Silicon-on-insulator Microring Resonator Research Articles

Performance evaluation of silicon-chip-based mid-infrared Kerr optical frequency combs with ridge cross section

We present a complementary metal-oxide-semiconductor (CMOS) compatible platform for on-chip frequency comb generation in the mid-infrared region based on a silicon-on-insulator (SOI) microring resonator with ridge cross section. Flat dispersion tailoring is performed with dispersion variation of 4.04 × 10−6 ps/nm/km by adjusting the geometry parameter and the low-loss SOI microring resonator with total quality factor (Q) up to 106 can be realized at wavelengths from 3.3 to 3.6 µm. Furthermore, the thresholdless frequency combs consisting of 50 comb lines spanning from 3.1 to 4.0 µm (over 900 nm) can be realized using SOI microring resonator with 50 mW pump power. Besides, the study shows that the frequency interval of the comb is related to the selection of the dual-pumped wavelength. The influences of the coupling coefficient and the radius of microring on the bandwidth of mid-infrared OFC are also investigated numerically which shows that remarkable enhancement of mid-infrared OFC bandwidth can reach 449 nm when the coupling coefficient varies from 0.012 to 0.05. This research work is instructive for realizing highly integrated photonics and achieving the experimental generation of mid-infrared optical frequency combs, which could enable substantial progress in spectroscopy applications.

Optical bistable SOI micro-ring resonators for memory applications

The present work focuses on experimental investigations of a bistable silicon-on-insulator (SOI) micro-ring resonator (MRR). The resonator exploits a continuous-wave operation of the carrier-induced bistability demonstrating a stable hysteresis response at the through and drop ports when the input power exceeds the threshold value. Flipping the optical input power provides a convenient mechanism for a switching of the MRR output characteristics between two steady states having a long holding time. The transition of the resonator output between these states is experimentally investigated. It is shown that the switching speed is limited by a low-to-high transition of 188 ns. Obtained results shows an application of the passive SOI MRR as an all-optical memory cell with two complementary outputs.

Etched Silicon-on-Insulator Microring Resonator for Ultrasound Measurement

A novel integrated optical ultrasound sensor based on silicon-on-insulator (SOI) platform is proposed, theoretically analyzed and experimentally demonstrated. By using a selectively etched SOI microring resonator in an add-drop structure, the technique provides a linear and distortion-free sensing response to the ultrasound signal as it prevents the coupling region deformation and removes variations from the power fluctuation of the optical source. The proof-of-concept experimental demonstration of the proposed sensor shows the detection of air-coupled ultrasound pressure at different frequencies and magnitudes, a frequency sensing resolution of 30 Hz and a wide acceptance angle around 75 degrees.

Carbon-nanotube-on-waveguide thermo-optic tuners.

We demonstrate on-waveguide thermo-optic tuners based on solution-processed metallic carbon nanotubes (CNTs) on silicon-on-insulator (SOI) and silicon nitride (SiN) microring resonators operating around 1550nm. On SOI microring resonators using planarized wire waveguides, a thermo-optic power efficiency of 29mW/FSR and a thermal transient of 1.3μs are achieved. The heater is shown to be more power-efficient than conventional metal heaters and has lower thermal transient than both metal heaters and graphene-based heaters. On SiN microring resonators using rib waveguides, improvement in power efficiency with an increase in coverage of CNTs is demonstrated, indicating localized heating using the CNTs; this is favorable for low thermal cross-talk. An optimal power efficiency of 142mW/FSR and a thermal transient of 5.8μs are achieved.

Fast analytical modelling of an SOI micro-ring resonator for bio-sensing application

In this work, we present a closed-form model of silicon-on-insulator (SOI) micro-ring resonators, based on the conformal transformation method. We compute the propagation characteristics of the whispering gallery modes at resonance wavelengths. The results of the proposed model are compared to numerical simulations based on the finite element method (FEM). The proposed method allows comparable accuracy to that of FEM simulations, with a significant reduction in computer resource requirements (time, speed, memory). To further validate the proposed modelling, we also compare the modelling results to experimental data. Finally, we model a ring resonator for biosensing applications. We compute the bulk refractive index sensitivity (S), the figure of merit (FOM) and the intrinsic limit of detection (ILOD). In the geometry under study, our proposed model predicts an ideal ILOD of refractive index units, which is 0.24 smaller than what has been reported in SOI optimized structure. These results validate the proposed modelling technique for the fast design of optical biosensors where both the figure of merit and the geometries can be optimized.

Antifouling coatings on SOI microring resonators for bio sensing applications

Methylated dendritic polyglycerol (dPG(OMe)) is proposed as an antifouling coating for the application with silicon on insulator (SOI) bio sensors. Sensors were coated with dPG(OMe). Fibrinogen was used to test the antifouling properties. Using SOI ring resonator sensors for the measurement, a reduction of 87% in the binding of fibrinogen to the silicon surface was shown experimentally.

Optimisation Design of Coupling Region Based on SOI Micro-Ring Resonator

Design optimization of the coupling region is conducted in order to solve the difficulty of achieving a higher quality factor (Q) for large size resonators based on silicon-on-insulator (SOI). Relations among coupling length, coupling ratio and quality factor of the optical cavities are theoretically analyzed. Resonators (R = 100 μm) with different coupling styles, concentric, straight, and butterfly, are prepared by the micro-electro-mechanical-systems (MEMS) process. Coupling experimental results show that micro-cavity of butterfly-coupled style obtains the narrowest (3 dB) bandwidth, and the quality factor has been greatly improved. The results provide the foundation for realization of a large size, high-Q resonator, and its development and application in the integrated optical gyroscopes, filters, sensors, and other related fields.

High performance SOI microring resonator for biochemical sensing

Abstract In this work we have investigated different silicon-on-insulator (SOI) microcavities based on a planar geometry having a footprint on chip as small as 100 μm 2 with a ring, disk and hybrid configurations with the aim of being poorly intrusive for both in-body and out-of-body biosensing purposes. Accurate numerical results have been achieved by using the 3D finite element method and compared to 3D finite discrete time domain ones with a good agreement for both methods. The most promising resonator among the devices we have analyzed shows a Q -factor of the order of 10 5 , that allows a limit of detection for the sensor equal to 10 −6 RIU and a sensor sensitivity of 120 nm/RIU. The resonator has been designed for glucose biosensing, considering both the homogeneous sensing and the surface one, that enhances the sensor selectivity by the device functionalization with a glucose-oxidase (GOD) layer. The glucose concentration has been evaluated both with the microcavity surrounded by a water solution and with water only in the inner part of the cavity. The achieved performance is really attractive not only for the reduced size of the cavity, but also for the planar coupling configuration of the annulus and the waveguides composing the cavity since it appears to be a very promising configuration for the practical packaging of micro systems containing whispering gallery mode resonators. In this paper the concept of an on-chip platform for a high throughput and multichannel detection relying on an array of resonant cavities interacting with a single nanofluidic channel, is also discussed.

Doubled temperature measurement range for a single micro-ring sensor

A novel SOI (silicon on insulator) temperature sensor based on a U-shaped waveguide-coupled single micro-ring is proposed in this paper. Refractive index and length of the temperature-sensing part will change as the temperature changes, leading to the shift of the output spectrum of the sensor. The transfer function of the U-shaped waveguide coupled with a single micro-ring is obtained based on the theory of coupling modes and transfer matrix method. And we have studied the output spectrum properties of the system from different temperature-sensing parts. Results show that the whole structure of U-shaped waveguide coupled with the single micro-ring proves to be the best temperature-sensing part as the output spectrum with no spurious modes and a deep extinction ratio of 31 dB. Compared with the traditional two waveguides coupled with a single micro-ring resonator, when the distance between the two coupling points of the U-shaped waveguide is an integer multiple of circumference of the micro-ring, the free spectrum range (FSR) can be expanded to 56 nm, the sensitivity can achieve 89.2 pm/℃, and the measurement range be 298720 K, achieving a high temperature measurement of SOI micro-ring resonator.

Modeling of coupling loss in ultra-compact SOI microring resonators

Ultra-compact microring resonators, made of high index contrast (HIC)-silicon on insulator (SOI) materials, have become key optical devices in integrated photonics systems. Both computer simulations and actual experiments have showed that coupling loss was a significant contributor to the total losses in ultra-compact microring resonators. In this paper, a computable model derived from step approximation method was present to theoretically determine the coupling loss. Excellent matching results between the model and literatures were achieved. The proposed model can be applied to evaluate the coupling loss for microring resonators with various geometries and guide the design of low loss optical devices based on ultra-compact microring resonators.

Performance of the Active Microring Resonator Based on SOI Rib Waveguide

Micro-ring resonator based on silicon-on-insulator (SOI) has been extensively studied due to its many advantages, thus promising to improve the optoelectronic integrated circuit performance. This paper highlights the study of the free carrier injection effect on the silicon rib waveguide with p-i-n diode structure integrated in the SOI micro-ring resonator. The free carrier concentrations have been modulated by the electrical signal that can cause change of refractive index of the micro-ring resonator. The device performances are predicted by using numerical modelling software 2D SILVACO and Finite Difference Time Domain method simulation software RSOFT. The results show the change of refractive index is maximized at a greater applied voltage. A shift in resonant wavelength of around 6.7 nm was predicted at 0.9V with 1.14x10-3refractive index change. It is also shown that 8.5dB change of the output response obtained through the output.

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.