Measurement of the refractive index (RI) can be used in many applications. Rapid monitoring and detection of ultra-small-volume samples are in great demand. However, accurate RI measurements in nanolitor volumes still present a significant challenge. Here we present a measurement system consists of an optical circuit system, a temperature control system and a CCD detention system. The measurement system extracts the interference fringes based on a microinterferometric backscatter detector (MIBD) by a linear CCD. Relative changes of the fringe pattern with respect to the change in solute concentration (RI). So, we can get the information about the refractive index by probing the position of the fringes with the FFT analysis. Using this method, we have obtained the detection limits of 1.49×10 −7  Δn, corresponding to 8.37×10 −5  g/mL.
['Wenjun Ma', 'Yingchun Ding']
A system of refractive index detection based on microinterferometric backscatter