Single Microring Resonator Research Articles

Research on sensing characteristics of diamond multilayer waveguide structure racetrack micro-ring resonator

A racetrack micro-ring resonant cavity sensor based on the diamond's material is proposed in this paper. In the model, the vertical-section of the waveguide adopts a five-layer ridge-type waveguide structure based on CH3NH3PbI3, SiO2 and diamond, i.e. CH3NH3PbI3-SiO2-Diamond-SiO2-CH3NH3PbI3. First, on the basis of the resonant principle and coupled mode theory, this study investigated the light field intensity distribution characteristics of the integral resonant cavity, the longitudinal section of a single straight waveguide, the racetrack micro-ring, and the longitudinal section of the straight waveguide by using the finite element method in COMSOL. The analysis shows that the introduction of CH3NH3PbI3 as an isolation layer can avoid the light scattering loss and leakage loss, and significantly enhance the filtering performance. In addition the sensing characteristics of the Add-drop racetrack resonator were further studied. Results showed that the structure could achieve a quality factor of 105, and the sensitivity could reach 14833.33 dB/RIU. In the detection system with a signal-to-noise ratio of 30 dB, the detection limit was 2.02 × 10−7 RIU. Compared with the traditional All-pass single micro-ring resonator, the proposed structure shows advantages of high tenability, high sensitivity and low detection limit.

A compound optical microresonator design for self-referencing and multiplexed refractive index sensing

We propose a new type of self-referencing and multiplexed refractive index (RI) sensor based on a compound optical microresonator structure consisting of Fabry-Pérot (FP) resonators coupled with microring resonators. The transmission spectra shows resonant features that are superimposed on a background defined by FP oscillations. The resonances have asymmetric Fano-like non-Lorentzian shapes, which are used as sensing peaks, while the FP oscillations are used as reference peaks for internal self-referencing. The sensing peaks shift linearly with the increased RI of the cladding in the microring resonator, while FP peaks stay constant. When the temperature is increased, both the FP peaks and the Fano resonances shift linearly at the same rate, which eliminates the temperature effect on RI measurements. We theoretically analyzed that the two-mirror FP resonator coupled with a single microring resonator and optimized its sensing performance through finite-difference time-domain simulations. A sensitivity value of 220 nm/RIU and a maximum figure of merit of 4400 RIU-1 were achieved. We also proposed two possible multiplexing schemes consisting of two-mirror and three-mirror FP resonators coupled with two microring resonators of different radii. The proposed sensor concept is simple, easy-to-fabricate, self-calibrating and can be used for simultaneous measurements of different samples.

Single-cavity bi-color laser enabled by optical anti-parity-time symmetry

The exploration of quantum inspired symmetries in optical systems has spawned promising physics and provided fertile ground for developing devices exhibiting exotic functionalities. Founded on the anti-parity–time (APT) symmetry that is enabled by both spatial and temporal interplay between gain and loss, we demonstrate theoretically and numerically bi-color lasing in a single micro-ring resonator with spatiotemporal modulation along its azimuthal direction. In contrast to conventional multi-mode lasers that have mixed-frequency output, our laser exhibits stable, demultiplexed, tunable bi-color emission at different output ports. Our APT-symmetry-based laser may point out a new route for realizing compact on-chip coherent multi-color light sources.

Design of all-optical logical mode-switching using micro-ring resonator

This paper highlights the implementation of all-optical mode alteration using a simple micro-ring resonator (MRR). The polarization-based switching happens if a suitable input polarized light is applied as a source and pump power. The mode-conversion with respect to change in the behavior of the input and in the pump signal is used to realize all-optical OR/NOR and XOR/XNOR logic gates in both the output ports of the single MRR simultaneously. The all-optical switching behavior is also justified by its time-graph. The model is verified using the finite-difference time-domain simulation approach. Some characteristics parameters are also explained to highlight its benefits. The architecture may also be used to design new polarization-conversion centered logical and arithmetic circuits.

Various resonance lineshapes available in a single microring resonator

To accommodate different application requirements, resonances of microring resonator (MRR)-based devices have been developed into various lineshapes, such as electromagnetically induced transparency, electromagnetically induced absorption, and Fano lineshapes. However, these lineshapes are mainly achieved in large-footprint structures demanding precise control. Under such context, this work investigates the formation of various resonance lineshapes in a single MRR with two partially reflecting elements incorporated into the bus waveguide. The transfer matrix model of the compact structure is established with the reflective wave in the MRR included. It is revealed that the abundant resonance lineshapes originate from the mode-coupling between the Fabry–Perot cavity and the MRR. Based on this model, the formation of each resonance lineshape is analyzed. The conditions under which each resonance lineshape can occur are identified and the characteristics of these resonance lineshapes are studied. In addition, the significant role of the reflective wave in the formation of these lineshapes is emphasized. Under the theoretical guidance of the presented work, various resonance lineshapes can be achieved and designed flexibly in a single MRR. Thus, the lineshapes required for a range of applications can be realized in a simple and reproducible MRR.

Analysis of Compact Silicon Photonic Hybrid Ring External Cavity (SHREC) Wavelength-Tunable Laser Diodes Operating From 1881–1947 nm

The “ $2~\mu \text{m}$ waveband”, specifically the $1.9~\mu \text{m}$ wavelength region, is playing an increasingly imperative role in photonics. Development into compact tunable light sources operating at the wavelength region can unlock numerous technological applications. Instances, while not exhaustive, include alleviating the capacity load in fiber communications, H2O spectroscopy, optical logic, signal processing as well as enabling the optical Kerr effect on silicon. Silicon photonics is a disruptive technology. Through mature silicon processing, recent developments suggest that silicon will emerge as the workhorse of integrated optics. While the realization of a monolithic light source has proved to be challenging, the hybrid/heterogenous Si platforms, consisting of silicon and III-V materials, has stepped to the fore. In this work, we present the study of Vernier-based hybrid silicon photonic wavelength-tunable lasers with an operating range of 1881–1947 nm (66 nm), subject to different coupling gaps (Gapmrr) between the silicon microring resonators (MRRs) and bus waveguide. Wavelength tuning functionality is enabled via the thermo-optic effect of MRRs. Gapmrr, being the smallest feature in the assemble, is highly influential to the characteristics of the SHREC. As such, trends in hybrid laser performance with respect to Gapmrr are measured and analyzed. Slope efficiency, laser output power and side-mode suppression ratio of 0.232 W/A, 28 mW and 42 dB respectively are obtained across the developed lasers. Through the design of the Vernier spectrum and Gapmrr, tuning of laser wavelength from 1881–1947 nm can be achieved by applying only 47.2 mW of thermal power to a single MRR.

Reflective-Type Microring Resonator for On-Chip Reconfigurable Microwave Photonic Systems

Microring resonator (MRR) is regarded as one of the most widely-used building blocks in photonic integration, which is employed to implement optical filtering, routing, sensing, true time delay, signal processing, logic operations and so on. However, a single MRR intrinsically produces Lorentzian or Lorentzian-derivative shape responses with very sharp peaks, which is incapable of handling wideband signals for microwave photonic systems. In this paper, we introduce a reflective-type MRR with a reflector connected to the drop port of an add-drop MRR. Thanks to the reflector, reconfigurable intensity and group delay responses can be achieved by setting the coupling coefficients of the MRR, leading to the implementation of flat-top filtering, wideband optical true time delay, XNOR/XOR optical logic operation and electro-optic modulation. Both theoretical analysis and experimental demonstration are carried out. This new MRR structure may enable a new, compact and low-cost design strategy for the integrated reconfigurable or programmable microwave photonic systems.

All-optical pseudo noise sequence generator using a micro-ring resonator.

A scheme for the generation of a pseudo noise (PN) sequence in the optical domain is proposed. The cascaded units of micro-ring resonator (MRR)-based D flip-flop are used to design the device. D flip-flops consist of a single MRR and share the same optical pump signal. Numerical analysis is performed, and simulated results are discussed. The proposed device can be used as a building block for optical computing and for creating an information processing system.

Design of an Ultra-Compact and Highly-Sensitive Temperature Sensor Using Photonic Crystal Based Single Micro-Ring Resonator and Cascaded Micro-Ring Resonator

In the present report, a photonic crystal based micro-ring resonator (MRR) structure is proposed which is very compact in size and has very fast response and is employed for temperature sensing purpose. Temperature sensing application for both the single MRR and cascaded MRR is illustrated in this paper. The sensitivity of the reported structure is increased from 2.9 nm/°C to 3.4 nm/°C by cascading two MRR. The refractive index of the material is subjected to change with the variation in temperature which results in the shift of the resonant wavelength of the proposed sensor. The finite difference time domain (FDTD) simulation is utilized to see the transmission spectrum of the proposed structure and analyzing the shift in the resonance wavelength the temperature is calculated. The proposed design is simple, reliable and may be integrated into different transducer and sensing applications.

Hitless Wavelength-Selective Switch Using a Single Microring Resonator Assisted With a Symmetric MZI

We demonstrate an optical hitless wavelength-selective switch using a single microring resonator assisted with a symmetric Mach-Zehnder interferometer (MZI). A part of the ring waveguide and its symmetrical waveguide are designed to be an equally armed MZI as an on-off switch for the resonant state of the microring. The symmetric MZI is insensitive to the spectrum and it avoids free spectral range (FSR) matching or alignment in use. The FSR of the structure is 2.18 nm and the insertion loss (IL) at the drop-port is 1.8 dB. Our experimental results reveal that the fabricated device permits on-chip hitless rerouting of multi-wavelength signals, which means the intermediate wavelength remains unaffected during wavelength switching.

Measuring on-chip waveguide losses using a single, two-point coupled microring resonator.

We demonstrate a method for measuring on-chip waveguide losses using a single microring resonator with a tunable coupler. By tuning the power coupling to the microring and measuring the microring's through-port transmission at each power coupling, one can separate the waveguide propagation loss and the effects of the coupling to the microring. This method is tolerant of fiber-chip coupling/alignment errors and does not require the use of expensive instruments for phase response measurements. In addition, this method offers a compact solution for measuring waveguide propagation losses, only using a single microring (230 µm×190 µm, including the metal pads). We demonstrate this method by measuring the propagation losses of silicon-on-insulator rib waveguides, yielding propagation losses of 3.1-1.3 dB/cm for core widths varying from 400-600 nm.

Manipulation microwave photonic filter response of single microring by using optical frequency combs

We proposed a reconfigurable microwave photonic filter combining the multiple resonances of single microring resonator and optical frequency combs. By manipulating the number of comb lines, the frequency spacing of the comb lines and the relative power between the comb lines, the MPF can be reconfigured from a notch filter with ultra-high rejection ratio to a flat bandstop filter. The mechanism of the reconfigurable microwave photonic filter was clarified theoretically. And in experiments, a notch filter with an ultra-high RF rejection ratio exceed 60 dB and a flat stopband filter with a 10 dB rejection ratio and a stopband ripple less than 0.53 dB were easily reconfigured by manipulating the optical frequency comb lines.

A silicon-based compact triplexer using Bragg grating assisted non-reciprocal single microring resonator

An ultra-compact silicon triplexer based on waveguide Bragg grating assisted non-reciprocal optical ring add-drop filter has been proposed. This novel scheme consists of two straight strip waveguides laterally coupled to a microring resonator. A magneto-optically active material deposited inside the microcavity is etched to induce strong non-reciprocity, which can cause resonance wavelength splitting ΔλMO of two counter propagating modes. Uniform Bragg grating reflector is fabricated in proximity to one of the input/output (I/O) ports. As a result, two downstream WDM channels (1490 nm/1550 nm) can be separated into the output ports of strip waveguide below the ring resonator, while the third channel considered as upstream signal is transmitted through the waveguide above the microring without any interaction with either the microring resonator or the waveguide Bragg grating reflector. Results show that a total length of 13.5 μm with the highest isolation ratio (IR) of 35 dB is obtained at the adjacent ports of the same strip waveguide; the lowest crosstalk (XT) of −38 dB for 1310 nm channel has also been obtained.

Ultra-low power all-optical wavelength conversion of high-speed data signals in high-confinement AlGaAs-on-insulator microresonators

Wavelength conversion technology is imperative for the future high-speed all-optical network. Nonlinear four-wave mixing (FWM) has been used to demonstrate such functionality in various integrated platforms because of their potential for the realization of a chip-scale, fully integrated wavelength converter. Until now, waveguide-based wavelength conversion on a chip requires a pump power beyond the reach of available on-chip lasers. Although high-quality factor (Q) microresonators can be utilized to enhance the FWM efficiency, their narrow resonance linewidths severely limit the maximal data rate in wavelength conversion. In this work, combining the ultrahigh effective nonlinearity from a high-confinement aluminum gallium arsenide waveguide and field enhancement from a microring resonator with a broad resonance linewidth, we realize all-optical wavelength conversion of a 10-Gbaud data signal by using a pump power, for the first time, at a submilliwatt level. With such a low operation power requirement, a fully integrated high-speed wavelength converter is envisioned for the future all-optical network. The waveguide cross-sectional dimension is engineered in a submicron scale to enhance the light confinement, which pushes the device effective nonlinearity to 720 W−1 m−1 while maintaining a broad operation bandwidth covering the telecom S-, C-, and L-bands. Moreover, we demonstrate that a single microring resonator is capable of handling a high-speed data signal at a baud rate up to 40 Gbit/s. All the wavelength conversion experiments are validated with bit-error rate measurements.

Design and Modeling of Polarization-Conversion Based all-Optical Basic Logic Gates in a Single Silicon Ring Resonator

The demonstration of all-optical basic logic gates using single silicon micro-ring resonator is presented in the paper. Based on the nature of the pump signal rather than its intensity, the polarization-conversion in ring resonator occurs with the response time of 0.2 ps. To validate the proposed model, the finite-difference time domain (FDTD) and Matlab simulation results are included in the report. The Q-factor and operational speed are also calculated to justify its utility. The ring parameters are optimized through numerical simulation to obtain the conversion of polarization in the ring resonator. The nature of the pump and source signal is responsible to obtain polarization conversion based all-optical switch and all-optical logic gates in the ring resonator. The design in this paper is simple and stable.

Digital electro-optic exclusive OR and NOR gates utilizing a single micro-ring resonator

In this paper, we present the concept design and implementation of a single silicon-based micro-ring resonator in order for it to operate as exclusive OR and NOR mode. The micro-ring resonator utilizes carrier-injection based electro-optic modulation scheme, with modulation voltage ranging from 0 V up to 1.4 V. A single micro-ring resonator is used to simultaneously generate both XOR and XNOR digital output mode operation at the drop as well as through port respectively. The modulation voltage required for the proposed design together with its operation wavelength is found by resonance spectra analysis on the ring. Time domain simulations where two electrical information bit streams of 10 Gbps data rate injected into the circuit design have been carried out to display its working operation.

Design of all-optical universal logic gates using mode-conversion in single silicon microring resonator

All-optical universal logic gates are theoretically investigated and demonstrated in a single silicon microring resonator due to mode conversion. Mode conversion takes place at the switching speed of 0.2 ps and at ultrahigh quality factor (Q-factor) and requires low power. Simulated results obtained from the finite-difference-time-domain method verified our proposed model. The Q-factor for NOT, NAND, and NOR logic gates is noted as high as around 1500, 1500, and 2400, respectively. The design is simple and silicon-on-insulator compatible.

Mid-infrared tunable Vernier filter on a germanium-on-insulator photonic platform

We demonstrate the operation of a tunable Vernier filter at a mid-infrared wavelength of approximately 1.95 μm. To enable efficient tuning through the thermo-optic effect, the filter is implemented on a germanium (Ge)-on-insulator photonic platform. Heat is generated from an overlaying metal heater line to induce the thermo-optic effect to tune the filter output without incurring excessive loss. Owing to the higher thermo-optic coefficient of Ge, the tunability of a single microring resonator is 0.083 nm/mW or 0.175 nm/°C, which is approximately twofold higher than that of silicon. Through the implementation of the Vernier effect by cascading two microring resonators, the tunability of the filter is increased to 0.753 nm/mW or 1.487 nm/°C, which is more than ninefold higher than that of a single microring resonator.

Integrated microwave photonic phase shifter with full tunable phase shifting range (> 360°) and RF power equalization.

We report a novel microwave photonic phase and amplitude control structure based on a single microring resonator with a tunable Mach Zehnder interferometer reflective loop, which enables the realization of a continuously tunable microwave photonic phase shifter with enhanced phase tuning range while simultaneously compensating for the RF power variations. The complimentary tuning of the phase and amplitude presents a simplistic approach to resolve the inherent trade-off between maintaining a full RF phase shift while eliminating large RF power variations. Detailed simulations have been carried out to analyze the performance of the new structure as a microwave photonic phase shifter, where the reflective nature of the proposed configuration shows an effective doubling of the phase range while the amplitude compensation module provides a parallel control to potentially reduce the RF amplitude variations to virtually zero. The phase range enhancement, which is first verified experimentally with a passive only chip, demonstrates the capability to achieve a continuously tunable RF phase shift of 0-510° with an RF amplitude variation of 9 dB. Meanwhile, the amplitude compensation scheme is incorporated onto an active chip with a continuously tunable RF phase shift of 0-150°, where the RF power variations is shown to be reduced by 5 dB while maintaining a constant RF phase shift.

Reconfigurable On-Chip Mode Exchange for Mode-Division Multiplexing Optical Networks

Data exchange plays a key role in enhancing network resources utilization and optimizing network performance. In this paper, a data exchange device based on mode-division multiplexing (MDM) technology is proposed and demonstrated, which is capable of exchanging data information between a fundamental mode (TE0) signal and an arbitrary high-order mode (TE x ) signal. We experimentally demonstrate the exchange between a TE0 mode signal and a TE1 mode signal using single microring resonator. The insertion loss is about 7.5 dB, including terminal coupling loss, the extinction ratio is more than 20 dB within the C -band. The crosstalk for the TE1-to-TE0 and TE0-to-TE1 mode conversions is measured to be less than −22 and −16 dB, respectively. Clear and open-eye diagrams of two different wavelength signals at 10 Gb/s are obtained. The proposed scheme is expected to be used for on-chip MDM networks in the future due to its scalability, compact size, and low power consumption.