High-precision broadband measurement of refractive index by picosecond real-time interferometry

The refractive index is one of the most important quantities that characterize a material's optical properties. However, it is hard to measure this value over a wide range of wavelengths. Here, we demonstrate a new technique to achieve a spectrally broad refractive index measurement. When a broadband pulse passes through a sample, different wavelengths experience different delays. By comparing the delayed pulse to a reference pulse, the zero path difference position for each wavelength can be obtained and the material's dispersion can be retrieved. Our technique is highly robust and accurate, and can be miniaturized in a straightforward manner.