Dynamically Tunable and Multifunctional Polarization Beam Splitters Based on Graphene Metasurfaces

Based on coupled-mode theory (CMT) and the finite-difference time-domain (FDTD) approach, we propose a graphene metasurface-based and multifunctional polarization beam splitter that is dynamically tunable. The structure, comprising two graphene strips at the top and bottom and four triangular graphene blocks in the center layer, can achieve triple plasma-induced transparency (PIT). In a single polarization state, the computational results reveal that synchronous or asynchronous six-mode electro-optical switching modulation may be performed by modifying the Fermi levels of graphene, with a maximum modulation degree of amplitude (MDA) of 97.6% at 5.148 THz. In addition, by varying the polarization angle, a polarization-sensitive, tunable polarization beam splitter (PBS) with an extinction ratio and insertion loss of 19.6 dB and 0.35 dB at 6.143 THz, respectively, and a frequency modulation degree of 25.2% was realized. Combining PIT with polarization sensitivity provides a viable platform and concept for developing graphene metasurface-based multifunctional and tunable polarization devices.

Deep Learning-Assisted Enhanced Fano Resonances in Symmetry-Breaking SOI Metasurface

Ultra-compact spot size converter based on digital metamaterials

Compact waveguide bend with digital meta-structures on the silicon-on-insulator platform

Fiber Optic Sensor with a Gold Nanowire Group Array for Broad Range and Low Refractive Index Detection

To achieve high performance and wide range detection, we propose an ultra-wide range high sensitivity plasmonic fiber optic sensor with a gold (Au) nanowire group array, which has both propagating surface plasmon resonance (PSPR) and local surface plasmon resonance (LSPR) sensing characteristics. The PSPR, LSPR, and PSPR+LSPR are presented as Au thin layers, Au spheres (or Au nanowires), and Au nanowire group arrays, respectively, and their respective properties are analyzed from theoretical, simulated, and numerical aspects. When detection is performed, the presence of both evanescent wave and electric field forces in the Au nanowire group array combines to significantly improve the sensor’s detection capability. Detection simulation analysis was performed using COMSOL Multiphysics software. The range of refractive indices that can be detected is 1.08 to 1.37 in the optical band from 1210 nm to 2140 nm. In the detection range, the maximum sensitivity of the detected wavelength is 13,000 nm/RIU. Our proposed sensor has a broad range, high sensitivity, and low refractive index detection, and has good research value and application prospects.

Asymmetric-ration optical power couplers based on nano-pixel structure

An optical power coupler is one of the most well-used components in integrated photonics. Although couplers with an output power ratio 1:1 have been widely studied in the past, constructing asymmetric-ration optical power couplers is still an issue that is difficult to be addressed by using traditional Y-branch waveguides. Artificial intelligence (AI) assisted design is an effective technique for realizing complex optical structures. In this work, we have designed asymmetric-ration optical power couplers by using AI assisted design. Two couplers with the targeted splitting power ratio as 1:9 and 1:99 have been designed, respectively. In the AI assisted design, the coupler area was divided into discrete nano-pixels in the shape of circular holes with the same dimension. The AI controlled each pixel to be occupied by waveguide or air and trialed the occupation of each pixel one by one. In a 3.4 × 3.2 µm2 area, it took 1452 trials to obtain one optimized coupler. As a result, a splitting power ratio of 1:9.007 and 1:99.004 for the two couplers has been confirmed by using the finite-difference time-domain method. In addition, the waveguide configuration was further modified as the excess loss of the AI-designed coupler was a bit high, more than 3.50 dB. The way to reduce the loss is as follows: 1) positioning optimization of the output waveguide to avoid light scattering at the boundary between the coupler and the output waveguide, and 2) widening the output waveguide width to avoid insufficient light coupling. As a result, a scattering loss reduction of 1.7 dB by position optimization, and a coupling loss reduction of 1.6 dB by width widening were confirmed. The achieved design also exhibited a wide operation wavelength ranging from 1500–1600 nm in addition to sufficient fabrication tolerance of ±10 nm (± 11%).

1:9 and 1:99 Optical Power Couplers Based on Nano-Pixel Structure

Sensing Accuracy Improvement for Waveguide CRDS toward Compact Breath Sensing

Vertical Field Enhancement of Spot Size Converter by Using Nano-Pixel Waveguide and Window Structure

Amplifier-assisted CRDS (cavity ring-down spectroscopy) toward compact breath sensing

Tunable metamaterial-induced transparency with gate-controlled on-chip graphene metasurface

Reconfigurable and tunable flat graphene photonic crystal circuits

Coherent-interference-induced transparency based on long-range air-hole assisted subwavelength waveguides