Symmetric Microring Research Articles

Research on sensing characteristics of third-order runway series symmetric microring resonator based on hybrid plasma waveguide and metal insulator metal.

In this paper, a high-sensitivity refractive index sensor based on a hybrid plasma waveguide and metal-insulator-metal waveguide combined third-order runway series mosaic microring resonator is proposed. In this structure, a GaAs waveguide ring surrounds a gold waveguide ring in the middle, and the innermost layer is a disk made of gold material. The outer groove waveguide is composed of GaAs-air-alloy, and the inner groove waveguide is made of the Gold-Air-Gold material disc. By filling different substances in the groove, the change of refractive index will affect the optical signal strength of the output spectrum. The finite element method simulates the transmission spectrum and electric field distribution of the sensor structure. The amplitude coupling coefficient and attenuation factor affecting the resonator's performance are analyzed, and the structural parameters of the slot waveguide are optimized. The numerical simulation results show that the sensor quality factor of this structure is 1.54 × 104 , the sensitivity is 1.2 × 103 nm/RIU which is about 1.5 times higher than that of the Si ring with the same structure, the detection limit can reach 8.1892 × 10-7 RIU, and the free spectral range can reach 109 nm. Compared with the traditional microring structure, this microring has higher design freedom and free spectral range and is more suitable for producing biosensors with high sensitivity, low detection limit, and multi-parameter measurement.

An integrated parity-time symmetric wavelength-tunable single-mode microring laser

Mode control in a laser cavity is critical for a stable single-mode operation of a ring laser. In this study we propose and experimentally demonstrate an electrically pumped parity-time (PT)-symmetric microring laser with precise mode control, to achieve wavelength-tunable single-mode lasing with an improved mode suppression ratio. The proposed PT-symmetric laser is implemented based on a photonic integrated circuit consisting of two mutually coupled active microring resonators. By incorporating multiple semiconductor optical amplifiers in the microring resonators, the PT-symmetry condition can be achieved by a precise manipulation of the interplay between the gain and loss in the two microring resonators, and the incorporation of phase modulators in the microring resonators enables continuous wavelength tuning. Single-mode lasing at 1,554.148 nm with a sidemode suppression ratio exceeding 36 dB is demonstrated and the lasing wavelength is continuously tunable from 1,553.800 to 1,554.020 nm.

Parity-time-symmetric microring lasers.

The ability to control the modes oscillating within a laser resonator is of fundamental importance. In general, the presence of competing modes can be detrimental to beam quality and spectral purity, thus leading to spatial as well as temporal fluctuations in the emitted radiation. We show that by harnessing notions from parity-time (PT) symmetry, stable single-longitudinal mode operation can be readily achieved in a system of coupled microring lasers. The selective breaking of PT symmetry can be used to systematically enhance the maximum attainable output power in the desired mode. This versatile concept is inherently self-adapting and facilitates mode selectivity over a broad bandwidth without the need for other additional intricate components. Our experimental findings provide the possibility to develop synthetic optical devices and structures with enhanced functionality.

Gap solitons and symmetry breaking in parity-time symmetric microring coupled resonator optical waveguides

The propagation properties of optical fields in linear and nonlinear parity-time symmetric microring coupled resonator optical waveguides are studied. The effects described include the existence of symmetry breaking thresholds, the propagation of gap solitons in nonlinear transmission lines and the existence of quasi stable propagation regimes outside the broken symmetry regions.

Generation of amplitude-shift-keying optical signals using silicon microring resonators

We demonstrate the generation of amplitude-shift-keying (ASK) optical signals using a system of parallel microring resonators. By independently modulating two symmetric microring resonators arranged in a Mach-Zehnder configuration, we realize the generation of three levels. The proposed scheme can be extended to any number of logic levels, which effectively increases the data rate of an optical link using slower modulators. Here, we separately utilize thermo-optic and ultrafast all-optical modulation schemes to generate ASK signals on a silicon photonic chip.

Canonic Design of Parallel Cascades of Symmetric Two-Port Microring Networks

A method for obtaining the optimal canonic design of optical filters based on parallel-cascaded arrays of symmetric two-port microring networks is presented. The approach is based on the all-pass decomposition of the parallel-cascaded microring architecture, whereby the filter is transformed into an equivalent sum-difference all-pass microring circuit via a similarity transformation of the transfer matrix. The sum-difference transformation also helps reveal important properties of the parallel-cascaded microring architecture, such as the doubly complementary nature of its transfer functions, and the existence and uniqueness of the canonic form of parallel-cascaded arrays of symmetric microring networks.

Experimental determination of coupledmicroring filter parameters via pole-zero extraction

A method for directly extracting the coupling coefficients, the resonant frequency detunings and the loss of an N(th)-order serially-coupled microring resonator filter from the measured power spectral responses is presented. The device parameters are obtained from the through-port complex transfer function, which is constructed from the experimentally extracted poles and zeros of the filter. We applied the method to determine the parameters of a symmetric microring doublet fabricated in the Silicon-on- Insulator material platform. Simulated spectral responses using the extracted parameters showed good agreement with the measured data. The extracted parameters along with the poles and zeros of the device provide important information about the fabrication process and can be used to guide the post-fabrication trimming of high-order microring filters.

Generalized parallel-cascaded microring networks for spectral engineering applications

The transfer characteristics of parallel-cascaded arrays of generalized two-port microring networks with interstage phase shifts are investigated for potential applications in spectral engineering. It is found that these structures can exactly realize optical transfer functions with quadrantal symmetric zeros if the microring networks are even-symmetric. The proposed filter architectures have advantages in that the microring networks have all-positive coupling coefficients, and the array can always be reduced to the canonical form that contains only one interstage π phase-shift element. A method for exactly synthesizing cascaded symmetric microring networks based on the transfer matrix factorization technique is presented, and an example of an eighth-order generalized Chebyshev filter is given to illustrate the application of these microring lattice architectures for realizing very high-order optical transfer functions.

Exact Realization of Optical Transfer Functions With Symmetric Transmission Zeros Using the Double-Microring Ladder Architecture

Arrays of parallel-cascaded microring doublets with inter-stage differential phase shifts are proposed for realizing general optical filter transfer functions whose zeros are located on or symmetrically distributed about the imaginary jomega-axis. Compared to previously proposed microring filters capable of realizing transmission zeros, the double-microring ladder architecture has the advantages in that it is compact and requires only synchronously tuned microring resonators with nonnegative coupling coefficients. Furthermore, the building blocks of the filter are simple symmetric microring doublets, which can be separately optimized to achieve good fabrication tolerance and repeatability. A procedure for exactly synthesizing the device given a prescribed transfer function is developed in both the s- and z-domains. Examples of an optical elliptic filter and a linear-phase filter with flat-top spectral responses in both the amplitude and group delay are presented to illustrate the applications of the proposed ladder filter architecture. Sensitivity analysis also shows that the device is robust with respect to microring loss as well as variations in the coupling parameters and phase shift factors.

Photonic logic NOR gate based on two symmetric microring resonators

We demonstrate an all-optical NOR logic gate based on symmetric GaAs-AlGaAs microring resonators whose resonances are closely matched. Two input pump data streams are tuned close to one resonance of the symmetric microrings to switch a probe beam tuned to another resonance by two-photon absorption. The switching energy of the gate is 20 pJ/pulse, and the switching window is 40 ps, limited by the carrier lifetime. The use of two rings provides for better cascading in photonic logic circuits because of the higher number of available ports.