Index contrast measurement using scanning optical frequency domain reflectometry,” Submitted to OSA

Abstract: We demonstrate direct measurements of local refractive index contrast using a scanning optical frequency domain reflectometer. Measurement results for step index fiber, gradient index fiber, and a volume holographic grating are presented. OCIS codes: (060.2300) Fiber measurements; (180.5810) Scanning microscopy Most conventional methods for measuring refractive index, such as minimum deviation, critical angle, autocollimation, and ellipsometry are well suited for measuring the index of bulk samples or thin films of homogeneous solids or liquids [1]. In general, however, these methods are not well suited to measuring variations of refractive index that occur on length scales of 10−3 to 10−6 m. For characterization of transparent objects with index variations on these small length scales, various methods of phase microscopy are typically used. Traditional techniques such as Zernike phase-contrast microscopy and Nomarski differential interference contrast (DIC) microscopy render transparent phase structures visible, but do not offer a quantitative measure of the refractive index. Efforts towards quantitative phase microscopy, such as quantitative DIC microscopy [2], structured-illumination phase microscopy [3], digital holography [4], and optical coherence tomography [5], provide quantitative measures of optical path length, but not a direct measure of refractive index. For applications such as the characterization of integrated optical devices, fiber measurements, and development of holographic materials, a direct measurement of refractive index variations is needed. We present