Bradley Jonathan Luff

GHz-bandwidth optical filters based on high-order silicon ring resonators

Previously demonstrated high-order silicon ring filters typically have bandwidths larger than 100 GHz. Here we demonstrate 1-2 GHz-bandwidth filters with very high extinction ratios (~50 dB). The silicon waveguides employed to construct these filters have propagation losses of ~0.5 dB/cm. Each ring of a filter is thermally controlled by metal heaters situated on the top of the ring. With a power dissipation of ~72 mW, the ring resonance can be tuned by one free spectral range, resulting in wavelength-tunable optical filters. Both second-order and fifth-order ring resonators are presented, which can find ready application in microwave/radio frequency signal processing.

Power-efficient III-V/Silicon external cavity DBR lasers

We report the design and characterization of external-cavity DBR lasers built with a III-V-semiconductor reflective-SOA with spot-size converter edge-coupled to SOI waveguides containing Bragg grating mirrors. The un-cooled lasers have wall-plug-efficiencies of up to 9.5% at powers of 6 mW. The lasers are suitable for making power efficient, hybrid WDM transmitters in a CMOS-compatible SOI optical platform.

Fabrication Insensitive Echelle Grating in Silicon-on-Insulator Platform

We demonstrate a compact, low crosstalk, low loss, and flat passband demultiplexer based on an echelle grating fabricated in the silicon-on-insulator (SOI) platform. The demonstrated 12 channel demultiplexer has an 8-nm channel spacing, 5.5-nm flat passband, 1.7-dB on-chip loss, and better than 25-dB optical crosstalk. By arranging the output waveguides very close to the zero degree angle of the echelle grating, the performance of the demonstrated device is made insensitive to the vertical angle of the grating facet. The fabricated devices have a very small footprint and have the potential to provide a low-cost demultiplexer solution for multichannel data transmission applications.

Compact single-chip VMUX/DEMUX on the silicon-on-insulator platform

We demonstrate a compact, single-chip 40-channel, dense wavelength division multiplexing (DWDM) variable attenuator multi/demultiplexer (VMUX/DEMUX) by monolithic integration of an echelle grating and high-speed p-i-n VOA on the silicon-on-insulator (SOI) platform. The demonstrated device has a flat-top filter shape, on chip loss of 5.0 dB, low PDL of 0.3 dB after compensation of the polarization dependent frequency (PDF) shift, a fast attenuation response speed of 3 MHz, and an area of only 25 mm by 10 mm.

High-Speed Receiver Technology on the SOI Platform

Low power, low-cost, and high-speed photonic links are required in data centers. After significant research and development work over the last few years, silicon photonics has become a promising candidate to provide this technology. The receiver is one of the critical components for a photonic link. In this paper, we report recent progress in receiver technology on the silicon-on-insulator platform, particularly regarding its application to links that utilize wavelength division multiplexing (WDM). First, we discuss the key building blocks for WDM receivers: echelle grating demultiplexers and high-speed Ge photodetectors. We then report on the demonstration of a Terabit/s WDM receiver chip through monolithic integration of 40 high-speed Ge photodiodes with a 40-channel dense wavelength division multiplexing echelle grating. The device demonstrates that silicon photonics is a key technology to enable low-power and low-cost data center applications.

Silicon waveguide coupled resonator infrared detector

We present a silicon photodiode implemented in a waveguide coupled ring resonator structure. Infrared detection was achieved by Si+ ion implantation. A 15 μm-radius ring-based detector demonstrated an equivalent responsivity to a 3 mm straight waveguide device.

A programmable optical filter unit cell element for high resolution RF signal processing in silicon photonics

We demonstrate the first reconfigurable, cascadable silicon photonics unit cell fabricated in commercial wafer-scale processes using a single 500 ps delay line and allowing independent FIR and IIR response for high-resolution RF filtering and correlation applications.