Alan Tsay

Ultracompact SOI Microring Add–Drop Filter With Wide Bandwidth and Wide FSR

We report the design and fabrication of an ultracompact silicon-on-insulator add-drop microring filter with a 1.5-mum radius for wavelength-division-multiplexing on-chip interconnect applications. The fabricated device was measured to have a wide free-spectral range of 52 nm and a wide channel bandwidth of 210 GHz, with a 2.9-dB insertion loss and a deep through-port extinction of nearly 25 dB.

Extreme Miniaturization of Silicon Add–Drop Microring Filters for VLSI Photonics Applications

We theoretically and experimentally investigated the performance of silicon-on-insulator (SOI) microring add-drop filters in the limit of extreme miniaturization for potential application in very dense integration of silicon photonic devices. Rigorous numerical analyses were performed to predict the theoretical limit of achievable intrinsic quality factors as the microring radius is scaled down to 1 μm. Experimental measurements of fabricated SOI microring resonators showed that ultracompact add-drop microring filters with radii as small as 1 μm can be achieved with a free spectral range exceeding 80 nm and an insertion loss of only 1 dB. These devices are also shown to exhibit intrinsic quality factors approaching the theoretically achievable limit set by the bending loss in ultracompact microring resonators.

Analytic Theory of Strongly-Coupled Microring Resonators

Analytic theory for strongly-coupled microring resonators of general 2-D coupling topologies is developed based on the field coupling formalism. The theory allows simple characteristic equation for coupled microring resonators (CMR) of general coupling topology to be formulated, from which closed form analytical expressions of the transmission responses of the device can be derived. It is also shown that any CMR structure is characterized by a field coupling matrix which can be decomposed into a direct and indirect coupling term. The indirect coupling matrix can give rise to prominent strong coupling effects, such as indirect coupling induced transparency, that are not observed in weakly coupled microring resonators.

A Method for Exact Synthesis of

We present a simple method for synthesizing coupled microring resonator networks having a 2 × N coupling topology. The method is based on the field coupling formalism of 2-D coupled microrings and is applicable for designing broadband filters in the z-domain.

2\times N

We present a field coupling method for analyzing coupled microring resonators (CMRs) in sheared 2-D lattices. Shearing has the effect of imparting phase shifts to certain coupling elements in the lattice, and is shown to be a simple way for realizing negative couplings in CMR networks. We mathematically show that the operation of shearing can be described by a similarity transformation on the field coupling matrix of the microring network. The analysis presented can be generalized to account for the position dependence of the coupling junctions of arbitrary 2-D CMR networks.

Coupled Microring Resonator Networks

We present an analytical method for designing coupled microring resonator (CMR) networks of general 2-D coupling topologies. The method is based on the “field coupling in space” formalism of microring resonators, which gives a more rigorous and accurate description of CMRs than formulations based on “energy coupling in time,” especially under strong coupling conditions. Given the discrete-time transfer functions of the optical filter, this method enables the field coupling matrix of the CMR network to be extracted, so that an optimum coupling topology and the field coupling coefficients between the microring resonators can be determined.

Analysis of Coupled Microring Resonators in Sheared Lattices

We present a method for directly synthesizing coupled microring resonator filter networks of general 2-D coupling topologies. The method is based on the “energy coupling in time” formalism of systems of microring resonators and can be used to synthesize optical filter transfer functions in the s-domain. An example of a class of microring filters with equiripples in both the amplitude and group delay responses is also given to illustrate the application of the method to the design of complex microring filter architectures.

Field Coupling Method for the Direct Synthesis of 2-D Microring Resonator Networks

We present a method for synthesizing strongly coupled microring networks of general 2D coupling topologies. The method is based on the power coupling formalism of coupled microrings and can be used to design broadband filters.

Direct Synthesis of 2-D Coupled Microring Resonator Filter Networks

We report the design and realization of a 4th-order pseudo-elliptic microring filter with negative coupling in SOI. Measured filter response showed the effect of coupling phase dispersion and sharp skirt roll-off due to negative coupling.

Analytical Method for Designing Strongly Coupled Microring Resonator Networks

Spectral characteristics of 2D arrays of strongly-coupled microring resonators are investigated using power coupling analysis. It is shown that non-adjacent resonator coupling can give rise to distinct resonance features not observed in weakly-coupled microring arrays.