Premium
Lock‐in detection in Raman spectroscopy with charge‐shifting CCD for suppression of fast varying backgrounds
Author(s) -
Sowoidnich Kay,
Towrie Michael,
Matousek Pavel
Publication year - 2019
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.5597
Subject(s) - raman spectroscopy , charge coupled device , optoelectronics , reproducibility , optics , materials science , interference (communication) , analytical chemistry (journal) , chemistry , computer science , physics , telecommunications , chromatography , channel (broadcasting)
The susceptibility to unwanted light interference significantly limits the potential of Raman spectroscopy by often restricting its applications to environments with controlled ambient light exposure. To overcome this issue, which is particularly relevant to portable, in‐field Raman instrumentation, we present an approach based on fast optical lock‐in detection using a charge‐shifting charge‐coupled device operation, with charge retention on the chip, for the rejection of varying ambient light interference. In proof‐of‐concept experiments we used polytetrafluoroethylene as a test sample and Raman spectra were recorded at 830‐nm excitation in the presence of fluorescent or incandescent ambient light. Results demonstrate that the charge‐shifting read‐out mode (carried out at 1,000 Hz) has a significant benefit over conventional read‐out (limited in practice often to ≲ 10 Hz) in terms of the removal of dynamically changing ambient light background contributions from Raman spectra. Library‐based spectral matching revealed superior reconstruction performance and improved reproducibility for individual spectra obtained using the charge‐shifting mode, particularly for interfering lights with spectrally narrow lines and spatially inhomogeneous emission profiles. The approach overcomes fundamental technical limitations of conventional charge‐coupled device operation and is of particular benefit to mobile Raman systems used in the field in the presence of dynamically changing background light conditions.