This paper reviews developments in cascaded microresonator-based matrix switches for silicon photonic interconnection networks in many-core computing applications. Specifically, we emphasize our recently proposed 5 times 5 matrix switch comprising two-dimensionally cascaded microring resonator-based electrooptic switches coupled to a waveguide cross-grid on a silicon chip. The cross-grid adopts low-loss low-crosstalk multimode-interference-based waveguide crossings. Such a microresonator-based matrix switch offers nonblocking interconnections among multiple inputs and multiple outputs, with the key merits of i) a tens to hundreds of micrometers-scale footprint, ii) gigabit/second-scale data transmission, iii) nanosecond-speed circuit-switching, iv) 100-muW-scale DC power consumption per link, and v) large-scale integration for networks-on-chips applications. We analyze in detail the microring resonator-based cross-grid switch design for high-data-rate signal transmission in the context of our proposed 5 times 5 matrix switch. We also study the feasibility of large-scale integration of the matrix switch. We report proof-of-concept experiments of a single cross-grid switch element and a 2 times 2 matrix switch, propose design guidelines, and discuss future engineering challenges.

Cascaded Microresonator-Based Matrix Switch for Silicon On-Chip Optical Interconnection

We report the design and characterization of Si3N4/SiO2 optical waveguides which are specifically developed for optical delay lines in microwave photonics (MWP) signal processing applications. The waveguide structure consists of a stack of two Si3N4 stripes and SiO2 as an intermediate layer. Characterization of the waveguide propagation loss was performed in race track-shaped optical ring resonators (ORRs) with a free-spectral range of 20 GHz and a bending radius varied from 50 μm to 125 μm. A waveguide propagation loss as low as 0.095 dB/cm was measured in the ORRs with bend radii ≥ 70 μm. Using the waveguide technology two types of RF-modulated optical sideband filters with high sideband suppression and small transition band consisting of an Mach-Zehnder interferometer and ORRs are also demonstrated. These results demonstrate the potential of the waveguide technology to be applied to construct compact on-chip MWP signal processors.

Low-loss, high-index-contrast Si3N4/SiO2 optical waveguides for optical delay lines in microwave photonics signal processing

An erratum is presented to correct the calculation of the filtering bandwidth of the micro-ring resonator.

Four-channel reconfigurable optical add-drop multiplexer based on photonic wire waveguide

A novel and simple bandwidth and wavelength-tunable optical bandpass filter based on silicon microrings in a Mach-Zehnder interferometer (MZI) structure is proposed and demonstrated. In this filter design, the drop transmissions of two microring resonators are combined to provide the desired tunability. A detailed analysis and the design of the device are presented. The shape factor and extinction ratio of the filter are optimized by thermally controlling the phase difference between the two arms of the MZI. Simultaneous bandwidth and wavelength tunability with in-band ripple control is demonstrated by thermally tuning the resonance offset between the two microring resonators.

/pdf/bandwidth-and-wavelength-tunable-optical-bandpass-filter-3w5x8kdniq.pdf

Bandwidth and wavelength-tunable optical bandpass filter based on silicon microring-MZI structure.

We demonstrate a 120 GHz 3-dB bandwidth on-chip silicon photonic interleaver with a flat passband over a broad spectral range of 70 nm. The structure of the interleaver is based on an asymmetric Mach-Zehnder interferometer (MZI) with 3 ring resonators coupled to the arms of the MZI. The transmission spectra of this device depict a rapid roll-off on the band edges, where the 20-dB bandwidth is measured to be 142 GHz. This device is optimized for operation in the C-band with a channel crosstalk as low as −20 dB. The device also has full reconfiguration capability to compensate for fabrication imperfections.

High bandwidth on-chip silicon photonic interleaver

We present an ultracompact and high-performance optical interleaver based on a microring assisted Mach-Zehnder interferometer using an ultrahigh-index-contrast waveguide (17% Delta). The device, a 100/200-GHz interleaver at 1.55-mum region, exhibits flat and nearly square passband and better than -30-dB stopband extinction ratio. Fiber-to-fiber loss is -2.2 dB. Passband bandwidth is 90 and 121 GHz at -1 and -20 dB, respectively. The dimension of this interleaver chip is 12times1 mm. Design optimization is also discussed for further performance improvement.

A High-Performance Ultracompact Optical Interleaver Based on Double-Ring Assisted Mach–Zehnder Interferometer

A compact optical switch array based on microrings using a high-index-contrast waveguide is presented with excellent performance. The 84 optical switch matrix occupies just 103mm and its extinction ratio is greater than 30 dB at a low control power consumption of 0.1 W per unit cell. The drop loss is around 2 dB. This device is particularly suitable for applications as a tunable filter array and wavelength selective optical switch.

A Compact and Low Power Consumption Optical Switch Based on Microrings

We have demonstrated a novel universal-waveguide crossing design to reduce intersection-loss in HIC PLCs. This design provides superior performance and feature-size-efficiency than existing designs. We have successfully applied the scheme to Delta = 1.5%, Delta = 17%, and SOI materials and verified experimentally on Delta = 1.5% material.

A Novel Approach to Reduce Waveguide Intersection Loss of HIC Materials

We present an ultra-compact and high-performance optical interleaver based on micro-ring assisted Mach-Zehnder interferometer (MZI) using ultra-high-index-contrast (UHIC) waveguide (Deltan=17%). This interleaver exhibits flat and near-square passband and better than -30 dB stopband extinction ratio.

Shih-Jung Chang

Papers

A High-Performance Ultracompact Optical Interleaver Based on Double-Ring Assisted Mach–Zehnder Interferometer

A Compact and Low Power Consumption Optical Switch Based on Microrings

A Novel Approach to Reduce Waveguide Intersection Loss of HIC Materials

An Ultra-Compact Optical Interleaver with High Performances Based on Double-Ring Assisted Mach-Zehnder Interferometer