Raman Hyperspectral Imaging Spectrometer Utilizing Crystalline Colloidal Array Photonic Crystal Diffraction

We fabricated a novel hyperspectral Raman imaging spectrometer that, for the first time, uses a photonic-crystal wavelength-selecting device to select a narrow-wavelength spectral interval. The photonic crystal consists of an array of highly charged, monodisperse polystyrene particles that self-assemble into a face-centered cubic crystal. The photonic crystal Bragg-diffracts a narrow spectral interval that can be tuned by altering the incident angle of collimated Raman scattered light. Our prototype spectrometer diffracts a ∼200 cm⁻¹ interval of the 488 nm excited visible Raman spectrum of Teflon. This enabled us to select a close-lying triplet of Teflon Raman bands. We imaged the Teflon surface by focusing this narrow region onto a charge-coupled device to create a Raman image of the sample surface that spectrally details the chemical composition.