Affiliation:
1. University of Applied Sciences and Arts Northwestern Switzerland
2. Mems AG
3. vario-optics AG
Abstract
In this contribution, we present the development of a passively
demodulated interferometer based on
3
×
3
waveguide couplers to measure light
absorption of trace gases and aerosol particles via the photothermal
effect. In contrast to a “classical” interferometer with
two outputs, active quadrature control is not required to ensure a
high sensitivity of the system. An algorithm for the evaluation of the
photothermal interferometry signal from the outputs of asymmetric
3
×
3
couplers is detailed. The performance
of the algorithm is demonstrated with
N
O
2
calibration experiments using
couplers with different working principles (i.e., fused-fiber
and planar-waveguide based). The results of a laboratory measurement
campaign using aerosolized nigrosin are discussed, and the measured
aerosol absorption is compared to a reference instrument. A noise
analysis shows interferometer phase noise to be the primary noise
component. Improvements to the setup are recommended, which should
improve the current instrumental detection limit in terms of
absorption coefficient to below the current value of
100
M
m
−
1
(
1
σ
, 60 s). This corresponds to
mass concentrations of about
10
µ
g
/
m
3
for submicrometer-size black carbon
particles.
Funder
H2020 Research and Innovation
Programme
Innosuisse–Swiss Innovation
Agency
Subject
Atomic and Molecular Physics, and Optics,Engineering (miscellaneous),Electrical and Electronic Engineering
Cited by
1 articles.
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