Showing papers by "Shuisheng Jian published in 2018"

Refractive Index and Temperature Sensing Based on an Optoelectronic Oscillator Incorporating a Fabry–Perot Fiber Bragg Grating

Abstract: An ultrafast high-sensitivity refractive index (RI) and temperature-sensing system based on an optoelectronic oscillator (OEO) is proposed and demonstrated in this paper. A Fabry–Perot fiber Bragg grating (FP-FBG), which combines a gap with two FBGs in a silica V-shaped slot and characterizes a narrow notch in the reflection spectrum, is incorporated in the OEO to implement a microwave photonic filter and perform oscillating frequency selection. A microwave signal is generated by the OEO, whose oscillating frequency is determined by the center frequency of the FP-FBG notch, which varies with the surrounding environments. The RI or the temperature change can be accordingly measured by monitoring the frequency shift of the microwave signal using an electrical spectrum analyzer or a digital signal processor. An experiment is performed to verify the proposal. An RI sensitivity of 413.8 MHz/0.001RIU and a temperature sensitivity of 2516 MHz/°C are successively demonstrated.

A dual-band THz absorber based on graphene sheet and ribbons

Abstract: A dual-band graphene absorber is proposed and investigated in this paper. The absorber consists of the gold substrate, the graphene sheet sandwiched by dielectric layers and the array of graphene ribbon placed on the top. The two absorption peaks of the dual-band are 99.8% at 4.95 THz and 99.6% at 9.2 THz, respectively. Due to the characteristic of tunable surface conductivity of graphene, the absorption can be controlled by adjusting the chemical potential of graphene. We also investigate the dependence of the absorption curve of the proposed absorber on the structure parameters. In addition, the structure of the absorber is very simple and it can be manufactured by chemical vapor deposition (CVD).

Magnetic field and temperature sensor based on D-shaped fiber modal interferometer and magnetic fluid

Abstract: A novel optical fiber magnetic field sensor based on D-shaped fiber modal interferometer and magnetic fluid is proposed and experimentally investigated. Thanks to the etched cladding of D-shaped fiber, the resulting interference is strongly influenced by the surrounding magnetic fluid, which leads to a high magnetic field sensitivity. Simultaneous measurement of the magnetic field and temperature was realized by monitoring the wavelength shift of the two resonance dips at the same time. In the experiment, the magnetic field and temperature sensitivity can reach 99.68 pm/Oe and −77.49 pm/°C, respectively. The proposed magnetic field sensor based on D-shaped fiber is featured with high sensitivity, low cost and simple configuration.

Simultaneous strain and temperature sensor based on polarization maintaining fiber and multimode fiber

Abstract: A novel, simultaneous strain and temperature sensor utilizing polarization maintaining fiber (PMF) and multimode fiber (MMF) is proposed and experimentally demonstrated in this paper. The sensing head of this sensor can be obtained by splicing PMF and MMF in the structure of PMF-MMF-PMF. The extinction ratio of the transmission spectrum can be over 30 dB. The strain sensitivities of sensor by two spectrum dips can be 1.01 pm/μe and 1.27 pm/μe in the range from 0 to 2000 μe. Meanwhile, the temperature sensitivities of 49 pm/°C and 41 pm/°C can be achieved by two spectrum dips in the range from 30 °C to 70 °C. The sensitivity difference between the two spectrum dips can be used to realize dual parameters fiber sensing. This sensor exhibits the advantages of simple fabrication, compact structure and multi-purpose measuring. It may have the great potential in fields of robot arms and artificial limbs.

High-sensitivity measurement of angular velocity based on an optoelectronic oscillator with an intra-loop Sagnac interferometer.

Abstract: A novel scheme for angular velocity measurement is proposed and demonstrated by using an optoelectronic oscillator (OEO) incorporating a Sagnac interferometer. In the OEO resonant cavity, the optical carrier (OC) and the first-order sidebands propagate in opposite directions in the Sagnac loop. Thus, the rotation-induced Sagnac phase difference between the OC and first-order sidebands will produce an oscillating frequency shift of the OEO which is proportional to the rotation angular velocity. Then a high-sensitivity angular velocity measurement is realized by monitoring the oscillating microwave frequency. The system is free from the lock-in problem, and the sensitivity scale is measured to be 51.8 kHz/(rad/s) which is equivalent to a minimally detectable angular velocity of 3.98°/h with a frequency shift of 1 Hz.

Hole-assisted polarization-maintaining few-mode fiber

Abstract: We propose a novel polarization-maintaining few-mode fiber by introducing four identical circular side-holes surrounding an elliptical ring core. In addition to the parameters of ring core, this kind of fiber endows new degrees of freedom to adjust the modal birefringence of guided modes. Numerical simulations indicate that such fiber could support 10 distinct polarization modes, including the effectively separated fundamental modes. The influences of side-hole size and positions on the polarization-maintaining property are investigated for the 10-mode fiber. With appropriate parameters of side-holes, the minimum effective refractive difference (Δneff) between adjacent modes is 1.65 × 10−4 at 1550 nm. Compared with the fiber excluding side-holes, the modal effective refractive indexes are decreased while most Δneff values are enlarged in the proposed fiber. Moreover, all the Δneff values could be higher than 1.52 × 10−4 over a bandwidth ranging from 1510 nm to 1630 nm. The chromatic dispersion covering the broadband is analyzed subsequently. Furthermore, 16 vector modes could be guided in the proposed fiber structure with modified parameters. The proposed fiber is capable of supporting extended modes and might be a promising candidate toward high–capacity spatial-division-multiplexing communications.

Polarization-maintaining terahertz bandgap fiber with a quasi-elliptical hollow-core

Abstract: We present a polarization-maintaining photonic bandgap fiber (PBGF) in terahertz (THz) regime, consisting of a quasi-elliptical hollow-core (QEHC) and triangularly arranged hexagonal holes in cladding. Thanks to the specially designed core shape, the QEHC-PBGF can support two stable polarization-maintaining fundamental modes. From numerical simulations, birefringence, confinement loss and group velocity dispersion of the fundamental mode group are 9.4 × 10−4, 3 × 10−3 cm−1 and 0.39 psTHz−1 cm−1 at 0.9 THz, respectively. Moreover, we investigate the fiber fabrication tolerance in the context of polarization-maintaining and confinement performances. The proposed QEHC-PBGF is anticipated to be useful in polarization sensitive THz applications.

Few-mode fiber Bragg grating-based multi-wavelength fiber laser with tunable orbital angular momentum beam output

Abstract: We experimentally demonstrate a multiwavelength fiber ring laser with tunable orbital angular momentum (OAM) beam output The laser is embedded with a few-mode fiber Bragg grating and a mode selective coupler (MSC) The mode conversion from LP01 mode to LP11 mode is realized by using the MSC as a mode converter By rotating a polarizer set at the output end of the MSC, the topological charge of the OAM beam can be tuned from l = −1 to l = +1 and thus a tunable OAM beam is obtained By adjusting the polarization controllers (PCs), the laser can operate under single-, dual- and triple-wavelength lasing conditions

Plasmon-phonon-polariton modes and field enhancement in graphene-coated hexagon boron nitride nanowire pairs

Abstract: Both plasmon-phonon-polariton (SPP-PHP) modes and phonon-polariton (PHP) modes supported in graphene-coated hexagon boron nitride (h-BN) single nanowire are presented. The field distributions of the lowest 5 order modes of SPP-PHP modes supported in graphene-coated hexagon boron nitride nanowire pairs (SPP-PHP-GHNP) and the lowest 5 order modes of PHP modes supported in graphene-coated hexagon boron nitride nanowire pairs (GHNP) are also demonstrated and analyzed, respectively. The results of numerical calculation show that SPP-PHP-GHNP mode 0 owns the strongest confinement and lowest loss among the lowest 5 order modes of SPP-PHP-GHNP. Furthermore, the field enhancement of SPP-PHP-GHNP mode 0 can reach over 105 by controlling the geometry parameters of GHNP. Meanwhile, the influence of tuning the Fermi level of graphene on the field enhancement is also presented in the paper. The proposed structure may improve the development of graphene-h-BN-based optoelectronic devices.

Polarization-Maintaining Hollow-Core Photonic Bandgap Few-Mode Fiber in Terahertz Regime

Abstract: We propose a terahertz (THz) hollow-core photonic bandgap fiber (HC-PBGF) supporting few-mode operation with large birefringence. The periodic arrangement of square lattice with round corners in fiber cladding offers bandgap guidance. Numerical simulation indicates that a 21-cell HC-PBGF could support six vector modes in the bandgap. Characteristics of guided modes are comprehensively investigated, suggesting modal confinement loss of the order of 10−3 cm−1, group velocity dispersion under 1 psTHz−1cm−1, and modal birefringence higher than 10−4 for all modes at around 0.92 THz. Moreover, 24-cell and 32-cell HC-PBGFs are discussed to explore the influence of HC geometry on guided mode number and modal birefringence.

Compound comb filter based on Sagnac interferometer and phase shifted fiber Bragg grating using for tunable and switchable fiber ring laser

Abstract: A kind of stable, switchable and tunable erbium-doped fiber ring laser based on a Sagnac interferometer (SI) is presented and experimentally demonstrated. The SI is composed of a section of an elliptical-core spun fiber sandwiched between two polarization controllers (PCs) in a Sagnac loop. The proposed compound comb filter, which consists of an SI cascaded with a phase shifted fiber Bragg grating, is developed to suppress the mode competition in the laser oscillation. By adjusting the PCs, a stable and tunable single-wavelength lasing output can be achieved. The optical signal-to-noise ratio (OSNR) is better than 40 dB, and the 3 dB linewidth is less than 15 pm. Furthermore, stable dual-wavelength lasing outputs with different wavelength intervals of 0.132 nm, 0.336 nm and 0.418 nm can also be obtained by carefully adjusting the PCs. The power difference between the two lasing peaks is less than 2 dB, and the OSNR is about 50 dB.

SMFs With a Ge/F Co-Doped Inner Core for SBS-Based Discriminative Sensing of Temperature and Strain

Abstract: Three-layered single mode fibers with a GeO2 and F co-doped inner core are proposed. Stimulated Brillouin scattering properties in the fibers are investigated for the discriminative sensing of strain and temperature. The optical properties of the proposed fibers are designed to be well compatible with those of the widely used standard single mode fibers. The acoustic properties, including effective acoustic velocity, Brillouin frequency shifts, and peak Brillouin gain efficiencies of the first three acoustic modes, are numerically calculated and elaborately analyzed under different structural and doping parameters. The co-doped fibers with three different structural and doping parameters are chosen for simultaneous sensing of temperature and strain because of their capability of supporting two comparable peaks, which can be easily identified and distinguished in the Brillouin gain spectrum. The sensing properties of the fibers are estimated and discussed. The temperature and strain sensitivities as well as the temperature and strain errors are calculated to be comparable to those of the few mode fibers and multimode fibers.

A Nanoscale Fano Resonator by Graphene-Gold Dipolar Interference

Abstract: A nanoscale Fano resonator composed of a hybrid graphene disk-gold ring combination is reported in this letter. The inner narrow dipolar resonance of a discrete state induced by graphene interferes with the outside broad dipolar resonance of a continuum state induced by gold, thus forming an asymmetric Fano transparency within the absorption window. The metastructure exhibits a wide tunable band along with an excellent refractive index sensing capability of 2344 nm/RIU. The geometry adjustment modulates the spectral response giving chances to the equivalent of electromagnetically induce transparency. Moreover, the group index exceeds 760 within the transparency window enabling a potential use in slow light or light storage applications. The analytic analysis is in accordance with the numerical simulation results.

Magnetically Controlled Nanofocusing of a Graphene Plasmonic Lens

Abstract: In this paper, we propose a method to tailor the nanofocusing of plasmons on graphene plasmonic lens, which is composed of graphene and circular dielectric gratings of magneto-optical material beneath it. With an external magnetic field parallel to graphene surface, the magneto-optical effect of substrate leads to the difference in modal indices of graphene plasmons, which also introduces an additional relative phase difference between these two plasmons during excitation and propagation. Together, these two effects enable us to tailor the position of focal points through external magnetic field, which has been described by an analytical approach based on phase matching and verified by numerical simulations. With an operation wavelength of 8500 nm and an external magnetic field from B = −1 T to B = 1 T, a shift distance over one and a half times of plasmons wavelength for focal points or donut-shaped field profiles can be obtained under linearly or circularly polarized light. The proposed scheme has potentials in diverse applications, such as the tunable nanofocusing and particle manipulation.

Multimode interference-based fiber-optic strain and temperature sensor using polarization-maintaining fiber

Abstract: A cost-efficient fiber-optic strain and temperature sensor has been proposed and demonstrated experimentally. The sensor consists of a segment of polarization-maintaining fiber (PMF) and two segments of multimode fiber (MMF). Two segments of MMF, which are used as beam splitter and combiner, are embedded on both ends of the PMF. The all-fiber sensor is put in the middle of the single-mode fiber. Due to the ratio of the strain and temperature responses of the sensor, the measurement of strain and temperature can be achieved by monitoring the transmission spectrum. The experimental result shows that the strain sensitivity is up to −3.16 pm / μϵ in the range of 0 to 1000 μϵ and the temperature sensitivity is 0.071 nm / ° C in the range from 10°C to 45°C. This sensor exhibits the advantages of low cost and high sensitivity and may have potential application in strain and temperature measurement.

Optical modulation format recognition for polarization-multiplexed coherent system using Chinese restaurant process

Abstract: -In digital coherent optical receivers for various polarization-multiplexed high-order modulation formats such as BPSK、QPSK、8PSK and 16QAM signals, we propose and investigate a blind modulation format recognition method using the Chinese Restaurant Process, a kind of Dirichlet model, which is based on the observation of samples in Stokes space. The recognition rates of different number of data points under different optical signal-to-noise ratios (OSNRs) are investigated in detail for four modulation formats. In addition, the recognition characteristics of the proposed method are compared with other format recognition methods in Stokes space. It is shown that the approach has a better performance with higher recognition rates, particularly under a lower OSNR.

Analogue of Fano resonance and electromagnetically induced transparency in a graphene strip-ring compact resonator

Abstract: A compact graphene strip-ring hybrid resonator working in the mid-infrared regime is proposed as an analogue of Fano resonator or electromagnetically induced transparency. The dipolar surface plasmon resonance induced by the ring interferes with the x-polarized strip resonance forming a symmetric or asymmetric transparency window within the absorption profile. The spectral response can be modulated not only by the Fermi energy level of graphene, but also the geometry shape of the configuration. The sensitivity reaches 2450 nm/RIU and the light in the transparency window is slowed down to over 1/1090 times the speed in vacuum. The analytic analysis is in accordance with the 3D simulation results. Our compact design may have potential view in optical sensors, optical switches and light storage field.