© 2026 Aqora Quantum S.A.S.

Terms Privacy Legal Notice

Optica

Ultra-broadband quantum infrared spectroscopy

Toshiyuki Tashima, Yu Mukai, Masaya Arahata, N. Oda, Mamoru Hisamitsu, Katsuhiko Tokuda, Ryo Okamoto, Shigeki Takeuchi

Published Dec 4, 2023• 43 citations

Abstract

Spectroscopy in the mid-infrared region is an indispensable tool for identifying molecular types in various fields, including physics, chemistry, and medical sciences. However, conventional infrared light sources, detectors, and noise from blackbody radiation have been the obstacles to miniaturization and higher sensitivity of infrared spectrometers. Quantum infrared spectroscopy, which uses visible and infrared photon pairs in a quantum entangled state, has attracted attention as a new sensing technology that enables infrared spectroscopy with detectors in the visible range. However, the bandwidth of conventional quantum entangled light sources is at most 1 µm or less, which hinders broadband measurements, which are important in spectroscopic applications. Here we have realized an ultra-broadband entangled state of visible–infrared photons with wavelengths from 2 to 5 µm, harnessing a specially designed nonlinear crystal with chirped poling structure inside. Furthermore, we constructed a nonlinear quantum interferometer using the ultra-broadband quantum entangled photons and realized broadband infrared spectroscopy of inorganic and organic materials using a visible detector made of silicon. Our results show that quantum infrared spectroscopy can achieve ultra-broadband spectroscopic measurements and pave the way for the highly sensitive, ultra-compact infrared spectrometers using quantum entangled photons.

DOI: 10.1364/optica.504450

Related papers

High resolution Fourier-transform mid-infrared spectroscopy using nonlinear interferometers

Jachin Kunz, Chiara Lindner, Simon J. Herr +3 more

Nonlinear interferometers based on correlated photon pairs allow mid-infrared spectroscopy by measuring only near-infrared photons with a silicon-based detector, which offers higher detectivities than mid-infrared detectors. Here, we use the nonlinear interferometer not only to determine the transmission of a sample but also for spectral analysis - analogue to classical Fourier transform infrared (FTIR) spectrometers. The Quantum FTIR analyzes the absorption of gas mixtures with high spectral resolution over a broad mid-infrared wavelength range. Improved emission rates of the photon pair source yield sensitivities similar to a classical FTIR despite an extremely low light exposure on the sample.

Optical and Quantum Sensing and Precision Metrology II•Mar 8, 2023•1 citation

Broadband infrared light source by simultaneous parametric down-conversion

Masayuki Hojo, Kōichiro Tanaka

Spontaneous parametric down-conversion is an essential tool for a quantum light source in the infrared region ranging 2-5 µm for the purpose of material identification, chemical analysis, and gas sensing. So far, photon pairs from the process in a nonlinear crystal have low tunability and a narrow spectral range because of the phase-matching condition. Here, we propose a novel type of spontaneous parametric down-conversion processes that overcomes these challenges, where two photon pairs are simultaneously produced in the visible and infrared regions in periodically poled stoichiometric lithium tantalite. It allows broadband and tunable generation of infrared photon pairs that can be employed as an alternative light source for quantum infrared spectroscopy.

Scientific Reports•Sep 9, 2021•16 citations

Nonlinear interferometers for Fourier-transform infrared spectroscopy with visible light

Chiara Lindner, Jachin Kunz, Sebastian Wolf +2 more

Nonlinear interferometers based on non-degenerate spontaneous parametric down-conversion (SPDC) create a link between separate spectral ranges. This allows for measurements in remote spectral regions while detecting light in easily accessible wavelengths. In our work, we use periodically poled lithium niobate to create correlated signal (visible or near-infrared) and idler (mid-infrared) photon pairs. Using a nonlinear interferometer in Michelson geometry, we obtain broadband mid-infrared spectra from light detected with a silicon avalanche photodiode. Combining the nonlinear interferometer with a measurement scheme in close analogy to classical Fourier-transform infrared spectroscopy allows for sub-wavenumber spectral resolution, which opens up possibilities for applications such as precise spectroscopic gas analysis.

Nonlinear Frequency Generation and Conversion: Materials and Devices•Mar 4, 2021•0 citations

Spectral resolution of quantum Fourier transform infrared spectroscopy using pulsed laser excitation

Jasleen Kaur, Yu Mukai, Ryo Okamoto +1 more

In recent years, nonlinear quantum interferometry has been widely explored for applications like spectroscopy, optical coherence tomography, and imaging [1]. Quantum infrared spectroscopy (QIRS) uses quantum interference of generation processes of frequency-entangled visible-IR photon pairs to perform infrared spectroscopy using visible light sources and silicon-based detectors [2]. This technique utilizes a nonlinear quantum interferometer configuration where the generated IR photons pass through the sample, and the correlated visible photons are detected. The change in the detected visible photon flux with and without the sample helps extract the complex transmittance of the sample in the IR region.

JSAP-OSA Joint Symposia•Jan 1, 2024•0 citations

Quantum Fourier-transform infrared spectroscopy in the fingerprint region

Yu Mukai, Ryo Okamoto, Shigeki Takeuchi

Infrared quantum absorption spectroscopy is one of the quantum sensing techniques, by which the infrared optical properties of a sample can be estimated through visible or near infrared photon detection without need for infrared optical source or detector, which has been an obstacle for higher sensitivity and spectrometer miniaturization. However, experimental demonstrations have been limited to wavelengths shorter than 5 µm or in the terahertz region, and have not been realized in the so-called fingerprint region of 1500–500 cm−1 (6.6 to 20 µm), which is commonly used to identify chemical compounds or molecules. Here we report the experimental demonstration of quantum Fourier-transform infrared (QFTIR) spectroscopy in the fingerprint region, by which both absorption and phase spectra (complex spectra) can be obtained from Fourier transformed quantum interferograms obtained with a single pixel visible-light detector. As demonstrations, we obtained the transmittance spectrum of a silicon wafer at around 10 µm (1000 cm−1) and complex transmittance spectrum of a synthetic fluoropolymer sheet, polytetrafluoroethylene, in the wavelength range of 8 to 10.5 µm (1250 to 950 cm−1), where absorption due to stretching modes of C-F bonds is clearly observed. These results open the way for new forms of spectroscopic devices based on quantum technologies.

arXiv:2110.14247•Optics Express•May 24, 2022•69 citations

On-chip mid-infrared spectroscopy without mid-infrared photons

Boyi Xue, Renhong Gao, Yicheng Zhu +7 more

Mid-infrared (mid-IR) spectra revealing the distinct “fingerprint” of molecules are of critical importance for both science and technology in chemistry, physics, materials science, and biology. Mid-IR sensing and spectroscopy provide unique and powerful tools for crucial applications in greenhouse gas monitoring, hazardous emission detection, and medical breath diagnosis. However, the low-photon energy characteristic of the mid-IR spectrum poses significant challenges for both mid-IR light sources and detectors, hindering their compact and cost-efficient applications in various areas. Here, we experimentally demonstrate mid-IR gas spectroscopy without mid-IR photons solely using convenient near-IR optical components. This is realized by generating photon pairs (i.e., a mid-IR photon and a near-IR one) through a spontaneous parametric downconversion in a microscale optical cavity. The generation rate of near-IR photons strongly relies on the absorption of the mid-IR photon due to their quantum correlation. Through interacting with evanescent fields around the microcavity, the absorptive mid-IR resonances of the surrounding gas greatly affect the detected near-IR photons without harassing any mid-IR photon. This scheme presents a cost-effective and compact solution for on-chip quantum gas spectroscopy without requiring expensive mid-IR lasers and detectors or lasers, thereby paving new avenues for applications in environmental monitoring/safety, healthcare, and agriculture.

Applied Physics Reviews•Jan 5, 2026•2 citations

Spectroscopy in the mid-infrared region is an indispensable tool for identifying molecular types in various fields, including physics, chemistry, and medical sciences. However, conventional infrared light sources, detectors, and noise from blackbody radiation have been the obstacles to miniaturization and higher sensitivity of infrared spectrometers. Quantum infrared spectroscopy, which uses visible and infrared photon pairs in a quantum entangled state, has attracted attention as a new sensing technology that enables infrared spectroscopy with detectors in the visible range. However, the bandwidth of conventional quantum entangled light sources is at most 1 µm or less, which hinders broadband measurements, which are important in spectroscopic applications. Here we have realized an ultra-broadband entangled state of visible–infrared photons with wavelengths from 2 to 5 µm, harnessing a specially designed nonlinear crystal with chirped poling structure inside. Furthermore, we constructed a nonlinear quantum interferometer using the ultra-broadband quantum entangled photons and realized broadband infrared spectroscopy of inorganic and organic materials using a visible detector made of silicon. Our results show that quantum infrared spectroscopy can achieve ultra-broadband spectroscopic measurements and pave the way for the highly sensitive, ultra-compact infrared spectrometers using quantum entangled photons.

Nonlinear interferometers based on correlated photon pairs allow mid-infrared spectroscopy by measuring only near-infrared photons with a silicon-based detector, which offers higher detectivities than mid-infrared detectors. Here, we use the nonlinear interferometer not only to determine the transmission of a sample but also for spectral analysis - analogue to classical Fourier transform infrared (FTIR) spectrometers. The Quantum FTIR analyzes the absorption of gas mixtures with high spectral resolution over a broad mid-infrared wavelength range. Improved emission rates of the photon pair source yield sensitivities similar to a classical FTIR despite an extremely low light exposure on the sample.

Spontaneous parametric down-conversion is an essential tool for a quantum light source in the infrared region ranging 2-5 µm for the purpose of material identification, chemical analysis, and gas sensing. So far, photon pairs from the process in a nonlinear crystal have low tunability and a narrow spectral range because of the phase-matching condition. Here, we propose a novel type of spontaneous parametric down-conversion processes that overcomes these challenges, where two photon pairs are simultaneously produced in the visible and infrared regions in periodically poled stoichiometric lithium tantalite. It allows broadband and tunable generation of infrared photon pairs that can be employed as an alternative light source for quantum infrared spectroscopy.

Nonlinear interferometers based on non-degenerate spontaneous parametric down-conversion (SPDC) create a link between separate spectral ranges. This allows for measurements in remote spectral regions while detecting light in easily accessible wavelengths. In our work, we use periodically poled lithium niobate to create correlated signal (visible or near-infrared) and idler (mid-infrared) photon pairs. Using a nonlinear interferometer in Michelson geometry, we obtain broadband mid-infrared spectra from light detected with a silicon avalanche photodiode. Combining the nonlinear interferometer with a measurement scheme in close analogy to classical Fourier-transform infrared spectroscopy allows for sub-wavenumber spectral resolution, which opens up possibilities for applications such as precise spectroscopic gas analysis.

In recent years, nonlinear quantum interferometry has been widely explored for applications like spectroscopy, optical coherence tomography, and imaging [1]. Quantum infrared spectroscopy (QIRS) uses quantum interference of generation processes of frequency-entangled visible-IR photon pairs to perform infrared spectroscopy using visible light sources and silicon-based detectors [2]. This technique utilizes a nonlinear quantum interferometer configuration where the generated IR photons pass through the sample, and the correlated visible photons are detected. The change in the detected visible photon flux with and without the sample helps extract the complex transmittance of the sample in the IR region.

Infrared quantum absorption spectroscopy is one of the quantum sensing techniques, by which the infrared optical properties of a sample can be estimated through visible or near infrared photon detection without need for infrared optical source or detector, which has been an obstacle for higher sensitivity and spectrometer miniaturization. However, experimental demonstrations have been limited to wavelengths shorter than 5 µm or in the terahertz region, and have not been realized in the so-called fingerprint region of 1500–500 cm−1 (6.6 to 20 µm), which is commonly used to identify chemical compounds or molecules. Here we report the experimental demonstration of quantum Fourier-transform infrared (QFTIR) spectroscopy in the fingerprint region, by which both absorption and phase spectra (complex spectra) can be obtained from Fourier transformed quantum interferograms obtained with a single pixel visible-light detector. As demonstrations, we obtained the transmittance spectrum of a silicon wafer at around 10 µm (1000 cm−1) and complex transmittance spectrum of a synthetic fluoropolymer sheet, polytetrafluoroethylene, in the wavelength range of 8 to 10.5 µm (1250 to 950 cm−1), where absorption due to stretching modes of C-F bonds is clearly observed. These results open the way for new forms of spectroscopic devices based on quantum technologies.

Mid-infrared (mid-IR) spectra revealing the distinct “fingerprint” of molecules are of critical importance for both science and technology in chemistry, physics, materials science, and biology. Mid-IR sensing and spectroscopy provide unique and powerful tools for crucial applications in greenhouse gas monitoring, hazardous emission detection, and medical breath diagnosis. However, the low-photon energy characteristic of the mid-IR spectrum poses significant challenges for both mid-IR light sources and detectors, hindering their compact and cost-efficient applications in various areas. Here, we experimentally demonstrate mid-IR gas spectroscopy without mid-IR photons solely using convenient near-IR optical components. This is realized by generating photon pairs (i.e., a mid-IR photon and a near-IR one) through a spontaneous parametric downconversion in a microscale optical cavity. The generation rate of near-IR photons strongly relies on the absorption of the mid-IR photon due to their quantum correlation. Through interacting with evanescent fields around the microcavity, the absorptive mid-IR resonances of the surrounding gas greatly affect the detected near-IR photons without harassing any mid-IR photon. This scheme presents a cost-effective and compact solution for on-chip quantum gas spectroscopy without requiring expensive mid-IR lasers and detectors or lasers, thereby paving new avenues for applications in environmental monitoring/safety, healthcare, and agriculture.