Near-infrared refractometer for liquids based on Cerenkov second-harmonic generation

Summary form only given. Accurate measurement of the refractive index of liquids is gaining great importance. Many methods have been proposed but few of them have been extended to the infrared range. We propose a new method in the near-infrared range exploiting Cerenkov second-harmonic generation from a planar nonlinear waveguide. The advantages of our method are (i) the determination of the refractive index of the liquid in the infrared while making measurements on a visible beam, (ii) the compactness of the integrated optics technology, (iii) the simplicity of the measurement technique, and (iv) the need for just a few drops of liquid per measure. The experiments have shown that the method proposed allows the determination of the refractive index of liquids in the near-infrared with a straightforward procedure. The accuracy of the method can be further improved by using waveguides on substrates with a refractive index nearer to that of the sample.