查看更多>>摘要：Active transverse electric and transverse magnetic pass polarizers with lengths of only 1.92 mu m and 5.95 mu m based on silicon waveguides and phase change material VO2 films are theoretically demonstrated. The optical characteristics of the polarizers are simulated by using finite difference mode simulation. By controlling the phase state of VO2 film, the polarizers can realize the regulation of TE and TM polarizations. The insertion losses of both polarizers are less than 2.2 dB in the insulating state. When trigger to the metallic state, the unwanted polarization attenuation exceeds 21.07 dB while insertion losses are kept below 0.71 dB at a center wavelength of 1550 nm. Both polarizers have a high extinction ratio in the operating bandwidth of 200 nm. This provides a new way for polarizers based on VO2 film and silicon waveguide.
查看更多>>摘要：Based on Rotational Doppler Effect of light beam carrying orbital angular momentum, the lateral rotational velocity of the target is able to be measured. However, most of current researches about rotational velocity measurement only focus on the case of constant rotational velocity. Here, a novel method of non-constant rotational velocity measurement is proposed. This method uses the signal processing method of time-frequency analysis, and can simultaneously obtain the rotational velocity and rotational acceleration, without increasing the complexity of the system. A flat disk is fixed to the electric adjustable motor for simulating any non-constant rotational velocity, and a proof-of-concept experiment system is established. Experimental results show that the relative accuracy of rotational velocity is better than 0.7% and the relative accuracy of rotational acceleration is better than 1%. This is of great significance to the field of complex rotating target measurement.
查看更多>>摘要：This paper proposes a numerical simulation of an optical frequency comb scheme at 1550 nm based on a dual-frequency laser pump in the AlGaAs-on-insulator waveguide. Optical frequency comb with a 5 dB spectral bandwidth of approximately 125 nm is obtained within a 0.08-m normal-dispersion AlGaAs waveguide based on pulse compression, self-phase modulation, and optical wave breaking. The influences of power difference and frequency spacing of the dual-frequency lasers on the optical frequency comb are investigated along with the improvements in comb flatness due to pulse shaping.
查看更多>>摘要：We have developed a sensing platform using a long-period fiber grating (LPFG) integrated black phosphorus (BP) thin film from the numerical simulation analysis and experimental process verification. Due to the high optical absorption of BP, the attenuated depth of the cladding mode in the BP coated LPFG (named BP-LPFG) sensor can be varied by the change of external environment. Benefited from the BP film, the sensing system shows a superior enhancement in the refractive index (RI) detection compared to the use of bare LPFG. The sensitivity can reach 122.1 dB/RIU, 139.5 dB/RIU, and 931.9 dB/RIU in the RI regions of 1.33-1.38, 1.39-1.44, and near 1.455, respectively. Moreover, this sensing system has been applied to implement the highly sensitive and label-free detection for the bovine hemoglobin (BHb) molecules, with a sensitivity of 5.6 dB/(mg/mL) and a detection limit of 0.05 mg/mL achieved. The detection limit is 2600 times lower than the hemoglobin threshold for the confirmation of men's anemia illness, defined by the World Health Organization (WHO). This newly sensing platform is promising in the early clinical diagnose for anemia illness.
查看更多>>摘要：A fiber optic temperature sensor utilizing a thin polarization maintaining fiber (PMF) based Sagnac loop is proposed and experimentally demonstrated. A Sagnac loop consisting of a thin PMF has a large fringe visibility of up to 46.16 dB. Except polarization eigen modes, cladding modes are excited owing to fiber mismatch to enhance the temperature sensitivity. The resonant dips of the wavelength spectrum are utilized to investigate the temperature characteristics. Experimental results show that the excited cladding modes in the thin PMF can improve the sensitivity. The temperature sensitivity of the sensor is enhanced by exciting more cladding modes, and it reaches as high as -1.55 nm/degrees C and the corresponding linearity is 99.96%. The sensor is anticipated to has promising prospects in temperature measurement for harsh environment.
查看更多>>摘要：In this paper, an asymmetric directional coupler (DC) based on a GaAs-CaF2 hybrid plasmonic waveguide (HPW) and a GaAs nanowire (NW) is designed for the mid-infrared polarization beam splitter (PBS). The mode characteristics of the GaAs-CaF2 HPW and GaAs NW-based PBS are simulated by using the finite element method (FEM). With the appropriate widths of the HPW and NW, the TE polarization mode in the HPW and NW is phase-matched, whereas the TM polarization mode is phase mismatch. Hence, the TE mode undergoes a strong coupling to the GaAs NW while the TM mode pass through the GaAs-CaF2 HPW directly. The results show that the PBS achieves the extinction ratio (ER) of 19.78 dB and insertion loss (IL) of 1.64 dB for the TE mode, ER of 7.78 dB and IL of 2.64 dB for the TM mode at the operating wavelength of 3.5 mu m. The PBS based on an asymmetric DC paves the way to achieve integrated waveplates, which has potential applications in the detection and analysis of airborne molecules and the optical communication techniques with large signal transmission capacity.
查看更多>>摘要：As a new proposed spectrometer, the filter-based spectrometer uses a group of filters with known transmittance to modulate the spectrum of an incident light beam. After employing a post-processing algorithm, the spectrum of the beam can be reconstructed. For such spectrometers, the transmittance curve characteristics of the filters have a crucial impact on the spectrum reconstruction results. To better capture the details of the spectrum curve of the incident light beam, we propose a new nano-structure spectrometer by introducing gold nano-pillars to the photonic crystal (PC) filters. Because of the surface plasmon resonance effect of the gold nano-pillars, narrow bands will be generated on the transmittance curve of the new filters, which can improve the spectral reconstruction capability of the filters. In this paper, we first briefly introduce the principle of the filter-based spectrometer. Then, the transmittance curves of the filters are simulated by multiple random Gaussian functions according to the waveform of the transmittance curve of practical filters. And the simulated transmittance curves are used to reconstruct the spectrum of a beam to study their anti-noise capability. Next, new filters are designed by introducing gold nano-pillars to the PC filters. And their transmittance curves are calculated by the finite-difference time-domain (FDTD) approach. Finally, the spectrum reconstruction results are compared with those of the PC filters. The simulation results show that the introduction of gold nano-pillars can significantly improve the spectrum reconstruction ability of the PC filters.
Thanh Hai LeQuoc Hung PhanThi-Thu-Hien PhamHuy-Mai Le...
5页
查看更多>>摘要：Dengue fever is one of the most common diseases in tropical and sub-tropical regions of the world, and has a variety of unpleasant and painful symptoms, including fever, bleeding, and even death. Thus, effective methods for its early-stage detection and diagnosis are urgently required. Accordingly, the present study proposes a method for detecting dengue virus through an inspection of the anisotropic polarization properties of blood serum samples, as measured using a backscattering polarimetry technique and Mueller matrix imaging method. The feasibility of the proposed approach is demonstrated using 31 real-world blood samples comprising 17 dengue-infected samples and 14 healthy non-dengue samples. It is shown that the values of the diagonal elements of the Mueller matrix for the non-dengue samples are significantly higher than those for the dengue samples. By contrast, the depolarization index of the dengue samples is higher than that of the non-dengue samples. Moreover, among the four Mueller matrix transformation (MMT) parameters considered in the present study (A, B, T and G), three of them (A, B and T) exhibit significant differences between the non-dengue and dengue samples, respectively. Thus, overall, the results indicate that the proposed method has significant potential as a rapid, low-cost, and effective technique for dengue fever diagnosis applications.
Hajshahvaladi, LeilaKaatuzian, HassanDanaie, Mohammad
13页
查看更多>>摘要：In this paper, a refractive index biosensor is proposed which employs Si photonic nanorings coupled to ring-shaped plasmonic nanohole arrays (PNA) on a hybrid substrate to facilitate sensing of different glucose concentrations in water solution. The proposed structure can be used as a single-mode refractive index biosensor with a high sensitivity of 1278 nm/RIU, a figure of merit (FoM) of 168.1 RIU-1, and good detection accuracy of 0.13 nm(-1). The sensitivity and FoM values of the proposed structure are highest in comparison with many reported structures in recent years, while it uses a simple structural topology. The effects of various structural parameters on the reflection spectrum and sensing performance are comprehensively surveyed using the 3D FDTD method. Using the proposed structure, the strength of the interaction between the applied light and the analyte is effectively enhanced and the propagation loss is relatively reduced. Hence, the designed structure is an appropriate candidate for ultrasensitive biosensing applications.
查看更多>>摘要：In this paper, a dynamically switchable dual-band absorber based on electromagnetically induced reflection (EIR) in metal-graphene hybrid metamaterial is proposed. The unit cell of metamaterial absorber has three layers. The top layer consists of two split-ring resonators (SRRs) and two orthogonal cut-wires (CWs) with different lengths. Due to the low reflection dips in EIR structure and good absorption of graphene, two absorption bands accompanied with more than 90% absorptions are obtained under y-polarized and x polarized incident waves, respectively. The power loss densities at the absorption points clearly reveal the absorption positions of the metamaterial absorber. In addition, the electric field, magnetic field and surface current distributions explain the reason of high absorption. According to the surface currents at four resonant points, we draw the schematic diagrams of multipole moments, which are confirmed by multipole scattering theory. The tunable absorption performance of metamaterial absorber can be observed by tuning the Fermi level of graphene. The metamaterial absorber exhibits excellent wide polarization angle behavior and shows great prospects in multi-band metamaterial absorber under oblique incidence. The proposed metamaterial absorber expands the development of metamaterial and shows great potential for multifunctional metamaterial absorber.
NSTL
Elsevier