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New Crystals for Nonlinear Optics

#1897


Development of a Technology of Growing Mercury Thiogallate and Cadmium-Mercury Thiogallate Nonlinear Crystals for Optical Parametric Oscillators of the Middle Infrared Range Pumped by 1 m Laser Radiation

Tech Area / Field

  • MAT-SYN/Materials Synthesis and Processing/Materials
  • PHY-OPL/Optics and Lasers/Physics

Status
8 Project completed

Registration date
07.06.2000

Completion date
29.07.2004

Senior Project Manager
Mitina L M

Leading Institute
NPO Astrophysica, Russia, Moscow

Supporting institutes

  • Kuban State University, Russia, Krasnodar reg., Krasnodar

Collaborators

  • Universite De Bourgoone / Laboratoire de Physique, France, Dijon\nCILAS (Companie Industrielle des Lasers), France, Marcoussis

Project summary

The purpose of the project is the development of the technology for the growth nonlinear mercury thiogallate and cadmium-mercury thiogallate crystals, producing test specimens of high optical quality and their approbation in mid-IR OPOS with laser pumping (=1 m).

By now there are many nonlinear crystals in which the variance of refractive indexes ensures, in principium, the possibility of their use for realization of different parametric processes. However only single crystals are really used. The reason is that besides the requirements imposed on their optical characteristics: low absorption coefficient at frequencies of interacting waves ( 0.01cm-1); high effective nonlinear susceptibility ( 10-11 m/V for chalcogenide crystals); resistance to laser radiation, the crystals must be technologically effective. It is the last requirement that is not met by the most known nonlinear chalcogenide crystals.

Devices of sum and difference frequency mixing and OPOS really used in IR region only argentum thiogallate (AgGaS2), argentum selenogallate (AgGaSe2)and germanium zinc phosphide (ZnGeP2). The last because of weak absorption bands in about 2 and 9-10 m is mainly used in research. Cleveland Crystals, Inc. (USA), SUE “SPA Astrophysica” and the Laboratory of Novel Technologies (LNT) of the Kuban State University (Russia) are the main manufacturers of argentum thiogallate and selenogallate. AgGaS2, HgGa2S4, ArGaGeS4, AgGaSe2, AgGa1-xInxS2, AgGa1-xInxSe2, Hg1-xCdxGa2S4 crystals produced in the Laboratory in 1980s had been actively investigated and used in devices of sum frequency mixing for visualization of CO2-laser radiation. Nanosecond pulsed radiation of Nd:YAG-laser or its second harmonic were used for pumping. The efficiency of such devices was rather low, as the mentioned crystals’ resistance to laser radiation did not exceed, on the average, 20-60 MW/cm2.

For mid-IR OPOS with Nd:YAG-laser pumping (=1 m) the crystals of argentum thiogallate, mercury thiogallate and cadmium-mercury thiogallate are optimal for such characteristics as the value of effective sguare-low nonlinear susceptibility, the transparent region and the value of absorption coefficient, the type of variance of principle values of refractive indexes, potential optical quality and resistance to laser radiation. In argentum selenogallate the processes of parametric oscillation are realized only at a pump wavelength more than 1.2 m whereas in mentioned crystals pumping is acceptable at more short-waves. According to the experts, the creation of powerful tunable mid- and far IR sources of light pulses is most real on the basis of chalcogenide crystals of argentum thiogallate, mercury thiogallate and cadmium-mercury thiogallate [1-5]. It should be pointed out that in HgGa2S4 and Hg1-xCdxGa2S4 crystals the parametric oscillation with pumping by the radiation of the second harmonic of the Nd:YAG-laser is possible because of specificity of refractive indexes variance in visible region (the lack of -isotropic point typical for chalcogenide crystals).

As for resistance to nanosecond pulsed laser radiation of pumping mercury thiogallate, as the minimum, exceeds twice argentum thiogallate and selenogallate. For these crystals the typical value is 20-30 MW/cm2, whereas in mercury thiogallate – 60 MW/cm2 (E.Takaoka, K.Kato. Tunable IR generation in HgGa2S4 // CLEO’98, European in Glasgow. CWF39. Pp.253-254), 100-200 MW/cm2 (S.A.Komarow, V.S.Solomatin et al.// Sov.Tech.Phys.Lett. 1980.V.6. pp.375-376).

When using the idea of parameter of quality def2/n3 that normalized depending on an angle of synchronism, according to this criterion, AgGaSe2 /HgGa2S4/ AgGaS2 = 6 : 6 : 1, that is mercury thiogallate is comparable with argentum selenogallate as for efficiency of processes of synchronous conversion (with other things being equal).

The crystals in a system of Hg1-xCdxGa2S4 solid solutions first of all are of interest that the value of birefringence is a function (generally nonlinear) of composition. It opens up widespread opportunities for Hg1-xCdxGa2S4 crystals optimization for a given type of interaction (optimization of phase-matching angles, spectral and angular widths of synchronism etc.). Such procedure allows doubling once more the value of a quality parameter.

Thus the development of the technology for the growth of nonlinear mercury thiogallate and cadmium-mercury thiogallate crystals of high optical quality will allow to create an effective element base for powerful tunable mid- and far IR sources of light pulses. The experience on the growth of nonlinear chalcogenide crystals accumulated in the Laboratory of Novel Technologies enables to hope for the successful solution of the formulated problem.

In opinion of the authors, the Project meets the purposes of ISTC for support of applied research, aimed at creation of element base of devices for environmental monitoring. The powerful tunable mid- and far IR sources of light pulses are undoubtedly such devices.

When performing the project the technology for the growth of HgGa2S4 and Hg1-xCdxGa2S4 crystals with optimal composition for mid- IR OPOs by Bridgeman-Storkbarger technique will be developed.

Collaborators on the project will take part in works on control of optical characteristics of mercury thiogallate and cadmium-mercury thiogallate crystals as well as in approbation of nonlinear components made of these crystals in OPOs.

The growth of the mercury thiogallate and cadmium-mercury thiogallate crystals will be performed in quartz containers by Bridgeman-Stockbarger technique. Exploration of their structural and optical characteristics will be carried out using the installation “Dron-2” and special optical benches. The approbation of nonlinear components will be carried out on the stands of SUE “SPA Astrophysica” and collaborators.

Literature

1. V.V.Badikov, I.N.Matveev, S.N.Pshenichnikov et al. Growth and nonlinear properties of HgGa2S4. // Kvantovaya Elektronika. 1980. V.7. p.2235-2237. (in Russian).

2. S.A.Andreev, N.P.Andreeva, V.V.Badikov et al. Up Conversion in Cdx Hg1-x Ga2S4-type crystals // KiNO’1980. Kiev. Theses of papers. Part I. P. 60-61/ (in Russian).

3. S.A.Andreev, N.P.Andreeva, V.V.Badikov et al. Up Conversion in mercury thiogallate crystals. // Kvantovaya Elektronika. 1980. V.7. P.2003-2006. (in Russian).

4. S.A.Trushin, V.V.Badikov, P.F.Gonzales-Diaz et al. High-energy second harmonic and sum frequency generation in wide-aperture AgGaSe2 crystals with TEA CO2 lasers. // CLEO’95, Baltimore, USA.

5. V.V.Badikov, P.S.Blinov, A.A.Kosterev et al. Effective parametric mid-IR oscillators of picosecond pulses on the base of AgGaS2 crystals. // Kvantovaya Elektronika. 1997. V.24. P.2235-2237.


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