A. Maillard

Nonlinear optical properties of Ca 5 (BO 3 ) 3 F crystal

A high quality Ca5(BO3)3F (CBF) crystal, grown by flux method, was investigated for its non linear optical properties. This material is non hygroscopic and possesses a moderate birefringence suitable for UV light generation. On the basis of its refractive index dispersion curves, it is inferred that CBF has great potential applications as non linear optical material, notably for UV light generation at 355 and 266nm. In order to characterize its non linear optical properties, CBF samples were first cut and oriented in phase matching conditions for second harmonic generation of 1064nm. Experimental results demonstrate that CBF has the moderate NLO coefficients. The optical conversion efficiency from 1064nm to 532nm was investigated for the first time: up to 54% were achieved. Non linear deff coefficients were also estimated as well as the external angular acceptance bandwidth of SHG at 1064nm.

Absolute non-linear optical coefficients measurements of BBO single crystal and determination of angular acceptance by second harmonic generation

Abstract We report second harmonic generation measurements of a continuous Nd-YAG laser beam propagating in a β barium metaborate (β-BaB 2 O 4 ) crystals cut in the type I and type II phase matching directions. The absolute values of the effective non-linear optical coefficients d eff I and d eff II are determined by measuring conversion efficiency and the d 22 and d 31 coefficients involved in d eff developments coefficients are deduced. Experimental and theoretical investigations of the BBO angular acceptance for different focusing conditions, lengths of crystal and phase matching conditions are comparatively presented. On the basis of the perfect agreement reached, an extrapolation of the angular acceptance is proposed for crystal lengths from 0.1 to 10 mm and waist sizes from 20 to 200 μm.

Raman scattering and non-linear optical properties in Li2B4O7

A complete Raman scattering study on a lithium tetraborate single crystal is reported. The frequency and scattered intensity of Raman modes are carefully determined in the various geometrical configurations. These Raman data are then used to relate to the electro-optical and non-linear optical properties. Raman scattering efficiencies of A1(a), A1(b) and E phonons are consistent with the values of the EO coefficients r13, r33 and r51 respectively.

Absolute non-linear optical coefficients of LiNbO3 for near stoichiometric crystal compositions

Abstract We present absolute measurements of the effective non-linear optical coefficients d eff of two lithium niobate crystals by second harmonic generation using a continuous Nd-YAG laser source. The experiments were carried out at room temperature, on crystals containing 49.6 and 49.96 mol% Li 2 O respectively and cut perpendicular to type I phase matching directions. For each composition, two configurations were studied with light propagating in the xz and yz planes, respectively, characterized by different combinations d eff of the non-linear optical coefficients. The d 31 and d 22 values, deduced from these d eff measurements are shown to be very sensitive to the crystal composition.

Crystal defects revealed by Schlieren photography and chemical etching in nonlinear single crystal LYSB

Large single crystals of a nonlinear optical material LaxYyScz(BO3)4 have been obtained by High Temperature Top-Seeded Solution Growth (HTTSSG). This material is very interesting due to its easy growth procedure, its non hygroscopic properties, a suitable hardness to be reliably cut and polished, a large transparency wavelength range and also good nonlinear properties with potential for UV generation. However, the crystals show inhomogeneities and growth imperfections which can be observed by light scattering and by Schlieren photography method. Chemical etching is used to reveal defects. Observed striations can be related to the growth of rhombohedral facets.

Considerations of Angular Acceptance and Non-Linear Optical Coefficient Measurements by Second Harmonic Generation in LiNbO3 Crystals

We propose in the present work second harmonic generation (SHG) measurements on near stoichiometric crystals with a composition of 49.96 mol% Li2O. These experiments are carried out with a continuous Nd-YAG laser, at room temperature. Samples are cut perpendicular to the type I phase matching direction, with two different configurations of light propagation planes and with two different lengths. The corresponding absolute non-linear effective coefficients and therefore the d31 and d22 coefficients, are deduced from SHG efficiency measurements. By recording the SHG efficiency as function of the variation of angle around the phase matching direction, the angular acceptance measured for the different crystal lengths and incident beam waist sizes is shown to be dependent on experimental conditions. A theoretical interpretation is given and an extrapolation to other crystal lengths and beam waist sizes is proposed.

Absolute Effective Non-Linear Coefficient and Angular Acceptance Measurements in LTB by Second Harmonic Generation

The non-linear optical properties of pure and MgO-doped lithium tetraborate (Li2B4O7, LTB) are studied by second harmonic generation (SHG) using a continuous Nd:YAG laser. The non-linear effective coefficients, deff, are measured absolutely and compared for pure and MgO doped LTB crystals both cut for type I phase matching. The d31 coefficient of both crystals are deduced. The dependence of the frequency conversion efficiency is measured as function of the deviation from the phase matching direction. The angular acceptance is deduced from these experimental data and discussed on the basis of theoretical calculation implying the gaussien beam approximation.

Experimental determination of the electro-optic coefficients in BaTiO3:Rh at 633 nm and 850 nm

The absorption spectrum of BaTiO3:Rh is measured from 400 nm to 1100 nm, there is strong absorption peak (α = 7 cm−1 at 633 nm) while at 850 nm the absorption is rather weak: α = 2 cm−1. Then, we propose an experimental investigation of the EO coefficients, for two different wavelengths corresponding to strong and weak absorption, based on an interferometric and ellipsometric assembly using application of a static electric field and leading to the measurement of the coefficients r13 and r33 separately and the linear combination rc.

Frequency Behaviour of Dielectric Constants of Raw and Reduced Li2B4O7 (LTB)

An investigation of the dielectric constant according to the frequency (20 Hz and 1 GHz) for as-grown and reduced samples of lithium tetraborate (LTB) is done. Anisotropy of ϵ′ and ϵ″ at low frequency decreases by reducing crystal then at frequency higher the 104 Hz the reduced state does not affect ϵ. The disappearance of relaxations in both real and imaginary part of ϵx in as-grown LTB, shows the unidirectional conductivity of the lithium ions along the ‘Z’ axis. When the samples are reduced we notice the appearance of relieving in the imaginary and real parts of ϵx and an increase in these relaxations for the two components of ϵz, that shows the appearance of a new mechanism of conduction in two directions X and Z other than that of lithium.