forces the second OPG to operate in a narrowband operation comparable with that of the seed source. Linewidth of the YAG-pumped OPG is 5-25 nm, in the tuning range of 1.61-1.83 microm (signal), narrowed to 1.48-1.05 nm. Methods of further reduction of linewidth also have been discussed.

Generation of continuously tunable, 5–12 µm radiation by difference frequency mixing of output waves of a KTP optical parametric oscillator in a ZnGeP2 crystal

Signal and idlers waves obtained from a Nd : YAG laser pumped KTP optical parametric oscillator (OPO) are difference frequency mixed in a ZnGeP2 (ZGP) crystal to generate radiation in the mid-infrared. The KTP OPO is operated in the type-II phase matching mode, and the extraordinary and ordinary waves are tunable from 1.76 µm to 2.36 µm and from 2.61 µm to 1.90 µm, respectively. The orthogonally polarized waves are difference frequency mixed in a ZGP crystal to generate mid-IR radiation tunable from 5 to 12 µm.

Temperature tuning of 5–12 μm by difference frequency mixing of OPO outputs in a AgGaS2 crystal

We report a temperature tuned mid-IR generating system ranging from 5 to 12 μm by difference frequency mixing of output waves from two optical parametric oscillators (OPOs) in a silver gallium sulfide (AgGaS2) crystal. One of the OPOs generate signal wave of 1.6 μm, while the other produced tunable radiation from 1.846 to 2.353 μm. The AgGaS2 crystal is temperature tuned to allow phasematching for tunable output from 5 to 12 μm.

Seed-source tuning of a broadband noncollinear optical parametric generator based on periodically poled LiNbO3

We report a noncollinear optical parametric generator (OPG) using periodically poled LiNbO 3 (PPLN) pumped by a Nd:YAG laser. Signal tuning is achieved from 1.58 to 1.81 μm by angular rotation of the PPLN crystal. A signal linewidth of 68 nm was found at 1.76 μm. A 532-nm-pumped narrow-linewidth OPG is employed for its idler to serve as a seed source for the Nd:YAG-pumped broadband OPG. Tuning the seed wavelength only, tuning of the noncollinear OPG is achieved, with its linewidth reduced to 1.7 nm throughout its bandwidth. Such a system can be employed for wavelength division multiplexing, optical coherence tomography, and spectroscopy.

Difference-frequency mixing of output waves from a periodically poled lithium niobate optical parametric oscillator in a GaSe crystal

We report on an optical parametric oscillator (OPO) based on periodically poled lithium niobate (PPLN) pumped by a Nd:YAG laser, and on extending its tuning range by difference-frequency mixing of OPO output waves in GaSe crystal. Maximum combined signal and idler pulse energy of 2.7 mJ and slope efficiency of 25% have been achieved. The tuning range is 1.71 to 1.98 mm for the signal wave and 2.81 to 2.30 mm for the idler wave, using a single set of mirrors. As an application of this PPLN OPO, the signal and the idler waves are difference-frequency- mixed in a GaSe crystal to produce tunable mid-IR from 4.35 to 14.25 mm. The efficiency of the mixing has been analyzed, considering the experimental results.

Temperature tuning from 5-12 /spl mu/m by difference frequency mixing of OPO outputs in a AgGaS/sub 2/ crystal

We report a temperature tuned mid-IR generating system ranging from 5-12 /spl mu/m by difference frequency mixing of output waves from two OPOs in a AgGaS/sub 2/ crystal. The AgGaS/sub 2/ crystal is temperature tuned to allow phase-matching.

Difference frequency mixing of periodically poled lithium niobate (PPLN) OPO output waves in GaSe crystal

Summary from only given. We employed type-I phase matching in GaSe IR pulses (DFG) were separated from the optical parametric oscillator (OPO) pulses by two dielectric coated Ge filters and detected with a liquid-nitrogen-cooled HgCdTe detector.

Growth of Twin-Free AgGaS2 Single Crystals by a Self-Seeding Vertical Gradient Freezing Method and Difference Frequency Generation Using These Crystals

We investigated different conditions for the growth of twin-free crystals of AgGaS2 and then examined difference frequency generation (DFG) using the crystals to apply the new technology to coherent light sources tunable from 5 to 12µm. The number of lamellar twins in a crystal decreased with increasing growth rate and vanished at growth rates greater than or equal to about 1 mm/hour. Growth under these conditions allowed us to obtain the twin-free AgGaS2 single crystals. Using these crystals, a DFG output of 5-12µm was obtained by angle tuning on phase matching angle ranges of 32-37° for type-I and 38-43° for type-II respectively. These phase-matching angles coincided with angles of the growth directions from the c-axis. It was found that longer optical crystals capable of producing difference frequency waves tunable from 5 to 12µm could be prepared from the AgGaS2 single crystal boules grown by our VGF method, without suffering cutting losses.