NEAR-INFRARED REFRACTOMETRY OF LIQUIDS BY MEANS OF WAVE-GUIDE CERENKOV 2ND-HARMONIC GENERATION

A new, to our knowledge, method for measuring the refractive index of liquids in the near infrared by means of waveguide Cerenkov second-har monic generation is presented. It makes use of a nonlinear planar wave guide whereby the liquid sample is put into place as the cover. By mea surement of the output angle of the Cerenkov radiation mode (in the vi sible) the Liquid sample refractive index (in the near infrared) is de termined. Experiments were performed by means of a proton-exchanged Li NbO3 waveguide as the sensor and a set of liquids with known refractiv e index. The values obtained are in good agreement with the expected o nes, and the average accuracy is on the third decimal place. (C) 1998 Optical Society of America. OCIS codes: 230.7400, 130.6010.