Papers Published

1. Changhuei Yang and Wax, A. and Dasari, R.R. and Feld, M.S., 2π ambiguity-free optical distance measurement with subnanometer precision with a novel phase-crossing low-coherence interferometer, Opt. Lett. (USA), vol. 27 no. 2 (2002), pp. 77 - 9 .
   (last updated on 2007/04/14)

   Abstract:
   We report a highly accurate phase-based technique for measuring arbitrarily long optical distance with subnanometer precision. The method employs a Michelson interferometer with a pair of harmonically related light sources, one cw and the other low coherence. By slightly detuning (~2 nm) the center wavelength of the low-coherence source between scans of the target sample, we can use the phase relationship between the heterodyne signals of the cw and the low-coherence light to measure the separation between reflecting interfaces with subnanometer precision. As this technique is completely free of 2π ambiguity, an issue that plagues most phase-based techniques, it can be used to measure arbitrarily long optical distances without loss of precision. We demonstrate one application of this technique, the high-precision determination of the differential refractive index

   Keywords:
   distance measurement;laser ranging;Michelson interferometers;refractive index measurement;