Abstract:Awireless powered small volume light source composed of light emitting diode (LED) array is developed for implantation. According to the volt-ampere characteristics of LED and the load characteristics of coil coupling power supply, the light power and work distance of implant LED-array are optimized by changing the number and series-parallel connection mode of LEDs in receiver. The wireless powered implant can provide 5.4 mW light. The entire implant is seamlessly packaged within parylene, a biocompatible material, coating by chemical vapor depositing. The volume of the implant is 9 mm×4 mm×3 mm, the weight of which is only 0.25 g. The device can work continuously for more than three weeks in 0.9% saline and the prime prototype of the device has been validated by animal implantation.

Abstract:An AlGaN-based deep ultraviolet laser diode with convex quantum wells structure is proposed. The advantage of using a convex quantum wells structure is that the radiation recombination is significantly improved. The improvement is attributed to the increase of the effective barrier height for electrons and the reduction of the effective barrier height for holes, which results in an increased hole injection efficiency and a decreased electron leakage into the p-type region. Particularly, comparisons with the convex quantum barriers structure and the reference structure show that the convex quantum wells structure has the best performance in all respects.

Abstract:Color tunable thin film polymer solar cells have demonstrated the potentials of a wide applications in photovoltaics printing, which is significant for ink pollution reduction and energy saving. This work presents a new effective approach to realize color-tuning photovoltaic cells with optical microcavity structures. Aluminum-doped zinc oxide is utilized as electron transport layer material. With its high electrical conductivity, the thickness tuning range can be quite large, which means the cavity length has a wide variation range. It thus provides sufficient space for optical thin film design to obtain multi colors. By the transfer matrix method, device reflection and absorption spectra are numerically investigated. Based on that, the optical principles for color tunability are explored. In further step, the relationship between device photovoltaics performance and reflective colors are also discussed. Finally, the color coordinates and luminosities are calculated. As results, the colors of the devices designed are capable to cover a relatively large region in Commission Internationale de l´Eclairage (CIE) 1931 x, y chromaticity diagram, which is available to be integrated into the advertisement poster boards, building wall printing and other display applications.

Abstract:In recent years, magnetic interference thin films have gained wide attention in optical security devices field by virtue of their gonioapparent and dynamic 3D effects. Based on the color mechanism of metal-dielectric Fabry-Perot structure, a novel seven-layer magnetic thin film structure is proposed by adopting the ultrathin metal layer as a bonding layer and a pure metallic Ni layer as a magnetic layer as well as a reflective layer. Color target optimization optimac method is utilized that realizes the seven-layer metal-dielectric optically variable magnetic thin film structure with green at the normal incidence and purple-red at 60°. The structure effectively solves the delaminate problem and simplifies the multilayer structure. Through different combined magnetic field designs, the magnetic orientation experiment of the prepared magnetic optically variable thin film is carried out, and the 3D anti-counterfeiting with remarkable dynamic color change effect is obtained, which provides a new solution for optical security devices.

Abstract:Using the rate equation, several optical methods of characterizing the threshold of a laser diode (LD) were analyzed. The thresholdsdetermined by all methods are consistent if the spontaneous-emission-coefficient (β) is small. If β>0.05, the thresholds obtained by different methods are different. Especially, for micro-nano LDs with a large β, these methods are starting to become inaccurate. However, the d2S/dI2-I is a relatively accurate method to characterize threshold of these LDs compared to other methods. The effects of the spontaneous-emission-lifetime (τsp) and the photon-lifetime (τp) on thresholds were analyzed. The exact functions between the thresholdand the β, τsp and τp were obtained.

Abstract:A method based on polynomial regression algorithm (PRA) is proposed in this paper to compensate the nonlinear phase noise in optical frequency domain reflection (OFDR) systems. In this method, the nonlinear phase of OFDR systems is represented by the polynomial phase function, and then the coefficients of the polynomial phase function are estimated by PRA. Finally, the nonlinearity is compensated by match Fourier transform (MFT). Simulation results demonstrate that the proposed algorithm has good performance in compensating both weak and strong nonlinear phase noises of OFDR systems.

Abstract:In order to achieve broadband and efficient optical absorption, the multiple silver nanolayer was introduced into the photonic crystals to form a one-dimensional ternary periodic symmetric structure. The effects of thickness of each layer on the band range, absorption bandwidth, absorbance and absorption energy field distribution of the solar spectrum high absorption band were studied by the transfer matrix method. The absorption band with wavelength range from 724 nm to 1 188 nm, spectral width of 464 nm, and average absorbance of 0.78 was obtained by structural adjustment. The absorbed energy is mainly distributed in the first half of the symmetrical structure of the photonic crystal. When the thickness of the silver layer decreased from 30 nm to 15 nm, the local energy in each period increased significantly. At the same time, the distribution and transfer of energy in silicon and MgF2 layers can be controlled. The results of this paper can be used to improve the absorption of solar radiation, and provide an important basis for the design of photonic crystal and their application in solar energy utilization.

Abstract:Gallium oxide (Ga2O3) thin films were prepared on Si substrate by magnetron sputtering. The obtained samples were comprehensively characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM). Ti, Pt, Ni and AZO were deposited on the Ga2O3 thin films as electrodes. This paper mainly studies the metal-semiconductor contact formed by these four materials on the films and the influence of annealing at 500 °C on the metal-semiconductor contact. The I-V characteristics show a good linear relationship, which indicates ohmic contact between Ga2O3 and other electrodes.

Abstract:In this work, inherent data-erasing functionality of a saturated erbium doped fibre amplifier (EDFA) is exploited to achieve an all-optical wavelength reuse with pulse amplitude modulation (PAM) format. A 10 GHz bandwidth distributed feedback laser (DFB) is directly modulated with 17 Gbit/s PAM-3 data signal and transmitted downstream over a 26.58 km fibre optical line terminal (OLT) incurring a maximum penalty of 1.81 dB. A saturated EDFA deployed at the optical network unit (ONU) terminal is utilized to optically suppress the extinction ratio of residual 17 Gbit/s PAM-3 downstream data significantly from 7.1 dB to 830 mdB. This facilitates direct reuse of the downstream carrier without the need for an additional electrical data eraser. With the all optical data erasing capability of EDFA over −10 dBm input power, the carrier re-used upstream transmission successfully delivers 17 Gbit/s PAM-3 data with a maximum transmission penalty of 0.99 dB. PAM-3 modulation format maximizes network efficiency by doubling the transmitted bits per symbol. Our technique is all-optical, it can support ultrafast systems with higher modulation formats and is power efficient.

Abstract:The approach for homogeneous core structure design and selection based on low crosstalk, low dispersion, and acceptable mode effective area have been explored. The forward and backward crosstalk behaviors with respect to wavelength, fiber bending radius, and twisting rate in 12-core, and 21-core single-mode trench-assisted homogenous multicore fiber have been analyzed. The new expression for forward crosstalk under bending and twisting conditions has been derived using the conventional method. For the analysis and optimization of crosstalk, three different core structures are considered, it helps to draw the attention to select the appropriate core structure model for multicore fiber, which follows the standards used in telecom services.

Abstract:In this paper, to reduce the non-linear phase error caused by gamma effect of the digital projector, a novel phase difference extraction method is proposed. First, through multi-layer discrete wavelet decomposition (DWT), the components of the original phase difference at different frequencies are extracted. Subsequently, the effective components are taken by the orthogonal matching pursuit (OMP) algorithm, and the phase difference is reconstructed. According to the upper and lower envelopes of the original phase difference extracted by cubic spline interpolation, the residual threshold of OMP is set. According to the results of three-dimensional (3-D) reconstruction experiment on a standard sphere, the proposed method is capable of reducing the errors in the original phase difference and achieving a better imaging result.

Abstract:For the design of the underwater laser detection system, the echo power equation of underwater target is derived, and the effects of water’s attenuation coefficient and incident angle on target’s echo power are analyzed. The bidirectional reflection distribution function (BRDF) of the single-station model is used to study the reflection characteristics of the target. The influence of the correlation coefficients of specular and diffuse reflection components on the reflected light intensity of special axisymmetric targets is studied. The signal-to-noise ratio (SNR) values of three types of target under different surface BRDF are given. The simulation results show that the larger the attenuation coefficient is, the smaller the echo power received, and the incidence angle is closer to 90°, the echo power is equal to 0. A smaller surface slope or a larger diffuse reflected coefficient will cause a smaller reflected intensity.

Abstract:When measured by laser induced breakdown spectroscopy, the characteristic parameters of the plasma fluctuate significantly with the experimental parameters, which would have a greater impact on the quantitative measurement. The effects of two experimental parameters, lens to sample distance (LTSD) and delay time, on plasma temperature and electron density were analyzed. Thereafter the optimal LTSD and delay time for quantitative analysis of Pb and Ni in soil were identified. Two element calibration curves were calculated by the internal standard method under the optimal LTSD and delay time. About the two elements, correlation coefficient of the calibration curves is above 0.993. The maximum relative standard deviation (RSD) were 4.47% and 4.76%, respectively, and the maximum relative errors were 12% and 4.8%, respectively. The experimental results showed that laser induced breakdown spectroscopymethod in combination with plasma characteristic parameter analysis shows the advantage on quantitative analysis of heavy metals in soil.

Abstract:The visibility of the underwater image is reduced due to the backscattering and signal attenuation, especially in highly turbid media. In this paper, we propose a polarization-based underwater image restoration method using logarithmic transformation and dark channel. Logarithmic transformation is first performed while maintaining the degree of polarization of the scene to increase the details of the images. Then we calculate the backscatter value through dark channel to estimate the degree of polarization of backscatter. The restored image can be obtained by the polarimetric recovery method. The experimental results illustrate the capabilities of the proposed method.

Abstract:The article provides a design of all-optical non-gate and NOR gate based on two-dimensional photonic crystal ring resonator structure. This design extracts the energy band structure of two-dimensional photonic crystals by plane wave expansion method and analyzes the steady-state electric field distribution of the device structure by the finite-time-domain difference method. The results demonstrate that the non-gate and NOR gate can achieve logic functions with a response period of 0.388 ps, a contrast ratio of 8.98 dB and 7.88 dB. The high extinction ratio and small structure sizes which are only 15.2 μm×15.2 μm and 13.984 μm×24.928 μm also contribute to convenient integration. The design with ring resonator makes optical logic gate devices more diverse, providing a basis for the optimal design of integrated circuits, and it also has important application research value.