Modified Ring Resonator Research Articles

Generation principle for robust and regularly spaced resonant modes in a nontopological photonic crystal ring resonator

Generation principle for robust and regularly spaced resonant modes in a nontopological photonic crystal ring resonator

Highly efficient lead zirconate titanate ring modulator

Advanced photonic integrated circuits require large-scale integration of high-speed electro-optic (EO) functional components on a chip. Low power consumption and high operation speed are thus key metrics for almost all integrated EO devices. Here, we demonstrated a ring resonator modulator based on lead zirconate titanate (PZT) on a SiO2/Si substrate. The ridge waveguides were employed to keep a large spatial overlap between the optical field and the electric field within the PZT layer. The device exhibits a data rate of 56 Gbit/s and significant tuning efficiency, reaching up to 35.8 pm/V, corresponding to 1.17 V·cm. The demonstration of energy efficient and high-speed EO modulation paves the way for realizing dense PZT photonics integrated circuits.

Entangling Interactions Between Artificial Atoms Mediated by a Multimode Left-Handed Superconducting Ring Resonator

Superconducting metamaterial transmission lines implemented with lumped circuit elements can exhibit left-handed dispersion, where the group and phase velocity have opposite sign, in a frequency range relevant for superconducting artificial atoms. Forming such a metamaterial transmission line into a ring and coupling it to qubits at different points around the ring results in a multimode bus resonator with a compact footprint. Using flux-tunable qubits, we characterize and theoretically model the variation in the coupling strength between the two qubits and each of the ring-resonator modes. Although the qubits have negligible direct coupling between them, their interactions with the multimode ring resonator result in both a transverse exchange coupling and a higher-order ZZ interaction between the qubits. As we vary the detuning between the qubits and their frequency relative to the ring-resonator modes, we observe significant variations in both of these interqubit interactions, including zero crossings and changes of sign. The ability to modulate interaction terms such as the ZZ scale between zero and large values for small changes in qubit frequency provides a promising pathway for implementing entangling gates in a system capable of hosting many qubits. Published by the American Physical Society 2024

Modelling of Whispering Gallery Mode Resonators for Dielectric Measurement Applications

This study presents a method for measuring the permittivity of dielectric materials using a whispering gallery mode ring resonator. By detecting changes in coupling resulting from variations in resonant frequency caused by alterations in dielectric constant, the method offers a reliable means of characterizing dielectric properties. Operating within the 5-6 GHz frequency range, the presented resonator design leverages printed circuit board (PCB) technology and FR4 substrate material for cost-effective fabrication and flexibility in design. Through comprehensive electromagnetic simulations using ANSYS HFSS software, the study optimizes resonator parameters to enhance sensitivity and effectiveness for various applications. Experimental validation demonstrates exceptional coupling efficiency and sensitivity, underscoring the potential of whispering gallery mode resonators for environmental monitoring, chemical sensing, telecommunications, and biomedical diagnostics. This research contributes to advancing sensing technology, offering valuable insights into the design and optimization of whispering gallery mode resonators for practical use. Further exploration is warranted to fully realize their potential across diverse applications and operating conditions.

Improving the performance of ring resonator refractive index sensor through structural modifications

In this work, different types of whispering gallery mode ring resonator structures such as strip, slotted, hybrid plasmonic mode, and subwavelength grating ring resonators are simulated using the finite difference time domain method (FDTD). The proposed devices are modeled to be used as refractive index sensor. The comparative analysis of strip, slotted, hybrid plasmonic mode, and subwavelength grating ring resonators is done in terms of sensitivity, Q factor, and figure of merit (FOM) to find out the most suitable device according to the requirement. Additionally, the effect of waveguide width on sensitivity and Q factor is analyzed. The analysis shows that, compared to other simulated whispering gallery mode ring resonator sensor designs, the subwavelength grating ring resonator produces the best sensitivity of 1012 nm/RIU, and the slotted ring resonator produces the best FOM of 1610.

Experimental realization of convolution processing in photonic synthetic frequency dimensions.

Convolution is an essential operation in signal and image processing and consumes most of the computing power in convolutional neural networks. Photonic convolution has the promise of addressing computational bottlenecks and outperforming electronic implementations. Performing photonic convolution in the synthetic frequency dimension, which harnesses the dynamics of light in the spectral degrees of freedom for photons, can lead to highly compact devices. Here, we experimentally realize convolution operations in the synthetic frequency dimension. Using a modulated ring resonator, we synthesize arbitrary convolution kernels using a predetermined modulation waveform with high accuracy. We demonstrate the convolution computation between input frequency combs and synthesized kernels. We also introduce the idea of an additive offset to broaden the kinds of kernels that can be implemented experimentally when the modulation strength is limited. Our work demonstrate the use of synthetic frequency dimension to efficiently encode data and implement computation tasks, leading to a compact and scalable photonic computation architecture.

Polariton lasing in AlGaN microring with GaN/AlGaN quantum wells

Microcavity polaritons are strongly interacting hybrid light–matter quasiparticles, which are promising for the development of novel light sources and active photonic devices. Here, we report polariton lasing in the UV spectral range in microring resonators based on GaN/AlGaN slab waveguides, with experiments carried out from 4 K up to room temperature. Stimulated polariton relaxation into multiple ring resonator modes is observed, which exhibit threshold-like dependence of the emission intensity with pulse energy. The strong exciton-photon coupling regime is confirmed by the significant reduction of the free spectral range with energy and the blueshift of the exciton–like modes with increasing pulse energy. Importantly, the exciton emission shows no broadening with power, further confirming that lasing is observed at electron–hole densities well below the Mott transition. Overall, our work paves the way toward the development of novel UV devices based on the high-speed slab waveguide polariton geometry operating up to room temperature with the potential to be integrated into complex photonic circuits.

ENHANCED NEAR-FIELD RADIATION TRANSPORT AND NANO-ENTITY DETECTION IN AQUEOUS SOLUTION WITH A SI3N4-BASED INTEGRATED WGM/SPR MICROSENSOR

In this emerging proof-of-concept simulation study, we demonstrated the enhancement of near-field radiation transport in a whispering-gallery mode (WGM) ring resonator via integration with surface plasmon resonance (SPR). The integrated sensor is made of a Si<sub>3</sub>N<sub>4</sub> micro-ring with the internal core coated with a thin metal film of silver or gold. It is used for nano-entity detection in an aqueous solution environment. The radiation enhancement F-factor is adopted to quantify the performance of the integrated sensor. It was found that the sensitivity of the integrated sensor was enhanced about 2 to 4.8 times compared to a pure Si<sub>3</sub>N<sub>4</sub> WGM ring sensor without SPR. The integrated WGM/SPR microsensor may be combined with the reverse transcription-polymerase chain reaction technology to extend the limit of detection. The Q-factor of the proposed Si<sub>3</sub>N<sub>4</sub>-based integrated sensor is one to two orders of magnitude higher than that of a similar silica-based integrated sensor; thus, the new sensor may effectively detect nano-entities in aqueous solutions and has outstanding advantages in terms of small size, rapid detection with fewer samples, and high accuracy.

Temperature and wavelength drift tolerant WDM transmission and routing in on-chip silicon photonic interconnects.

We demonstrate a temperature and wavelength shift resilient silicon transmission and routing interconnect system suitable for multi-socket interconnects, utilizing a dual-strategy CLIPP feedback circuitry that safeguards the operating point of the constituent photonic building blocks along the entire on-chip transmission-multiplexing-routing chain. The control circuit leverages a novel control power-independent and calibration-free locking strategy that exploits the 2nd derivative of ring resonator modulators (RMs) transfer function to lock them close to the point of minimum transmission penalty. The system performance was evaluated on an integrated Silicon Photonics 2-socket demonstrator, enforcing control over a chain of RM-MUX-AWGR resonant structures and stressed against thermal and wavelength shift perturbations. The thermal and wavelength stress tests ranged from 27°C to 36°C and 1309.90 nm to 1310.85 nm and revealed average eye diagrams Q-factor values of 5.8 and 5.9 respectively, validating the system robustness to unstable environments and fabrication variations.

Observation of flat-band and band transition in the synthetic space

Constructions of synthetic lattices in photonics attract growingly attentions for exploring interesting physics beyond the geometric dimensionality, among which modulated ring resonator system has been proved as a powerful platform to create different kinds of connectivities between resonant modes along the synthetic frequency dimension with many theoretical proposals. Various experimental realizations are investigated in a single ring resonator, while building beyond simple synthetic lattices in multiple rings with different types remains lacking, which desires to be accomplished as an important step further. Here, we implement the experimental demonstration of generating the one-dimensional Lieb lattice along the frequency axis of light, realized in two coupled ring resonators while the larger ring undergoing dynamic modulation. Such synthetic photonic structure naturally exhibits the physics of flat band. We show that the time-resolved band structure read out from the drop-port output of the excited ring is the intensity projection of the band structure onto specific resonant mode in the synthetic momentum space, where gapless flat band, mode localization effect, and flat to non-flat band transition are observed in experiments and verified by simulations. Our work gives a direct evidence for the constructing synthetic Lieb lattice with two rings, which hence makes a solid step towards experimentally constructing more complicated lattices in multiple rings associated with synthetic frequency dimension.

Frequency Chirp Characterization of Silicon Ring Resonator Modulators

The frequency chirping properties of silicon ring resonator modulators (RRMs) are experimentally investigated under sinusoidal modulation. The modulated electric field at the output of an RRM is measured in the time domain thanks to a coherent detection system. The power and phase waveforms are then analyzed in terms of their temporal phase and amplitude for different wavelength detunings between the optical source and the resonance and for different modulation frequencies. The evolution of the frequency chirp, described through a peak-to-peak chirp parameter, is quantified as a function of wavelength detuning and modulation frequency for the first time.

Compact and high Q-factor multimode racetrack ring resonator based on transformation optics.

The ring resonator is a versatile and functional component in the silicon-based integrated optical circuit. Most of the previously reported ring resonators work in the single-mode case. With the rapid development of mode division multiplexing technology, a multimode ring resonator (MMRR) has been proposed and the usage beyond the limit of a conventional single mode ring resonator has been explored. However, the reported MMRRs are either large in size or low in quality factor. In this paper, we designed a compact silicon MMRR with a small bending radius of 15µm, in which the three lowest TE modes all have high Q-factors. For suppressing the mode loss and inter-mode crosstalk in MMRR, a multimode waveguide bend (MWB) with mode adiabatic evolution was designed based on transformation optics and waveguide shape optimization. The independent excitation of each order mode of the MMRR is realized by using bending directional coupler and asymmetric directional coupler. We successfully fabricated the device on a silicon-on-insulator (SOI) platform using simple one-step lithography. The measured loaded Q-factors of the three lowest TE modes are 5.9 × 104, 4.5 × 104, and 4.7 × 104, respectively.

A Si Optical Modulator Based on Fano-Like Resonance

In this letter, we present an experimental demonstration of a Si optical modulator based on Fano-like resonance, which is the first of its kind in the literature. The Fano-like resonance is obtained through weak coupling between two optical resonators in the prototype device and a PN junction is designed for carrier-depletion type electro-refractive modulation. 20 Gb/s data rate on-off keying (OOK) is obtained experimentally on the prototype device. Compared with a ring resonator modulator with a similar optical resonance linewidth, a Fano-like resonance based modulator can potentially have a higher extinction ratio (ER) because the Fano-like resonance has an asymmetric spectrum line shape and the line shape on one side can be sharper than the Lorentz resonance line shape of a ring resonator.

Design of low power silicon electro optic modulators based on hybrid plasmonic ring resonator

In this paper, an ITO-based hybrid plasmonic ring resonator modulator has been designed and proposed. Improving the extinction ratio (ER) and the quality factor is considered in designing the modulator. The proposed structure in this paper seeks to reduce the capacitance by reducing the surface between silicon and ITO/HfO2 interface in the ring. Two structures have been proposed based on the ring resonator. In the first structure, high-quality factor, low insertion loss (IL), and low power consumption are obtained, equal to 777, 0.28 dB, and 103fJ. In the second proposed structure, the ER is 12.22 dB, and the quality factor is 514. The finite-difference time-domain (FDTD) method has been used to investigate the modulator characteristic.

Fast thermo-optical modulators with doped-silicon heaters operating at 2 μm.

The 2-μm-waveband has been recognized as a potential telecommunication window for next-generation low-loss, low-latency optical communication. Thermo-optic (TO) modulators and switches, which are essential building blocks in a large-scale integrated photonic circuit, and their performances directly affect the energy consumption and reconfiguration time of an on-chip photonic system. Previous TO modulation based on metallic heaters at 2-μm-waveband suffer from slow response time and high power consumption. In this paper, high-performance thermo-optical Mach-Zehnder interferometer and ring resonator modulators operating at 2-μm-waveband were demonstrated. By embedding a doped silicon (p++-p-p++) junction into the waveguide, our devices reached a record modulation efficiency of 0.17 nm/mW for Mach-Zehnder interferometer based modulator and its rise/fall time was 3.49 μs/3.46 μs which has been the fastest response time reported in a 2-μm-waveband TO devices so far. And a lowest Pπ power of 3.33 mW among reported 2-μm TO devices was achieved for a ring resonator-based modulator.

Synthetic frequency dimensions in dynamically modulated ring resonators

The concept of synthetic dimensions in photonics has attracted rapidly growing interest in the past few years. Among a variety of photonic systems, the ring resonator system under dynamic modulation has been investigated in depth both in theory and experiment and has proven to be a powerful way to build synthetic frequency dimensions. In this Tutorial, we start with a pedagogical introduction to the theoretical approaches in describing the dynamically modulated ring resonator system and then review experimental methods in building such a system. Moreover, we discuss important physical phenomena in synthetic dimensions, including nontrivial topological physics. This Tutorial provides a pathway toward studying the dynamically modulated ring resonator system and understanding synthetic dimensions in photonics and discusses future prospects for both fundamental research and practical applications using synthetic dimensions.

Ring resonator modulators based on double-layer graphene and Chalcogenide glasses waveguide in mid-infrared light

A ring resonator modulator based on double-layer graphene and Chalcogenide glasses waveguide is presented and investigated. Wide bandwidth mid-infrared light operation can be achieved. A strong interaction between mid-infrared light and graphene is obtained, which change the effective mode index in the waveguide significantly while the change of applied voltage. Besides, the modulator we proposed owns a large extinction ratio of 33.57 dB.

Generating arbitrary topological windings of a non-Hermitian band.

The nontrivial topological features in the energy band of non-Hermitian systems provide promising pathways to achieve robust physical behaviors in classical or quantum open systems. A key topological feature of non-Hermitian systems is the nontrivial winding of the energy band in the complex energy plane. We provide experimental demonstrations of such nontrivial winding by implementing non-Hermitian lattice Hamiltonians along a frequency synthetic dimension formed in a ring resonator undergoing simultaneous phase and amplitude modulations, and by directly characterizing the complex band structures. Moreover, we show that the topological winding can be controlled by changing the modulation waveform. Our results allow for the synthesis and characterization of topologically nontrivial phases in nonconservative systems.

Topology in the open

Topological Optics Controlling the topology of a system provides a route to develop devices that are robust against defects. Whereas earlier developments of topological band theory focused on Hermitian (closed) systems, recent efforts have been toward non-Hermitian (open) systems. K. Wang et al. report on the measurement and control of topologically nontrivial windings of a non-Hermitian energy band. By implementing non-Hermitian lattice Hamiltonians along a frequency synthetic dimension formed by optical frequency modes in a modulated ring-resonator, they directly visualized the nontrivial topological band winding and showed that the winding can be controlled. Such control provides a route for the experimental synthesis, characterization, and control of topologically nontrivial phases in open physical systems. Science , this issue p. [1240][1] [1]: /lookup/doi/10.1126/science.abf6568

Electro-optic polymer ring resonator modulators [Invited

Electro-optic (EO) ring resonator modulators have a number of communications and scientific applications, including analog optical links, optical signal processing, and frequency comb generation. Among the EO materials used to fabricate ring modulators, the EO polymer has many promising characteristics, including a high EO coefficient of 100–200 pm/V (3–7 times larger than that of LiNbO3), an ultrafast EO response time (<10 fs), a low dielectric constant (3 to 4) with very little dispersion up to at least 250 GHz, and a straightforward spin-coating fabrication process. These inherent characteristics will be able to combine excellent EO properties with simple processing in achieving exceptional performance in a variety of high-speed optical modulation and sensing devices. This review focuses on the research and recent development of ring resonator modulators based on EO polymers. The first part describes the operation principle of EO ring resonator modulators, such as modulation mechanism, EO tunability, and 3 dB bandwidth. Subsequently, the emphasis is placed on the discussion of the ring modulators with EO polymers as the waveguide core and the improvement of EO modulation by using an EO polymer/titanium dioxide hybrid core. At the end, a series of EO polymers on silicon platforms including slot modulators, etching-free modulators, and athermal modulators are reviewed.