Kavli Affiliate: Alireza Marandi
| First 5 Authors: Mingchen Liu, Robert M. Gray, Arkadev Roy, Charles R. Markus, Alireza Marandi
| Summary:
Dual-comb spectroscopy has been proven a powerful tool in molecular
characterization, which remains challenging to implement in the mid-infrared
(MIR) region due to difficulties in the realization of two mutually locked comb
sources and efficient photodetection. An effective way to overcome those
limitations is optical upconversion; however, previously reported
configurations are either demanding or inefficient. Here we introduce and
experimentally demonstrate a variant of dual-comb spectroscopy called
cross-comb spectroscopy, in which a MIR comb is upconverted via sum-frequency
generation (SFG) with a near-infrared (NIR) comb with a shifted repetition rate
and then interfered with a spectral extension of the NIR comb. We
experimentally demonstrate a proof-of-concept measurement of atmospheric CO2
around 4.25 micrometer, with a 350-nm instantaneous bandwidth and 25000
resolved comb lines. Cross-comb spectroscopy can be realized using up- or
down-conversion and offers an adaptable and efficient alternative to dual-comb
spectroscopy outside the well-developed near-IR region, where having two
mutually coherent sources and efficient photodetection is challenging.
Moreover, the nonlinear gating in cross-comb spectroscopy promises a superior
dynamic range compared to dual-comb spectroscopy.
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