Interferometric Sensor of Wavelength Detuning Using a Liquid Crystalline Polymer Waveplate.

Paweł Wierzba

doi:10.3390/s16050633

Abstract

Operation of a polarization interferometer for measurement of the wavelength changes of a tunable semiconductor laser was investigated. A λ/8 waveplate made from liquid crystalline polymer is placed in one of interferometers’ arms in order to generate two output signals in quadrature. Wavelength was measured with resolution of 2 pm in the wavelength range 628–635 nm. Drift of the interferometer, measured in the period of 500 s, was 8 nm, which corresponded to the change in the wavelength of 1.3 pm. If needed, wavelength-dependent Heydemann correction can be used to expand the range of operation of such interferometer.

Highlights

Liquid crystalline polymers (LCPs) have been used to manufacture several innovative optical components, such as spiral phase plates, patterned polarizers and vortex retarders
A good example is the λ/8 waveplate, which can be used in polarization interferometers measuring displacement or wavelength, especially for operation in the UV-VIS spectral region, where zero-order crystalline waveplates are difficult to produce and expensive
A polarization interferometer using a λ/8 waveplate made from liquid crystalline polymer was demonstrated

Summary

Introduction

Liquid crystalline polymers (LCPs) have been used to manufacture several innovative optical components, such as spiral phase plates, patterned polarizers and vortex retarders. The unique properties of these components have resulted in their use in numerous sensing and metrology areas, such as astronomy, polarimetry, and microscopy (cf e.g., [1,2,3], respectively), enabling the development of new scientific instruments and measurement techniques. A good example is the λ/8 waveplate, which can be used in polarization interferometers measuring displacement or wavelength, especially for operation in the UV-VIS spectral region, where zero-order crystalline waveplates are difficult to produce and expensive. The laser is a part of a measurement system that uses a technique similar to Swept-Source Optical Coherence Tomography (SS-OCT) to investigate properties of liquids. Operating in the wavelength range from 628 nm to 635 nm, the laser provides information about the instantaneous value of the wavelength with uncertainty better than

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