D. Haertle

Refractive indices of Sn2P2S6 at visible and infrared wavelengths

We report on the refractive indices of Sn2P2S6 crystals in the wavelength range 550 - 2300 nm. The measurements are performed at room temperature using the minimum deviation method. The dispersion is described by a two oscillator model yielding the oscillator energies and strengths (Sellmeier parameters) for all polarization directions. The rotation of the indicatrix in the mirror plane and the direction of the optical axes have also been determined in the wavelength range lambda= 550-2200 nm.

Nonlinear optical coefficients and phase-matching conditions in Sn 2 P 2 S 6

Phase matching conditions and second and third order nonlinear optical coefficients of Sn2P2S6 crystals are reported. The coefficients for second harmonic generation (SHG) are given at lambda = 1542 nm and 1907 nm at room temperature. The largest coefficients at these wavelengths are d111 = 17+/-1.5pm/V and d111 = 12+/-1.5pm/V, respectively. The third-order subsceptibilities chi(3) 1111 = (17 +/- 6) . 10-20m2/V2 and chi(3) 2222 = (9 +/- 3) . 10-20m2/V2 were determined at lambda = 1907 nm. All measurements were performed by the Maker-Fringe technique. Based on the recently determined refractive indices, we analyze the phase-matching conditions for second harmonic generation, sum- and difference-frequency generation and parametric oscillation at room temperature. Phase-matching curves as a function of wavelength and propagation direction are given. Experimental phase-matched type I SHG at 1907 nm has been demonstrated. The results agree very well with the calculations. It is shown that phase-matched optical parametrical oscillation is possible in the whole transparency range up to 8 microm with an effective nonlinear coefficient deff approximately 4pm/V.

Optical and Electro-Optical Properties of Sn 2 P 2 S 6

We report on the rotation of the indicatrix in the mirror plane and the refractive indices of Sn₂P₂S₆ single crystals in the wavelength range 550-2200 nm at room temperature. Electro-optical properties of Sn₂P₂S₆ were also measured by direct interferometric technique for electric fields applied parallel to the crystallographic x-axis that lies near the spontaneous polarization vector. The room temperature free electro-optical coefficient r₁₁₁ ^T reaches 174plusmn10 pm/V at lambda=633 nm and shows only weak dispersion in the wavelength range between lambdaap0.6... 1.3mum. The temperature dependence of the electro-optical coefficients near the structural phase transition at T_C=65degC is well described by a Curie-Weiss law with a peak value r₁₁₁ ^Tcong4500 pm/V

Interband photorefraction in Sn 2 P 2 S 6 at visible wavelengths

Continuous-wave photorefractive experiments in Sn2P2S6 crystals and interband photorefraction at the visible wavelengths of 514 and 488 nm are presented. Two-wave mixing and Bragg diffraction measurements at 514 nm show grating response times of around 100 μs at moderate light intensities of 0.6 W/cm2, i.e., 2 orders of magnitude faster than measured in the same crystal in the conventional photorefractive regime. A large two-wave mixing gain of up to Γ=60±8 cm−1 is measured, and holes are identified as dominant charge carriers for the interband photorefractive effect.

Sn2P2S6 Crystals for Fast Near-Infrared Photorefraction

Optical and physical properties of Sn 2 P 2 S 6 ferroelectric crystals suitable for photorefractive applications in the red and near-infrared spectral range are reported. The main advantage of Sn 2 P 2 S 6 is its high beam-coupling gain combined with considerably faster response in the near infrared compared to conventional oxide-type photorefractive materials. We show that modifying the growth conditions and doping with Te can efficiently improve the photorefractive properties of Sn 2 P 2 S 6 . Photorefractive two-beam coupling gain at 860 nm increases from about 2 cm − 1 in conventional “yellow” Sn 2 P 2 S 6 to about 7 cm − 1 in Te-doped samples and 14 cm−1 in modified “brown” samples. We examine the self-pumped optical phase conjugation properties of Sn 2 P 2 S 6 in a ring-cavity scheme. Phase-conjugate signals with amplitudes close to the theoretical limit and rise times of about 10 ms for 4 W/cm 2 pump intensity at 780 nm and 50 ms for 2.5 W/cm 2 pump intensity at 860 nm are obtained. *Present Address: Laboratoire Matériaux Optiques, Photonique et Systèmes (LMOPS), University of Metz and Supélec, F-57070 Metz, France.

Optical and Electro-Optical Properties of Sn2P2S6

We report on the rotation of the indicatrix in the mirror plane and the refractive indices of Sn₂P₂S₆ single crystals in the wavelength range 550-2200 nm at room temperature. Electro-optical properties of Sn₂P₂S₆ were also measured by direct interferometric technique for electric fields applied parallel to the crystallographic x-axis that lies near the spontaneous polarization vector. The room temperature free electro-optical coefficient r₁₁₁ ^T reaches 174plusmn10 pm/V at lambda=633 nm and shows only weak dispersion in the wavelength range between lambdaap0.6... 1.3mum. The temperature dependence of the electro-optical coefficients near the structural phase transition at T_C=65degC is well described by a Curie-Weiss law with a peak value r₁₁₁ ^Tcong4500 pm/V

High Rate Vander Lugt and Joint Fourier Transform Correlators

Compared to electronic systems, optical correlators are potentially faster because processing is performed in a single parallel step. Here we demonstrate correlation rates of 10.000 correlations/s using two different approaches.

Optical and Electro-Optical Properties of Sn>inf /inf inf /inf inf /inf<

We report on the rotation of the indicatrix in the mirror plane and the refractive indices of Sn₂P₂S₆ single crystals in the wavelength range 550-2200 nm at room temperature. Electro-optical properties of Sn₂P₂S₆ were also measured by direct interferometric technique for electric fields applied parallel to the crystallographic x-axis that lies near the spontaneous polarization vector. The room temperature free electro-optical coefficient r₁₁₁ ^T reaches 174plusmn10 pm/V at lambda=633 nm and shows only weak dispersion in the wavelength range between lambdaap0.6... 1.3mum. The temperature dependence of the electro-optical coefficients near the structural phase transition at T_C=65degC is well described by a Curie-Weiss law with a peak value r₁₁₁ ^Tcong4500 pm/V

Optical phase conjugators for near-infrared lasers using Sn/sub 2/P/sub 2/S/sub 6/

We examine the self-pumped optical phase conjugation properties of Sn/sub 2/P/sub 2/S/sub 6/ in a ring-cavity scheme. We investigate also the influence of new dopands and oxidation/reduction treatment on the photorefractive properties of Sn/sub 2/P/sub 2/S/sub 6/ crystals. Further improving of the relevant parameters by modifying Sn/sub 2/P/sub 2/S/sub 6/ crystal growth parameters and dopands is expected.

Optical and electro-optical properties of Sn/sub 2/P/sub 2/S/sub 6/

Tin thiohypodiphosphate (Sn/sub 2/Pn/sub 2/S/sub 6/) is a wide bandgap semiconductor ferroelectric with interesting nonlinear optical properties and large electro-optical coefficients. In addition it is also a very attractive photorefractive material showing fast photorefractive grating recording times and large refractive index change in the red and near infrared spectral region. These properties make Sn/sub 2/Pn/sub 2/S/sub 6/ an interesting material for several applications where laser diodes are employed (laser stabilization, beam cleanup, optical phase conjugation). The wide optical transparency range extending from /spl lambda/=0.53 /spl mu/m to /spl lambda/=8 /spl mu/m also allows optical parametric generation of infrared wavelengths not accessible with standard nonlinear optical crystals.