Microring Arrays Research Articles

Hitless two-dimensional focal plane switch array based on Mach-Zehnder interferometer-embedded micro-ring resonators

Empowered by compact micro-ring (MRR) arrays, wavelength-division-multiplexing (WDM)-based focal plane switch array (FPSA) chip is a promising solution for light detection and ranging (LiDAR) due to its parallelism and high-level integration. However, an MRR channel with a shifting central wavelength may interrupt another channel by dropping an optical signal with an unexpected wavelength, which causes discontinuous beam scanning. To overcome this bottleneck, we propose and fabricate a hitless two-dimensional (2-D) FPSA chip based on a 2 × 8 Mach-Zehnder interferometer-embedded micro-ring resonator (MZER) array. The FPSA chip realizes a beam divergence of 0.18° × 0.05°, a field of view (FoV) of 9.07° × 6.42° with single-ended emission, and a FoV of 10.75° × 6.42° with dual-ended field-of-view splicing technology. Besides, we demonstrate the hitless function of our FPSA chip by performing continuous wavelength sweeping and further applying it to a free-space optical communication link. The experimental results validate the feasibility of our proposed hitless FPSA chip, which efficiently prevents signal interruptions during beam steering.

Multi-Interfacial Confined Assembly of Colloidal Quantum Dots Quasisuperlattice Microcavities for High-Resolution Full-Color Microlaser Arrays.

Colloidal quantum dots (CQDs) are considered a promising material for the next generation of integrated display devices due to their designable optical bandgap and low energy consumption. Owing to their dispersibility in solvents, CQD micro/nanostructures are generally fabricated by solution-processing methods. However, the random mass transfer in liquid restricts the programmable construction in macroscopy and ordered assembly in microscopy for the integration of CQD optical structures. Herein, a multi-interfacial confined assembly strategy is developed to fabricate CQDs programmable microstructure arrays with a quasisuperlattice configuration through controlling the dynamics of three-phase contact lines (TPCLs). The motion of TPCLs dominates the division of liquid film for precise positioning of CQD microstructures, while pinned TPCLs control the solvent evaporation and concentration gradient to directionally drive the mass transfer and packing of CQDs. Owing to their long-range order and adjustable structural dimensions, CQD microring arrays function as high-quality-factor (high-Q) lasing resonant cavities with low thresholds and tunable lasing emission modes. Through the further surface treatment and liquid dynamics control, the on-chip integration of red (R), green (G), and blue (B) multicomponent CQD microlaser arrays are demonstrated. The technique establishes a new route to fabricate large-area, ultrahigh-definition, and full-color CQD laser displays.

Parallel-Output Flat-Top Microring Arrays for WDM Demultiplexer Applications

Parallel-Output Flat-Top Microring Arrays for WDM Demultiplexer Applications

Microring structure for flexible polymer waveguide-based optical pressure sensing.

Flexible pressure sensors provide a promising platform for artificial smart skins, and photonic devices provide a new technique to fabricate pressure sensors. Here, we present a flexible waveguide-based optical pressure sensor based on a microring structure. The waveguide-based optical pressure sensor is based on a five-cascade microring array structure with a size of 1500 µm × 500 µm and uses the change in output power to linearly characterize the change in pressure acting on the device. The results show that the device has a sensing range of 0-60 kPa with a sensitivity of 23.14 µW/kPa, as well as the ability to detect pulse signals, swallowing, hand gestures, etc. The waveguide-based pressure sensors offer the advantages of good output linearity, high integration density and easy-to-build arrays.

Silicon Photonic Wavelength-Selective Switch Based on an Array of Adiabatic Elliptical-Microrings

A compact silicon photonic wavelength-selective switch (WSS) based on an array of elliptical microrings with adiabatically varied radii and widths is proposed and demonstrated experimentally. A 1×4 WSS is designed and realized by integrating four cells sharing the same bus waveguide. Particularly each cell contains four elliptical microring units corresponding to four wavelength-channels. For the fabricated WSS, the average excess loss at the output port of all the channels is measured to be less than 1 dB, while the crosstalk between adjacent channels is less than −20 dB. Leveraging the thermo-optic effect and fine wavelength-tuning linearity, precise alignment of the resonance peak can be implemented, enabling the selection of arbitrary wavelength-channel for any port. The fabricated WSS is used for realizing wavelength-selective data routing with 30 Gbps non-return-to-zero signals and open eye diagrams are obtained. The proposed architecture has excellent scalability, which can facilitate the development of reconfigurable optical add/drop multiplexers in wavelength-division-multiplexing systems, and is suitable for building large-scale optical data center interconnects.

Flow-based approach for scalable fabrication of Ag nanostructured substrate as a platform for surface-enhanced Raman scattering

The droplet-based biphasic reaction is an efficient strategy for the fabrication of surface-bound nanostructures. Here, we developed a process of fabricating ordered micro-ring arrays of silver (Ag) nanostructures from surface nanodroplet reaction on a micro-patterned hydrophobic substrate for reproducible detection by surface-enhanced Raman spectroscopy (SERS). Our process consisted of the generation of surface nanodroplet arrays, followed by a biphasic chemical reaction between droplets and the continuous flow of silver nitrate (AgNO3) precursor solution. The parameters in the formation and reaction of the droplet array were well controlled to maintain the uniformity of Ag nanostructures throughout the substrate. By scaling up the process parameters and the size of the microchamber, we were able to produce a SERS substrate with a surface area of ¿60 cm2 in a single run. Such a large area could be sufficient for analyzing more than a thousand samples. We demonstrated the repeatability of SERS measurements using Ag nanostructures by analyzing three environmental (rhodamine 6G, chlorpyrifos, triclosan), a biological (indoxyl sulfate), and a psychoactive drug (tetrahydrocannabinol) compounds. 2D mapping of SERS intensities was also performed for both small and large-scale substrates by collecting data from more than 100 locations on the substrate. Our work demonstrated droplet-based biphasic reaction as a simple approach for the fabrication of SERS substrate with a large area. The technique may help to eliminate the requirement for sophisticated equipment for the fabrication of SERS active substrate.

Controllable terahertz beam focusing and rotating by graphene-assisted microring metasurfaces

This research proposes a terahertz (THz) metalens for focusing THz waves with an electrically controllable focal length. The dynamic of tuning of THz metalenses with graphene provides high controllability, fast responses, and compact structures for beam focusing. An array of graphene microrings has been presented with significant phase variations possibility. The three-dimensional finite-difference time-domain method has been employed for the analysis of the proposed structure. Applying a voltage to the graphene layer changes the graphene Fermi level, and the focal length can be controlled. As the chemical potential of graphene varies from 0.1 to 0.3 eV, the focal length changes 20.5λ (from 4 to 12.2 mm at the frequency of 0.75 THz). In addition, by biasing every array of graphene microrings with different gate voltages, we can electrically rotate the focal beam up to 32.02 deg. An equivalent circuit model (CM) is proposed for fast analysis and the verification of the FDTD results as well. The achieved results of the CM comply very well with those derived by the FDTD method. The proposed structure has the potential to be used in THz imaging.

Ultrathin SU-8 membrane for highly efficient tunable cell patterning and massively parallel large biomolecular delivery.

Cell patterning is a powerful technique for the precise control and arrangement of cells, enabling detailed single-cell analysis with broad applications in therapeutics, diagnostics, and regenerative medicine. This study presents a novel and efficient technique that enables massively parallel high throughput cell patterning and precise delivery of small to large biomolecules into patterned cells. The innovative cell patterning device proposed in this study is a standalone, ultrathin 3D SU-8 micro-stencil membrane, with a thickness of 10 μm. It features an array of micro-holes ranging from 40 μm to 80 μm, spaced apart by 50 μm to 150 μm. By culturing cells on top of this SU-8 membrane, the technique achieves highly efficient cell patterns varying from single-cell to cell clusters on a Petri dish. Utilizing this technique, we have achieved a remarkable reproducible patterning efficiency for mouse fibroblast L929 (80.5%), human cervical SiHa (81%), and human neuroblastoma IMR32 (89.6%) with less than 1% defects in undesired areas. Single-cell patterning efficiency was observed to be highest at 75.8% for L929 cells. Additionally, we have demonstrated massively parallel high throughput uniform transfection of large biomolecules into live patterned cells by employing an array of titanium micro-rings (10 μm outer diameter, 3 μm inner diameter) activated through infrared light pulses. Successful delivery of a wide range of small to very large biomolecules, including propidium iodide (PI) dye (668.4 Da), dextran (3 kDa), siRNA (13.3 kDa), and β-galactosidase enzyme (465 kDa), was accomplished in cell patterns for various cancer cells. Notably, our platform achieved exceptional delivery efficiencies of 97% for small molecules like PI dye and 84% for the enzyme, with corresponding high cell viability of 100% and 90%, respectively. Furthermore, the compact and reusable SU-8-based membrane device facilitates highly efficient cell patterning, transfection, and cell viability, making it a promising tool for diagnostics and therapeutic applications.

An Eight-Channel Switching-Linear Hybrid Dynamic Regulator With Dual-Supply LDOs for Thermo-Optic Tuning

A novel switching-linear hybrid dynamic regulator architecture with dual-supply low dropout regulators (LDOs) is presented in this paper. This architecture leverages the intrinsic dual supplies to extend the operating range of the LDOs. Furthermore, it increases the thermo-optic tuning efficiency by reducing the LDO dropout voltage through dynamic supply modulation. This architecture is suitable for large-scale thermo-optic tuning in silicon photonics. The efficiency improvement is particularly effective when tracking signals of several adjacent channels are close to each other, e.g., wavelength tuning of a microring array. The principle of this architecture is general and can be implemented using different switching converters and LDOs. A specific design with extensive post-layout simulation results is used to verify the effectiveness of our architecture. Implemented in a 130 nm CMOS process, this design can simultaneously regulate eight output channels with an output swing of 0.8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text V_{\text {pp}}$ </tex-math></inline-formula> . Its peak efficiency when driving 100 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> loads is 92% at 1 V output, and the dynamic efficiency is around 86% when tracking 50 kHz sinusoidal signals. To the best of our knowledge, this is the first time that dynamic supply modulation has been applied to multi-channel thermo-optic tuning of silicon photonic devices.

Silicon-on-Insulator Optical Buffer Based on Magneto-Optical 1 × 3 Micro-Rings Array Coupled Sagnac Ring

Optical buffer is a key technology to control optical routing and solve channel competition, which directly determines the performance of information processing and storage. In this study, a switchable optical buffer using the nonreciprocal silicon-on-insulator (SOI) magneto-optical micro-ring (MOMR) array coupled with Sagnac ring was introduced, which can exceed the time-bandwidth limitation. The transmission equations and propagation characteristics of optical signal in 1 × 3 micro-rings and Sagnac ring coupled 1 × 3 micro-rings based on two kinds of phase-change materials were studied. The group time delay, effective buffer time and readout operation in the buffer were also investigated.

Fabrication of Metallic Nano-Ring Structures by Soft Stamping with the Thermal Uplifting Method

In this study, the unconventional microfabrication method by the combined processes of the chemical soft stamping technique with the thermal uplifting technique to fabricate metal nanoarrays on a glass plate is proposed and their feasibility verified. The gold micro-ring arrays on a quartz glass plate are realized by utilizing a chemical template with the thermal uplifting method. Their optical properties are studied experimentally. First, a plastic mold is made of a Biaxially Oriented Polyethylene Terephthalate (BOPET) via the hot embossing method. Then, the Methanal micropatterns are transferred onto an etched surface of a substrate via a soft stamping process with a BOPET mold. The gold thin film is coated onto the methanol patterned glass plate via the Ar+ sputter coating process. Finally, the metallic micro-ring structures are aggregated on a glass plate via the thermal uplifting technique. The LSPR optical properties as the extinction spectrums of the gold micro-ring structure arrays are investigated experimentally. It is confirmed that this method was able to fabricate plasmonic micro-ring arrays with low cost and high throughput.

A small microring array that performs large complex-valued matrix-vector multiplication

As an important computing operation, photonic matrix–vector multiplication is widely used in photonic neutral networks and signal processing. However, conventional incoherent matrix–vector multiplication focuses on real-valued operations, which cannot work well in complex-valued neural networks and discrete Fourier transform. In this paper, we propose a systematic solution to extend the matrix computation of microring arrays from the real-valued field to the complex-valued field, and from small-scale (i.e., 4 × 4) to large-scale matrix computation (i.e., 16 × 16). Combining matrix decomposition and matrix partition, our photonic complex matrix–vector multiplier chip can support arbitrary large-scale and complex-valued matrix computation. We further demonstrate Walsh-Hardmard transform, discrete cosine transform, discrete Fourier transform, and image convolutional processing. Our scheme provides a path towards breaking the limits of complex-valued computing accelerator in conventional incoherent optical architecture. More importantly, our results reveal that an integrated photonic platform is of huge potential for large-scale, complex-valued, artificial intelligence computing and signal processing.

Silicon-Based MZI-Embedded Microring Array With Hitless and FSR-Alignment-Free Wavelength Selection

We demonstrate a silicon-based Mach-Zehnder interferometer (MZI)-embedded microring array consisting of four wavelength channels. The embedded MZI in each microring resonator (MRR) works as an ON/OFF key of the resonance, and can offer larger operating wavelength range. The footprint of the core elements is only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$180.6\,\,\mu \text{m}\,\,\times 476.1\,\,\mu \text{m}$ </tex-math></inline-formula> . The transmission performances of four wavelength channels keep with good consistency within a 35.2-nm-wide wavelength range. The insertion loss of each channel is less than 3.05 dB. Its rising response time of the ON/OFF status transition is about <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4.8~\mu \text{s}$ </tex-math></inline-formula> . Moreover, since the array does not require the free spectral range (FSR)-alignment and the on-chip thermal crosstalk is slight, the hitless wavelength selection can be realized simply without any electronic control assistance. Our experiment results indicate that such compact, and scalable array with the function of easily-implemented hitless wavelength selection may provide another solution for large-scale wavelength division multiplexing (WDM) network.

Generation of Hofstadter's butterfly spectrum using circular arrays of microring resonators.

Hofstadter's butterfly spectrum, which characterizes the energy bands of electrons in a 2D lattice under a perpendicular magnetic field, has been emulated and experimentally characterized in periodic bandgap structures at microwave and acoustic frequencies. However, measurement of the complete spectrum at optical frequencies has yet to be demonstrated. Here, we propose a simple topological photonic structure based on a circular array of microrings with periodic resonant frequency detunings that can be implemented on an integrated optics platform. We show that this ring-of-rings structure exactly emulates the Harper equation and propose an experimental approach for measuring Hofstadter's butterfly spectrum at optical frequencies.

A gold coated polystyrene ring microarray formed by two-step patterning: construction of an advanced microelectrode for voltammetric sensing.

A two-step patterning process was developed based on nanosphere lithography and plasma etching to fabricate an array of electrodes with two different gold ring structures: the arrays of Au micro-ring electrode (Au-MRE) and Au covered with polystyrene micro-ring electrode (Au-PS-MRE). The Au-MRE structure was fabricated by etching a monolayer ofpolystyrene (PS) spheres on indium tin oxide (ITO) surface to generate PS rings on ITO glass. PS rings served as a mask in secondary etching for blocking an interaction of oxygen plasma and ITO surface to create a ring-patterned ITO surface. Then, the PS residue was removed and gold was deposited. The site-selective electrodeposition of gold was carried out and an array of a gold ring structure was formed on the ITO glass. The Au-PS-MRE structure was fabricated by keeping the PS residue from second etching before deposition of gold. The Au-PS-MRE microelectrode was studied by using hexacyanoferrate as an electrochemical probewhere it displayed steady state current in cyclic voltammetry. The respective calibration plots were acquired at a working potential of 0.31V and 0.12V (vs. Ag/AgCl) for oxidation and reduction reaction, respectively. The sensitivity is as high as 163.4-220.7 μA·mM-1·mm-2 which is larger by a factor of 95-132 compared to a conventional gold film macroelectrode. The detection limit (at a signal-to-noise ratio of 3) is 2.2μM. This approach thus yields relatively effective and low-cost fabrication without resorting to high resolution instruments. Conceivably, the technique may be used to produce microelectrode arrays on a large scale. Graphical abstract Schematic presentation of a novel fabrication process of micro-ring electrode arrays. Two-step patterning based on nanosphere lithography leads to electrodes with great electrochemical performance. Direct deposition metal in the presence of polystyrene (PS) mask induces the formation of a new structure with arrays of gold covered with PS microring on the indium tin oxide (ITO) coated glass. The microelectrode-like behavior has been achieved using this fabrication process.

Deriving a Lumped Element Surface Impedance Model for Periodic Arrays of Graphene Micro-Rings

In this paper, a lumped element circuit model for a periodic array of Graphene rings is derived using analytical procedures. The computations are in the subwavelength regime and under normal incidence. It is shown that the model is also valuable for a single Graphene ring. The methodology includes solving the surface current integral equation for the rings by designing an eigenvalue problem. The absorption spectrum of proposed model is compared with full-wave simulations to verify the model accuracy. Furthermore, inspection of the simulation results for different Fermi energies and unit cell dimensions, helped us examine the validity of analytical formulas. This model opens up the way to control the structure performance and refine it in favor of our requirements for different applications.

Tunable microfluidic device fabricated by femtosecond structured light for particle and cell manipulation.

Smart devices made of stimuli-responsive (SR) hydrogel can realize accurate shape control with high repeatability attributed to their fast swelling and shrinking upon the change of external stimuli. Integrating these devices into microfluidic chips and utilizing their controllable deformation capability are highly promising approaches to enrich the functions of microfluidic devices and reduce their external apparatuses. Herein we propose and demonstrate a tunable microfluidic device (TMFD) by integrating a pH-sensitive hydrogel microring array into a microchannel. Instantaneous and reversible deformation of the microrings can be finished in less than 200 ms. The array gaps of the microrings are reversibly switched to realize the capture or release of microobjects. In addition, a femtosecond laser holographic processing method is firstly used to pattern and integrate the pH-sensitive hydrogel microrings into a microchannel, and the pH-responsive properties of the hydrogel affected by laser processing dosages are theoretically and experimentally investigated. With this method, the height, diameter (6-16 μm), swelling ratio (35-65%), and diameter change (2-5 μm) can be precisely controlled. As a proof of concept, the filtering of polystyrene particles with multiple sizes and complete trapping of PS particles and cells are demonstrated by these TMFDs. The developed TMFD can be easily integrated by the femtosecond laser holographic processing method, and operates robustly without the need for external precision apparatuses, which hold great promise in the applications of microobject manipulation and biomedical analysis.

基于改进型并联微环阵列的路由器设计

基于改进型并联微环阵列的路由器设计

2D Ruddlesden-Popper Perovskites Microring Laser Array.

3D organic-inorganic hybrid perovskites have featured high gain coefficients through the electron-hole plasma stimulated emission mechanism, while their 2D counterparts of Ruddlesden-Popper perovskites (RPPs) exhibit strongly bound electron-hole pairs (excitons) at room temperature. High-performance solar cells and light-emitting diodes (LEDs) are reported based on 2D RPPs, whereas light-amplification devices remain largely unexplored. Here, it is demonstrated that ultrafast energy transfer along cascade quantum well (QW) structures in 2D RPPs concentrates photogenerated carriers on the lowest-bandgap QW state, at which population inversion can be readily established enabling room-temperature amplified spontaneous emission and lasing. Gain coefficients measured for 2D RPP thin-films (≈100 nm in thickness) are found about at least four times larger than those for their 3D counterparts. High-density large-area microring arrays of 2D RPPs are fabricated as whispering-gallery-mode lasers, which exhibit high quality factor (Q ≈ 2600), identical optical modes, and similarly low lasing thresholds, allowing them to be ignited simultaneously as a laser array. The findings reveal that 2D RPPs are excellent solution-processed gain materials potentially for achieving electrically driven lasers and ideally for on-chip integration of nanophotonics.

Characteristics of silicon-based Sagnac optical switches using magneto-optical micro-ring array

ABSTRACTThe miniaturization and integration of optical switches are necessary for photonic switching networks and the utilization of magneto optical effects is a promising candidate. We propose a Sagnac optical switch chip based on the principle of nonreciprocal phase shift (NPS) of the magneto-optical (MO) micro-ring (MOMR) array, composed of SiO2/Si/Ce:YIG/SGGG. The MO switching function is realized by controlling the drive current in the snake-like metal microstrip circuit layered on the MOMRs. The transmission characteristics of the Sagnac MO switch chip dependent on magnetization intensity, waveguide coupling coefficient and waveguide loss are simulated. By optimizing the coupling coefficients, we design an MO switch using two serial MOMRs with a circumference of 38.37 μm, and the 3dB bandwidth and the extinction ratio are respectively up to 1.6 nm and 50dB for the waveguide loss coefficient of . And the switching magnetization can be further reduced by increasing the number of parallel MOMRs. The frequency response of the MO Sagnac switch is analyzed as well.