We report on the realization, calibration, and test outdoor of a 19-inches rack 3-units sized Quartz Enhanced Photoacoustic Spectroscopy (QEPAS) trace gas sensor designed for real-time carbon monoxide monitoring in ambient air. Since CO acts as slow energy relaxer when excited mid-infrared spectral region, its QEPAS signal is affected by presence relaxation promoters, such water vapor, or quenchers like molecular oxygen. analyzed detail all processes with typical collisional partners an air...

Interferometric methods have been recently investigated to achieve sub-Rayleigh imaging and precision measurements of faint incoherent sources up the ultimate quantum limit. Here we consider single-photon two point-like emitters unequal intensity. This is motivated by fact that pairs natural typically brightness, for example, binary star systems exoplanets. We address problem estimating transverse separation d or relative intensity . Our theoretical analysis shows associated statistical...

The current state of the art single-photon detectors operating in mid-infrared wavelength range is reported this review. These devices are essential for a wide applications, such as quantum communications, sensing, and metrology, which require with high detection efficiency, low dark count rates, dead times. technological challenge moving from well-performing commercially available near-infrared to discussed. Different approaches explored, spanning stoichiometric or geometric engineering...

The design and realization of two highly sensitive easily interchangeable spectrophones based on custom quartz tuning forks, with a rectangular (S1) or T-shaped (S2) prongs geometry, is reported. have been implemented in QEPAS sensor for ethylene detection, employing DFB-QCL emitting at 10.337 μm an optical power 74.2 mW. A comparison between their performances showed signal-to-noise ratio 3.4 times higher when implementing the S2 spectrophone. For S2-based sensor, linear dependence signal...

We report on a fiber-coupled, quartz-enhanced photoacoustic spectroscopy (QEPAS) near-IR sensor for sequential detection of methane (CH4 or C1) and ethane (C2H6 C2) in air. With the aim developing lightweight, compact, low-power-consumption suitable unmanned aerial vehicles (UAVs)-empowered environmental monitoring, an all-fiber configuration was designed realized. Two laser diodes emitting at 1653.7 nm 1684 CH4 C2H6 detection, respectively, were fiber-combined fiber-coupled to collimator...

In this paper the performances of two spectrophones for quartz-enhanced photoacoustic spectroscopy (QEPAS)-based ethane gas sensing were tested and compared. Each spectrophone contains a quartz tuning fork (QTF) acoustically coupled with pair micro-resonator tubes having fundamental mode resonance frequency 32.7 kHz (standard QTF) 12.4 (custom QTF), respectively. The implemented into QEPAS acoustic detection module (ADM) together preamplifier gain bandwidth optimized respective QTF...

The use of statistical estimation theory to boost the metrological performance measurement apparatus is becoming increasingly popular in a wide range applications. Recently, such an approach has been adopted Hong Ou Mandel interferometry, setting new record time delay and polarization measurement. Here, we extend these pioneering experiments telecom unlock full potential information-based combined with versatile spectral range, aiming for its adoption fiber-coupled devices up hundreds...

The application of statistical estimation theory to Hong–Ou–Mandel interferometry led enticing results in terms the detection limit for photon reciprocal delay and polarisation measurement. In following paper, a fully fibre-coupled setup operating telecom wavelength region proves achieve, first time, common-path Hong–Ou–Mandel-based interferometry, phase at zeptosecond scale. experimental are then framed theoretical model by calculating Cramer–Rao bound (CRB) and, after comparison with...

Traditional Hong-Ou-Mandel (HOM) interferometry, insensitive to photons phase mismatch, proved be a rugged single-photon interferometric technique. By introducing post-beam splitter polarization-dependent delay, it is possible recover phase-sensitive fringes, obtaining temporal quantum eraser that maintains the ruggedness of original HOM with enhanced sensitivity. This setup shows promising applications in biological sensing and optical metrology, where high sensitivity requirements are...

We report on the development of a gas sensor system based quartz-enhanced photoacoustic spectroscopy (QEPAS) for detection trace levels ethylene using quantum cascade laser operating at ~ 10.3 μm. To realize compact architecture, dedicated acoustic module was designed and implemented. The includes QEPAS spectrophone, composed quartz tuning fork, micro-resonator tube low-noise pre-amplifier chip signal readout. volume ADM is ~30 cm³. A minimum limit 30 part-per-billion in...

This paper presents an all-fiber telecom-range optical gyroscope employing a spontaneous parametric down conversion crystal to produce ultra-low intensity thermal light by tracing-out one of the heralded photons. The prototype exhibits detection limit on photon delay measurements $249$ zs over $72$ s averaging time and 26 in differential at $t=10^4$ averaging. scheme proves be most resource-efficient possible, saturating $>99.5\%$ Cram\'er-Rao bound. These results are groundbreaking context...

Abstract This work presents an all‐fiber telecom‐range optical gyroscope employing a spontaneous parametric down conversion crystal to produce ultra‐low intensity thermal light by tracing‐out one of the heralded photons. The prototype exhibits detection limit on photon delay measurements 249 zs over 72 s averaging time and 26 in differential at averaging. scheme proves be most resource‐efficient possible, saturating Cramér–Rao bound. These results are groundbreaking context low‐photon regime...

We demonstrate spectroscopy of incoherent light with sub-diffraction resolution. In a proof-of-principle experiment we analyze the spectrum pair point-like sources whose separation is below diffraction limit. The two mimic planetary system, brighter source for star and dimmer one planet. Acquiring spectral information about secondary hard because images have substantial overlap. This limitation solved by leveraging structured measurement based on spatial-mode demultiplexing, where first...

We report on the detection of isotopologues ¹²CH₄ and ¹³CH₄ by employing a quartz-enhanced photoacoustic spectroscopy (QEPAS)-based sensor. By properly selecting exciting light source working conditions, two absorption lines, having negligible cross-section ratio temperature coefficient -6.7‰/°C cross section ~ 0.06 for natural abundance each isotope, can be targeted. The QEPAS signal was acquired mixtures in nitrogen methane wide range...

We developed a high sensitivity optical sensor for circular birefringence using heralded photon source. The can be employed chirality measurements and, being based on single photons, exploited fragile biological sample or in metrological applications where the light intensity must kept as low possible. found best operational condition; then, we calibrated and tested its performance up to very long acquisition time, obtaining excellent stability sub-ppm detection limit (for 100 μm sample),...

Interferometric methods have been recently investigated to achieve sub-Rayleigh imaging and precision measurements of faint incoherent sources up the ultimate quantum limit. Here we consider single-photon two point-like emitters unequal intensity. This is motivated by fact that pairs natural will typically brightness, as for example binary star systems exoplanets. We address problems estimating transverse separation $d$ relative intensity $\epsilon$. Our theoretical analysis shows associated...

In oil and gas exploration environmental monitoring fields is extremely important to rely on versatile rugged trace sensors that can be mounted remote-controlled unmanned vehicles monitor dangerous areas inaccessible a human operator. Thereby, compact fiber-coupled dual-gas QEPAS sensor employing custom tuning fork was designed tested. Two distributed feedback pigtailed diode lasers emitting at 1654 nm 1684 nm, for methane ethane detection respectively, were also employed. The calibrated...