Highly sensitive digital optical sensor with large measurement range based on the dual-microring resonator with waveguide-coupled feedback

We propose a novel high-performance digital optical sensor based on the Mach-Zehnder interferential effect and the dual-microring resonators with the waveguide-coupled feedback. The simulation results show that the sensitivity of the sensor can be orders of magnitude higher than that of aconventional sensor, and high quality factor is not critical in it. Moreover, by optimizing the length of the feedback waveguide to be equal to the perimeter of the ring, the measurement range of the proposed sensor is twice as much as that of the conventional sensor in the weak coupling case.

A large bandwidth photonic delay line using passive cascaded silicon-on-insulator microring resonators

This paper investigated the design and the characterization of a photonic delay line based on passive cascaded silicon-on-insulator （SOI） microrings. We considered the compromise of group delay, bandwidth and insertion loss. A 3-stage double channel side-coupled integrated spaced sequence of resonator （SCISSOR） device was optimized by shifting the resonance of each microring and fabricated with electron beam lithography and dry etching. The group delay was measured to be 17 ps for non-return-to-zero signals at different bit rates and the bandwidth of 78 GHz was achieved. The experiment result agreed well with our simulation.

Bandwidth-tunable silicon nitride microring resonators

We designed a reconfigurable dual-interferometer coupled silicon nitride microring resonator.By tuning the integrated heater on interferometer's arms,the"critical coupling"bandwidth of resonant mode is continuously adjustable whose quality factor varies from 7.9×10^(4) to 1.9×10^(5) with the extinction ratio keeping higher than 25 dB.Also a variety of coupling spanning from"under-coupling"to"over-coupling"were achieved,showing the ability to tune the quality factor from 6.0×10^(3) to 2.3×10^(5).Our design can provide an adjustable filtering method on silicon nitride photonic chip and contribute to optimize the nonlinear process for quantum photonics and all-optical signal processing.

Design,fabrication and characterization of a high-performance microring resonator in silicon-on-insulator

A high-performance microring resonator in a silicon-on-insulator rib waveguide is realized by using the electron beam lithography followed by inductively coupled plasma etching. The design and the experimental realization of this device are presented in detail. In addition to improving relevant processes to minimize propagation loss, the coupling efficiency between the ring and the bus is carefully chosen to approach a critical coupling for high performance operating. We have measured a quality factor of 21,200 and an extinction ratio of 12.SdB at a resonant wavelength of 1549.32nm. Meanwhile, a low propagation loss of 0.89dB/mm in a curved waveguide with a bending radius of 40μm is demonstrated as well.

Modeling and analysis of silicon-on-insulator elliptical microring resonators for future high-density integrated photonic circuits

We propose a novel resonator containing an elliptical microring based on a silicon-on-insulator platform. Simu- lations using the three-dimensional finite-difference time-domain method show that the novel elliptical microring can efficiently enhance the mode coupling between straight bus waveguides and resonator waveguides or between adjacent resonators while preserving relatively high intrinsic quality factors with large free spectral range. The proposed resonator would be an alternative choice for future high-density integrated photonic circuits.

Bright 547-dimensional Hilbert-space entangled resource in 28-pair modes biphoton frequency comb from a reconfigurable silicon microring resonator

High-dimensional entanglement provides valuable resources for quantum technologies,including quantum communication,quantum optical coherence tomography,and quantum computing.Obtaining a high brightness and dimensional entanglement source has significant value.Here we utilize a tunable asymmetric Mach–Zehnder interferometer coupled silicon microring resonator with 100 GHz free spectral range to achieve this goal.With the strategy of the tunable coupler,the dynamical and extensive tuning range of quality factors of the microring can be obtained,and then the biphoton pair generation rate can be optimized.By selecting and characterizing 28 pairs from a more than 30-pair modes biphoton frequency comb,we obtain a Schmidt number of at least 23.4 and on-chip pair generation rate of 19.9 MHz/m W;under a low on-chip pump power,which corresponds to 547 dimensions Hilbert space in frequency freedom.These results will prompt the wide applications of quantum frequency comb and boost the further large density and scalable on-chip quantum information processing.

Integrated reconfigurable optical add-drop multiplexers based on cascaded microring resonators

We report on an eight-channel reconfigurable optical add-drop multiplexer based on cascaded microring resonators with a high tuning power consumption and a compact footprint. Microheaters are fabricated on top of the microring resonators and can be modulated using the thermo-optic effect to achieve the reconfigurable functionality of the device. We demonstrate the reconfigurable add-drop multiplexing functionality for channel spacings of 1 O0 GHz and 50 GHz, with the centre wavelengths of the channels aligned to International Telecommunication Union grid specifications. The crosstalk for channel spacings of 100 GHz and 50 GHz are less than -22.5 dB and -15.5 dB, respectively. The average tuning efficiency is about 4.5 mW/nm, and the response speed is about 13.0 kHz.

Compact on-chip 1×2 wavelength selective switch based on silicon microring resonator with nested pairs of subrings

We propose and experimentally demonstrate compact on-chip 1×2 wavelength selective switches(WSSs) based on silicon microring resonators(MRRs) with nested pairs of subrings(NPSs). Owing to the resonance splitting induced by the inner NPSs, the proposed devices are capable of performing selective channel routing at certain resonance wavelengths of the outer MRRs. System demonstration of dynamic channel routing using fabricated devices with one and two NPSs is carried out for 10 Gb∕s non-return-to-zero signal. The experimental results verify the effectiveness of the fabricated devices as compact on-chip WSSs.

Effects of manufacturing errors on the characteristics of a polymer vertical coupling microring resonator

The effects of manufacturing errors on transmission characteristics are analyzed for a polymer vertical coupling microring resonator.Calculated results show that the errors cause a shift and shape change of the transmission spectrum compared to the designed case without errors.Furthermore,accumulation and compensation for the errors is researched.In order to realize the normal filtering for the fabricated microring resonator device,some allowed errors are discussed.

9.4 nm Tunable Vertically Coupled Microring Resonator Filter by Thermo-Optic Effect

A wide range (9.4nm) tuning of vertically coupled microring resonator filter was demonstrated utilizing a large TO coefficient of polymer. The power consumption was about 60m W and no degradation of filter response was observed.

Multiwavelength generation using an add-drop microring resonator integrated with an InGaAsP/InP sampled grating distributed feedback

A system of an add-drop microring resonator integrated with a sampled grating distributed feedback （SG-DFB） is investigated via modeling and simulation with the time-domain traveling wave （TDTW） method. The proposed microring resonator comprises a SiO2 waveguide integrated with an InGaAsP/InP SG-DFB, and the SiO2 waveguide consists of a silicon core having a refractive index of 3.48 and Kerr co- efficient of 4.5 × 10^-18 m2/W. The SG-DFB consists of a series of grating bursts that are constructed using a periodic apodization function with a burst spacing in the grating of 45 μm, a burst length of 5 μm, and I0 bursts across the total length of the SG-DBR. Transmission results of the through and drop port of the microring resonator show the significant capacity enhancement of the generated center wavelengths. The Q-factor of the microring resonator system, defined as the center wavelength （λ0） divided by 3 dB FWHM, without and with integration with the SG-DFB is calculated as 1.93 × 10^5 and 2.87 × 10^5, respectively. Analysis of the dispersion of the system reveals that increasing the wavelength results in a decrease of the dispersion. The higher capacity and efficiency are the advantages of integrating the microring resonator and the InGaAsP/InP SG-DFB.

Simultaneous measurement of refractive index and temperature using a microring resonator

An approach to the simultaneous optical ring resonators is proposed measurement of refractive-index （RI） and theoretically demonstrated. With and temperature changes using a liquid-core silica ring resonator as an example, two different-order whispering gallery modes （WGMs） might differ in not only RI but also temperature sensitivities. Thus, a second-order sensing matrix should be defined based on these WGMs to determine RI and temperature changes simultaneously. The analysis shows that the RI and temperature detection limits can be achieved on the order of 10.7 RI unit and 10-3 K at a wavelength of approximately 780 nm.

Vertically Coupled Microring Resonator Filter :Versatile Building Block for VLSI Filter Circuits

In this review, the recent progress in the development of vertically coupled micro-ring resonator filters is summarized and the potential applications of the filters leading to the development of VLSI photonics are described.

The resonance frequency shift in an SOI nano-waveguide microring resonator

To research the effect of a deposited SiO2 insulating layer on the resonance frequency modulation of an SOI nanowaveguide ring cavity during integration fabrication, a rib waveguide ring resonator was systemati- cally designed and fabricated. SiO2 insulating layers with different thicknesses were deposited for analysis of the frequency shift characteristics. By testing the resonance transmission spectrum power of this structure, it is found that there are blue shifts after SiO2 deposition, and the frequency shift value of a structure with a 500 nm SiO2 insulating layer deposited is 0.8 nm, that is 0.24 THz at the resonance point where wavelength is around 1550 nm. Taking advantage of this conclusion, efficient optical modulation is available by choosing different frequency band resonance wavelengths to narrow the frequency modulation range.

Analysis of characteristics of vertical coupling microring resonator

By using the coupled mode theory and the transfer matrix technique,the optical transfer function is presented for analyzing the size of the waveguide,radius of the microring,free spectral range and amplitude coupling ratio of the vertical coupling microring resonator.Under the central wavelength of 1550 nm,optimization and simulation are performed when the central deviation between the ring and the channel is 0,0.5,1μm,respectively, the 3-dB bandwidth of the spectral response is about 0.21,0.09,0.03 nm,and the intensity of the nonresonant light is below-30,-40,-50 dB,respectively.

Nested microring resonator with a doubled free spectral range for sensing application

The microring resonator has received increas- ing attention in the optical sensing application because of its micro-size, optical property, and high sensitivity. An additional waveguide is commonly used to change the output spectra in the early research on microring resonators. In this study, we proposed a nested microring resonator that doubles the free spectral range （FSR） compared with the conventional single microring. This structure improved the sensing property as the FSR in the filter output spectra could be considered as a measurement range in the microring sensor. Moreover, the parameters including the coupling coefficient of the three coupling sections, length of the U-bend waveguide, and effective index of a waveguide were tested and carefully selected to optimize the sensing properties. The relationship between these parameters and the output spectra was demonstrated. With linear sensitivity, the structure has a good potential in sensing application.

Comparison of wavelength conversion efficiency between silicon waveguide and microring resonator

Wavelength conversion based on degenerate four-wave mixing （FWM） was demonstrated and compared between silicon nanowire and microring resonator （MRR）. 15 dB enhancement of conversion efficiency （CE） with relatively low input pump power （5roW） was achieved experimentally in an MRR. The impacts of bus waveguide length and propagation loss were theoretically analyzed under the effect of nonlinear loss.

An electro-optic directed decoder based on two cascaded microring resonators

We demonstrate a directed optical decoder device consisting of two cascaded microring resonators, which are both modulated through the plasma dispersion effect. The inherent resonance wavelength mismatch between two microring resonators caused by fabrication errors is compensated for by using microheaters that are fabricated on top of the microring resonators. Two electrical signals generated by pulse pattern generators are used to modulate the PIN diodes that are embedded in the device, and the results are presented by optical signals detected at the four output ports of the device. The working wavelength and driving voltages of two MRRs are measured and analyzed by the static response spectra of the device. Dynamic experimental results show that the decoding operation is achieved at a speed of 100 Mbps.

MZI wavelength interleaving filter based on double microring structure

To improve the output characteristics of all-fiber Mach-Zehnder interferometer(MZI)-interleaver,a dual microring-assisted MZI interleaver is designed.According to its structure,the output expression of the device is derived from the signal flow diagram.After simulation analysis,the optimal structural parameters during the transmission process are obtained.In addition,the coupling coefficient and transmission loss of the coupler are analyzed.The results show that the improved interleaver output line wave is closer to the square wave,and its 25 dB cutoff band bandwidth and 0.5 dB passband bandwidth are significantly improved,with the values of 41.2 GHz and 18.9 GHz,respectively.The device has a certain resistantability to deviation,and the transmission loss has less influence on the extinction characteristics of the filter.

Chiral exceptional point and coherent suppression of backscattering in silicon microring with low loss Mie scatterer

Non-Hermitian systems with their spectral degeneracies known as exceptional points(EPs)have been explored for lasing,controlling light transport,and enhancing a sensor’s response.A ring resonator can be brought to an EP by controlling the coupling between its frequency degenerate clockwise and counterclockwise traveling modes.This has been typically achieved by introducing two or more nanotips into the resonator’s mode volume.While this method provides a route to study EP physics,the basic understanding of how the nanotips’shape and size symmetry impact the system’s non-Hermicity is missing,along with additional loss from both in-plane and out-of-plane scattering.The limited resonance stability poses a challenge for leveraging EP effects for switches or modulators,which requires stable cavity resonance and fixed laser-cavity detuning.Here we use lithographically defined asymmetric and symmetric Mie scatterers,which enable subwavelength control of wave transmission and reflections without deflecting to additional radiation channels.We show that those pre-defined Mie scatterers can bring the system to an EP without post tuning,as well as enable chiral light transport within the resonator.Counterintuitively,the Mie scatterer results in enhanced quality factor measured on the transmission port,through coherently suppressing the backscattering from the waveguide surface roughness.The proposed device platform enables pre-defined chiral light propagation and backscattering-free resonances,needed for various applications such as frequency combs,solitons,sensing,and other nonlinear optical processes such as photon blockade,and regenerative oscillators.