Abstract
We demonstrate the use of shallow diffraction gratings for quadrature phase interferometry. A single shallow diffraction grating-based Michelson interferometer yields only trivial (0(o) or 180(o) ) phase shift between different output ports. In comparison, a combination of two parallel shallow diffraction gratings can be useful to achieve desired phase shifts (e.g., 90 (o) for quadrature phase interferometry). We show that the phase at different output ports of a grating-pair based interferometer can be adjusted by shearing the two gratings with respect to each other. Two harmonically-related diffraction gratings are used to demonstrate phase shift control at the output ports of a modified Michelson interferometer. Our experimental data is in good agreement with theory.
Highlights
Accurate amplitude and phase measurements of optical signals are important in many applications ranging from metrology [1] to cell biology [2]
Traditional phase-contrast imaging techniques such as Zernike phase [3, 4] and Nomarski differential interference contrast (DIC) [5] render excellent phase contrast images; the phase information is only qualitative in nature
We show that as opposed to a single shallow diffraction grating-based interferometer, a pair of harmonically-related shallow diffraction gratings can be used to realize a modified Michelson interferometer where the phase shifts between different output ports can be adjusted
Summary
Accurate amplitude and phase measurements of optical signals are important in many applications ranging from metrology [1] to cell biology [2]. The phase shift can be adjusted by shearing one grating with respect to the other This approach does not change the path length relationships of the different interference beams within the interferometer – an advantage for metrology [1] and low coherence interferometry applications [20,21,22,23]. This reported method to obtain non-trivial phase shift opens new possibilities for full-field quadrature phase interferometry
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