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Abstract Faraday rotation spectroscopy and absorption spectroscopy are performed simultaneously in a dual comb spectroscopy arrangement with quantum cascade laser combs operating at ∼8μm. The system uses free-running laser combs that provide ∼70 cm−1spectral coverage and ∼2 MHz spectral resolution. Detection of NO2in an equilibrium mixture with N2O4and N2O is used to demonstrate selective measurements of paramagnetic NO2in the presence of spectrally interfering diamagnetic species.
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Digitally controlled optical sampling in dual-comb spectroscopy
Dual-comb spectroscopy (DCS) is a powerful method for the characterization of materials. It enables the rapid measurements of broad absorption spectra with high spectral resolution. However, dual-comb spectroscopy has a low duty cycle especially when used to study semiconductor materials whose excited states’ dephasing rates are much shorter than the spacing between the comb pulses. When DCS is applied to these systems, a vast majority of energy and acquisition time is wasted. Here, we demonstrate a simple approach that can aid efforts to solve this issue. In our approach, we use two frequency combs that have the same repetition frequencies and we digitally control the relative locking phase between the combs. This allows us to control the delay with very high precision and take the data rapidly and continuously only in the region where the signal is non-zero. We demonstrate the concept on a Neodymium-doped yttrium orthovanadate (Nd:YVO4) sample. We show that, we could scan the delay between the signal and local oscillator comb pulses up to ∼ 6 ps in under 150 µs. We compare an absorption spectrum of (Nd:YVO4) obtained using our approach to an absorption spectrum obtained using conventional DCS and they are in good agreement. This approach now makes DCS relevant for a wide range of materials.
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- Award ID(s):
- 2235597
- PAR ID:
- 10577477
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Optics Continuum
- Volume:
- 4
- Issue:
- 3
- ISSN:
- 2770-0208
- Format(s):
- Medium: X Size: Article No. 571
- Size(s):
- Article No. 571
- Sponsoring Org:
- National Science Foundation
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