Non-volatile 2 × 2 optical switch using multimode interference in an SbSe-loaded waveguide.

We propose a non-volatile 2 × 2 photonic switch based on multimode interference in an SbSe-loaded waveguide. The different modal symmetries of the TE and TE modes supported in the multimode region change their propagation constants distinctly upon the SbSe phase transition. Through careful optical design and FDTD optimization of the multimode waveguide dimensions, efficient switching is achieved despite the modest index contrast of SbSe relative to GeSbTe.

Ultra-broadband on-chip power splitters for arbitrary ratios on silicon-on-insulator.

We propose and demonstrate on-chip power splitters based on adiabatic rib waveguide enabling arbitrary splitting ratios on a monolithic silicon photonic platform. The devices are elaborately engineered based on adiabatic directional couplers with a trapezoid-structure in the longitudinal direction in the mode evolution region. The measurement results indicate that the proposed devices can achieve over 150 nm bandwidth for arbitrary splitting ratios of 50%:50%, 70%:30% and 90%:10%.

X-Intersected Silicon Modulator of Well-Rounded Performance.

In silicon modulator design, implantation is always a key factor, significantly influencing the doping profile and carrier distribution. As waveguide doping is limited by the compact footprint of the modulator rib, three-dimensional complex optimization is a viable option to improve performance. This work proposes an X-intersected modulator based on two inversely slanted junctions using the effective 3D Monte Carlo method for junction generation.

Compact, ultrabroadband and temperature-insensitive arbitrary ratio power splitter based on adiabatic rib waveguides.

We propose a compact, ultrabroadband and temperature-insensitive adiabatic directional coupler based on rib silicon waveguide-enabling arbitrary splitting ratios. Simulation results show that the device can achieve arbitrary splitting ratios from 1400 to 1600 nm, equal to 50%:50%, 60%:40%, 70%:30%, 80%:20%, and 90%:10% for the fundamental transverse electric mode. The designed device has an excess loss of less than 0.

Silicon modulator based on omni junctions by effective 3D Monte-Carlo method.

3D doping structure has significant advantages in modulation efficiency and loss compared with 2D modulator doping profiles. However, to the best of our knowledge, previous work on 3D simulation methods for interdigitated doping designs applied simplified models, which prohibited complex 3D doping. In this work, innovative omni junctions, based on the effective 3D Monte-Carlo method, are believed to be the first proposed for high-performance modulators.

Broadband and CMOS compatible polarization splitter-rotator based on a bi-level taper.

A silicon-on-insulator polarization diversity scheme is proposed. Based on an asymmetrical evanescent coupler, a broadband and compact polarization splitter-rotator comprising mode conversion tapers and mode sorting asymmetric Y junctions is optimized with silicon dioxide upper cladding and a silicon nitride waveguide. The simulation results show mode conversion loss is less than 0.

Compact, broadband, and low-loss silicon photonic arbitrary ratio power splitter using adiabatic taper.

The arbitrary ratio power splitter is widely used in photonic integrated circuits (PICs), for signal monitoring, power equalization, signal feedback, and so on. Here we designed a fabrication-tolerant, compact, broadband, and low-loss arbitrary ratio power splitter. The proposed arbitrary ratio power splitter was realized with an adiabatically tapered silicon rib waveguide with 70 nm shallow etches and an waveguide.

Compact multimode waveguide based temperature-insensitive Mach-Zehnder interferometer.

A novel multimode waveguide based Mach-Zehnder interferometer (MZI) is demonstrated on an SOI platform with the properties of compact footprint and temperature-insensitive operation. The device can achieve a thermal dependence around 13pm/°C in a wavelength range of 40nm. Owing to the utilization of one single straight multimode waveguide, the device is naturally immune to local temperature distributions.

A Simplified Solution Using Izbash's Equation for Non-Darcian Flow in a Constant Rate Pumping Test.

This paper derives an equivalent of Darcian Theis solution for non-Darcian flow induced by constant rate pumping of a well in a confined aquifer. The derivation, which is valid at later times only, is original. It utilizes Izbash's equation.

Analyzing modal power in multi-mode waveguide via machine learning.

A machine learning assisted modal power analyzing scheme designed for optical modes in integrated multi-mode waveguides is proposed and studied in this work. Convolutional neural networks (CNNs) are successfully trained to correlate the far-field diffraction intensity patterns of a superposition of multiple waveguide modes with its modal power distribution. In particular, a specialized CNN is trained to analyze thin optical waveguides, which are single-moded along one axis and multi-moded along the other axis.

Routing light with ultrathin nanostructures beyond the diffraction limit.

An open nanostructure consisting of a periodic chain of subwavelength-nanoparticles for compressing and routing light beyond the diffraction limit is proposed. The open nanostructure is ultrathin and compact, with a size much smaller than the wavelength of light. We demonstrate that our ultrathin open nanostructure provides functions that can route and manipulate light at the subwavelength scale and can also sharply bend and split light beams below the diffraction limit while exhibiting broadband, incident-angle-tolerant, and robust against disorder.

A silicon-on-insulator polarization diversity scheme in the mid-infrared.

We propose a silicon-on-insulator (SOI) polarization diversity scheme in the mid-infrared wavelength range. In consideration of absorption loss in silicon dioxide (SiO), the polarization splitter-rotator (PSR) is designed and optimized with silicon nitride (SiN) upper-cladding and SiO lower-cladding. This asymmetry allows the PSR, which consists of mode-conversion tapers and subsequent mode-sorting asymmetric Y-junctions, to be fabricated with a simple one-step etching process.

Broadband and fabrication-tolerant on-chip scalable mode-division multiplexing based on mode-evolution counter-tapered couplers.

A broadband and fabrication-tolerant on-chip scalable mode-division multiplexing (MDM) scheme based on mode-evolution counter-tapered couplers is designed and experimentally demonstrated on a silicon-on-insulator (SOI) platform. Due to the broadband advantage offered by mode evolution, the two-mode MDM link exhibits a very large, -1  dB bandwidth of >180  nm, which is considerably larger than most of the previously reported MDM links whether they are based on mode-interference or evolution. In addition, the performance metrics remain stable for large-device width deviations from the designed valued by -60  nm to 40 nm, and for temperature variations from -25°C to 75°C.

Experimental demonstration of in-plane negative-angle refraction with an array of silicon nanoposts.

Controlling an optical beam is fundamental in optics. Recently, unique manipulation of optical wavefronts has been successfully demonstrated by metasurfaces. However, these artificially engineered nanostructures have thus far been limited to operate on light beams propagating out-of-plane.

Reconfigurable radio-frequency arbitrary waveforms synthesized in a silicon photonic chip.

Photonic methods of radio-frequency waveform generation and processing can provide performance advantages and flexibility over electronic methods due to the ultrawide bandwidth offered by the optical carriers. However, bulk optics implementations suffer from the lack of integration and slow reconfiguration speed. Here we propose an architecture of integrated photonic radio-frequency generation and processing and implement it on a silicon chip fabricated in a semiconductor manufacturing foundry.

Proposal for fabrication-tolerant SOI polarization splitter-rotator based on cascaded MMI couplers and an assisted bi-level taper.

A novel silicon-on-insulator (SOI) polarization splitter-rotator (PSR) with a large fabrication tolerance is proposed based on cascaded multimode interference (MMI) couplers and an assisted mode-evolution taper. The tapers are designed to adiabatically convert the input TM(0) mode into the TE(1) mode, which will output as the TE(0) mode after processed by the subsequent MMI mode converter, 90-degree phase shifter (PS) and MMI 3 dB coupler. The numerical simulation results show that the proposed device has a < 0.

Novel ultra-broadband polarization splitter-rotator based on mode-evolution tapers and a mode-sorting asymmetric Y-junction.

A novel silicon-on-insulator (SOI) polarization splitter-rotator is proposed based on mode-evolution tapers and a mode-sorting asymmetric Y-junction. The tapers are designed to adiabatically convert the input TM0 mode into the TE1 mode, which will evolve into the TE0 mode in the wide output arm while the input TE0 mode excites the TE0 mode in the narrow arm. The numerical simulation results show that the mode conversion efficiency increases with the lengths of the tapers and the Y-junction for the output waveguide widths in a large range.

Low-loss and low-crosstalk 8 × 8 silicon nanowire AWG routers fabricated with CMOS technology.

Low-loss and low-crosstalk 8 × 8 arrayed waveguide grating (AWG) routers based on silicon nanowire waveguides are reported. A comparative study of the measurement results of the 3.2 nm-channel-spacing AWGs with three different designs is performed to evaluate the effect of each optimal technique, showing that a comprehensive optimization technique is more effective to improve the device performance than a single optimization.

Design of a SiO₂ top-cladding and compact polarization splitter-rotator based on a rib directional coupler.

A compact polarization splitter-rotator based on a silicon-on-insulator rib asymmetrical directional coupler with SiO2 top-cladding is proposed. Unlike previously reported PSRs which specifically required the top-cladding material to be different from the bottom cladding in order to break the symmetry of the waveguide cross-section, our proposed PSR has no such limitation on the top-cladding due to the horizontal asymmetry of the rib waveguide. In addition, the device is highly compact and has a total length as short as 24 μm.

A Silicon Optical Transistor.

We demonstrate an all-optical transistor with the modulated output signal simultaneously having an output/input ratio > 3 dB and ON/OFF ratio > 20 dB. The microring based device is ultra-compact and CMOS compatible.

Nonreciprocal Transmission of 10 Gbps OOK Data through an All-Silicon Passive Optical Diode.

An optical diode transmits forward 10Gbps data with less than 0.5dB power penalty, while suppressing and distorting backward data with a 11dB nominal power penalty. The nonreciprocal transmission is also demonstrated with a silicon modulator.

Optical beam steering based on the symmetry of resonant modes of nanoparticles.

We report a phenomenon that an optical beam transmits in a negative direction when passing through a single array of high-refractive-index dielectric nanorods. The mechanism of the negative directional transmission is believed to be due to the symmetry of resonant modes in the dielectric nanoparticles. It is expected to find applications in designing compact optical components to achieve the on-chip beam steering in photonic circuits.