Side-coupled Integrated Spaced Sequence Of Resonators Research Articles

Enhancement of slow and fast light devices characteristics, combining ring resonator with fiber bragg gratings

In this paper the transmission characteristics as well as group delay of a resonator which is coupled to a slab waveguide are studied. The theoretical formula of Side Coupled Integrated Spaced Sequence of Resonators (SCISSORs) is also presented. We propose a new structure so as to enhance the group delay of ring resonator structure while the area usage is almost constant. The structure is comprised of typical ring resonators and ring with Fiber Bragg Grating (FBG). By inserting a low reflectivity FBG in the part of ring’ circumference, enlarged group delay can be observed. Moreover, this ring containing FBG is employed not only as reflector in the structure causing light propagates each resonator chain twice, but also it provides delay which results in more time delay or advancement in the output port. Both slow and fast light can be observed in this structure and the results reveal that the amount of time delay is increased from 30 ps to more than 80 ps when one ring is employed alongside the FBG.

Low-Loss Continuously Tunable Optical True Time Delay Based on Si3N4 Ring Resonators

We design, fabricate, and characterize ultra-low loss continuously tunable optical true time delay devices based on Si3N4 ring resonators in a side-coupled integrated spaced sequence of resonators (SCISSOR) structure. A large tunable delay range up to 3.4 ns is demonstrated using the Balanced SCISSOR delay tuning scheme, for a record loss of only 0.89 dB/ns of delay. By optimizing the coupler design a device delay bandwidth of over 10 GHz is achieved with over 0.5 ns maximum time delay. This ultra-low loss delay line can enable distortion free operation for RF signals used in RF beamforming and other applications. Additionally, this device has the potential to be integrated with active photonic components to be part of a fully integrated photonic integrated circuit in an electronically scanned phased array system; utilizing a silicon photonics platform including heterogeneous integration.

Performance Comparison of Grating-Assisted Integrated Photonic Delay Lines

Incorporation of grating waveguides in optical delay lines based on integrated microring resonator structures is proposed. Specifically, transmittive apodized grating waveguides are implemented in two common microring configurations, namely, coupled-resonator optical waveguides (CROWs) and side-coupled integrated spaced sequence of resonators (SCISSORs). The performance of these proposed devices is compared with standard CROWs and SCISSORs (i.e., with no gratings), as well as with grating-assisted waveguides (cascaded complementary apodized grating waveguides). It is shown that, for the same minimum bit rate operation, the proposed grating-assisted SCISSORs exhibit the best performance in terms of delay tunability and delay per footprint. However, the maximum true time delay of grating-assisted waveguides possesses a close to linear dependence on length, while the true delay in mircoresonator-type structures (with or without gratings) do not increase efficiently with the number of rings. Also, it is argued that the grating-assisted waveguides are expected to have the lowest insertion loss per delay time.

An All Optical Method for Fabrication Error Measurements in Integrated Photonic Circuits

We propose an optical method to quantify the level of fabrication imperfections in a Silicon On Insulator wafer. The method is based on the use of Side Coupled Integrated Spaced Sequence of Resonators (SCISSOR) as test devices. Fabrication induced fluctuations of the effective index and of the coupling coefficient are mapped by comparing different spectral responses of nominally identical samples taken from different dies in the wafer. Random variations of the resonator's optical path are quantified in terms of standard deviations of normally distribuited variables by finding a statistical correlation with the coupled resonator induced transparency (CRIT) phenomena. We found a strong correlation between CRIT and fabrication errors. This led us to design a SCISSOR based test structure that allows to quantify the degree of local structural imperfections in a fast, accurate and non invasive way. Performances, possible applications and limitations are investigated with the help of transfer matrix simulations.

Coupled-resonator-induced-transparency concept for wavelength routing applications

The presence of coupled resonators induced transparency (CRIT) effects in side-coupled integrated spaced sequence of resonators (SCISSOR) of different radii has been studied. By controlling the rings radii and their center to center distance, it is possible to form transmission channels within the SCISSOR stop-band. Two different methods to exploit the CRIT effect in add/drop filters are proposed. Their performances, e. g. linewidth, crosstalk and losses, are examined also for random variations in the structural parameters. Finally, few examples of high performances mux/demux structures and 2 × 2 routers based on these modified SCISSOR are presented. CRIT based SCISSOR optical devices are particularly promising for ultra-dense wavelength division multiplexing applications.

Systematic design study of an all-optical delay line based on Brillouin scattering enhancedcascade coupled ring resonators

We present a technique to improve the slow-light performance of a side-coupled integratedspaced sequence of resonators (SCISSOR) combined with a stimulated Brillouin scattering (SBS)gain medium in optical fibers. We evaluate device performance of SCISSOR-only andSCISSOR + SBS systems for different numbers of cascaded resonators from 1 to 70 using two different datafidelity metrics including eye-opening and mutual information. A practical system design isdemonstrated by analyzing its performance in terms of fractional delay, power transmission,and data fidelity. We observe that the results from the two metrics are in good agreement.Based on system optimization under practical resource and fidelity constraints,the SCISSOR consisting of 70 cascaded resonators provides a fractional delay of ∼ 8 with 22 dB attenuation at a signal bit rate of 10 Gbps. The combined optimal SCISSOR(with 70 resonators) + SBS system provides a improved fractional delay up to ∼ 17 with unit power transmission under the same constraints.

Coupled Fano resonators

We theoretically investigate coupled Fano structures which combine the characteristics of both directly coupled Fabry-Perot cavities (DCFPC) and a side-coupled integrated spaced sequence of resonators (SCISSOR). Asymmetric and symmetric Fano resonances in a single and doubly-coupled Fano unit are analytically derived based on Fabry-Perot approach. It is found that doubly-coupled Fano units show a special asymmetric EIT-like lineshape. This structure shows an index changing sensitivity of 10(-6), about two orders higher than that of the single Fano resonator, which is promising for index sensor application. A unique frequency detuning method of EIT like lineshape is also found in the doubly-coupled Fano units. The multiple coupled Fano unit structure demonstrates potentials for applications of tunable optical filter and slow light, whereas for the latter it shows much higher group delay than that of SCISSORS and DCFPC with the same parameters.

Analysis of optical ARMA architectures in the slow-light regime

We study pulse propagation in the slow-light regime with positive and negative group delays in auto-regressive moving average (ARMA) filters, including the ring-enhanced Mach-Zehnder interferometer (REMZI) and side-coupled integrated spaced sequence of resonators (SCISSOR) optical architectures. Both architectures are optimized to maximize the delay-bandwidth product for a fixed output pulse-distortion level. In the negative-group-delay regime, absorption is incorporated in the rings. The REMZI architecture has the highest delay-bandwidth product in both the positive and negative-group-delay regimes due to greater efficiency in incorporating filter phase within the passband. We also explore the effects of pulse shape in the lossy regime and the limitations it poses in the amount of pulse advancement that is usable for practical applications.

Nonlinear pulse interaction in microresonator slow-light waveguides

Using the constraint of fixed pulse distortion, three slow-light waveguide architectures [coupled-resonator optical waveguide, side-coupled integrated spaced sequence of resonators (SCISSOR), and ring enhanced Mach-Zehnder interferometer (REMZI)] are studied for linear delay-bandwidth product, nonlinear phase shift, and nonlinear pulse interaction; pulse to pulse interaction is a limiting factor on the bit rate. For the same number of stages the REMZI architecture has the highest delay-bandwidth product and the best nonlinear sensitivity, but the SCISSOR architecture has the weakest nonlinear pulse interaction. We further define a phase efficiency factor, which represents the fraction of the total filter phase that contributes to the delay-bandwidth product. We also show that resonator loss reduces the nonlinear sensitivity and the delay-bandwidth product in the nonlinear regime.

Miniaturization of Fresnel phase matching using a side-coupled integrated spaced sequence of resonators (SCISSOR)

It is proposed that a side-coupled integrated spaced sequence of resonators (SCISSOR) be used to adapt Fresnel phase matching to the case of highly confining waveguides. As is the case for bulk media, this method of quasi-phase-matching (QPM) allows resonant or nonresonant QPM. This property can be used to control the spectral bandwidth of the phase-matching curve.

Uniform coil optical resonator and waveguide: transmission spectrum, eigenmodes, and dispersion relation

The coil optical resonator (COR) is an optical microfiber coil tightly wound on an optical rod. The resonant behavior of this all-pass device is determined by evanescent coupling between the turns of the microfiber. This paper investigates the uniform COR with N turns. Its transmission characteristics are surprisingly different from those of the known types of resonators and of photonic crystal structures. It is found that for certain discrete sequences of propagation constant and interturn coupling, the light is completely trapped by the resonator. For N ? degrees degrees , the COR spectrum experiences a fractal collapse to the points corresponding to the second order zero of the group velocity. For a relatively small coupling between turns, the COR waveguide behavior resembles that of a SCISSOR (side-coupled integrated spaced sequence of resonators), while for larger coupling it resembles that of a CROW (coupled resonator optical waveguide).

SCISSOR solitons and other novel propagation effects in microresonator-modified waveguides

We consider the linear and nonlinear optical properties of an optical waveguide consisting of a side-coupled integrated spaced sequence of resonators (SCISSOR). This fully transmissive system possesses large and controllable dispersion because the phase shift imparted by each resonator is strongly frequency dependent. Additionally, near resonance, the circulating power in each resonator can greatly exceed the power carried by the waveguide, leading to greatly enhanced nonlinear effects. We show that the effects of nonlinearity and dispersion can be balanced to create temporal solitons and that many other novel and useful pulse propagation effects can occur over short propagation distances in such a structure.