Zan Zhang

CMOS-Compatible Vertical Grating Coupler With Quasi Mach–Zehnder Characteristics

A vertical grating coupler on silicon-on-insulator substrates has been designed and demonstrated. The light from a vertical fiber can be coupled in and split equally into two arms with the fiber placed in the grating center. An optical combiner is used to collect the transmission from the two arms. The measured peak coupling efficiency is 37%. Our device can also function like a Mach-Zehnder interferometer. In a device with an arm difference of 30 μm, the normalized transmission spectra of 20-nm free spectral range and more than 12-dB extinction ratio at 1567 nm are obtained.

Optoelectronic Mixer Based on Graphene FET

We present optoelectronic mixing phenomenon in graphene FET (GFET) and give a brief analysis for the first time. Demonstrated by a measurement system, two operating modes of optoelectronic mixer (OE-mixer) circuits are proposed, either of them mixing optical and electrical signals directly using a single GFET. Optoelectronic conversion losses of 24 and 35 dB are obtained in a 50-Ω impedance system, respectively. GFET OE-mixer might be of strong importance for radio over fiber systems, millimeter wave, and terahertz frequencies applications.

Monolithic Integration of Si 3 N 4 Microring Filters With Bulk CMOS IC Through Post-Backend Process

An experimental demonstration of backend monolithic integration of Si3N4 microring filter with bulk complementary metal-oxide-semiconductor (CMOS) integrated circuit (IC) is accomplished using CMOS postbackend process. Si3N4 photonic layer is integrated on the top surface of CMOS IC die which is manufactured in commercial CMOS foundry. The Si3N4 microring filters in photonic layer are fabricated using CMOS postbackend process with only two additional lithography steps. The filters can be thermally tuned by microheaters integrated in CMOS circuits, which are controlled by transmission gates. A measured optical transmission spectrum and a dynamic characteristic of the integrated filter are provided.

Bidirectional grating coupler based optical modulator for low-loss Integration and low-cost fiber packaging

We proposed and demonstrated a novel optical modulator based on a bidirectional grating coupler designed for perfectly vertical fiber coupling. The grating functions as the fiber coupler and 3-dB splitter. To observe the interference, an arm difference of 30μm is introduced. As a result of the high coupling efficiency and near perfect split ratio of the grating coupler, this device exhibits a low on-chip insertion loss of 5.4dB (coupling loss included) and high on-off extinction ratio more than 20dB. The modulation efficiency is estimated to be within 3-3.84V•cm. In order to investigate the fiber misalignment tolerance of this modulator, misalignment influence of the static characteristics is analyzed. 10Gb/s Data transmission experiments of this device are performed with different fiber launch positions. The energy efficiency is estimated to be 8.1pJ/bit.

Progress in complementary metal-oxide-semiconductor silicon photonics and optoelectronic integrated circuits

Silicon photonics is an emerging competitive solution for next-generation scalable data communications in different application areas as high-speed data communication is constrained by electrical interconnects. Optical interconnects based on silicon photonics can be used in intra/inter-chip interconnects, board-to-board interconnects, short-reach communications in datacenters, supercomputers and long-haul optical transmissions. In this paper, we present an overview of recent progress in silicon optoelectronic devices and optoelectronic integrated circuits (OEICs) based on a complementary metal–oxide–semiconductor-compatible process, and focus on our research contributions. The silicon optoelectronic devices and OEICs show good characteristics, which are expected to benefit several application domains, including communication, sensing, computing and nonlinear systems.

Misalignment-Tolerant Silicon Optical Modulator With Surface-Normal Optical Interface

Compared with the performance evolution of silicon optical modulators, photonic packaging problem deserves more attention as a big obstacle of commercial applications. Edge couplers only have submicron-misalignment tolerance, while conventional grating couplers need angle polishing in fiber packaging. To achieve low-cost fiber packaging, a strong misalignment-tolerant optical modulator is proposed and demonstrated with surface normal optical interface. Benefit from the particular characteristics of the bidirectional grating structure, the silicon optical modulator can operate under ±2-μm fiber misalignment with clear open eyes.

Microwave photonic filter with reconfigurable and tunable bandpass response using integrated optical signal processor based on microring resonator

Abstract. A bandpass microwave photonic filter based on an integrated optical signal processor is proposed and demonstrated by numerical simulation. The optical signal processor consisting of double-bus-coupled and series-cascaded silicon microrings (MRs) is used to produce two bandpass responses to process optical carrier signal and sideband signal separately. Because of the tunability of MRs, variable −3  dB bandwidth and tunable operating frequency are achieved. The −3  dB bandwidth and operating frequency can be tuned from 1.5 to 12 GHz and from 15 to 34 GHz, respectively. The loss impact, tuning method, and fabrication error tolerance are also discussed.

Plasmon-Enhanced Emission From CMOS Compatible Si-LEDs With Gold Nanoparticles

Complementary metal-oxide-semiconductor (CMOS) compatible silicon (Si)-based light sources are attracting more and more attention for the potential to realizing on-chip optical interconnection ultimately. Annealed noble metal nanoparticles (NPs) are often used to enhance the emission efficiency of low-efficiency light emitters due to the surface plasmon (SP) effects. Compared with silver NPs (Ag NPs) and gold NPs (Au NPs) show excellent stability in the air environment. However, Au NPs are not always chosen to enhance the emission efficiency of light-emitting diodes (LEDs) due to the high annealing temperature and CMOS incompatible. Here, we report the first study of enhancing emission from CMOS compatible Si-based LEDs by transferring annealed Au NPs onto the device surfaces. A 4.3-fold total enhancement integrated across the electroluminescence spectrum and an eightfold enhancement at 900 nm are ultimately achieved. The enhancement is attributed to electrical performances improvement of the Si-based LEDs and enhanced scattering by Au NPs due to the coupling between the SP modes of Au NPs and the waveguide modes of Si slab waveguide.

Integrated GHz silicon photonics interconnect with perfectly vertical coupling interface

A novel silicon photonics interconnect was proposed and demonstrated, integrated with a bidirectional vertical grating coupler, optical modulator and germanium waveguide photodetector. Point-to-point optical interconnection with data rate of 3Gb/s was demonstrated.