The interference from Rayleigh and other elastic scattering is a serious intrinsic problem of Raman spectroscopy. This is especially the case with multichannel Raman spectroscopy, in which the spectrometer slits have to be widely opened so that they transmit the dispersed light of the whole spectral region to be detected. The standard multichannel Raman spectrometer therefore adopts a specially designed triple polychromator equipped with a subtractive double-grating filter. This type of polychromator is rather elaborate and needs careful handling because of complicated optical arrangements that include three gratings and at least six mirrors. The throughput of the filter is as low as a few tens of percent and this causes a difficulty if one needs to detect extremely weak light signals, say, in time-resolved resonance Raman spectroscopy. A high-effeciency line-elimination optical filter would solve these problems. Recently, Flaugh et al. demonstrated that a crystalline colloidal array of monodisperse polystyrene spheres was useful for that purpose. In this paper, we propose a simple and convenient line-elimination filter which utilizes an extremely sharp absorption of a J-aggregate of an organic dye molecule.
H. Hamaguchi and K. Kamogawa, "A Convenient Line-Elimination Optical Filter for Multichannel Raman Spectroscopy," Appl. Spectrosc. 40, 564-566 (1986)