A novel method to measure refractive index of liquid and curable liquid substances

A novel method to measure refractive index (RI) of liquid and curable liquid substances is presented. Planar microlenses with two refracting interfaces facing each other are fabricated with a planar lightwave circuit technology. A liquid, whose RI is to be determined, is filled between the two refracting surfaces and the width of the beam passing through the lens is measured. By comparing the measured beam width with the analytical results, the RI of the liquid can be determined accurately. This method is applicable for measurements of RI absolute values of almost any liquid or curable liquid substances, and can routinely achieve a precision of 1×10^-4 by using a simple setup with a standard beam profiler. The method easily enables measurements of RI dependences on temperature, wavelength, polarization, etc.