We present a programmable universal Si<sub>3</sub>N<sub>4</sub> optical filter that can be reconfigured to various filter functions. The basic compositive structure is the Mach-Zehnder interferometer (MZI) with each arm coupled with a ring resonator. The input and output couplers in the MZI and the ring couplers are all tunable with coupling ratio varying from zero to one, making the device highly flexible. We theoretically investigate six configurations using the transfer function, revealing that the device can produce versatile filtering shape. Experimental demonstration of three configurations agree with the theoretical prediction. With a careful control of the ring coupling ratio, the filter can successfully generate sub-GHz passband that allows for high spectral-resolution microwave signal processing.
A novel silicon reconfigurable optical processor (SROP) is proposed based on a self-coupled optical waveguide (SCOW) resonant architecture. The SCOW is formed by a single meandering waveguide self-coupled to form directional couplers at the input and output ends. The SROP consists of three-stages of SCOW resonators, where the directional couplers are replaced by Mach-Zehnder interferometers (MZIs) to work as tunable couplers. Both phase shifters and variable optical attenuators (VOAs) are integrated in the device for active phase and amplitude tuning, respectively. By reconfiguring the states of tunable couplers, phase shifters and VOAs, the SROP is implemented as ring resonator, MZI, and Fabry-Perot cavity-based optical structures for versatile optical processing applications.
We report our recent progress on high-throughput 16×16 silicon non-blocking optical switches based on Mach- Zehnder interferometers (MZIs) and dual-ring assisted MZIs (DR-MZIs). TiN microheaters and p-i-n diodes are both integrated in each switch element for thermo-optic phase error correction and GHz-speed electro-optic switching, respectively. The MZI switch exhibits a broad optical bandwidth and low crosstalk. The DR-MZI switch exhibits low electrical switching power but with a narrower optical bandwidth. The two types of switches are designed to have a chip size of 12.1 mm × 4.6 mm mainly restricted by the chip package requirement. The DR-MZI chip can potentially have a smaller footprint due to its much more compact switch element, suitable for high-density on-chip optical data exchange.
We report our recent progress on reconfigurable optical true time delay lines (RTTDL) and optical switches. The
RTTDL is composed of 8 stages of MZIs connected by 7 waveguide pairs with an incremental length difference.
Variable optical attenuators are inserted in the delay waveguides to suppress crosstalk caused by the residual signals
from noise paths. Transmission of a 25 Gbps PRBS signal confirms the signal fidelity after a maximum of 1.27 ns
delay. The optical switch is based on a Benes architecture with Mach-Zehnder interferometers (MZI) as the
switching elements. Both p-i-n diodes and silicon resistive micro-heaters are integrated in the MZI arms for
electrical tuning and phase correction, respectively. The measured on-chip insertion loss of the 4×4 switch is < 8 dB.
Transmission of a 50 Gb/s quadrature phase shift keying (QPSK) optical signal verifies its switching functionality.
We present our recent work on integrated silicon photonic devices for optical filter and delay applications. A microdisk
resonator integrated with interleaved p-n junctions is demonstrated. The resonance can be both blue- and red-shifted by applying a forward current or a negative voltage, respectively. A MZI-nested microring resonator is shown capable of
coupling tuning, enabled by a p-i-p junction based thermal heater across the waveguide. We also investigate cascaded
self-coupled optical waveguide (SCOW) resonators. Electromagnetically-induced transparency (EIT)-like resonances are
generated featuring a narrow lineshape and a high group delay. Finally, we present an athermal lattice filter made up of 10 cascaded Mach-Zehnder interferometer (MZI) units and show that the temperature sensitivity can be considerably