arXiv subjects

Santeri Larnimaa

Publications and source records attributed to Santeri Larnimaa.

5 recordsLinked to original sources

arXiv2024

Reference-free dual-comb spectroscopy with inbuilt coherence

We demonstrate a simple system for dual-comb spectroscopy based on two inherently coherent optical frequency combs generated via seeded parametric down-conversion. The inbuilt coherence is established by making the two combs share a common comb line. We show that the inbuilt coherence makes it possible to use a simple numerical post-processing procedure to compensate for small drifts of the dual-comb interferogram arrival-time and phase. This enables long-time coherent averaging of the interferograms.

physics.optics↗

arXiv2024

Vortex-comb spectroscopy

We propose a new Fourier-transform spectroscopy technique based on the rotational Doppler effect. The technique offers an application for optical vortex frequency combs, where each frequency component carries a unique amount of orbital angular momentum (OAM). Here, we emulate a vortex comb using a tunable single frequency laser and a collection of spiral phase plates, generating up to eleven distinct OAM modes. Unlike in traditional Fourier-transform spectroscopy based on the Michelson interferometer (linear Doppler effect), the spectral resolution of vortex-comb spectroscopy is not limited by the mechanical scan distance of the instrument but only by the measurement time. Although the spectrometer requires just one free-running frequency comb, the down-conversion scheme resembles dual-comb spectroscopy, leading to fast mode-resolved measurements.

physics.optics↗

arXiv2022

Photoacoustic phase-controlled Fourier-transform infrared spectroscopy

We demonstrate a 13-fold speed improvement in broadband cantilever-enhanced photoacoustic spectroscopy (CEPAS) by combining it with phase-controlled Fourier-transform spectroscopy (PC-FTS) instead of traditional Fourier-transform infrared spectroscopy (FTIR). PC-FTS is a modification of FTIR and capable of fundamentally faster interferogram acquisitions. The speed-improvement is beneficial for CEPAS, which is an especially sensitive version of the background-free photoacoustic spectroscopy technique. We used the PC-FTS-CEPAS technique to measure the absorption spectrum of methane in the mid-infrared region (3.3$-$3.5 $μ$m) with an optical frequency comb as the light source.

physics.optics↗

arXiv2021

Infrared spectroscopy of radioactive hydrogen chloride H$^{36}\!$Cl

We present the first report of optical absorption spectroscopy of H$^{36}\!$Cl, a radioactive isotopologue of hydrogen chloride. We used Fourier-transform infrared spectroscopy to determine the line center wavenumbers of the fundamental rovibrational band lines P(10)-R(10) and the first overtone band lines P(1)-R(7) with total uncertainty of less than 0.0018 cm$^{-1}$ (60 MHz) and 0.007 cm$^{-1}$ (0.2 GHz), respectively, at 68 % confidence level. We also performed a rotational analysis on the bands to determine the related molecular constants. We further compared the linewidths and relative intensities of the lines to those of the stable isotopologues H$^{35}\!$Cl and H$^{37}\!$Cl. The new spectroscopic information assists in developing optical instrumentation for the detection of H$^{36}\!$Cl.

physics.chem-ph↗

arXiv2020

High-resolution analysis of the ${ν_3}$ band of radiocarbon methane $^{14}CH_{4}$

We present the first high-resolution measurements and rotational analysis of the fundamental asymmetric stretching vibrational band ${ν_3}(F_2)$ of radiocarbon methane. A spectrometer consisting of a mid-infrared continuous-wave optical parametric oscillator and a cantilever-enhanced photoacoustic detector was employed to determine the wavenumbers of 43 rovibrational lines. A spectroscopic model could reproduce all the observed transition wavenumbers within the accuracy of the experiment. Our work contributes to the development of radiocarbon methane detectors based on laser spectroscopy.

physics.chem-ph↗