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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 Photonics North (PN) - Quebec City, QC, Canada (2019.5.21-2019.5.23)] 2019 Photonics North (PN) - Sensitive Temperature Sensors based on High Birefringence Liquid-Filled Photonic Crystal Fibers
摘要： We propose a new design of a highly birefringent photonic crystal fiber (HBPCF) via infiltration of two holes adjacent to the core of the fiber with two different liquids. As the refractive index of liquids is sensitive to temperature variations, the proposed HBPCF can be used in a Sagnac interferometer as a highly sensitive temperature sensor. The proposed HBPCF can show birefringence of 4 × 10-4 and birefringence sensitivity of 25% for a 5oc temperature variation around 25oc which corresponds to a sensitivity of around 10 nm/oc.
关键词： liquid filled photonic crystal fiber,fiber optic sensor,temperature sensor photonic crystal fiber
更新于2025-09-11 14:15:04
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Quasi-D-Shaped Fiber Optic Plasmonic Biosensor for High-Index Analyte Detection
摘要： In this paper, we propose a highly sensitive quasi-D-shaped fiber optic biosensor for detection of high refractive index (RI) liquid analytes via surface plasmon resonance. The main mechanism of sensing is interplay between photonic crystal fiber fundamental mode and plasmonic mode which leads to formation of different resonance peaks depending on the analyte RI. We numerically analyze the structure sensitivity to design parameters and demonstrate the sensing performance of the proposed biosensor using both spectral sensitivity and amplitude sensitivity methods. The proposed biosensor has a RI detection range of 0.15 refractive index unit (RIU) from 1.45 to 1.6. The sensor exhibits linear sensing performance with a RI spectral sensitivity of 9300 nm/RIU for analyte RI ranging from 1.45 to 1.525, 1176 nm/RIU for analyte RI ranging from 1.525 to 1.6 and in particular, 11800 nm/RIU for analyte RI between 1.475 and 1.5. Furthermore, an average RI sensitivity of 4800 nm/RIU for analyte RI ranging from 1.45 to 1.6 is demonstrated. We also study the amplitude sensitivities of the proposed sensor which show promising maximum values of 183.6 RIU-1 for 785 nm excitation and 820 RIU-1 for 1050 nm excitation. Due to the simple structure of the proposed biosensor, large detection range, high sensitivity and promising linear sensing performance, the proposed biosensor can be a promising candidate for detecting various high RI chemical and biochemical samples.
关键词： plasmonic biosensor,photonic crystal fiber,high index analyte detection,Fiber optic sensor,refractive index sensing
更新于2025-09-11 14:15:04
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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) - Ultrafast Tm-Doped Fiber Amplifier with 1 kW Average Output Power
摘要： Ultrafast thulium-doped fiber lasers emitting in the 2 μm wavelength region have recently attracted a significant amount of attention regarding applications in material processing, life sciences, as well as in fundamental science, e.g. high harmonic generation, particle acceleration, mid-IR generation. In addition to the application-relevant emission wavelength, Tm-doped silica fibers possess many interesting characteristics, such as a broad gain bandwidth spanning from 1700 nm to 2100 nm and more than 70% slope efficiency by exploiting cross-relaxation processes. Furthermore, the longer operation wavelength reduces the impact of detrimental nonlinear effects in fiber lasers, and allows for a larger mode field area with diffraction-limited beam quality as compared to the well-established ytterbium-doped fiber laser systems. In this contribution, we report on a new average power record from a thulium-doped fiber amplifier. We use state-of-the-art laser diodes to reach a combined pump power of more than 2 kW at 793 nm. The use of a polarization maintaining thulium-doped photonic crystal fiber allows for an optical-to-optical efficiency of more than 60% and a pump-limited average output power of 1150 W. After compression to 265 fs pulse duration, 1060 W of average power and 50 MW of peak power at 80 MHz pulse repetition rate are achieved, which represents a performance level that is currently not achievable with a single ultrafast ytterbium-doped fiber amplifier. Additionally, we confirmed a close to diffraction-limited beam quality (M2<1.1) up to the highest power level. From the simulation of the amplification process, the average heat-load of the fiber reaches 95 W/m at full power level, without the onset of transverse mode instability. This average heat-load is significantly higher than the critical value of about 30 W/m, which was found to be the threshold for transverse mode instability in ytterbium-doped fiber lasers.
关键词： ultrafast,high power,Tm-doped fiber amplifier,photonic crystal fiber
更新于2025-09-11 14:15:04
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Polarimetric Fiber Vibration Sensor Based on Polarization-Diversified Loop Using Short Polarization-Maintaining Photonic Crystal Fiber
摘要： In this paper, we demonstrated a polarimetric fiber vibration sensor based on a polarization-diversified loop (PDL) with short polarization-maintaining photonic crystal fiber (PM-PCF) as a sensor head and investigated the dependence of its frequency response on the sensing fiber length. The fabricated PM-PCF vibration sensor is composed of a polarization beam splitter for forming the PDL, PM-PCF as a sensor head, and two wave plates such as a quarter-wave plate and a half-wave plate. A laser diode and a photodetector were also utilized for intensity-based vibration measurement. In particular, two kinds of PM-PCF segments with fiber lengths of ～6 and ～10 cm were employed to explore the effect of the sensor head length on the sensor frequency response. The frequency response was examined over 1–3000 Hz using a piezoelectric transducer that can apply single-frequency vibration to the sensor head. Every measured frequency response showed a resonance peak at each sensor head length, and cut-off frequencies were measured as ～1240 and ～794 Hz for PM-PCF lengths of ～6 and ～10 cm, respectively. That is, a higher cut-off frequency was obtained in a shorter sensor head length. Moreover, it was observed that the sensor head length dependence of the frequency response was maximized in a frequency range from 1000 to 2400 Hz and faded away beyond 2400 Hz. From the measurement results, it is concluded that the short sensor head can provide higher normalized sensitivity, i.e., better signal to noise ratio, at frequencies higher than the resonance frequency, let alone convenience of installation and in sensitiveness to external perturbations in a PDL-based PM-PCF vibration sensor. The phase shift per unit strain and the minimum detectable strain perturbation, regarded as sensitivity and resolution, were measured as ～0.377 mrad/με and ～0.16 nε/Hz1/2 at 2000 Hz for ～6-cm-long PM-PCF, respectively.
关键词： Polarization-Maintaining Photonic Crystal Fiber,Polarization-Diversified Loop,Frequency Response,Optical Fiber Vibration Sensor
更新于2025-09-11 14:15:04
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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
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Pump-Probe Study of Plasma Dynamics in Gas-Filled Photonic Crystal Fiber Using Counterpropagating Solitons
摘要： We present a pump-probe technique for monitoring ultrafast polarizability changes. In particular, we use it to measure the plasma density created at the temporal focus of a self-compressing higher-order pump soliton in a gas-?lled hollow-core photonic crystal ?ber. This is done by monitoring the wavelength of the dispersive wave emission from a counterpropagating probe soliton. By varying the relative delay between pump and probe, the plasma density distribution along the ?ber can be mapped out. Compared with recently introduced interferometric side probing for monitoring the plasma density, our technique is relatively immune to instabilities caused by air turbulence and mechanical vibration. The results of two experiments on argon- and krypton-?lled ?ber are presented and compared to numerical simulations. The technique provides an important tool for probing photoionization in many di?erent gases and gas mixtures, as well as ultrafast changes in dispersion in many other contexts.
关键词： photoionization,solitons,plasma density,photonic crystal fiber,pump-probe technique
更新于2025-09-11 14:15:04
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Bending characteristic analysis and improvement of fusion splice between photonic crystal fiber and single mode fiber
摘要： We report a study of bending characteristic analysis and improvement of fusion splice between the photonic crystal fiber (PCF) and the single mode fiber (SMF). The poor bending characteristic of the splice between the PCF and the SMF is a threat to the fiber optic gyroscope (FOG). However, the tensile strength test shows that the splice should be able to withstand a much smaller bending radius. To solve this problem, we adopt three-dimensional (3D) X-Ray imaging to acquire the accurate structure of the splice and conclude that the stress concentration leads to the poor bending characteristic of the splice. A simple fiber tapering method is proposed to improve the bending characteristic of the splice without compromising the splice loss. The improved splice method for PCF has been used in FOG for space application successfully.
关键词： photonic crystal fiber,X-ray imaging,Bending characteristic,fiber splicing,fiber tapering
更新于2025-09-10 09:29:36
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Influences of Asymmetrical Geometric Structures on the Birefringence of Index-Guiding Photonic Crystal Fiber
摘要： We have numerically investigated the influences of asymmetrical geometric structures on the birefringence of the index-guiding photonic crystal fiber (IG-PCF), by the finite element method. The structure of a reported highly birefringent (HB) PCF with artificial defect in the core is modified to destruct the symmetry. Our proposed structural modifications include elliptical air hole cladding, squeezing lattice of air holes, rotational elliptical air holes, and horizontally shifted air holes, in the cladding. It is found that the birefringence is sensitive to the modifications in different cases due to the different mechanisms. For 1550 nm wavelength, the optimized birefringence can be obtained to be 0.0328 by the elliptical air holes with the major semi-axis in the direction of the long side of the rectangular core region. Furthermore, for the HB-PCF by the asymmetric core shape, the structural factor restricting the further increase of birefringence is that continuous increase of asymmetry leading to the multi-core transmission. It seems to be that This work is not only a proposing of the optimal design of HB-PCF, but also a reference of founding the essence of geometric birefringence.
关键词： structural anisotropy,high birefringence,polarization-maintaining fiber,Photonic crystal fiber (PCF),geometric birefringence
更新于2025-09-10 09:29:36
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Tri-core photonic crystal fiber based refractive index dual sensor for salinity and temperature detection
摘要： This article discusses the tri-core photonic crystal microstructure fiber for the process of simultaneous sensing for salinity and temperature of water substances. This kind of microstructure is preferred in many sensing application to scale the detection process in micrometer range. In this novel sensor, the sensitivity is calculated through coupling mechanism by tracking wavelength shift of various concentrations of salinity and temperature using finite element method. The sensible samples are in liquid and are infiltrated into the framed hollow cavity. Based on the coupling principle between silica substrate and the analyte material, the sense of the salt as well as temperature is obtained. Finally, it is noted that sensitivity of the salt level in water as 5404.9 nm/RIU for x polarization direction and 5674 nm/RIU for y polarization direction have been calculated with the temperature sensitivity of 4 nm/(cid:1)C in the same water substances.
关键词： photonic crystal fiber,finite element method,sensitivity and coupling mechanism
更新于2025-09-10 09:29:36