Open AccessCompact conical beam shaper and freeform segmented reflector for SERS analysis
Author(s) -
Qing Liu,
Michael Schmidt,
Hugo Thienpont,
Heidi Ottevaere
Publication year - 2020
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.391623
Subject(s) - optics , conical surface , reflector (photography) , materials science , numerical aperture , aperture (computer memory) , lens (geology) , beam (structure) , raman scattering , raman spectroscopy , physics , acoustics , wavelength , light source , composite material
We present a Raman spectroscopy setup containing a conical beam shaper in combination with a freeform segmented reflector for surface enhanced Raman scattering (SERS) analysis. The freeform segmented reflector and the conical beam shaper are designed by numerical approaches and fabricated by means of ultra-precision diamond tooling. The segmented reflector has a numerical aperture of 0.984 and a working distance of 1mm for SERS measurements. We perform systematic simulations using non-sequential ray tracing to assess the detecting abilities of the designed SERS-based system. We implement a proof-of-concept setup and demonstrate the confocal behavior by measuring the SERS signal of 10µM rhodamine B solution. The experimental results agree well with the simulations concerning the misalignment tolerances of the beam shaper with respect to the segmented reflector and the misalignment tolerances of the collecting fiber. In addition, we conduct benchmark SERS measurements by using a 60× objective lens with a numerical aperture of 0.85. We find that the main Raman intensity of rhodamine B at 1502 cm -1 obtained by our segmented reflector working together with the conical beam shaper is approximately 30% higher compared to the commercial objective lens.