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EXPRESS: Analysis of Natural Gas Using a Portable Hollow-Core Photonic-Crystal-Coupled Raman Spectrometer
摘要： The low accessibility of natural gas fields and transporting pipelines requires portable online analyzers of the composition of natural gas, ensuring nearly chromatographic precision and capable of in situ analysis of a wide range of gases, including infrared-inactive ones (hydrogen, oxygen, nitrogen, chlorine). We have developed an express method of gas analysis meeting all requirements for the analysis of natural gas and its derivative mixtures using a portable 532 nm Raman spectrometer rigidly connected to a hollow-core crystal photonic fiber.
关键词： hollow-core photonic crystal fiber,HC-PCF,Raman spectrometry,gas chromatography,natural gas,calibration gas mixture
更新于2025-09-23 15:21:01
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Photoreduction in Optofluidic Hollow-Core Photonic Crystal Fiber
摘要： Optofluidic hollow-core photonic crystal fiber (HC-PCF) uniquely allows light to be guided at the centre of a microfluidic channel. The system maximizes the interaction of light with infiltrated chemicals and (nano)particles, offering unique opportunities for in-situ optical monitoring of a range of photochemical and catalytic reactions [1,2]. Our current goal is to extend this work to hybrid colloidal systems comprising a particulate light absorber and a molecular catalyst for photocatalytic fuel production [3]. Here we use HC-PCF microreactors to study novel light-absorbing particles for such systems: graphitic, N-doped, and amorphous carbon-nanodots (CNDs) that offer a unique combination of scalability, biocompatibility, water solubility, and stable optical properties [4]. To test the CNDs’ absorption- and electron-transfer properties, we combine them with the redox-active heterocycle methyl viologen dichloride (MV2+·2Cl-). Upon absorption of UV light, CNDs can transfer an electron to MV2+, whose reduction to the radical cation (MV?+) creates a strong optical absorption peak around 600 nm (Figs. 1(a,c)). An electron donor (EDTA) is added to the solution to quench the photo-induced holes in the CNDs [4]. The mixture was infiltrated into the core of a 30 cm long liquid-filled kagomé style HC-PCF (Fig. 1(b)), designed to guide in the wavelength range of the MV?+ absorption peak. To ensure a homogeneous excitation of the CNDs, a 5 cm long section of the fiber was side-illuminated by a UV lamp (λ = 365 nm). A supercontinuum source, launched into a guided mode, was used to monitor the absorption spectrum. Despite sample volumes of less than 50 nL, we obtain highly-reproducible time traces of the MV?+ absorption (Fig 1(d-e)). Unexpectedly, a significant initial time-delay of 135 s was observed in the reduction of MV2+, revealing the presence of a previously unknown activation process of the CNDs. The initial delay was found to depend on the functionalization of the CNDs, with delays for a -COOH group (81 s) being ca. three times shorter than those for NH2 (176 s) and NMe2 (204 s) groups. The subsequent reaction rate was found to be independent of the surface-group. Our unexpected results highlight the scope for urgently needed in-situ analysis of photocatalytic systems. Future experiments will include the use of surface-sensitive higher-order modes [5] to selectively probe the diffusion of reaction products within the optofluidic reactor.
关键词： Carbon-Nanodots,Photoreduction,Hollow-Core Photonic Crystal Fiber,Optofluidic,Photocatalytic
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Controllable Photon-Pair Spectral Correlations
摘要： Photon-pair states, whether spectrally correlated or separable, can all be very useful in quantum technology applications. For example, the former are used for improving the security of quantum key distribution, whilst the latter are the backbone in heralded single photon sources. It has been shown that the amount of spectral correlations is well-described by the shape of the Joint Spectral Amplitude function (JSA), which mostly depends on the relative group velocity relation between the pump, signal and idler photons within the source medium [1]. Here, we report on a photon-pair source whose states can be controlled from separable to spectrally entangled. The source is based on four-wave mixing nonlinear effect within a gas-filled hollow-core photonic crystal fiber (HCPCF). It combines three important properties: (1) Raman-free generation thanks to the use of a noble gas and to a minute overlap with silica within the hollow-core [2]; (2) strong efficiency nonlinear medium and (3) a high versatility in the phase-matching conditions thanks to the fiber microstructuration and gas pressure tunability. The inhibited-coupling HCPCF (see Fig.1a) filled with xenon, was designed to operate at wavelengths that are convenient for heralded single photon sources; the idler lies in the telecom wavelength range (~ 1545 nm), while the signal wavelength is in the range of atomic transitions and Silicon single photon detectors (~ 778 nm). More importantly, we show how the multiband dispersion profile (see Fig. 1b) of such medium allows to tailor phase- and group velocity relations and possibly at any given wavelength from the UV to infrared [3]. We demonstrate experimentally an active control over the generated photon spectral-correlation that allows spectrally entangled and factorable states to be obtained within the same device (examples in Fig. 1c). More specifically, a gallery of different JSI, including exotic shape, is measured by tuning various parameters: gas pressure, pump spectral FWHM, spectral chirp and pump spectral envelope. Such a versatile photon-pair source can target both applications requiring factorable (heralded single photon) and correlated states (spectral entanglement) and paves the way to spectro-temporal mode encoding [4]. Furthermore, the photon-pair state is generated over an unprecedented tunable frequency-range that span well over tens of THz. We will present complete theoretical and experimental results demonstrating the full capacity of this platform to generate photon pair with controllable spectral properties.
关键词： photon-pair states,hollow-core photonic crystal fiber,spectral correlations,quantum technology,spectral entanglement,four-wave mixing
更新于2025-09-11 14:15:04