Asymmetrical Fabry-Perot cavity slot micro-ring resonator and its sensing characteristics

To achieve high quality factor and high-sensitivity refractive index sensor,a slot micro-ring resonator(MRR)based on asymmetric Fabry-Perot(FP)cavity was proposed.The structure consisted of a pair of elliptical holes to form an FP cavity and a microring resonator.The two different optical modes generated by the micro-ring resonator were destructively interfered to form a Fano line shape,which improved the system sensitivity while obtaining a higher quality factor and extinction ratio.The transmission principle of the structure was analyzed by the transfer matrix method.The transmission spectrum and mode field distribution of the proposed structure were simulated by the finite difference time domain(FDTD)method,and the key structural parameters affecting the Fano line shape in the device were optimized.The simulation results show that the quality factor of the device reached 22037.1,and the extinction ratio was 23.9 dB.By analyzing the refractive index sensing characteristics,the sensitivity of the structure was 354 nm·RIU−1,and the detection limit of the sensitivity was 2×10−4 RIU.Thus,the proposed compact asymmetric FP cavity slot micro-ring resonator has obvious advantages in sensing applications owing to its excellent performance.

A Highly Compact Third-Order Silicon Elliptical Micro-Ring Add-Drop Filter with a Large Free Spectral Range

We demonstrate a highly compact third-order elliptical micro-ring add-drop filter based on a silicon-on-insulator wafer. The elliptical micro-ring resonator has a major radius of 6μm （minor radius of 4.112μm） and a large free spectral range of 18 nm. Experimental results show a box-like channel dropping response, which has a 3 dB bandwidth of -2.7nm, high out-of-band signal rejection of around 40dB and a very low drop loss （〈0.5dB）. Simulation agrees well with the experiments. The footprint of the whole chip is only 0.0003mm2.

All-fibre micro-ring resonator based on tapered microfibre

In this paper, bendloss characteristics of an optical fibre are investigated in detail, and the results show that the resonator with a smaller ring radius, wider free spectrum range （FSR）, higher fineness （f） and quality-factor （Q） can be achieved by using microfibres. Based on the improved fused taper technique, a high-quality microfibre with 5 ttm radius has been fabricated, and an all-fibre micro-ring resonator with a radius of only 500μm is realized using self-coiling coupling method. The good-resonant characteristic makes the all-fibre device be expected to avoid bendloss and connection loss associated with planar waveguide integration.

Four-wave mixing in silicon-nanocrystal embedded high-index doped silica micro-ring resonator

A nonlinear integrated optical platform that allows the fabrication of waveguide circuits with different material composition,and at small dimensions,offers advantages in terms of field enhancement and increased interaction length,thereby facilitating the observation of nonlinear optics effects at a much lower power level.To enhance the nonlinearity of the conventional waveguide structure,in this work,we propose and demonstrate a microstructured waveguide where silicon rich layer is embedded in the core of the conventional waveguide in order to increase its nonlinearity.By embedding a 20 nm thin film of silicon nanocrystal(Si-nc),we achieve a twofold increase of the nonlinear parameter,γ.The linear relationship between the fourwave mixing conversion efficiency and pump power reveals the negligible nonlinear absorption and small dispersion in the micro-ring resonators.This simple approach of embedding an ultra-thin Si-nc layer into conventional high-index doped silica dramatically increases its nonlinear performance,and could potentially find applications in all-optical processing functions.

Compact Optical Add-Drop De-Multiplexers with Cascaded Micro-Ring Resonators on SOI

A four-channel integrated optical wavelength de-multiplexer is experimentally illustrated on a silicon-on-insulator （SO1） substrate. With the aid of cascaded micro-ring resonators, the whole performance of the wavelength de- multiplexer is improved, such as 3 dB bandwidth and channel crosstalk. Based on the transform matrix theory, a four-channel wavelength de-multiplexer with average channel spacing 4.5±0.5 nm （3 dB bandwidth - 2 ± 0.5 nm） is demonstrated at telecommunication bands. For each channel, the extinction at the adjacent channel is below -39dB and the out-of-band rejection ratio is up to 40dB. The channel dropping loss is below 5dB in the five FSR spectral response periods （near 100 nm）.

Near 100%spectral-purity photons from reconfigurable micro-rings

We propose an on-chip reconfigurable micro-ring to engineer the spectral-purity of photons.The micro-ring resonator is designed to be coupled by one or two asymmetric Mach-Zehnder interferometers and the coupling coefficients hence the quality-factors of the pump and the converted photons can be dynamically changed by the interferometer’s internal phase-shifter.We calculate the joint-spectrum function and obtain the spectral-purity of photons and Schmidt number under different phases.We show that it is a dynamical method to adjust the spectral-purity and can optimize the spectralpurity of photons up to near 100%.The condition for high-spectral-purity photons is ensured by the micro-ring itself,so it overcomes the trade-off between spectral purity and brightness in the traditional post-filtering method.This scheme is robust to fabrication variations and can be successfully applied in different fabrication labs and different materials.Such high-spectral-purity photons will be beneficial for quantum information processing like Boson sampling and other quantum algorithms.

Linear all-optical signal processing using silicon micro-ring resonators

Silicon micro-ring resonators （MRRs） are compact and versatile devices whose periodic frequency response can be exploited for a wide range of applications. In this paper, we review our recent work on linear all-optical signal processing applications using silicon MRRs as passive filters. We focus on applications such as modulation format conversion, differential phase-shift keying （DPSK） demodulation, modulation speed enhancement of directly modulated lasers （DMLs）, and monocycle pulse generation. The possibility to implement polarization diversity circuits, which reduce the polarization dependence of standard silicon MRRs, is illustrated on the particular example of DPSK demodulation.

Switchable microwave photonic filter using a phase modulator and a silicon-on-insulator micro-ring resonator

A switchable microwave photonic filter(MPF) using a phase modulator(PM) and a silicon-on-insulator microring resonator(MRR) is proposed and demonstrated. By adjusting the polarization controller between the PM and the MRR, the filtering function of the MPF can be switched between a band-stop filter and a band-pass filter. In a proof-of-concept experiment, an MPF with a rejection ratio of 30 dB(or 15 dB) for the band-stop(or band-pass) response and a frequency tuning range from 9.6 to 20.5 GHz is achieved.

A Study on Refractive Index Sensors Based on Optical Micro-Ring Resonators

In this work, the behavior of refractive index sensors based on optical micro-ring resonators is studied in detail. Using a result of waveguide perturbation theory in combination with numerical simulations, the optimum design parameters of the system, maximizing the sensitivity of the sensor, are determined. It is found that, when optimally designed, the sensor can detect relative refractive index changes of the order of △n/n≈3×10^-4, assuming that the experimental setup can detect relative wavelength shifts of the order of △λ/λ≈3×10^-5. The behavior of the system as bio-sensor has also been examined. It is found that, when optimally designed, the system can detect refractive index changes of the order of △n≈ 10^-3 for a layer thickness of t=- 10 nm, and changes in the layer thickness of the order of △t≈0.24 nm, for a refractive index change of △n=0.05.

Highly efficient tunable optical filter based on liquid crystal micro-ring resonator with large free spectral range

A highly efficient tunable optical filter of liquid crystal （LC） optical micro-r/rig resonator （MRR） was proposed. The 4-pro-radius ring consists of a silicon-on- insulator （SOI） asymmetric bent slot waveguide with a LC cladding. The geometry of the slot waveguide resulted in the strong electro-optic effect of the LC, and therefore induced an increase in effective refractive index by 0.0720 for the quasi-TE mode light in the slot-waveguide. The ultra-wide tuning range （56.0 nm） and large free spectral range （FSR） （-28.0nm） of the optical filters enabled wavelength reconfigurable multiplexing devices with a drive voltage of only 5 V. The influences of parameters, such as the slot width, total width of Si rails and slot shift on the device＇s performance, were analyzed and the optimal design was given. Moreover, the influence of fabrication tolerances and the loss of device were both investigated. Compared with state-of-the-art tunable MRRs, the proposed electrically tunable micro-ring resonator owns the excellent features of wider tuning ranges, larger FSRs and ultralow voltages.

Quantum wells micro-ring resonator laser emitting at 1746 nm for gas sensing

Gas sensing for measurement of gas components, concentrations, and other parameters plays an important role in many fields. In this Letter, a micro-ring resonator laser used for gas sensing is experimentally demonstrated. The multi-quantumwells micro-ring laser based on whispering-gallery modes with an annular resonator and an output waveguide was fabricated. A single-mode laser with a wavelength of 1746.4 nm was fabricated for the first time, to the best of our knowledge,experimentally. The output power of 1.65 m W under 40 m A injection current was obtained with a side-mode suppression ratio over 33 d B.

High-Q micro-ring resonators and grating couplers for silicon-on-insulator integrated photonic circuits

An ultra-small integrated photonic circuit has been proposed,which incorporates a high-quality-factor passive micro-ring resonator（MR） linked to a vertical grating coupler on a standard silicon-on-insulator（SOI） substrate.The experimental results demonstrate that the MR propagation loss is 0.532 dB/cm with a 10μm radius ring resonator,the intrinsic quality factor is as high as 202.000,the waveguide grating wavelength response curve is a 1 dB bandwidth of 40 nm at 1540 nm telecommunication wavelengths,and the measured fiber-to-fiber coupling loss is 10 dB.Furthermore,the resonator wavelength temperature dependence of the 450 nm wide micro-ring resonator is 54.1 pm/℃.Such vertical grating coupler and low loss MR-integrated components greatly promote a key element in biosensors and high-speed interconnect communication applications.

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 and fabrication of InP micro-ring resonant detectors

The quantum efficiency and the transient response of the InP semiconductor micro-ring resonant detector are analyzed to get the optimum design parameters.Then the side coupling micro-ring resonant is fabricated using the InP semiconductor material based on the parameters.The micro-ring resonant cavity has the raius of 80 μm,waveguide width of 3 μm and the coupler gap of 1 μm.The test results show that the FSR is 0.75 nm,and the FWHM is 0.5 nm,which are consistent with the theoretical calculation results.

Capacitive actuation and switching of add–drop graphene-silicon micro-ring filters

We propose and experimentally demonstrate capacitive actuation of a graphene–silicon micro-ring add/drop filter. The mechanism is based on a silicon–SiO_2–graphene capacitor on top of the ring waveguide. We show the capacitive actuation of the add/drop functionality by a voltage-driven change of the graphene optical absorption. The proposed capacitive solution overcomes the need for continuous heating to keep tuned the filter's in/out resonance and therefore eliminates "in operation" energy consumption.

异质微环谐振腔双稳态及全光存储器应用

提出了一种基于异质集成波导的微环谐振腔,对其双稳态现象进行了研究分析,并将其应用于全光存储功能的实现。异质集成波导具有超高的克尔非线性效应,不受热光效应和载流子响应的限制,在超快克尔非线性效应的支持下,该结构具有快速全光切换的能力。设计了一个高品质因子Q=77565的微环谐振腔,用耦合模式理论模拟了其双稳态现象。在峰值功率为474 fJ,宽度为20 ps的脉冲激励下,该微环谐振腔很好地实现了全光存储功能,并通过波分复用的串联微环结构展示了波长可寻址的四位光存储器。研究了基于超高克尔非线性效应的双稳态现象,为实现超快切换速度提供了可能性,在光存储、光开关、人工智能研究等方面具有一定的参考价值。

基于深度学习的微环谐振腔法诺效应调控

在微腔耦合波导上设计空气孔阵列,结合深度学习调控微腔的法诺线型,实现对微腔传感性能的优化。建立了正向预测网络模型,在24 ms内实现从空气孔阵列结构到微腔透射谱线的预测。结合卷积神经网络与逆向设计实现了对微腔透射谱线的定向调控,预测了不同指标下空气孔阵列的趋势,验证了空气孔阵列结构与微腔透射特性的关系。

基于硅基微环传感器的电缆接头测温系统

传统电缆接头测温装置体积大,且不容易贴近接头,难以满足对电缆接头的测温需求,文中设计了一款基于硅基微环传感器的电缆接头测温系统,主要技术手段为:在微环的加热电极上施加余弦函数平方根形式的扰动电压,监测出光频率与扰动电压的同频分量,获取频偏信号与温度的关系。文中进行了理论推导,并使用Python程序对理论进行仿真验证。在此基础上,搭建了实验验证平台,拟合了0~40℃下温度与频偏分量的关系,并进行了阶梯性升降温变化验证。实验结果表明:系统测温精度达到0.01℃,具有较高稳定性;且系统所需的设备简单,测温速度快,体积小,具有高的实用价值。

微孔几何轮廓对浮环气膜密封动压润滑特性的影响

目的充分研究微织构几何轮廓对浮环气膜密封润滑特性的影响,调节微尺度流动,提高密封综合性能,为气膜浮环密封的优化设计提供理论基础。方法基于气膜润滑理论,建立表面织构化浮环密封的润滑模型,以圆形、正方形、椭圆形、三角形4种轮廓微织构孔为研究对象,采用有限差分法对流体动压控制方程进行数值求解,获得密封间隙内气膜压力分布,通过试验验证理论模型的正确性和有效性,并考察不同几何轮廓的微织构孔对浮环密封性能的影响规律。结果微织构孔均可产生显著的流体动压效应,具有三角形轮廓特征的微织构孔在综合密封性能上表现出最佳效果,其次是椭圆形、正方形,最后是圆形。在相同工况条件下,不同几何轮廓的微织构孔对密封性能参数的影响具有相似的规律。其中,转速、压力和偏心率的增大均可提高气膜浮升力;随着压力和偏心率的增加,泄漏率迅速升高,随着转速的升高而缓慢下降;气体摩擦力随着转速、压力和偏心率的升高而升高。结论在轴套表面合理设计微纹理,并对不同几何轮廓微孔所适应的工况参数进行了研究,明确了不同工况下织构类型的选择和优化。研究结果可为浮环气膜密封的轴套加工制造提供理论依据,具有实际应用价值。

基于活塞环-缸套边界润滑模型的表面织构摩擦学性能评估

高强化柴油机活塞环-缸套在上止点处的工作环境恶劣,多处于边界润滑状态。表面微织构被证明是改善表面摩擦学性能的有效手段,然而目前仍缺少考虑表面织构的边界润滑数值模型。建立了考虑表面织构和摩擦膜影响的活塞环-缸套边界润滑模型,并应用该模型开展了考虑表面织构影响的磨损量计算,计算结果与边界润滑试验结果规律一致,且优选的表面织构方案较无织构方案磨损深度降低了33.7%。