Low-Cost 400 Gbps DR4 Silicon Photonics Transmitter for Short-Reach Datacenter Application.

Targeting high-speed, low-cost, short-reach intra-datacenter connections, we designed and tested an integrated silicon photonic circuit as a transmitter engine. This engine can be packaged into an optical transceiver module which meets the QSFP-DD Form Factor, together with other electrical/optical components. We first present the design and performance of a high-speed silicon modulator, which had a 3-dB EO bandwidth of >40 GHz and an ER of >5 dB. We then incorporated the engine onto a test board and injected a 53.125 Gbaud PAM4 signal. Clear eye patterns were observed at the receiver with TDECQ ~3 dB for all four lanes.

FSR-free silicon-on-insulator microring resonator based filter with bent contra-directional couplers.

High-speed optical interconnects drive the need for compact microring resonators (MRRs) with wide free spectral ranges (FSRs). A silicon-on-insulator MRR based filter with bent contra-directional couplers that exhibits an FSR-free response, at both the drop and through ports, while achieving a compact footprint is both theoretically and experimentally demonstrated. Also, using bent contra-directional couplers in the couping regions of MRRs allowed us to achieve larger side-mode suppressions than MRRs with straight CDCs. The fabricated filter has a minimum suppression ratio of more than 15 dB, a 3dB-bandwidth of ~23 GHz, an extinction ratio of ~18 dB, and a drop-port insertion loss of ~1 dB. High-speed data transmission through our filter is also demonstrated at data rates of 12.5 Gbps, 20 Gbps, and 28 Gbps.

Grating-assisted silicon-on-insulator racetrack resonator reflector.

We experimentally demonstrate a grating-assisted silicon-on-insulator (SOI) racetrack resonator reflector with a reflect port suppression of 10.3 dB and no free spectral range. We use contra-directional grating couplers within the coupling regions of the racetrack resonator to enable suppression of all but one of the peaks within the reflect port spectrum as well as all but one of the notches within the through port spectrum.

Process calibration method for designing silicon-on-insulator contra-directional grating couplers.

We present a process calibration method for designing silicon-on-insulator (SOI) contra-directional grating couplers (contra-DCs). Our method involves determining the coupling coefficients of fabricated contra-DCs by using their full-width-at-half-maximum (FWHM) bandwidths. As compared to the null method that uses the bandwidth measured at the first nulls, our FWHM method obtains more consistent results since the FWHM bandwidth is more easily determined. We also extract the coupling coefficients using curve-fitting which provide values that are in general agreement with the values obtained using our method. However, as compared to the curve-fitting method, our method does not require knowledge of the insertion loss and is easier to implement. Our method can be used to predict the FWHM bandwidths, the maximum power coupling factors, the minimum power transmission factors, and the through port group delays and dispersions of subsequent, fabricated devices, which is useful in designing filters.

Experimental demonstration of a silicon-on-insulator high-performance double microring filter using MZI-based coupling.

We have experimentally demonstrated, in silicon, a double microring resonator with Mach-Zehnder interferometer-based coupling that meets many commercial specifications. Our device has a ripple of 0.5 dB, an adjacent channel isolation of at least 41.0 dB, a nonadjacent channel isolation of at least 38.6 dB, an interstitial peak suppression of at least 37.5 dB, an express channel isolation of 10.0 dB, and a free spectral range greater than the span of the C-band of 37.23 nm.

Thermally tunable quadruple Vernier racetrack resonators.

The spectral responses of series-coupled racetrack resonators exhibiting the Vernier effect have many attractive features as compared to the spectral responses of identical series-coupled racetrack resonators, such as free spectral range (FSR) extension and enhanced wavelength tunability. Here we present experimental results of a thermally tunable quadruple series-coupled silicon racetrack resonator exhibiting the Vernier effect. We thermally tune two of the four racetrack resonators to enable discrete switching of the major peak by 15.54 nm. Also, our device has an interstitial peak suppression of 35.4 dB, a 3 dB bandwidth of 0.45 nm, and an extended FSR of 37.66 nm.

Experimental performance of DWDM quadruple Vernier racetrack resonators.

We demonstrate that one can meet numerous commercial requirements for filters used in dense wavelength-division multiplexing applications using quadruple Vernier racetrack resonators in the silicon-on-insulator platform. Experimental performance shows a ripple of 0.2 dB, an interstitial peak suppression of 39.7 dB, an adjacent channel isolation of 37.2 dB, an express channel isolation of 10.2 dB, and a free spectral range of 37.52 nm.

High performance Vernier racetrack resonators.

We demonstrate record performance of series-coupled silicon racetrack resonators exhibiting the Vernier effect. Our device has an interstitial peak suppression (IPS) of 25.5 dB, which is 14.5 dB larger than previously reported results. We also demonstrate the relationship between the inter-ring gap distance and the IPS as well as the 3 dB bandwidth (BW) both theoretically and experimentally. Namely, we show that as the inter-ring gap distance increases, the IPS increases and the 3 dB BW decreases.