Chunchuan Yang

Ultra-low temperature silicon nitride photonic integration platform

High-quality SiNx films with controllable low stress and low optical loss are deposited at ultra-low temperature (75 °C) using inductively coupled plasma chemical vapor deposition (ICP-CVD). Two kinds of integrated photonic structures have been demonstrated that exemplify its viability as a photonic integration platform. A microcavity consists of two distributed Bragg reflectors (DBR) formed by alternating a total of 49 layers of SiNx and SiO2 with a total thickness of about 11.5 μm is grown without any cracks, confirming the excellent stress control in the process. Microring resonators are also fabricated in as-deposited planar SiNx waveguide layer using electron-beam lithography (EBL) and plasma etching. Average waveguide loss of 0.79 ± 0.22 dB/cm has been achieved in the range of 1550-1600 nm for ring radii larger than 40 μm. The ultra-low temperature grown SiNx with properties of low loss and low stress is therefore a promising photonic integration platform for various photonic integration applications.

Demonstration of diamond microlens structures by a three-dimensional (3D) dual-mask method

Diamond is a promising platform for quantum information technologies (QITs) mainly due to the properties of color centers including spin read-out, magnetic field sensing, and entanglement between different nitrogen-vacancy (NV) centers. High photon collection efficiency is essential for a high fidelity optical single-shot readout of electronic spin in the color center. To avoid total internal reflection, sculpting solid immersion lenses in the diamond surface is an ideal natural choice. Three-dimensional (3D) microstructures can be made in a photoresist material by a special lithography method. These structures can be subsequently transferred into silicon, diamond or other semiconductors by plasma etching with appropriate selectivity. However, this method cannot be directly implemented into making large height diamond microlenses where the selectivity between diamond and the photoresist is very low. In this work, we propose and demonstrate a dual mask method to achieve an overall high selectivity between diamond and photoresist via the interlayer of single crystalline silicon. By tuning the process parameters of the two etching steps, diamond micro-lenses with large variable height are successfully demonstrated..

Compact high-efficiency vortex beam emitter based on a silicon photonics micro-ring

Photonic integrated devices that emit vortex beam carrying orbital angular momentum are becoming key components for multiple applications. Here we propose and demonstrate a high-efficiency vortex beam emitter based on a silicon micro-ring resonator integrated with a metal mirror. Such a compact emitter is capable of generating vortex beams with a high efficiency and small divergence angle. Vector vortex beams of various topological charges are selectively generated by the emitter at different wavelengths with an emission efficiency of up to 37%.

Cascaded metasurface structures

Metasurfaces are well known as a single-layer subwavelength structure with superior capability in wavefront shaping, and cascaded metasurfaces with multi-layer structures resulting in compact optical devices will further improve the performance and also bring in new functionalities, such as image correction, optical transformation and processing. However, in order to realize such cascaded metasurfaces, a key issue is to achieve high precision alignment of the structures in each layer usually with large distance in between. Here we propose and experimentally confirm two schemes based on optical alignment and electron-beam alignment respectively to align the frontside and backside of a wafer in order to realize cascaded metasurfaces on these two sides. Except for cascaded metasurface structures, these approaches may also have a wide range of applications in need of other cascaded structures for specific functionality.

Fabrication-friendly high-efficiency silicon nitride grating coupler

Grating coupler, as one of the key components can provide convenient on-wafer testing and packaging for integrated photonics. Silicon nitride (SiNx) grating coupler suffers from lower efficiency due to the relative low material refractive index. The efficiency of SiNx grating coupler can be improved by using high reflectivity silicon grating reflectors underneath. However, such silicon grating reflector requires several fabrication steps, including lithography, etching, high precision alignment (HPA), and chemical mechanical polishing (CMP). In this work, we demonstrate an easy-to-fabricate SiNx grating coupler only requiring a single patterning step without the need of HPA and CMP. A coupling coefficient of −2.5 dB and 1-dB-bandwidth of 65 nm have been experimentally measured.

InP-based Monolithic Tunable Narrow Linewidth Optical Radio Frequency Signal Generator with Direct Modulation

A monolithic tunable optical radio frequency signal generator consisting of one semiconductor ring laser and two DFB lasers with direct electrical modulation by coplanar waveguide is designed. The key obstacles in the fabrication process are investigated. First-order ridge waveguide DFB lasers with a grating aspect ratio larger than 15 are fabricated.

Integrated Orbital Angular Momentum Emitters Based on Silicon Nitride Photonic Platform

Integrated orbital angular momentum emitters have been studied widely in the past few years. Meanwhile, silicon nitride (SiNx) material provides a veritable platform for on-chip compact photonic integrated circuit. In this paper, we demonstrate integrated orbital angular momentum (OAM) emitters based on silicon nitride micro-ring resonators with angular gratings. By changing waveguide dimensions and duty cycle of gratings, several OAM emitters have been designed and fabricated. The relative high average emission efficiency was measured to be (

High responsivity photodetector based on monolayer molybdenum disulfide (MoS 2 )

13\pm 1.2

Hybrid Integrated Velocity Matched Travelling-wave InP/InGaAs Photodetectors with Silicon Nitride Waveguides

) %. The near and far-field fields of emitted OAM modes have excellent angular distributions. Therefore, the SiNx material raises the prospect of practical and flexible platform for on-chip integrated OAM devices that offers excellent performance and high reliability.

Graphene-on-silicon nitride microring resonators with high modulation depth

High-responsivity ultra-sensitive photodetectors are crucial for a broad range of applications in various fields. This work demonstrates a highly sensitive photodetector fabricated by using monolayer molybdenum disulfide (MoS2), a promising semiconductor from the family of transition-metal dichalcogenide, showing a promising photoresponsivity (230 mA/W @532 nm) in the wavelength of visible light region.