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An optical fiber strain sensor by using of taper based TCF structure
摘要： We propose an optical fiber strain sensor consisting of a spliced twin-core fiber (TCF). The sensor structure has two fiber tapers, which are weak taper and T-shaped taper. The taper waist of T-shaped taper is about half-size of the weak taper, but the length of the T-shaped taper is also about half-length of the weak taper. In the sensing structure, core mode and cladding modes of the TCF are excited simultaneously. Two tapered regions around the splicing interfaces can play the roles of splitting and combining the modes in the fiber. In experiment, the proposed device has good quality interferometric spectra, and the highest extinction ratio of 20 dB is achieved. When the stress increases from 0 με to 841.5 με, different wavelength sensitivities of 3.31 pm/με and 6.11 pm/με are achieved. Different intensity sensitivities of 7.5 × 10?3 dB/με and 9.9 × 10?3 dB/με are also achieved, respectively. The sensor has shown good test stability and low temperature sensitivity, which is good for precise strain measurement in practical applications.
关键词： Twin-core fiber,Fiber design and fabrication,Fiber optical sensor
更新于2025-11-28 14:23:57
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Twins in YAl3(BO3)4 and K2Al2B2O7 Crystals as Revealed by Changes in Optical Activity
摘要： Many borate crystals feature nonlinear optical properties that allow for efficient frequency conversion of common lasers down into the ultraviolet spectrum. Twinning may degrade crystal quality and affect nonlinear optical properties, in particular if crystals are composed of twin domains with opposing polarities. Here, we use measurements of optical activity to demonstrate the existence of inversion twins within single crystals of YAl3(BO3)4 (YAB) and K2Al2B2O7 (KABO). We determine the optical rotatory dispersion of YAB and KABO throughout the visible spectrum using a spectrophotometer with rotatable polarizers. Space-resolved measurements of the optical rotation can be related to the twin structure and give estimates on the extent of twinning. The reported dispersion relations for the rotatory power of YAB and KABO may be used to assess crystal quality and to select twin-free specimens.
关键词： optical activity,inversion twin,YAB,optical rotatory dispersion,KABO,second harmonic generation,frequency conversion,K2Al2B2O7,NLO crystals,YAl3(BO3)4
更新于2025-10-22 19:40:53
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All-optical graphene-oxide humidity sensor based on a side-polished symmetrical twin-core fiber Michelson interferometer
摘要： A high-sensitive graphene-oxide (GO) humidity sensor based on a side-polished twin-core fiber (SPTCF) Michelson interferometer (MI) has been demonstrated. The MI was fabricated by splicing a section of TCF to a standard single mode fiber (SMF) and tapering the splicing point. The exposed polished core has a stronger evanescent field and enhances the interaction between light and external environment. The GO-SPTCFMI can operate in the wavelength- and intensity- modulated sensor. The super-high humidity sensitivities of ~2.72 nm/RH% in the RH range of 40-75% and ~3.76 dB/RH% in the RH range of 60-62.1% are obtained experimentally. The high-performance GO-SPTCFMI is a promising candidate for potential applications, such as gas sensing and biochemical detection.
关键词： side-polished fiber,graphene oxide,Humidity sensor,twin core fiber,interferometer.
更新于2025-09-23 15:23:52
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Vapor Phase Epitaxy of (133) and (211) CdTe on (211) Si Substrates Using Metallic Cd Source
摘要： Single-crystalline CdTe films were grown in both (133) and (211) surface orientations on (211) Si substrates by vapor-phase epitaxy using metallic Cd source as a group-II precursor. The orientation of epitaxial films depended on the ratio of group-II and -VI precursors, i.e., II/VI. The orientation of epitaxial films was changed from (133) to (211) by increasing the II/VI under the CdTe growth condition. The surface morphology for (133) CdTe was smooth, whereas the surface for (211) CdTe was composed of hillocks with (111), (110), (101), and (100) facets. The full width at half maximum (FWHM) of the epitaxial films with the same thickness showed that the crystalline quality of (133) CdTe was better than that of (211) CdTe. The dependence of the orientation between (133) and (211) CdTe films on (211) Si substrates on the II/VI was explained by the difference between the step-flow growth on the step and the spontaneous nucleation on the terrace.
关键词： vapor phase epitaxy,twin,metallic cadmium,CdTe,II/VI
更新于2025-09-23 15:22:29
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European Microscopy Congress 2016: Proceedings || Fivefold symmetries in silicon thin films induced by multiple twinning
摘要： Fivefold symmetry, like any kind of n-fold rotational symmetry, can be identifiable when rotating a crystalline configuration 5 times (or n times) around a certain axis and realizing that the structure is transformed into a configuration that is equivalent to the initial one. The occurrence of this specific symmetry, forbidden by the conventional periodic crystallography, was attributed in the literature to the presence of a new state of matter 'the quasicrystals' [1] [2] or simply to an effect of multiple twinning. Particularly, the tendency of multiply twinning in a fivefold symmetry has been widely reported in small particles having a special morphology like the decahedral [3] or icosahedral [4] structures, usually called multiply twinned particles. In this study, we will highlight on the fivefold symmetry observed in the electron diffraction patterns of two types of materials elaborated in different growth conditions, originating from multiple twinning and not from the presence of multiply twinned particles. The first case concerns the fivefold symmetry on p-type doped silicon thin films containing a non-negligible amount of carbon and oxygen. These films were deposited in a plasma enhanced chemical vapor deposition reactor (PECVD) at 0.2 W/cm2 using silane, hydrogen, diborane and hexamethydisiloxane (C6H18OSi2, HMDSO) diluted in argon. Since all the diffraction patterns recorded on different regions of these films exhibit a fivefold symmetry along [0-11] zone axis (Figure 1), it is clear that this symmetry is real and characteristic of our films. Further diffraction measurements reveal that there is a relation of epitaxy with the (100) crystalline silicon substrate. This is also confirmed by high resolution TEM images, where {111} planes are continuing from the substrate to the film across the interface. Moreover, energy filtered TEM images were correlated with SIMS measurements to provide elemental mapping of silicon, carbon and oxygen with absolute values. The second case illustrates a quasi-fivefold symmetry recorded on intrinsic silicon thin films deposited by PECVD using silicon tetrafluoride, hydrogen and argon chemistry at a purposely high power density of 0.3 W/cm2. After few hundred nanometers of epitaxial growth, a high density of defects appears, followed by a multiply twinned part (as shown in Figure 2a). Fourier Transforms recorded on the first part reveal a monocrystalline structure (Figure 2c), and on the second part a fivefold symmetry (Figure 2b), which is, in this case also, linked to an epitaxial growth. It has been proved in some references [5] [6] that a high power density is responsible for a high ion energy impinging on the substrate and causing some surface or even bulk damage. Thus, the twin defects present in our films are most probably caused by the application of a high power density. However, to obtain a fivefold symmetry, it is necessary to have at least three orders of twinning that contribute to 10 spots in the diffraction pattern, i.e, if there only exist two orders of twinning, some additional diffraction spots appear without giving rise to a fivefold symmetry as it is the case of Figure 3. Detailed investigation of the multiple twinning in a fivefold symmetry fashion will be presented.
关键词： silicon,Transmission electron microscopy,epitaxy,twin,fivefold symmetry
更新于2025-09-23 15:22:29
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Sending-or-Not-Sending with Independent Lasers: Secure Twin-Field Quantum Key Distribution over 509??km
摘要： Twin-field (TF) quantum key distribution (QKD) promises high key rates over long distances to beat the rate-distance limit. Here, applying the sending-or-not-sending TF QKD protocol, we experimentally demonstrate a secure key distribution that breaks the absolute key-rate limit of repeaterless QKD over a 509-km-long ultralow loss optical fiber. Two independent lasers are used as sources with remote-frequency-locking technique over the 500-km fiber distance. Practical optical fibers are used as the optical path with appropriate noise filtering; and finite-key effects are considered in the key-rate analysis. The secure key rate obtained at 509 km is more than seven times higher than the relative bound of repeaterless QKD for the same detection loss. The achieved secure key rate is also higher than that of a traditional QKD protocol running with a perfect repeaterless QKD device, even for an infinite number of sent pulses. Our result shows that the protocol and technologies applied in this experiment enable TF QKD to achieve a high secure key rate over a long distribution distance, and is therefore practically useful for field implementation of intercity QKD.
关键词： remote-frequency-locking technique,repeaterless QKD,ultralow loss optical fiber,secure key distribution,Twin-field quantum key distribution
更新于2025-09-23 15:19:57
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Enhancement of Electrical Conduction and Phonon Scattering in Ga2O3(ZnO)9-In2O3(ZnO)9 Compounds by Modification of Interfaces at the Nanoscale
摘要： The Ga2O3(ZnO)9 and In2O3(ZnO)9 homologous phases have attracted attention as thermoelectric (TE) oxides due to their layered structures. Ga2O3(ZnO)9 exhibits low thermal conductivity, while In2O3(ZnO)9 possesses higher electrical conductivity. The TE properties of the solid solution of Ga2O3(ZnO)9-In2O3(ZnO)9 were explored and correlated with changes in the crystal structure. High-quality (1?x)Ga2O3(ZnO)9-xIn2O3(ZnO)9 (x = 0.0 to 1.0) ceramics were prepared by the solid-state route using B2O3 and Nd2O3 as additives. The crystal structures were analysed by x-ray diffraction, high-resolution transmission electron microscopy and atomic resolution scanning transmission electron microscopy–high-angle annular dark field imaging–energy dispersive x-ray spectroscopy (STEM–HAADF–EDS) techniques. A layered superstructure with compositional modulations was observed in all samples in the (1?x)Ga2O3(ZnO)9-xIn2O3(ZnO)9 system. All the ceramics exhibited nanoscale structural features identified as Ga- and In-rich inversion boundaries (IBs). Substitution of 20 mol.% In (x = 0.2) in the Ga2O3(ZnO)9 compounds generated basal and pyramidal indium IBs typically found in the In2O3(ZnO)m system. The (Ga0.8In0.2)2O3(ZnO)9 compound does not exhibit the structural features of the Cmcm Ga2O3(ZnO)9 compound, which is formed by a stacking of Ga-rich IBs along the pyramidal plane of the wurtzite ZnO, but features that resemble the crystal structure exhibited by the R3m In2O3(ZnO)m with basal and pyramidal indium IBs. The structural changes led to improved TE performance. For example, (Ga0.8In0.2)2O3(ZnO)9 showed a low thermal conductivity of 2 W/m K and a high power factor of 150 μW/m K2 giving a figure of merit (ZT) of 0.07 at 900 K. This is the highest ZT for Ga2O3(ZnO)9-based homologous compounds and is comparable with the highest ZT reported for In2O3(ZnO)9 homologous compounds.
关键词： thermoelectric,inversion boundaries,twin boundaries,ZnO,interfaces,homologous compounds
更新于2025-09-23 15:19:57
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Prevalence of right ventricular outflow tract abnormalities among recipients in twin–twin transfusion syndrome after fetoscopic laser surgery in 90 consecutive cases
摘要： Purpose Right ventricular outflow tract obstruction (RVOTO) is a severe complication in recipients in twin–twin transfusion syndrome (TTTS). This study investigated the prevalence of RVOTO in TTTS after laser surgery and examined the risk factors for RVOTO. Methods This retrospective study evaluated 90 patients who had undergone laser surgery and been followed for 6?months after birth. The diagnosis of RVOTO was made based on postnatal echocardiography findings. Ultrasound and clinical records, including maternal and neonatal data, were retrieved from our database. Risk factors for developing RVOTO were compared between recipients with and without RVOTO in a statistical analysis. Results Six surviving recipients were diagnosed with RVOTO. Three recipients had developed severe pulmonary stenosis (PS) that required percutaneous transluminal pulmonary valvuloplasty or balloon pulmonary angioplasty. A total of 6.7% of recipients (6/90) had RVOTO, consisting of PS and tricuspid regurgitation (TR), and 3.3% of recipients (3/90) required invasive treatment. The characteristic factors did not differ significantly between recipients with and without RVOTO. Conclusion This study revealed that 6.7% of recipients with TTTS had PS, and 3.3% required invasive treatment for PS. However, no significant association was noted between RVOTO development in recipients and maternal clinical data and fetal ultrasound examination findings. It is difficult to predict RVOTO development in recipients using only preoperative ultrasound and clinical information.
关键词： Twin–twin transfusion syndrome,Right ventricular outflow tract obstruction,Recipient,Fetoscopic laser surgery,Pulmonary stenosis
更新于2025-09-19 17:13:59
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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) - Direct Quantum Error Detection in Spatially Multiplexed Transmission
摘要： In this paper, we investigate the properties of transmission links amplified by phase-sensitive amplifiers (PSAs). Using an analytic description, we explain the principles enabling improved sensitivity compared to conventional links amplified by phase-insensitive amplifiers (PIAs) and mitigation of nonlinear transmission distortions. We demonstrate these features using numerical simulations, and in particular, we show the possibility of efficiently mitigating both self-phase modulation (SPM)-induced distortions and nonlinear phase noise (NLPN) if the link dispersion map is optimized. The properties of the noise on signal and idler are important and to enable NLPN mitigation, the noise must be correlated at the link input. We investigate the role of the dispersion map in detail and show that in a link with standard single mode fiber (SSMF) the optimum dispersion map for efficient nonlinearity mitigation corresponds to precompensation of an amount equal to the effective loss length. Furthermore, we experimentally demonstrate both improved sensitivity and mitigation of nonlinearities in a 105 km PSA-amplified link transmitting 10 GBd 16-ary quadrature amplitude modulation (16QAM) data. We measure a combined effect allowing for more than 12 dB larger span loss in a PSA-amplified link compared to a conventional PIA-amplified link to reach the same bit error ratio (BER) of 1 × 10?3.
关键词： phase-sensitive amplifiers (PSAs),Fiber nonlinearity mitigation,optical amplifiers,optical fiber communication,phase-conjugated twin waves,fiber optical parametric amplifiers (FOPAs)
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - GaAs Grown on Si (111) by inserting metal selenides films
摘要： In this study, the crystalline improvement of GaAs grown on metal (Ga or In) selenides films is studied. We have found that the inevitable bonding between Ga and Se on the top of In2Se3 was observed. Further, the wettability of GaAs nucleus has been improved by irradiating Ga2Se3 surface with As, Ga, and Se simultaneously. The twin-domain less than 2% for 1 μm-GaAs grown on an In2Se3/Si (111)4o off-cut to [11-2] has been achieved by introducing Ga2Se3 on In2Se3 with the subsequent (As-Ga-Se) treatment.
关键词： GaAs/Si,metal selenides,Twin
更新于2025-09-19 17:13:59