Enhanced Raman Scattering Based on Thickness of Oscillating Metallic Optical Waveguide
Lu Yan, Shi Xiaowen, Deng Xiaoyan, Tao Yumeng, Chen Hongli, Fang Jinghuai, and Zhong Chonggui
In this study, the Raman scattering of copper phthalocyanine is enhanced by adopting a millimeter-scale oscillating metallic optical waveguide structure. Different from the traditional surface-enhanced Raman spectroscopy (SERS) technology that creates hot spots by designing complex nanostructures of precious metals, we increase the distance between the upper and lower surface metal cladding layers of the metal optical waveguide, which can increase the thickness of the guided wave layer coupling of light energy into guided wave layer, thereby enhancing the interaction between light and matter. Although increasing the thickness of the guiding layer has the risk of a single-mode field strength drop, the advantages are obvious. First, the high mode density facilitated the coupling of incident light energy with the waveguide layer. Second, the excitation light could be incident nearly perpendicular to the waveguide surface, thereby simplifying the optical setup. Finally, the polarization-independent characteristics of the thick waveguide structure contributed to the Raman enhancement.
  • Jun. 07, 2021
  • Laser & Optoelectronics Progress
  • Vol.58 Issue, 11 1123002 (2021)
  • DOI:10.3788/LOP202158.1123002
Multibeam Formation Method for Silicon-Based Optical Waveguide Phased Array
Zhou Hengchao, Wang Chunyang, Wang Zishuo, Liu Xuelian, and Xiao Bo
Based on the background of multitarget detection in the lidar field, a multibeam formation method for a silicon-based optical waveguide phased array is proposed and the working mechanism of the optical waveguide phased array is introduced. Based on the principle of beam deflection, the total aperture array is divided into several continuous subapertures by the subaperture method. After passing through each subaperture, the beam will be subjected to different phase modulation. Finally, various beams that can be deflected through different angles are formed at the exit end. According to the target threat degree, the number of array elements of the subaperture is adjusted and the multiple beams are divided uniformly or non-uniformly. Then, the energy of each beam can be reasonably distributed. Simulation results show that the far-field diffraction pattern appears at the desired angle, verifying the feasibility and effectiveness of the proposed method. Besides, the proposed method can significantly increase the number of targets detected by a phased array lidar and reduce the scanning time.
  • Jun. 07, 2021
  • Laser & Optoelectronics Progress
  • Vol.58 Issue, 11 1123001 (2021)
  • DOI:10.3788/LOP202158.1123001
Integrating the optical tweezers and spanner onto an individual single-layer metasurface
Tianyue Li, Xiaohao Xu, Boyan Fu, Shuming Wang, Baojun Li, Zhenlin Wang, and Shining Zhu
Optical tweezers (OTs) and optical spanners (OSs) are powerful tools of optical manipulation, which are responsible for particle trapping and rotation, respectively. Conventionally, the OT and OS are built using bulky three-dimensional devices, such as microscope objectives and spatial light modulators. Recently, metasurfaces are proposed for setting up them on a microscale platform, which greatly miniaturizes the systems. However, the realization of both OT and OS with one identical metasurface is posing a challenge. Here, we offer a metasurface-based solution to integrate the OT and OS. Using the prevailing approach based on geometric and dynamic phases, we show that it is possible to construct an output field, which promises a high-numerical-aperture focal spot, accompanied with a coaxial vortex. Optical trapping and rotation are numerically demonstrated by estimating the mechanical effects on a particle probe. Moreover, we demonstrate an on-demand control of the OT-to-OS distance and the topological charge possessed by the OS. By revealing the OT–OS metasurfaces, our results may empower advanced applications in on-chip particle manipulation.
  • May. 27, 2021
  • Photonics Research
  • Vol.9 Issue, 6 06001062 (2021)
  • DOI:10.1364/PRJ.421121
Polarization-robust mid-infrared carpet cloak with minimized lateral shift
Yao Huang, Jingjing Zhang, Jinhui Zhou, Bo Qiang, Zhengji Xu, Lin Liu, Jifang Tao, Nicolas Kossowski, Qijie Wang, and Yu Luo
With the advent and rapid development of the transformation optics and metamaterials, invisibility cloaks have captivated much attention in recent years. While most cloaking schemes suffer from limited bandwidth, the carpet cloak, which can hide an object on a reflecting plane, can operate over a broadband frequency range. However, the carpet cloaks experimentally realized thus far still have several limitations. For example, the quasi-conformal mapping carpet cloak leads to a lateral shift of the reflected light ray, while the birefringent carpet cloak only works for a specific polarization. In this work, we propose a conformal transformation scheme to tackle these two problems simultaneously. As an example, we design a mid-infrared carpet cloak in a silicon platform and demonstrate its polarization-insensitive property as well as the minimized lateral shift over a broad frequency band from 24 to 28.3 THz.
  • May. 19, 2021
  • Photonics Research
  • Vol.9 Issue, 6 06000944 (2021)
  • DOI:10.1364/PRJ.414437
Array Waveguide Gratings for FBG Demodulation Design and Performance Analysis
Zhang Xianxiu, Wang Cunyi, Yuan Pei, Zhang Dongliang, and Wang Yongqian
We theoretically analyze influence of the crosstalk, insertion loss, and bandwidth of the arrayed waveguide grating on the dynamic range, wavelength resolution, and demodulation accuracy of the demodulation system. The results show that the larger the bandwidth, the larger is the dynamic range of the demodulation system; however, the wavelength resolution will decrease. It also shows that the smaller the crosstalk, the higher is the demodulation accuracy. Then, we theoretically investigate the factors affecting the output spectral bandwidth of the arrayed waveguide grating, such as the number of diffraction orders of the arrayed waveguide grating, the number of arrayed waveguides, and the width of the horn. The results show that the passband bandwidth of the arrayed waveguide grating is larger when the number of waveguides is smaller and the width of the tapered waveguide opening is larger. Finally, we design an arrayed waveguide grating based on a 2% refractive index difference silica material system, which has the characteristics of wide bandwidth, low loss, and low crosstalk. It provides theoretical guidance for research on fiber-grafting demodulation systems based on arrayed waveguide grating. We then specify the optimization direction of the device and system.
  • May. 19, 2021
  • Laser & Optoelectronics Progress
  • Vol.58 Issue, 9 0923002 (2021)
  • DOI:10.3788/LOP202158.0923002
Subwavelength Transmission Properties of Graphene- and Metal-Coated Nanowires
Wang Yuncheng, Teng Da, Hu Juyuan, Wang Feifei, Xu Tianzi, Ruan Congyan, Li Yiqiang, Zhao Yinghao, Ou Jinjin, and Wang Kai
In this study, a comparative investigation of the subwavelength transmission properties of graphene- and metal-coated nanowires is conducted. By using the finite element method, the modal field distribution and transmission properties of the lowest-order modes are investigated based on the frequency and structural dimensions for single nanowires and nanowire dimers. The results showed that when the thickness of the metal layer is larger than the skin-depth, graphene-coated nanowires exhibit better fundamental modal field confinement. However, when the thickness of the metal layer is far smaller than the skin-depth, the subwavelength transmission properties of the metal-coated nanowires are comparable to those of graphene-coated nanowires. These results will provide a reference for choosing plasmonic materials and have potential applications in subwavelength photonic devices.
  • May. 12, 2021
  • Laser & Optoelectronics Progress
  • Vol.58 Issue, 9 0923001 (2021)
  • DOI:10.3788/LOP202158.0923001
Bifurcation-tunable Diffractionless Light Propagation in One-dimensional Non-Hermitian Photonic Lattice
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 ? 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 ? respect the expression k+?=±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.
  • May. 11, 2021
  • Acta Photonica Sinica
  • Vol.50 Issue, 4 128 (2021)
  • DOI:10.3788/gzxb20215004.0423003
Second-order Microcavity Length Based on Top-emitting Organic Light-emitting Diodes
A Top-Emitting Organic Light-Emitting Diodes (TEOLEDs) with the configurations of Al (100 nm)/TAPC (x nm)/TCTA (10 nm)/TCTA:Ir(ppy)3 (10%, 25 nm)/TPBi (30 nm)/LiF (2 nm)/Al (1 nm)/Ag (20 nm)/Alq3 (y nm) (x=30, 130, 160, 170 and 180) (y=20, 40, 60 and 80) was fabricated. The experiments illustrate that photoelectric performance of the device can be improved by changing the thickness of the hole transport layer, which make the length of the device microcavity was in the enhancement zone of second-order microcavity effect. Moreover, by changing the light output coupling layer of the device, the transmittance and reflectance of the cathode of the device were changed, which can effectively improve the photoelectric performance of the device. A green TEOLEDs with the best photoelectric performance is achieved when the length of microcavity is 230 nm and the thickness of optical output coupling is 80 nm. The peak luminance, peak current efficiency and peak power efficiency of the TEOLEDs reach 25 960 cd/m2, 19.1 cd/A and 16.01 lm/W, respectively.
  • May. 11, 2021
  • Acta Photonica Sinica
  • Vol.50 Issue, 4 120 (2021)
  • DOI:10.3788/gzxb20215004.0423002
Digital Thermo-optic Switch of SOI Waveguide Based on Goos-Hänchen Spatial Shift of Reflected Mode
With the waveguide corner mirror structure and the effective combination of the Goos-Hanchen (GH) spatial shift and the thermo-optical effect refractive index modulation, a digital thermo-optical switch structure of waveguide reflected mode is proposed. The GH spatial shift is optimized under the condition of a given incident angle, and the reflected beam has a larger jump under an eigenstate with the GH effect. On a silicon-on-insulator platform with a 1.0 μm thick silicon film, the guided mode eigenstate matching between the single-mode input waveguide and the multimode interference waveguide structure verifies the function of a 1×3 digital optical switch. In experiment, the optical loss caused by the device structure is 0.3 dB, the switching power is 130~150 mW, the switching time is about 50 μs, and the isolation between adjacent output ports is 15 dB. The comparison with the latest results of the Mach-Zehnder interferometer 2×2 thermo-optic switch and the newly emerging plasma effect thermo-optic switch shows the advancement of this digital TO switch.
  • May. 11, 2021
  • Acta Photonica Sinica
  • Vol.50 Issue, 4 111 (2021)
  • DOI:10.3788/gzxb20215004.0423001
[in Chinese]
Chen Shuqi, Cheng Ya, and Zhao Jianlin
  • May. 08, 2021
  • Acta Optica Sinica
  • Vol.41 Issue, 8 0823000 (2021)
  • DOI: