PolSpec: polarisation-based detection for spectral classification of optical signals

Spectrally resolved imaging is typically realised using bandpass filters, which are inefficient when they reject "out-of-band" photons or using angularly dispersive devices with at least one image dimension requiring scanning to acquire a full hyperspectral dataset and therefore sequential data acquisition, unless cascades of dichroic beamsplitters are employed, for which cost and experimental complexity scale with the number of spectral channels. Here we present a new approach, "PolSpec", to realise rapid and flexible widefield hyperspectral imaging with lower cost and complexity using polarisation optics instead of dielectric coatings or dispersive devices. PolSpec utilises Lyot filters that provide continuously varying transmission across the desired spectral range to generate orthogonal "spectral modulation vectors" that can represent specific spectral signatures with significantly lower data volumes than full spectral profiles. We demonstrate single-shot widefield hyperspectral imaging using a polarisation-resolving camera and rapid, electronically reconfigurable, more photon efficient, hyperspectral imaging using a liquid crystal variable retarder.