Holographically formed polymer dispersed liquid crystal films for transmission mode spectrometer applications

We show proof of concept of a transmission-mode wavelength filtering device consisting of layered holographically formed polymer dispersed liquid crystal (H-PDLC) cells. H-PDLC cells were fabricated from a thiolene based polymer composite to have transmission notches in the near-IR wavelength range. Wavelength filtering was achieved by stacking four H-PDLC cells with transmission notches spaced at 10 nm intervals. Results show a broad transmission notch spanning the spectral width of the constituent cells. With bias applied to an individual cell within the stack, the transmission notch of the cell inverts and the overall transmission envelope changes shape. Using a transmitted energy sensing device and a lineshape mapping algorithm, spectral content can be determined to a resolution of 0.1 nm for narrow banded signals. Applications for this switchable wavelength filtering device include serial detection of spectral content for telecom data signals or chemical and biological sample identification through absorption or emission spectroscopy.