April 18, 2014, Friday, 107

Imaging Spectrometry


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Picture of experimental setup
Picture of experimental setup



Project Summary

In this project we create an imaging spectrometer system based on the polarization-independent Polarization Grating (PG) tunable optical filter. The system is completely polarization independent and shows great potential for low cost and compact implementation.

Motivation for Approach

General depiction of the spectrometer system setup
General depiction of the spectrometer system setup

This project aims to develop an imaging spectrometer system which is insensitive to input polarization and shows strong potential for low-cost, compact implementation. This novel design is based on a tunable optical filter constructed of bilayer polarization gratings (BPGs) whose functionality is completely independent of input polarization (thereby improving resolution and sensitivity compared to competing polarizer-based technology). By enabling more powerful, highly portable (with potential thin-film implementation) imaging spectrometers, this technology can have a significant impact in a wide variety of applications including in-vivo medical imaging, non-invasive real-time diagnostics, remote-sensing for surveillance or defense applications, and microscopy.

The concept of the imaging spectrometer based on the BPG tunable optical filter is depicted in very basic terms in the figure at the right. The key feature of this system is its simplicity. The system has no polarizers, no bulky lens systems, or complex drive electronics. The light source containing the spectral information to be imaged is incident on the BPG tunable filter stack. A simple aperture stop, spatial filter, total-internal-reflection prism, or a multimode fiber collimator blocks the diffracted orders to allow only the zero order beam to pass.

Anticipated Benefits

This spectrometer system will be completely independent of input polarization, which significantly improves resolution and sensitivity as compared to polarizer-based systems. We also show a potential for highly compact (possibly thin film) implementation for applications including medical imaging (real-time diagnostics, in-vivo imaging) and remote sensing (surveillance, defense applications).

Project Publications

  • Portable spectrophotometer based on polarization independent tunable optical filters,Proceedings of the SPIE - Optics & Photonics Conference, vol. 6661, no. 4, pp. TBA, 2007.

Background References

  • R. Komanduri and M.J. Escuti, Elastic continuum analysis of the liquid crystal polarization grating, Physical Review E 76, 2007.
  • J. W. McMurdy et al., Monolithic microspectrometer using tunable ferroelectric liquid crystals, Applied Physics Letters 89, 2006.
  • L. Nikolova and T. Todorov, Diffraction efficiency and selectivity of plarization holographic recording, Optica Acta 31, pp. 579-588, 1984