Determination of the electrooptic coefficients of 3-methyl 4-nitropyridine 1-oxide by an interferometric phase-modulation technique

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Abstract
We present a method for measuring linear electrooptic coefficients involving comparative measurement of interferometric phase-modulation indices at wavelength λ = 6328 Å. The accuracy of the method (8–16%) varies according to the crystalline quality. We have investigated a new nonlinear crystal, 3-methyl 4-nitropyridine 1-oxide. Our single crystals were grown from solution by an evaporation technique. We report some of their physical characteristics and the three electrooptic coefficients: ‖r41‖ = (3.6±0.6)×10−12 m/V; ‖r52‖ = (5.1±0.4)×10−12 m/V; ‖r63‖ = (2.6±0.3)×10−12 m/V. Comparison between second-harmonic generation and electrooptic results is discussed. It is shown that the electronic contribution is preponderant and is about 35% larger than the electrooptic susceptibility. The contribution of intermediate vibrations has therefore a sign opposite to the electronic one and is about four times smaller.