Enhanced linear and nonlinear optical phase response of AlGaAs microring resonators

We have constructed and characterized several optical microring resonators with scale sizes of the order of 10 microm. These devices are intended to serve as building blocks for engineerable linear and nonlinear photonic media. Light is guided vertically by an epitaxially grown structure and transversely by deeply etched air-clad sidewalls. We report on the spectral phase transfer characteristics of such resonators. We also report the observation of a pi-rad Kerr nonlinear phase shift accumulated in a single compact ring resonator evidenced by all-optical switching between output ports of a resonator-enhanced Mach-Zehnder interferometer.     

Electro-optically tunable microring resonators on lithium niobate

Electro-optical tuning of a microring resonator fabricated on lithium niobate (LiNbO3) is presented. The device structure, including microring resonator and couplers, is designed in detail and is produced by titanium diffusion on the wet-etched LiNbO3 ridge surface. The resonance wavelengths for TM and TE polarizations can be tuned by electro-optic effect. The output characteristics of through port and drop port in the microring resonators are measured, and the effect of applied voltage on the shift of resonant wavelength is discussed. The presented microring resonators have the features of fast tuning speed, high material stability, bidirection wavelength shift, and no heating interference. Realization of such a microring resonator on LiNbO3 makes the utilization of electro-optic tuning and nonlinear effects in the versatile photonic applications of microring resonators achievable.     

传输矩阵法分析微环谐振器阵列传输特性

微环谐振器可用作未来高密度、超大规模集成光路的基本构件,其重要发展方向之一是多环化、阵列化,微环谐振器阵列近来成为研究的热点。基于定向耦合器、环形谐振腔、直波导腔的基本单元传输矩阵,建立了用于分析微环谐振器阵列传输特性的传输矩阵模型。讨论了列间距对传输特性的影响,并数值模拟了不同尺度的奇数行和偶数行情况下谐振器阵列的传输特性。结合此传输矩阵模型,讨论了通过改变微环谐振器阵列的尺度以及耦合系数以实现滤波特性改善的方案。最后数值研究了最小尺度微环谐振器阵列传输特性与腔间耦合系数的关系。     

Generalized fast and slow lights using multi-state microring resonators for optical wireless links

We propose an interesting result on fast and slow light generation using nonlinear microring resonators. When a soliton pulse is generated within the first ring resonator, the specific signals can be generated using the chaotic filter characteristics of light pulses travelling within the microring devices. We have demonstrated that two different frequency bands can be generated and they are suitable for use in optical wireless links. The other application of fast and slow lights is also presented, whereas signal security can be formed using the add/drop device to retrieve the original signal from the chaotic noisy signals. The key advantage is that the original signal can be kept in secret without any tapping due to the problem of fast light pulses and noisy signals, which are difficult to intercept.     

Coupling between microring resonators in presence of Kerr effect

The high degree of intensity values in microring resonators needs a careful treatment of nonlinear phenomena. Nonlinear effects are analyzed in coupling problem of ring-ring directional couplers. It has been observed that the nonlinearity affects the coupling device dramatically, and can be used as controlling techniques in such as coupled resonator optical waveguides.     

Resonant modal conversion in a two-mode waveguide

We characterize a system consisting of a two-mode waveguide coupled to a single-mode microring resonator possibly presenting a nonlinear response of Kerr type. By using the scattering parameter formalism extended to the multimode domain, we show that in the linear regime and for an ideally transparent medium, each resonance of the system can be exploited to perform complete even-to-odd (respectively, odd-to-even) modal conversion. Moreover, when the Kerr nonlinearity is effective, the microring enables a power-dependent modal switching mediated by phase bistability. Thanks to its mode-processing capabilities, this configuration is suitable to find application as a functional building-block in mode-division multiplexing (MDM) photonic integrated circuits.     

Analysis of optical time domain demultiplexer using microring resonators

A time domain optical demultiplexer using electrooptic microring resonator is proposed. The switching window with pico-second order width is generated by using a sinusoidal electrical control voltage to shift the refractive index of the material. The modulation characteristics and switching window of the microring resonator are studied. The dependences of the width and extinction ratio of the switching window on the control voltage are analyzed. The demultiplexing performance of a 40–10 Gbps system is evaluated by numerical simulation technology. Results show that switching windows with required width and extinction ratio can be generated.     

Reflection Properties of Dual-Mode Filters Consisting of a Circular Array of Microring Resonators

A circular array consisting of an odd number of microring resonators is a dual-mode reflection filter. Based on the photonic energy band of a coupled microring resonator string and the resonant condition of the circular array, reflection characteristics of the circular array filter are discussed in detail. The parameters that influence the reflection characteristics and their effect mechanisms are demonstrated. The critical coupling phenomenon and its condition are revealed. We also show that the existence of loss in the rings can suppress split peaks and subsequently flatten the reflection spectrum to the whole pass band. Our work illuminates the application potential of a circular array of an odd number of microring resonators as an integrated photonics reflection filter.     

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. Simulations 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.     

All-optical set-reset flip-flop based on the passive microring-resonator bistability

In this paper, we propose a design for an all-optical R-S flip-flop with separate set and reset inputs, which is based on the optical bistability due to Kerr and two-photon absorption (TPA) effects in the microring resonators. Based on the steady state analysis of the light propagation in nonlinear microrings, variations of hysteresis parameters versus the system variables, such as transmission coefficient, nonlinear refractive index and detuning angle, are analyzed. The switching temporal behavior of the proposed flip-flop is obtained by the microring transient analysis. It is shown that the contrast ratio parameter and the switching power of the proposed all-optical flip-flop can be controlled by system parameters.     

Embedded ring resonators for microphotonic applications

We propose a new type of optical resonator that consists of embedded ring resonators (ERRs). The resonators exhibit unique amplitude and phase characteristics and allow designing compact filters, modulators, and delay elements. A basic configuration of the ERRs with two rings coupled in a point-to-point manner is discussed under two operating conditions. An ERR-based microring modulator shows a high operation speed up to 30 GHz. ERRs with distributed coupling are briefly described as well.     

Filter synthesis for periodically coupled microring resonators

The theory of filter synthesis using periodically coupled microring resonators is developed as a means to overcome the fabrication sensitivities inherent in conventional higher-order filters, while still achieving desirable spectral characteristics. Each resonator in the array can compensate for deficiencies in any of the others. These filters exhibit a boxlike shape and very high extinction ratios.     

Predistortion techniques for synthesizing coupled microring filters with loss

A general method based on the predistortion technique is presented for determining the optimum coupling parameters of multiple-coupled microring filters in the presence of known uniform resonator loss. The technique involves predistorting the filter transfer function by shifting its poles and zeros to compensate for loss in the microring resonators due to material absorption, surface roughness scattering, coupling loss and bending loss. It is shown that by sacrificing some in-band insertion loss, both the amplitude and group delay responses of the filter can be recovered when loss is present. Application of the method to synthesizing lossy microring filters in both the digital z-domain and analog s-domain will be presented. The proposed technique is general in that it can be applied to both amplitude and phase filters constructed of coupled microresonators in the most general two-dimensional coupling topology.     

Enhanced all-optical switching by use of a nonlinear fiber ring resonator

We predict dramatically reduced switching thresholds for nonlinear optical devices incorporating fiber ring resonators. The circulating power in such a resonator is much larger than the incident power; also, the phase of the transmitted light varies rapidly with the single-pass phase shift. The combined action of these effects leads to a finesse-squared reduction in the switching threshold, allowing for photonic switching devices that operate at milliwatt power levels in ordinary optical fibers.     

Proposed solar energy conversion and storage system using a nano-ring in an array waveguide

We propose the new solar energy conversion and storage system using the array waveguide. It can be used to generate and store solar energy within the nano-array waveguide system. The system consists of micro- and nano-ring resonators incorporating a Mach Zhender Interferometer (MZI) that can be integrated into a single system. The large bandwidth signal, i.e. white light, is generated using a soliton pulse in a Kerr-type nonlinear medium propagating within a micro-ring resonator system. The control light concept is applied using a nano-waveguide incorporating an MZI, whereas the incoherent light is filtered being coherence, which is amplified and stored within the system. The white light can be re-generated using the stored coherent light pulse. Furthermore, the combination of signals is formed by the array waveguide, which is allowed to generate the huge amount of solar energy output.     

Optical bistability and modulation of light in a thin-film resonator based on total internal reflection

An approximate theoretical analysis is given of the bistable behavior of a simple resonator based on total internal reflection. It is assumed that the medium within the resonator is simultaneously absorbing and nonlinear. It is found that the amplitude bistability characteristics can be comparable to analogous characteristics for more complicated total-internal-reflection structures whose operation is based on tunnel excitation of waveguide modes. It is shown that strong phase bistability is possible in nonabsorbing total-internal-reflection resonators, and the possibility of using total-internal-reflection resonators as light modulators is discussed. Zh. Tekh. Fiz. 67, 38–42 (December 1997)     

Beyond the absorption-limited nonlinear phase shift with microring resonators

We show that the nonlinear phase shift produced by a ring resonator constructed from a given nonlinear optical material can be greater than the phase shift produced by a single pass through an infinite length of the same material when linear and nonlinear absorption are taken into consideration. The figure of merit (defined by the phase shift times the throughput) also improves for the ring resonator over that of the native nonlinear absorbing material. We finally show that these benefits of using the ring resonator as a nonlinear phase-shifting element can enhance the switching characteristics of a Mach-Zehnder interferometer.     

All-optical time-division demultiplexing and spatial pulse routing with a GaAs/AlGaAs microring resonator

We report what is to our knowledge the first demonstration of all-optical time-division demultiplexing and spatial pulse routing in a compact nonlinear GaAs/AlGaAs microring resonator operating at 1.55 microm . Switching is through the refractive-index change induced by two-photon absorption. The switching time of the device, limited by the ring-charging time and the recombination time of the induced carriers, is measured to be 30 ps. The switching on-off contrast, limited by the slight mismatch between the input and output coupling coefficients, exceeds 8 dB. The device can be used for time-division multiplexing as well.     

Counter operation in nonlinear micro-electro-mechanical resonators

This Letter discusses a logical operation of multi-memories that consist of coupled nonlinear micro-electro-mechanical systems (MEMS) resonators. A MEMS resonator shows two coexisting stable states when nonlinear responses appear. Previous studies addressed that a micro- or nano-electrical-mechanical resonator can be utilized as a mechanical 1-bit memory or mechanical logic gates. The next phase is the development of logic system with coupled multi-resonators. From the viewpoint of application of nonlinear dynamics in coupled MEMS resonators, we show the first experimental success of the controlling nonlinear behavior as a 2-bit binary counter.     

Mode-locked self-pumping and squeezing photons model in a nonlinear micro-ring resonator

Photon squeezing and self-pumping within a nonlinear microring GaAsInP/P resonator are modeled and simulated, based on practical, published device parameters. A slowly varying amplitude pulse is input to the system, with a pulse width of 20 ns, a wavelength of 1.55 µm and peak power of 100 mW. The nonlinear effect resulting from the photons within the nonlinear ring resonator can be increased by adding external nonlinear coupling where, in this case, two nonlinear side rings are provided. The Dirac approach is used to generate the squeezed photons within the system. Three different device structures have been investigated, which include an add-drop filter, and a modified add-drop filter with two inner and outer side ring coupling resonators, where the nonlinear four-wave mixing effect is introduced. By using the commercial Opti-wave and MATLAB programs (in which suitable parameters have been chosen), the balance between the creation and annihilation operators can form the squeezed photons, which can be seen at the edge and center rings. The results obtained have shown that the squeezed center photon optical path (between 0 and 1 nm can be obtained) can be useful for interferometry, photon sources, and security code and sensor applications.