Coupled silicon ring resonator filters offer high-order spectral features such as steep roll-offs, high extinction ratios, and wide pass-bands, which are attractive to many applications in telecommunications and quantum computing systems. However, so far, their sensitivity to fabrication and temperature variations have limited the usability of such filters in practical applications. Here, by using in-resonator photoconductive heaters (IRPHs) to both sense and tune the resonance conditions of ring resonators, we demonstrate automatic configuration and wavelength locking of multiring resonator filters to an input laser's wavelength. We demonstrate the automatic configuration of a four-ring Vernier filter across a 36.7-nm wavelength range spanning the entire C-band and the wavelength locking of the same filter to counteract a practical chip temperature variation of 65  ${^\circ }$C. As IRPHs do not require additional material depositions, photodetectors, or power taps and use the same contact pads for both the sense and the tune operations, these results are achieved without compromising the cost or area of the devices. Furthermore, by localizing the feedback loops to only rely on the resonance conditions of adjacent rings, we present a tuning algorithm in which the number of iterations scales linearly with the number of coupled rings in the system. As this method does not rely on the output spectral shape of the system, it is, in general, applicable to a wide range of coupled resonator systems. Our results pave a path toward practical deployment of high-order and large-scale silicon ring resonator systems.

Using in-resonator photoconductive heaters to monitor and tune the light intensity inside the resonators, a four-ring Vernier filter is automatically tuned across the entire C-band and stabilized over a 40 °C temperature range.

We experimentally demonstrate a silicon-on-insulator microring resonator filter that uses bent contradirectional couplers to eliminate the filter's free spectral range. The filter's measured side-mode suppression is greater than 15 dB, the extinction ratio is ∼19 dB, and the 3-dB bandwidth is ∼23 GHz.

We propose a Vernier assisted Mach-Zehnder modulator (VAMZM) design that employs phase modulation on series-coupled Vernier rings' suppressed notches at the through ports to achieve a large extinction ratio and a small insertion loss.

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.

Using in-resonator photoconductive heaters to both sense and control the intra-cavity light intensity of microring resonators, automatic tuning of a silicon-on-insulator two-ring Vernier filter is demonstrated across the entire C-band.

We demonstrate 12.5 Gbit/s data transmission through a silicon contra-directional grating coupler optical add-drop multiplexer while signals are being simultaneously added and dropped at the same wavelength.

A tunable silicon quadruple Vernier racetrack resonator filter has been experimentally demonstrated. Data was sent through our filter at 12.5 Gbps which resulted in open eye diagrams, even at a suppressed through port notch.

We demonstrate theoretically a silicon resonator reflector, having no free spectral range, using a distributed Bragg reflector and a contra-directional grating coupler. The spectral response of the device meets numerous commercial specifications for a clear window of 5 GHz and a channel spacing of 100 GHz.

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.

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.

We present a theoretical sensitivity analysis of silicon-on-insulator quadruple Vernier racetrack resonators based on varying, one at a time, various fabrication-dependent parameters. These parameters include the waveguide widths, heights, and propagation losses. We show that it should be possible to design a device that meets typical commercial specifications while being tolerant to changes in these parameters. (C) 2015 Society of Photo-Optical Instrumentation Engineers (SPIE)

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.

Vernier racetrack resonators offer advantages over single racetrack resonators such as extending the free spectral range (FSR).1-3 Here, we have presented a theoretical sensitivity analysis on quadruple Vernier racetrack resonators based on varying, one at a time, various fabrication dependent parameters. These parameters include the waveguide widths, heights, and propagation losses. We have shown that it should be possible to design a device that meets typical commercial specifications while being tolerant to changes in these parameters.

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.

We present the design and experimental demonstration of a contra-directional grating-coupled racetrack resonator exhibiting the Vernier effect. The device consists of two racetrack resonators that are coupled together in a cascaded configuration. The input coupler in each racetrack resonator of the cascaded configuration consists of contra-directional gratings. The benefit of using contra-directional couplers is their small bandwidth, as compared to co-directional couplers that do not have gratings. The simulation results show that this device provides numerous performance advantages compared to cascaded racetrack resonators exhibiting the Vernier effect without contra-directional grating couplers. Specifically, we eliminate the free spectral range (FSR, i.e., in both the drop port and the through port) and show substantial improvement in the interstitial peak suppression and the through port insertion loss for the cascaded racetrack resonator with gratings, as compared to the case without gratings. In addition, experimental results are presented, which show an interstitial peak suppression of 29.3 dB, as well as the elimination of the FSR in the drop port and the through port.

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.