Integrating inverse design and partially etched platform: an ultra-compact polarization splitter and rotator as an example.

Silicon photonics devices benefit greatly from a partially etched platform and inverse design. Herein, we propose a bi-layer polarization splitter and rotator with a topology pattern and demonstrate it on a silicon-on-insulator platform. Our device exhibits a significantly reduced physical footprint of only 2µ×6µ, compared to traditional directional couplers and tapered waveguides.

Compact dual-mode waveguide crossing based on adjoint shape optimization.

We design, fabricate, and characterize a compact dual-mode waveguide crossing on a silicon-on-insulator platform. The dual-mode waveguide crossing with high performance is designed by utilizing the adjoint shape optimization. This adjoint-method-based optimization algorithm is computationally efficient and yields the optimal solution in fewer iterations compared with other iterative schemes.

Compact hybrid five-mode multiplexer based on asymmetric directional couplers with constant bus waveguide width.

We experimentally demonstrate a hybrid mode division multiplexer (MDM) based on asymmetric directional couplers (ADCs) without transition tapers in between. The proposed MDM can couple five fundamental modes from access waveguides into the bus waveguide as the hybrid modes (TE, TE, TE, TM, and TM). To eliminate the transition tapers between cascaded ADCs as well as to enable arbitrary add-drop to the bus waveguide, we maintain the bus waveguide width to be the same, while a partially etched subwavelength grating is introduced to reduce the effective refractive index of the bus waveguide.

Multi-task topology optimization of photonic devices in low-dimensional Fourier domain via deep learning.

Silicon photonics enables compact integrated photonic devices with versatile functionalities and mass manufacturing capability. However, the optimization of high-performance free-form optical devices is still challenging due to the complex light-matter interaction involved that requires time-consuming electromagnetic simulations. This problem becomes even more prominent when multiple devices are required, typically requiring separate iterative optimizations.

Correction: Cheng et al. Grating Couplers on Silicon Photonics: Design Principles, Emerging Trends and Practical Issues. 2020, , 666.

In the original publication [...

Ultra-compact dual-mode mode-size converter for silicon photonic few-mode fiber interfaces.

Fiber couplers usually take a lot of space on photonic integrated circuits due to the large mode-size mismatch between the waveguide and fiber, especially when a fiber with larger core is utilized, such as a few-mode fiber. We demonstrate experimentally that such challenge can be overcome by an ultra-compact mode-size converter with a footprint of only 10 µm. Our device expands TE and TE waveguide modes simultaneously from a 1-µm wide strip waveguide to an 18-µm wide slab on a 220-nm thick silicon-on-insulator, with calculated losses of 0.

Ultra-broadband and ultra-compact polarization beam splitter based on a tapered subwavelength-grating waveguide and slot waveguide.

In this work, we propose an ultra-broadband and ultra-compact polarization beam splitter (PBS) on a standard silicon-on-isolator platform. Assisted by a tapered subwavelength-grating waveguide and a slot waveguide, the working bandwidth of the directional-coupler-based PBS covers the entire O-, E-, S-, C-, L- and U-bands and the coupling length is only 4.6 µm.

High-efficiency dual-band-multiplexing three-port grating coupler on 220-nm silicon-on-insulator with 248-nm deep-UV lithography.

We experimentally demonstrate a novel, to the best of our knowledge, three-port grating coupler (TPGC) for dual-wavelength-band operation. The TPGC can couple light to/from two ports for S/C-band with polarization diversity and a third port for O-band. Such a coupling scheme could be applied in an integrated wavelength-division-multiplexing passive optical network (PON) unit, benefiting a polarization-diverse receiver for downstream S/C-band and transmitter for upstream O-band.

Full-duplex high-speed indoor optical wireless communication system based on a micro-LED and VCSEL array.

We built a full-duplex high-speed optical wireless communication (OWC) system based on high-bandwidth micro-size devices, for which micro-LED and VCSEL arrays are implemented to establish downlink and uplink, respectively. The high-capacity downlink based on a single-pixel quantum dot (QD) micro-LED can reach a data rate of 2.74 Gbps with adaptive orthogonal frequency division multiplexing (OFDM).

A compact and polarization-insensitive silicon waveguide crossing based on subwavelength grating MMI couplers.

In this work, we proposed and experimentally demonstrated a compact and low polarization-dependent silicon waveguide crossing based on subwavelength grating multimode interference couplers. The subwavelength grating structure decreases the effective refractive index difference and shrinks the device footprint. Our designed device is fabricated on the 220-nm SOI platform and performs well.

Propagation analysis and experiment of near-infrared VCSEL-based diffuse optical wireless communication.

Diffuse communication plays a more significant role than the usual point-to-point scenario in indoor optical wireless communication (OWC). We present, for the first time to our knowledge, a Monte Carlo simulation and experiment for a 922.39-nm vertical cavity surface-emitting laser array-based non-line-of-sight OWC system with three common reflective materials.

Grating Couplers on Silicon Photonics: Design Principles, Emerging Trends and Practical Issues.

Silicon photonics is an enabling technology that provides integrated photonic devices and systems with low-cost mass manufacturing capability. It has attracted increasing attention in both academia and industry in recent years, not only for its applications in communications, but also in sensing. One important issue of silicon photonics that comes with its high integration density is an interface between its high-performance integrated waveguide devices and optical fibers or free-space optics.

State-of-the-Art and Perspectives on Silicon Waveguide Crossings: A Review.

In the past few decades, silicon photonics has witnessed a ramp-up of investment in both research and industry. As a basic building block, silicon waveguide crossing is inevitable for dense silicon photonic integrated circuits and efficient crossing designs will greatly improve the performance of photonic devices with multiple crossings. In this paper, we focus on the state-of-the-art and perspectives on silicon waveguide crossings.