In this paper, a novel all-fiber online Raman sensor with
significant signal enhancement via Fabry-Perot (FP)
cavity is proposed and demonstrated. The FP cavity
structure is formed by inserting a long-pass coated fiber
and a gold-plated capillary into a silver-lined capillary
with a gap. A corroded single mode fiber is inserted into
the gold-plated capillary to guide the excitation light into
the FP cavity. The multiple reflections of excitation light
in the FP cavity have significantly increased the
interaction volume between the light and the sample.
Experiment results have demonstrated an enhancement
factor of 5 times in the detected Raman signal for ethanol
compared to that is measured using the silver-lined
hollow-core fiber based Raman cell without FP cavity, or
86 times compared with direct detection using bare fiber
tip. The measurement results are in good agreements
with theoretical analyses. This Raman sensor with signal
enhancement via FP cavity has the potential to realize
rapid sample replacement and online detection with high
sensitivity and high accuracy for biochemical
applications.
License type:
http://creativecommons.org/licenses/by-nc-nd/4.0/
Funding Info:
This work was sponsored by National Natural Science Foundation of China (nos. 61875083, 61535005), and Social Development Project of Jiangsu Province (BE2019761).