A Fourier analysis approach for capillary polarimetry

Abstract

A new method of fringe interrogation based on Fourier analysis was implemented and tested for a capillary polarimetry detector. It has significant advantages over the previously employed depth of modulation (DOM) approach, including speed and alignment insensitivity. The new and old methods were compared using a set of interference fringes typically used to facilitate nanoliter volume polarimetric determinations. Polarimetric response was calculated with both methods over the range from 0 degrees to 180 degrees. The results were found to be in good agreement with Malus Law and indicate that an fast Fourier transform (fft) could be used for real-time capillary scale polarimetry in a probe volume of 40 nL.

Absolute Refractive Index Determination by Microinterferometric Backscatter Detection

“…As one increases the refractive index of the liquid in the capillary, the intensity profile shifts toward lower backscatter angles (see Figure ). However, the high-frequency variation component is spatially fixed and does not move as one changes the refractive index in accordance with previous observations 3 CCD camera images of a typical MIBD interference pattern (A, B) and corresponding line profiles (C, D).…”