Abstract:Traditional multi-mode fiber spectrometers rely on algorithms to reconstruct the transmission matrix of the fiber, facing the challenge that the same wavelength can lead to many totally de-correlated speckle patterns as the transfer matrix changes rapidly with environment fluctuations (typically temperature fluctuation). In this manuscript, we theoretically propose a multi-mode-fiber (MMF) based, artificial intelligence assisted spectrometer which is ultra-robust to temperature fluctuation. It has been demonstrated that the proposed spectrometer can reach a resolution of 0.1 pm and automatically reject the noise introduced by temperature fluctuation. The system is ultra-robust and with ultra-high spectral resolution which is beneficial for real life applications.

Abstract:Due to the changeable brightness outside the tunnel, the lighting brightness at the exit and entrance of the tunnel needs to be adjusted in time, so as to ensure that the driver can feel the difference of light intensity within the range that the human eye can adapt to when passing through the tunnel. In this paper, a tunnel lighting control strategy based on variable reduction factor is proposed, which can ensure that the lighting around the tunnel is within the range that the human eye can adapt to at any time. Through the field data collection and comparison and experiments, it can be shown that the lighting control method not only can improve the lighting quality in the tunnel, but also have better energy-saving effect and can reduce the cost of manual operation and maintenance.

Abstract:A novel nanostructure based on a simple metal-dielectric-metal (MDM) bus waveguide with sliver baffle as well as an E-shaped cavity is proposed to generate double Fano resonances arising from interference between broad continuous state and narrow discrete state. The commercial software COMSOL based on finite element methods is used to explore the Fano resonances properties and the senor properties of the system. According to the simulation results, it is demonstrated that E-shaped cavity can generate two discrete states, and the continuous sate is constructed by loading sliver baffle in bus waveguide. Moreover, it can be found that the Fano peak wavelengths and profiles can easily be tuned via structural parameters. Interestingly, the independent control of the left Fano resonance (LFR) can be accomplished by changing horizontal cavity length of E-shaped cavity. Meanwhile, our proposed nanostructure has a higher sensitivity of 1 440 nm/RIU as well as a higher figure of merit (FOM) value approximately 5 244. In conclusion, the proposed independently tunable Fano nanostructure may have a great promising in the fields of nanosensors, filters and other optical devices.

Abstract:A Sagnac fiber interferometer with the population grating formed in saturable erbium-doped fiber (EDF) for fiber Bragg grating (FBG) dynamic strain sensing is proposed. In this configuration, a semiconductor optical amplifier (SOA)-based fiber ring laser with an FBG reflector is employed in the sensing part and a Sagnac interferometer based on transient two-wave mixing (TWM) via dynamic population gratings in single-mode polarization maintaining erbium-doped fiber (PM-EDF) is used in this detecting part. Experimental results show that the Sagnac fiber interferometer detection system can stably respond to dynamic strains at high frequencies. As an example of application, the response of the sensor system to continuous sinusoidal ultrasonic signals is presented. The proposed simple and robust configuration has an all-fiber design based on commercially available elements, which makes it promising for applications in fiber optic ultrasonic sensors.

Abstract:In this paper, we report an experimental observation of different states of multi-pulse operation in an actively Q-switched Er-doped fiber laser, which has applications in pulse coding in optical communications. The Q factor is switched by an electro-optic modulator. Completely separated multiple pulses are obtained due to the short response time of the modulator. The influence of pump power and modulation frequency on output pulse state is investigated. In the experiment, the repetition rate of Q-switched pulse is not always consistent with the modulation signal. Single-pulse, single-dual-pulse, dual-pulse, dual-triple pulse, and multiple pulses are observed in one modulation period by increasing pump power. Single-pulse is also observed in two or three modulation periods by increasing the frequency of modulation signal. In addition, the waveform of modulating signal and the polarization state of modulated signal also affect the multi-pulse operation accordingly.

Abstract:Following the previous work, in this paper, the antireflective films thicknesses, refractive indexes and reflectance spectra of different color categories of the polycrystalline silicon cells are tested and compared. It is found that the color difference of polycrystalline silicon cells is mainly caused by the antireflective film. Then the matrix transfer method is used to simulate the reflection spectra according to the actual tested parameters of the samples, and the effectiveness of the simulation is verified. Finally, according to the distribution of the spectral solar irradiance, the total solar absorption of the polycrystalline silicon cells with different antireflective film thicknesses is simulated. The optimal value of the antireflective film thickness of the polycrystalline silicon cell is calculated. This study has important guiding significance for photovoltaic (PV) enterprises to realize the optimal production of plasma enhanced chemical vapor deposition (PECVD) process in production.

Abstract:Visible light communication (VLC) technology is a new type of wireless communication technology, which employs a light source as the carrier of information to realize illumination and communication simultaneously. This paper adopts a single InGaN/GaN-base multi-quantum well blue micro-light emitting diode (LED) as the light source, designs pre-emphasis circuit, LED driver circuit, impedance matching network, etc., and builds a high-speed real-time VLC system. It has been verified that the LED achieves a 3 dB modulation bandwidth of 450 MHz or more; and the real-time communication rate reaches over 800 Mbit/s at a distance of 2 m. The communication bit error rate (BER) is as low as at a communication rate of 622 Mbit/s. Experimental indicators including 3 dB bandwidth, communication rate, and communication BER are all taken into account. Therefore, this VLC system supports high-quality high-speed real-time communication.

Abstract:Quantum logic gates are the basic building blocks of quantum computing system. Single qubit Pauli-X, Y and Z quantum gates are very much well known in quantum computing community. In this paper, we develop tri-state Pauli-X, Y and Z quantum gates using phase encoding technique of light. This phase encoding mechanism makes the implementation of those gates easier even with tri-state approach. As light is used for signal representation, one can exploit the parallelism in operation.

Abstract:In this study, using surfactant monoethanolamine (MEA), zinc oxide (ZnO)-MEA humidity sensor based on ZnO was successfully prepared by hydrothermal method. MEA makes the surface of the ZnO-MEA have more oxygen vacancy and hydrophilic functional groups, which improves the performance of ZnO humidity sensor. ZnO-MEA achieved a change of 4 orders of magnitude at room temperature in the relative humidity (RH) from 11% to 95%, and it shows better linearity, shorter response/recovery time (20 s/15.9 s), smaller humidity lag and long-term stability. In addition, the distribution of ZnO-MEA particles is more uniform and provides more active sites for adsorption of water molecules to enhance humidity sensing performance.

Abstract:According to the chemiluminescence reaction mechanism of nitric oxide (NO) and ozone (O3), a new cylindrical total reflection S-type optical cavity design for rapid detection of NO gas is proposed. The optical cavity model is based on the total reflection S-type structure on the inner wall of the cylinder. Optical software ZEMAX was used to simulate the optical path of the model, and software FLUENT was used to simulate and verify the structure. The comparative analysis showed that the chemiluminescence collection efficiency of the S-type optical cavity collection path was 36.6%, and the gas reaction and mixing in the S-type optical cavity model was more sufficient, and the reaction mixing stability error was 0.049, which was 2 times higher than the traditional stability error. The model is simple in structure and meets the new national standards. It provides a practical idea of design for the real-time exhaust gas detection.

Abstract:A detection system based on supercontinuum laser absorption spectroscopy (SCLAS) technology was built up in this study. The absorption spectra of CH4 in different near-infrared bands were measured based on the SCLAS detection system. Under normal temperature and pressure, the absorption spectra of CH4 at different concentrations in the bands of 1 319—1 339 nm and 1 656—1 676 nm were measured. The linear models of CH4 concentrations in different bands were established. The fitting coefficient (R2) of the models were 0.995 7 and 0.996 1, respectively. In order to improve the concentration inversion ability of the model, the weight distribution of each model was determined by R2 and sum of squared error (SSE) to obtain a new combined model. The maximum relative error of the concentration inversion was reduced from 2.3% to 1.3%. The experimental results show the feasibility of applying the SCLAS technology to CH4 concentration measurement, and it also verifies that the dual-band combination model can improve the accuracy and stability of the CH4 concentration measurement.