Optical Devices|18 Article(s)
Concentration Performance Analysis of Solar Simulator Based on Compound Parabolic Concentrator
Hao WANG, Yue-gang FU, Guo-yu ZHANG, Gao-fei SUN, Shi LIU, Jian ZHANG, Da XU, Ling-hao WU, and Jun-jie YANG
To solve the problem of low irradiance caused by the low energy utilization rate of an existing solar simulator, a Compound Parabolic Concentrator (CPC) based on the basic imaging principle of the solar simulator was proposed to improve the concentrating system of the simulator. The condensing mechanism of the CPC and a traditional condenser was analyzed, and the parameter design method of the CPC was derived based on the edge-ray principle. Using the LightTools software combined with a nested body light source and the CPC to build a condenser model, the ideal maximum receiving angle of the CPC was analyzed. A comparison model between the ellipsoidal condenser and the combined condenser system was established to verify the theoretical analysis. The optimal intercept ratio was obtained through an intercept analysis to optimize the initial structure and to determine the final structure of the CPC. Results show that the energy utilization rate of xenon lamps used in the CPC is as high as 94.86%. Furthermore, the irradiance of the entire solar simulator can be greatly improved. The findings of this study present a reference for designing highly energy efficient and high-irradiance solar simulators.
Acta Photonica Sinica
  • Publication Date: Dec. 25, 2020
  • Vol. 49, Issue 12, 1 (2020)
Study on Ionization Efficiency of Cesium Ion Source for Microchannel Plate Test
Ye-ping WANG, Yun-sheng QIAN, Yi-zheng LANG, Zi-heng WANG, and Xiang-yu KONG
In order to study the performance test technology of cesium ion bombarding microchanne plate, a cesium ion beam generator was used as an experimental device. To analyze the whole process of cesium ion beam generation and study the factors affecting the ionization efficiency of cesium plasma generated by cesium atom bombarding ionized filament (tantalum, with a desorption work of 4.12 eV). From the physical process, it is found that the ionization efficiency is affected by the ionization environment temperature, the power of ionization filament and the focusing voltage. Combined with the of Saha-Langmuir equation, it is analyzed that the emitted ion current can be used as the actual characterization of the ionization efficiency. In the experiment, the ion current was measured by feedback current method of operational amplifier by changing the factors of ionization environment temperature and ionization filament power. The experimental results show that the number of cesium atoms can be kept stable by controlling the ionization environment temperature, and the ionization efficiency of cesium ion is greatly affected by the ionization environment temperature and the ionization filament power. When other working conditions remain unchanged, the ionization efficiency reaches the maximum when the ionization filament power Qc is 2.818 W; when the ionization environment temperature Tc is 110℃, the ionization process is stable and the most sufficient, and the maximum output ion current is about 25 nA. The experimental results are in good agreement with the theoretical model. By controlling these factors, the incident intensity of cesium ion beam can be stably adjusted.
Acta Photonica Sinica
  • Publication Date: Dec. 25, 2020
  • Vol. 49, Issue 12, 11 (2020)
Resolution Research of Low-light-level Image Intensifier Based on Electronic Trajectory Tracking
Ya-feng QIU, Wu-ling YAN, and Sang-tun HUA
Aiming at the problem that the current theoretical models for calculating the resolutions of low-light-level image intensifiers are not accurate enough and can’t provide the optimization conditions intuitively, a theoretical model based on electron tracking is proposed. Electron scattering formula of uniform-doping GaAs photocathodes is used for obtainig the distribution of emitted electrons, which is different from the Lambertian distribution. The proximity system is approximated to a longitudinal uniform electric field to establish the electron transport model. Based on the secondary electron emission distribution, the electron transport model in the microchannel plate is established under non-abnormal working conditions. With the distribution of the electron beams on the phosphor screen, the modulation transfer function is calculated by Monte Carlo method, and the limiting resolution is obtained by taking the standard value as 0.3. The resolutions of four different types of image intensifiers are calculated, and the results show that the largest error between the model simulation results and the experimental results is only 5.0%, less than the errors from the existing models(more than 10%), which proves the practical value and good application prospect of the model.
Acta Photonica Sinica
  • Publication Date: Dec. 25, 2020
  • Vol. 49, Issue 12, 19 (2020)
Effect of Optical Window on Optical Response Characteristics of SiGe/Si Heterojunction Phototransistor
Pei MA, Hong-yun XIE, Yin SHA, Yang XIANG, Liang CHEN, Min GUO, Xian-cheng LIU, and Wan-rong ZHANG
The effects of different optical window positions and different optical window areas on the optical response characteristics of SiGe/Si Heterojunction Phototransistor (HPT) are analyzed. HPTs with emitter optical window can generate more photo-generated carriers due to the longer absorption region, and then bring out a larger optical-generated voltage at emitter junction interface, which is beneficial for electronsto inject from the emitter into the base. Therefore, a larger collector current and optical gain are obtained. When the optical window area is 10 μm×10 μm, the maximum optical gain of SiGe/Si HPT can reach 9.24 with 650 nm incident light wavelength and 2.0 V collector voltage. HPTs with base optical window get larger photo-generated carrier density in the absorption region when incident power become larger, then the possibility of rapid relaxation for photo-generated holes increases, which relieves the limitation of the operating speed from hole's low mobility to some extent, so the optical characteristic frequency is increased. When the optical window area is 10 μm×10 μm, the optical characteristics frequency of SiGe/Si HPT can reach 16.75 GHz with 650 nm incident light wavelength and 2.0 V collector voltage. For the SiGe/Si HPTs with emitter optical window that can achieve higher optical gain and optical characteristic frequency merit, when the optical window area gradually increases from 3 μm×10 μm to 50 μm×10 μm, the effective injection area of electrons at emitter junction interface gradually increases. However, at the same time the emitter junction capacitance and collector junction capacitance increase and results the RC delay time increasing, so the optical characteristic frequency gradually decreases. The optical gain and optical characteristic frequency merit increase gradually with the increase of the optical window area, but the rate of increase slows down and the optical gain and optical characteristic frequency merit tends to become saturated.
Acta Photonica Sinica
  • Publication Date: Aug. 25, 2020
  • Vol. 49, Issue 8, 0823001 (2020)
Orthogonal Phase Detection Method of Light-addressable Potentiometric Sensor
Xing-yuan TONG, Xiao-guang YAN, and Dong CHEN
The amplitude detection method of the Light-Addressable Potential Sensor (LAPS) is susceptible to noise interference, low sensitivity, low precision, low signal-to-noise ratio, and is greatly affected by the modulated light signal, which affects the accuracy of the detection results. Therefore, a LAPS detection method based on orthogonal phase detection is proposed. In this method, the LAPS photocurrent signal is multiplied by two orthogonal signals, and the direct current component is extracted by low-pass filters and divided, so that the phase information of LAPS photocurrent signal can be obtained. Compared with the existing LAPS phase detection method, the proposed method has the advantages of low algorithm complexity and high real-time performance. The influence of the modulated light intensity on the amplitude detection and phase detection of LAPS is studied. The sensitivity, linearity and signal-to-noise ratio of the conventional amplitude detection method and the orthogonal phase detection method of LAPS to the detection of pH are compared. The results show that, compared with the amplitude detection method, the modulated light intensity has less effect on the phase detection of LAPS. When the frequency at 10 kHz, the pH is from 1.68 to 10.01, the sensitivity of the phase detection method is increased by 7 mV/pH, the precision accuracy is increased by 14.9 mpH, the nonlinear error is reduced by 0.003%, the mean square error is reduced by 0.105 1×10-5, the signal-to-noise ratio is increased by 8.2827. The proposed method is especially suitable for LAPS detection in weak modulated light intensity.
Acta Photonica Sinica
  • Publication Date: Apr. 25, 2020
  • Vol. 49, Issue 4, 0423002 (2020)
Near-infrared Properties of Optical Planar Waveguides Formed by H+ Ion Implantation in Yb3+-doped Phosphate Glasses
Jing-yan LÜ, Hai-tao GUO, Jun XU, and Chun-xiao LIU
The Yb3+-doped phosphate glass waveguides by the hydrogen-ion implantation under the condition of energies of (0.5+0.55) MeV and doses of (1.0+2.0)×1016 ions/cm2 were fabricated, and characteristics of the waveguide were studied in the near-infrared band. The change of refractive index after the implantation was measured by the prism coupling method, which corresponded well with the calculated effective refractive index by the reflectivity calculation method. The formation theory of the ion-implanted planar waveguides was discussed through simulating the vacancy distribution induced by the irradiation. The propagation mode of light in the waveguide was simulated by using the FD-BPM, which suggested that the near-infrared waveguide structure could be fabricated by irradiating the Yb3+-doped phosphate glass with the energetic hydrogen ions.
Acta Photonica Sinica
  • Publication Date: Apr. 25, 2020
  • Vol. 49, Issue 4, 0423001 (2020)
Design of Metasurface Lens with Two Focal Spots Based on Polarization Response
Peng-jiu ZHAO, Shou-peng LIU, Yu LUO, Wei REN, and Xiao-hu CHEN
A focusing lense with two focal spots based on dielectric metasurface was designed which can extend the focus axially. The device modulates the propagation phase and the geometric phase at the same time and realizes the independent control of a group of orthogonal polarized incident light by varying the aspect ratio and the rotation angle of the titanium dioxide pillars. The designed metasurface focuses the left-handed and right-handed circularly polarized light at contiguous positions to extend the focus axially. We extend the length of focus twice as initial value at 650 nm wavelength and maintain the lateral width of the focus in the meantime. The optimization of the focus shape and the switch of focus position with different focal lengths can be realized by adjusting the incident light into an elliptically polarized light.
Acta Photonica Sinica
  • Publication Date: Sep. 01, 2020
  • Vol. 49, Issue 9, 0923002 (2020)
Research on Auto-split GaN-based Vertical Structure LED
Xu-liang SU, Can WANG, Lei-ying YING, Huan XU, Rong-bin XU, Yang MEI, Zhi-wei ZHENG, Hao LONG, and Bao-ping ZHANG
In order to solve the problem of damage to LED chip caused by inductively coupled plasma etching and substrate cutting, and improve the yield of devices, a new process for fabricating GaN-based vertical structure LED is proposed. The auto-split vertical structure LED without substrate cutting is successfully fabricated. In the process of device preparation, chemical mechanical polishing is used to reduce the thickness of n-GaN instead of inductively coupled plasma etching , which avoids the damage to the side wall and active region of the device caused by inductively coupled plasma etching. The problem of substrate cutting is solved by temporary substrate transfer technology, and a single LED chip can be obtained without substrate cutting. Compared with the regular LED, the electrical characteristics of 300 μm × 300 μm auto-split vertical structure LED are greatly improved. The forward voltage at 20 mA decreases from 3.17 V to 2.88 V, which decreases by 9%; the saturation current increases from 240 mA to 280 mA, increasing by 17%. The influence of electrode shape on the device performance is studied. The electrode shape is changed from disk shape to ring shape, the saturation current of 500 μm × 500 μm auto-split vertical structure led is increased from 450 mA to 490 mA, which is increased by 9%. The performance of auto-split vertical structure LED is expected to be improved by optimizing the electrode structure.
Acta Photonica Sinica
  • Publication Date: Dec. 25, 2020
  • Vol. 49, Issue 12, 27 (2020)
Research on Partial Negative Curvature Terahertz Hollow-core Waveguide
Qi-yuan MU, Yuan-feng ZHU, Lu XUE, Ya-ni ZHANG, De-peng KONG, Zheng-quan HE, Hong-jun LIU, and Li-li WANG
A novel partial negative curvature anti-resonance hollow-core terahertz waveguide is proposed. The waveguide cladding consists of two parts, one part is composed of a dielectric circular tube, which provides a part of the negative curvature boundary for the core; the other part is composed of a plurality of rectangular dielectric layers, and multiple dielectric layers for reducing confinement loss. This waveguide structure does not introduce a new cladding node while adding anti-resonant layers, and it is easy to achieve broadband low-loss transmission of terahertz waves. The full vector finite element method is used for the numerical simulation of the waveguide, and the broadband low loss characteristic is investigated. Based on the simulation analysis, the designed waveguide is printed via 3D printing technology, and the transmission characteristics are tested using a terahertz time-domain spectroscopy system. Experimental results show that the transmission loss of this negative curvature anti-resonance terahertz waveguide is less than 10 dB/m in the range of 0.29~0.42 THz, which is in good agreement with the numerical simulation.
Acta Photonica Sinica
  • Publication Date: Sep. 01, 2020
  • Vol. 49, Issue 9, 0923001 (2020)
Bifurcation-tunable Diffractionless Light Propagation in One-dimensional Non-Hermitian Photonic Lattice
Zhenjuan LIU, Haohao WANG, Yanan DAI, Zhiqing ZHANG, Yishan WANG, and Xinyuan QI
The light bifurcation transmission without diffraction in one-dimensional periodic compound photonic lattice was studied theoretically and numerically. When the lattice equals to degenerated Su-Schrieffer-Heeger model, the incident light with the wave number k=±π will bifurcate into two symmetric branches without any diffractionand the angles between two beams can be controlled by the coupling J between two lattice sites. In addition, a modulation phase ϕ is introduced. When the non-Hermitian perturbations satisfy the parity-time symmetry, the diffractionless light bifurcation phenomenon with any incident light wave can be realized as long as the incident wave vector k and the modulation phase ϕ respect the expression k+ϕ=±π. Further studies have shown that the next-nearest coupling can control the transmission angle and power division of two branches. This research provides new ideas for the design of optical switches and future all-optical paths.
Acta Photonica Sinica
  • Publication Date: Apr. 25, 2021
  • Vol. 50, Issue 4, 128 (2021)