Jérôme Debray

Widely tunable optical parametric oscillator in a 5 mm thick 5% MgO:PPLN partial cylinder

A 5 mm thick and 38 mm long 5% MgO-doped periodically poled lithium niobate (MgO:PPLN) cylinder with a grating period of 28 μm has been engineered as a partial cylinder with an angular aperture of 45°. An optical parametric oscillator based on this crystal and pumped at 1.064 μm is reported. The output energy is comparable to that generated in the same kind of sample cut as a slab, but the wavelength tunability from 1.41 to 4.3 μm is much broader and continuous.

Phase-matching properties and refined Sellmeier equations of the new nonlinear infrared crystal CdSiP2.

We directly measured the second harmonic generation and difference frequency generation phase-matching directions of the nonlinear crystal CdSiP(2) until 9.5 μm using the sphere method. The simultaneous fit of the experimental angular data allowed the Sellmeier equations of the ordinary and extraordinary principal refractive indices to be refined over the entire transparency range of the crystal.

Angle noncritical phase-matched second-harmonic generation in the monoclinic crystal BaGa 4 Se 7

We performed a complete study of angle noncritical phase-matched second-harmonic generation in BaGa4Se7 in the mid-infrared region. We measured the dielectric frame orientation and showed that it does not rotate as a function of wavelength. We determined the phase-matching wavelengths and the associated spectral and angular acceptances along the x and y axes of the dielectric frame. We also estimated the magnitude of the nonlinear coefficients involved.

Phase-matching directions, refined Sellmeier equations, and second-order nonlinear coefficient of the infrared Langatate crystal La 3 Ga 5.5 Ta 0.5 O 14

We directly measured phase-matching directions of second harmonic, sum, and difference frequency generations in the Langatate La₃Ga(5.5)Ta(0.5)O₁₄ (LGT) uniaxial crystal. The simultaneous fit of the data enabled us to refine the Sellmeier equations of the ordinary and extraordinary principal refractive indices over the entire transparency range of the crystal, and to calculate the phase-matching curves and efficiencies of LGT for infrared optical parametric generation.

High-power, widely tunable, room-temperature picosecond optical parametric oscillator based on cylindrical 5%MgO:PPLN.

We report a high-power picosecond optical parametric oscillator (OPO) based on cylindrical MgO:PPLN synchronously pumped by an Yb-fiber laser. The singly resonant OPO is tunable in the near-infrared signal across 1413-1900 nm and mid-infrared idler over 2418-4307 nm by angle tuning of the crystal at room temperature. With non-optimized output coupling of ∼10%, the OPO simultaneously delivers 2.4 W of signal at 1664 nm and 1.7 W of idler at 2950 nm at an overall extraction efficiency of ∼45% with high beam-pointing stability <30  μrad and <14  μrad for the signal and idler, respectively. The generated signal and idler exhibit passive power stability better than 1% rms and 0.8% rms over 15 h, respectively, in high beam quality with TEM(00) profile. The extracted signal pulses from the OPO have duration of 15.2 ps with a spectral bandwidth of 0.7 nm, corresponding to a time-bandwidth product of ΔυΔτ∼1.2.

Dual-wavelength source from 5%MgO:PPLN cylinders for the characterization of nonlinear infrared crystals

We conceived a unique fully parametric source based on two independent cylindrical OPOs simultaneously pumped by the same Nd:YAG laser. Each OPO delivers more than 2 mJ and is continuously tunable between 1.41 µm and 4.3 µm. This source is of particular interest for the study of the generation of infrared parametric light in nonlinear crystals. It was validated by performing difference frequency generation experiments in CdSe crystals with output in the range 8 - 10 µm.

Irreversibility of the martensitic transformation in Ni-Mn-In single crystal studied by resistivity under pressure and in situ optical observations

Optical observations under uniaxial pressure and in-situ resistivity measurements were undertaken in Ni-Mn-In single crystals as a function of temperature to study the thermal hysteresis of the martensitic transformation. The irreversibility of the isothermal transformation under pressure was clearly observed, and it was possible to stabilize the martensitic phase with large and coarsen variants by applying a pressure at a stable temperature Ms reached during cooling down (cooling branch of the hysteresis). When the uniaxial pressure is applied in the heating branch of the hysteresis, the martensitic transformation occurs in a complete reversible way as the hysteresis delimitates the metastability of the martensitic/austenitic phases and the energy barrier to overcome for the transformation. This procedure leads to a piezoresistance as large as 200%.

Dielectric frame, Sellmeier equations, and phase-matching properties of the monoclinic acentric crystal GdCa 4 O(BO 3 ) 3

We directly measured the phase-matching properties of the biaxial GdCa4O(BO3)3 (GdCOB) crystal using the sphere method. We studied second-harmonic generation and difference frequency generation in two principal planes of the crystal. All these data allowed us to refine the Sellmeier equations of the three principal refractive indices. These equations are valid over the entire transparency range of GdCOB and then could be used to calculate the tuning curves of infrared optical parametric generation.

Bulk cylinders and spheres: from shaping to the use for linear and nonlinear optics

Bulk crystals cut and polished as spheres or cylinders are unique tools for measuring the angular distribution of any linear or nonlinear optical property as well as for designing widely and continuously tunable parametric devices. The aim of this article is to describe the specific techniques of shaping such high quality samples, and their use in methods of optical measurements and devices that we implemented.

Validation of the angular quasi-phase-matching theory for the biaxial optical class using PPRKTP

We report the first experimental validation of angular quasi-phase-matching (AQPM) theory in a biaxial crystal by performing second-harmonic generation (SHG) in the periodically-poled Rb-doped KTiOPO4 (PPRKTP) crystal cut as a sphere. Both AQPM and birefringence phase-matching (BPM) angles were measured thanks to a Kappa circle.