Coupled Microring Resonator Research Articles

Direct Synthesis of 2-D Coupled Microring Resonator Filter Networks

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.

Silicon technology compatible photonic molecules for compact optical signal processing

Photonic molecules (PMs) based on multiple inner coupled microring resonators allow to surpass the fundamental constraint between the total quality factor (QT), free spectral range (FSR), and resonator size. In this work, we use a PM that presents doublets and triplets resonance splitting, all with high QT. We demonstrate the use of the doublet splitting for 34.2 GHz signal extraction by filtering the sidebands of a modulated optical signal. We also demonstrate that very compact optical modulators operating 2.75 times beyond its resonator linewidth limit may be obtained using the PM triplet splitting, with separation of ∼55 GHz.

Field Coupling Method for the Direct Synthesis of 2-D 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 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.

Silicon High-Order Coupled-Microring-Based Electro-Optical Switches for On-Chip Optical Interconnects

We demonstrate an electro-optically (EO) tunable switch using tenth-order coupled-microring resonators in silicon-on-insulator using complementary metal-oxide-semiconductor fabrication technology. The measured drop-port transmission spectra show box-like transmission passband with ~100-GHz bandwidth and ~50-dB extinction ratio. With a DC voltage supply to the integrated p-i-n diodes surrounding the microrings, the optical switch shows, respectively, ~10 and ~45-dB on/off ratios from throughputand drop-port. The measured EO switching times are ~1 ns upon a 1.2-Vpp low-speed driving signal and a DC power consumption of ~37 mW. Up to 30-Gb/s pseudorandom binary sequence (2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">31</sup> -1) signal transmissions suggest high-data-rate signal switching capability.

Chirp-free optical return-to-zero modulation based on a single microring resonator

This paper proposes a chirp-free optical return-to-zero (RZ) modulator using a double coupled microring resonator. Optical RZ modulation is achieved by applying a clock (CLK) driving signal to the input coupling region and a non-return-to-zero (NRZ) driving signal to the output coupling region. Static and time-domain coupled-mode theory (CMT) based dynamic analyse are performed to theoretically investigate its performance in RZ modulation. The criteria to realize RZ modulation are deduced. Various RZ modulation formats, including RZ phase-shift-keying (RZ-PSK), carrier-suppressed RZ (CSRZ), and RZ intensity modulation formats, can be implemented by using CLK and NRZ signals with different combinations of polarities. Numerical simulations are performed and the feasibility of our modulator at 10 Gbit/s for the multiple RZ modulation formats is verified.

Nonlinear Bloch modes, optical switching and Bragg solitons in tightly coupled micro-ring resonator chains

We study nonlinear wave phenomena in coupled ring resonator optical waveguides in the tight coupling regime. A discrete model for the system dynamics is put forward and its steady-state nonlinear Bloch modes are derived. The switching behaviour of the transmission system is addressed numerically and the results are explained in the light of this analytical result. We also present a numerical study on the spontaneous generation of Bragg solitons from a continuous-wave input.

A Method for Exact Synthesis of $2\times N$ Coupled Microring Resonator Networks

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.

Numerical scheme for simulation of self-pulsing and chaos in coupled microring resonators

Nonlinear coupled equations that describe propagation of optical pulses in waveguide structures under the slowly varying envelope approximation are solved by a simple explicit finite-difference scheme.The technique, which is based on upwind differencing, is used for modeling of Kerr-nonlinear structures with microring resonators in all-pass filter configuration. We show numerical examples that demonstrate existence of self-pulsing and chaotic solutions. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2238–2242, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26242

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.

Demonstration of OCDM Coder and Variable Bandwidth Filter Using Parallel Topology of Quadruple Series Coupled Microring Resonators

The quadruple series coupled microring resonator (MRR) can realize a boxlike spectral response and lower adjacent channel crosstalk. Utilizing these features, we demonstrated the element of Optical Code Division Multiplexing (OCDM) coding circuit using two wavelength selective switches (WSSs) consisting of quadruple series coupled MRRs laid out in parallel topology and a phase shifter incorporated in the one arm between them. In addition, a digitally variable bandwidth filter was successfully demonstrated using the same circuit as the OCDM coder.

All-optical switching of dark states in nonlinear coupled microring resonators

We propose and analyze an on-chip all-optical dynamic tuning scheme for coupled nonlinear resonators employing a single control beam injected in parallel with a signal beam. We show that the nonlinear Kerr response can be used to dynamically switch the spectral properties between a "dark state" and electromagnetically induced transparency configurations. Such a scheme can be realized in integrated optical applications for pulse trapping and delaying.

UV trimming of Polarization-independent Microring Resonator by Internal Stress and Temperature Control

The temperature dependence of the resonant wavelength of vertically coupled microring resonator can be controlled via internal stress caused by the thermo-optic and photo-elastic effects. In the case of strong internal stress, a polarization-independent microring resonator can be realized by controlling the device surface temperature using a heater module; the temperature dependence of TE and TM polarizations are different due to the internal stress and thus manipulating temperatures, the resonant wavelengths for TE and TM can be equalized at a specific temperature. In this study, the UV trimming of polarization-independent wavelength was demonstrated using UV-sensitive SiON as a core material. The temperature dependence of TE polarization was almost athermalized and that of TM was made negative by controlling internal stress. As a result, the simultaneous realization of the UV trimming and the polarization-independent microring was made possible more easily than before; the UV trimming can be done at room temperature due to the athermalized resonant wavelength for TE polarization.

Silicon dual-ring modulator

A silicon electro-optic modulator based on coupled microring resonators is proposed. The dual-ring modulator has wide optical bandwidth, high extinction ratio and low insertion loss. A simple integrated circuit connecting the two rings allows for fast modulation speed of >40 Gbit/s. This device has both improved optical and electrical performance over a single-ring modulator. The dual-ring modulator can provide a feedback signal for active control of the modulation wavelength.

Optical frequency doubling for multichannel radio-over-fibre system based on integrated phase modulator and silicon coupled microring notch filter

An integrated optical millimetre-wave signal generator based on a coupled microring resonator, which doubles the frequency of the electrical signal driving a phase modulator, is proposed and experimentally demonstrated for future radio-over-fibre systems. The coupled microring notch filter was fabricated on a silicon-on-insulator wafer. A high extinction ratio optical millimetre-wave signal was obtained.

A reflective microring notch filter and sensor

We present a new design of wavelength selective reflector composed of a Y junction and a singly coupled microring resonator, and demonstrate its biochemical sensing applications with a prototype device. In contrast with other reflectors like distributed Bragg reflectors, this device acts as notch filter at its reflection port. One promising application of the device is for remote sensing of harsh or inaccessible site, where only one optical fiber is required to transmit the input and reflected light signal over a long distance. The design can also be used to make microring cavity lasers.

Comments on "Performances of a Fully Integrated All-Optical Pulse Reshaper Based on Cascaded Coupled Nonlinear Microring Resonators" [Sep 07 2417-2426

In the above paper (ibid., vol. 25, no. 9, pp. 2417-2426, Sep 07), the authors did not accurately evaluate the Q-factors given in Table 1. The corrected values are presented in the revised table. Other corrections based on these changes are also noted.

双波导耦合微环传感器灵敏度及探测极限研究

We show that a linear relation exists between the device sensitivity and the quality (Q) factor of a dual-waveguide coupled microring resonator optical biosensor when the optimal conditions are satisfied. We also show that the detection limit depends on the loss coefficient and signal-to-nosie ratio (SNR) of the overall system, rather than the circumference of the ring. For a microring resonator sensor whose Q factor is 20000, the detection limit is found to be about 10^{-7} with 30-dB SNR, which is in good agreement with reported experimental data. These results indicate that loss reduction is the top priority in the design and fabrication of highly sensitive microring resonator optical biosensors.

Modes of the infinite square lattice of coupled microring resonators

The infinite square lattice of coupled microring optical resonators is studied for what we belive to be the first time. Using the standard matrix formalism and the classical Bloch's theorem for propagation in periodic optical media, the dispersion equation and the amplitudes of propagating Bloch modes are derived analytically. It is found that the dispersion equation omega(kx,ky) of this 2D microring array is expressed as the sum of two independent dispersion equations of the 1D microring array with wavenumbers kx and ky. As a result, the width of the passband is twice that of a microring coupled-resonator optical waveguide and there are no stop bands for an interresonator power coupling ratio greater than 1/2. The evanescent modes that are important to the analysis of lattices with interrupted periodicity are also studied. The reported analysis is the prerequisite to the future study of superresonators consisting of large finite microring arrays.

Demonstration of defect modes in coupled microresonator arrays fabricated in silicon-on-insulator technology

We show experimentally the existence of defect modes in mutually coupled microring resonator arrays fabricated in silicon-on-insulator technology. The movements of donor-like and acceptor-like modes are demonstrated for various defect lengths, in good agreement with earlier theoretical prediction.