Showing papers on "Coupled mode theory published in 2014"
TL;DR: This work investigated the dispersions and electromagnetic field patterns of a symmetric CSP structure in which the two sides of the planar metal strip are symmetrically corrugated by groove arrays and designed and analyzed two planar CSP waveguide devices in the terahertz frequency.
Abstract: Recently, a conformal surface plasmon (CSP) structure has been successfully proposed, which is very promising for application of planar plasmonic devices in the frequency ranging from microwave to mid-infrared [Proc. Natl. Acad. Sci. U.S.A. 110, 40-45 (2013)]. Here we investigated the dispersions and electromagnetic (EM) field patterns of a symmetric CSP structure in which the two sides of the planar metal strip are symmetrically corrugated by groove arrays. The symmetric CSP structure can support both the symmetric mode (even mode) and the anti-symmetric mode (odd mode) of surface wave propagation. Based on the even mode, we analyzed the EM wave coupling between two adjacent symmetry CSP strips, and then designed and analyzed two planar CSP waveguide devices in the terahertz frequency: a frequency splitter and a 3 dB directional coupler. To verify the functionality and performance of these waveguide devices, we scaled down the working frequency to microwave and designed similar devices with scaled geometry. We implemented microwave experiments on the fabricated prototypes, and the tested device performances have clearly validated the functionality of our designs. The symmetric CSP structure is believed to be very applicable in future design of novel planar plasmonic device and circuitry.
127 citations
TL;DR: In this paper, the authors demonstrate experimentally close total absorption in monolayer graphene based on critical coupling with guided resonances in transfer printed photonic crystal Fano resonance filters at near infrared.
Abstract: We demonstrate experimentally close to total absorption in monolayer graphene based on critical coupling with guided resonances in transfer printed photonic crystal Fano resonance filters at near infrared. Measured peak absorptions of 35% and 85% were obtained from cavity coupled monolayer graphene for the structures without and with back reflectors, respectively. These measured values agree very well with the theoretical values predicted with the coupled mode theory based critical coupling design. Such strong light-matter interactions can lead to extremely compact and high performance photonic devices based on large area monolayer graphene and other two–dimensional materials.
118 citations
TL;DR: A classic analog of electromagnetically induced transparency (EIT) in a metal-dielectric-metal bus waveguide coupled to two stub resonators is investigated, and the theoretical results agree well with the finite difference time domain simulations.
Abstract: We investigate a classic analog of electromagnetically induced transparency (EIT) in a metal-dielectric-metal (MDM) bus waveguide coupled to two stub resonators. A uniform theoretical model, for both direct and indirect couplings between the two stubs, is established to study spectral features in the plasmonic stub waveguide, and the theoretical results agree well with the finite difference time domain simulations. Adjusting phase difference and coupling strength of the interaction, one can realize the EIT-like phenomena and achieve the required slow light effect. The theoretical results may provide a guideline for the control of light in highly integrated optical circuits.
93 citations
TL;DR: A novel combination of a radiation field model and the transfer matrix method (TMM) is proposed to demonstrate plasmon-induced transparency (PIT) in bright-dark mode waveguide structures and the large group index can be achieved in these periodic H-shaped resonators.
Abstract: We propose a novel combination of a radiation field model and the transfer matrix method (TMM) to demonstrate plasmon-induced transparency (PIT) in bright-dark mode waveguide structures. This radiation field model is more effective and convenient for describing direct coupling in bright-dark mode resonators, and is promoted to describe transmission spectra and scattering parameters quantitatively in infinite element structures by combining it with the TMM. We verify the correctness of this novel combined method through numerical simulation of the metal-dielectric-metal (MDM) waveguide side-coupled with typical bright-dark mode, H-shaped resonators; the large group index can be achieved in these periodic H-shaped resonators. These results may provide a guideline for the control of light in highly integrated optical circuits.
89 citations
TL;DR: In this paper, an analytical model was proposed to describe the dynamic transmission in metal-dielectric-metal (MDM) waveguide aperture-side-coupled with slot cavity.
Abstract: By taking the aperture as a resonator, we propose an analytical model to describe the dynamic transmission in metal-dielectric-metal (MDM) waveguide aperture-side-coupled with slot cavity. The theoretical results and the finite-difference time-domain (FDTD) simulations agree well with each other, and both demonstrate the mode selectivity and filtering tunability of the plasmonic structure. By adjusting the phase shifts in slot cavity or resonance frequency determined by the aperture, one can realize the required transmission spectra and slow light effect. The theoretical analysis may open up avenues for the control of light in highly integrated optical circuits.
83 citations
TL;DR: A laser with a mirror realized by Fano interference between a waveguide and a nanocavity can be modulated at frequencies exceeding 1 THz, not being limited by carrier dynamics as for conventional lasers.
Abstract: We suggest and analyze a laser with a mirror realized by Fano interference between a waveguide and a nanocavity. For small-amplitude modulation of the nanocavity resonance, the laser can be modulated at frequencies exceeding 1 THz, not being limited by carrier dynamics as for conventional lasers. For larger modulation, a transition from pure frequency modulation to the generation of ultrashort pulses is observed. The laser dynamics is analyzed by generalizing the field equation for conventional lasers to account for a dynamical mirror, described by coupled mode theory.
81 citations
TL;DR: A two-port wavelength demultiplexer is designed, which can separate resonant modes inside the nanodisk with high transmission up to 70% and may become a potential application for the design of devices in highly integrated optical circuits.
Abstract: A compact wavelength band-pass filter based on metal-insulator-metal (MIM) nanodisk cavity is proposed and numerically investigated by using Finite-Difference Time-Domain (FDTD) simulations. It is found that the transmission characteristics of the filter can be easily adjusted by changing the geometrical parameters of the radius of the nanodisk and coupling distance between the nanodisk and waveguide. By extending the length of input/output waveguides, the filter shows the resonant mode inhibition function. Basing on this characteristic, a two-port wavelength demultiplexer is designed, which can separate resonant modes inside the nanodisk with high transmission up to 70%. The waveguide filter may become a potential application for the design of devices in highly integrated optical circuits.
73 citations
TL;DR: It is shown that an array of photonic crystal cavities enables high-order temporal integration and the effect of the value of the cavity's free spectral range on the accuracy of the integration is considered.
Abstract: In this paper, we propose and numerically investigate an all-optical temporal integrator based on a photonic crystal cavity. We show that an array of photonic crystal cavities enables high-order temporal integration. The effect of the value of the cavity's free spectral range on the accuracy of the integration is considered. The influence of the coupling coefficients in the resonator array on the integration accuracy is demonstrated. A compact integrator based on a photonic crystal nanobeam cavity is designed, which allows high-precision integration of optical pulses of subpicosecond duration.
59 citations
TL;DR: An all-optical temporal differential-equation solver that can be used to solve ordinary differential equations (ODEs) characterizing general linear time-invariant systems and test the effectiveness of the fabricated device as a tunable photonic ODE solver.
Abstract: We propose and experimentally demonstrate an all-optical temporal differential-equation solver that can be used to solve ordinary differential equations (ODEs) characterizing general linear time-invariant (LTI) systems. The photonic device implemented by an add-drop microring resonator (MRR) with two tunable interferometric couplers is monolithically integrated on a silicon-on-insulator (SOI) wafer with a compact footprint of ~60 μm × 120 μm. By thermally tuning the phase shifts along the bus arms of the two interferometric couplers, the proposed device is capable of solving first-order ODEs with two variable coefficients. The operation principle is theoretically analyzed, and system testing of solving ODE with tunable coefficients is carried out for 10-Gb/s optical Gaussian-like pulses. The experimental results verify the effectiveness of the fabricated device as a tunable photonic ODE solver.
58 citations
TL;DR: It is shown that the wavelength splitting in two evanescently-coupled Photonic Crystal L3 cavities can be continuously controlled up to 5× the initial value upon ∼ 30% of hole-size modification in the barrier.
Abstract: We demonstrate a large tuning of the coupling strength in Photonic Crystal molecules without changing the inter-cavity distance. The key element for the design is the "photonic barrier engineering", where the "potential barrier" is formed by the air-holes in between the two cavities. This consists in changing the hole radius of the central row in the barrier. As a result we show, both numerically and experimentally, that the wavelength splitting in two evanescently-coupled Photonic Crystal L3 cavities (three holes missing in the ΓK direction of the underlying triangular lattice) can be continuously controlled up to 5× the initial value upon ∼ 30% of hole-size modification in the barrier. Moreover, the sign of the splitting can be reversed in such a way that the fundamental mode can be either the symmetric or the anti-symmetric one without altering neither the cavity geometry nor the inter-cavity distance. Coupling sign inversion is explained in the framework of a Fabry-Perot model with underlying propagating Bloch modes in coupled W1 waveguides.
54 citations
TL;DR: In this article, the authors consider light trapping in photonic crystals in the weak material absorption limit and show that the upper bound on the angle-integrated absorption enhancement is proportional to the photonic density of states.
Abstract: We consider light trapping in photonic crystals in the weak material absorption limit. Using a rigorous electromagnetic approach, we show that the upper bound on the angle-integrated absorption enhancement by light trapping is proportional to the photonic density of states. The tight bound can be reached if all the states supported by the structure are coupled to external radiation. Numerical simulations are used to illustrate the theory and the design of both two- and three-dimensional photonic crystals for the purpose of light trapping. Using the van Hove singularities, the angle-integrated absorption enhancement in two-dimensional photonic crystals could surpass the conventional limit over substantial bandwidths.
TL;DR: A two-dimensional photonic crystal design of four defect dielectric rods, which form a microcavity with eigenfrequencies residing in the propagating band of a directional waveguide, resulting in a novel transmission resonance.
Abstract: We present a two-dimensional photonic crystal design of four defect dielectric rods, which form a microcavity with eigenfrequencies residing in the propagating band of a directional waveguide. In this system, a nonrobust bound state in the continuum (BSC) occurs as a result of full destructive interference of the monopole and quadrupole modes, with the same parity at certain values of the material parameters of the defect rods. Due to the Kerr effect, a robust BSC arises in a self-adaptive way without necessity to tune the material parameters. The absence of the superposition principle in that nonlinear system gives rise to coupling of the BSC with injected light, resulting in a novel transmission resonance.
TL;DR: A novel mode converter in silicon waveguide is designed, analyzed and experimentally demonstrate based on a graded index co-directional grating coupler based on the basis of numerical simulations and microscope images of modes' far field.
Abstract: We propose, design and analyze a novel mode converter in silicon waveguide based on a graded index co-directional grating coupler. The device has a periodic variation in its refractive index along the propagation direction and a graded index profile along the transverse direction. The graded index profile is realized by the implementation of nanoscale dielectric metamaterial consisting of silicon features that are etched into the waveguide based on the concept of effective medium. Design considerations are discussed and analyzed in details in the framework of the coupled mode theory (CMT) and the effective medium theory (EMT). Using 3D finite difference time domain (FDTD) simulations we show that the mode converter can couple between different symmetric and asymmetric modes which are propagating along a single bus multimode waveguide. Mode purity on the order of 96%, crosstalk with the input mode of better than −23dB, and transmission of more than 96% can be obtained, with device length as short as 20µm, and over ~25nm spectral bandwidth around the design wavelength of 1550nm.
TL;DR: It is shown theoretically that this modulator scheme has lower power consumption compared to a standard silicon ring modulator at high carrier frequencies and could enable future on-chip high-frequency analog communication and photonic signal processing on a silicon photonics platform.
Abstract: We demonstrate the modulation of silicon ring resonators at RF carrier frequencies higher than the resonance linewidth by coupling adjacent free-spectral-range (FSR) resonance modes. In this modulator scheme, the modulation frequency is matched to the FSR frequency. As an example, we demonstrate a 20 GHz modulation in a silicon ring with a resonance linewidth of only 11.7 GHz. We show theoretically that this modulator scheme has lower power consumption compared to a standard silicon ring modulator at high carrier frequencies. These results could enable future on-chip high-frequency analog communication and photonic signal processing on a silicon photonics platform.
TL;DR: In this article, an expanded analytical analysis of the plasmonic patch geometry, applying an eigenmode expansion method to arrive at a more accurate description of the field distribution underneath a film-coupled planar nanocube, is presented.
Abstract: Planar metallic nanoparticles separated by nanoscale distances from a metal film support unique plasmonic resonances useful for controlling a wide range of photodynamic processes. The fundamental resonance of a film-coupled planar nanoparticle arises from a transmission-line mode localized between nanoparticle and film, whose properties can be roughly approximated by closed form expressions similar to those used in patch antenna theory. The insight provided by the analytical expressions, and the potential of achieving similar closed-form expressions for a range of plasmonic phenomenon such as spasing, fluorescence enhancement, and perfect absorbers, motivates a more detailed study of the film-coupled patch. Here, we present an expanded analytical analysis of the plasmonic patch geometry, applying an eigenmode expansion method to arrive at a more accurate description of the field distribution underneath a film-coupled plasmonic nanocube. The fields corresponding to the inhomogeneous Maxwell's equations are expanded in a set of lossless waveguide eigenmodes. Radiation damping and Ohmic losses are then perturbatively taken into account by considering an equivalent surface impedance. We find that radiative loss couples the lossless eigenmodes, leading to discernible features in the scattering spectra of the nanocubes. The method presented can be further applied to the case of point source excitations, in which accounting for all potential eigenmodes becomes essential.
TL;DR: In this article, a model based on coupled mode theory was proposed to predict the spontaneous generation of periodic nanostructures under homogeneous exposure, and it was shown that the waveguiding metallic photonic crystals can self-emerge from thin films homogeneously loaded with metallic precursors under continuous-wave and homogeneous laser excitation.
Abstract: Using a monochromatic plane wave to generate periodic arrays of metallic nanoparticles with tunable features buried in thin films is the original work we report here. We focus on the way such waveguiding metallic photonic crystals can self-emerge from thin films homogeneously loaded with metallic precursors under continuous-wave and homogeneous laser excitation. This paper fully describes the conditions leading to the formation of periodic structures and highlights the role of several parameters in the underlying physical mechanisms. The laser exposure parameters, especially, fix the geometrical and optical properties of the generated structures. Grating lines are parallel to the laser polarization and the period is directly linked to the laser wavelength. Both electron resonances of metal nanoparticles and optical resonances of guided modes interact to form the periodic patterns under homogeneous exposure. A model, based on the coupled mode theory, can be proposed to predict the spontaneous generation of such periodic nanostructures. It concludes that the guided waves exponentially enhance during illumination due to a positive feedback loop with the ordered growth of particles. This process opens up new fabrication techniques for making optical devices and may find applications in various fields such as polarization imaging, displays, security or lighting.
TL;DR: This work derives general coupled-mode equations describing the nonlinear interaction of electromagnetic modes in periodic media with loss and gain based on the Lorentz reciprocity theorem and predicts novel effects on self- and cross-phase modulation in multilayer nonlinear fishnet metamaterials.
Abstract: We derive general coupled-mode equations describing the nonlinear interaction of electromagnetic modes in periodic media with loss and gain. Our approach is rigorously based on the Lorentz reciprocity theorem, and it can be applied to a broad range of metal–dielectric photonic structures, including plasmonic waveguides and metamaterials. We verify that our general results agree with the previous analysis of particular cases, and predict novel effects on self- and cross-phase modulation in multilayer nonlinear fishnet metamaterials.
TL;DR: In this paper, optical bistability and self-pulsation in silicon microring resonators (MRRs) are experimentally observed and theoretically studied by adopting the coupledmode theory and linear stability analysis method for differential equations, with theoretical results fitting well with the experimental ones.
Abstract: Optical bistability and self-pulsation (SP) in silicon microring resonators (MRRs) are experimentally observed. The waveforms and frequencies of SP can be controlled by changing input light power and its wavelength, and the region of SP can be modulated readily by applying a reverse voltage on the PN junction embedded in the MRR. These phenomena are theoretically studied by adopting the coupled-mode theory and linear stability analysis method for differential equations, with theoretical results fitting well with the experimental ones.
TL;DR: A family of synthetic "photonic molecule"-like, coupled-cavity systems to implement optimum FWM is suggested, where structure design for control of resonant wavelengths can be separated from that of optimizing nonlinear conversion efficiency, and where furthermore pump, signal, and idler coupling to bus waveguides can be controlled independently.
Abstract: We propose optimal designs for triply-resonant optical parametric oscillators (OPOs) based on degenerate four-wave mixing (FWM) in microcavities. We show that optimal designs in general call for different external coupling to pump and signal/idler resonances. We provide a number of normalized performance metrics including threshold pump power and maximum achievable conversion efficiency for OPOs with and without two-photon (TPA) and free-carrier absorption (FCA). We find that the maximum achievable conversion efficiency is bound to an upper limit by nonlinear and free-carrier losses independent of pump power, while linear losses only increase the pump power required to achieve a certain conversion efficiency. The results of this work suggest unique advantages in on-chip implementations that allow explicit engineering of resonances, mode field overlaps, dispersion, and wavelength-and mode-selective coupling. We provide universal design curves that yield optimum designs, and give example designs of microring-resonator-based OPOs in silicon at the wavelengths 1.55 μm (with TPA) and 2.3 μm (no TPA) as well as in silicon nitride (Si3N4) at 1.55 μm. For typical microcavity quality factor of 106, we show that the oscillation threshold in excitation bus can be well into the sub-mW regime for silicon microrings and a few mW for silicon nitride microrings. The conversion efficiency can be a few percent when pumped at 10 times of the threshold. Next, based on our results, we suggest a family of synthetic “photonic molecule”-like, coupled-cavity systems to implement optimum FWM, where structure design for control of resonant wavelengths can be separated from that of optimizing nonlinear conversion efficiency, and where furthermore pump, signal, and idler coupling to bus waveguides can be controlled independently, using interferometric cavity supermode coupling as an example. Finally, consideration of these complex geometries calls for a generalization of the nonlinear figure of merit (NFOM) as a metric for performance in nonlinear photonic systems, and shows different efficiencies for single and multi-cavity geometries, as well as for standing and traveling wave excitations.
TL;DR: Four-channel all-optical wavelength multicasting using only 1 mW of control power, with converted channel spacing of 40-60 GHz, based on a compact embedded microring design fabricated on a scalable SOI platform is demonstrated.
Abstract: Single microring resonators have been used in applications such as wavelength multicasting and microwave photonics, but the dependence of the free spectral range with ring radius imposes a trade-off between the required GHz optical channel spacing, footprint and power consumption. We demonstrate four-channel all-optical wavelength multicasting using only 1 mW of control power, with converted channel spacing of 40-60 GHz. Our device is based on a compact embedded microring design fabricated on a scalable SOI platform. The coexistence of close resonance spacing and high finesse (205) in a compact footprint is possible due to enhanced quality factors (30,000) resulting from the embedded configuration and the coupling-strength dependence of resonance spacing, instead of ring size. In addition, we discuss the possibility of achieving continuously mode splitting from a single-notch resonance up to 40 GHz.
TL;DR: In this paper, the enhancement of sound inside a two-dimensional exponentially chirped crystal during the soft reflections of waves is experimentally and theoretically explored in the system by means of a chirp of the lattice constant, which is produced at some planes of the crystal in which the wave is softly reflected due to a progressive slowing down of the sound wave.
Abstract: The enhancement of sound inside a two dimensional exponentially chirped crystal during the soft reflections of waves is experimentally and theoretically explored in this work. The control of this enhancement is achieved by a gradual variation of the dispersion in the system by means of a chirp of the lattice constant. The sound enhancement is produced at some planes of the crystal in which the wave is softly reflected due to a progressive slowing down of the sound wave. We find that the character of the sound enhancement depends on the function of the variation of dispersion, i.e., on the function of the chirp. A simple coupled mode theory is proposed to find the analytical solutions of the sound wave enhancement in the exponentially chirped crystal. Harmonic and time domain numerical simulations are performed to interpret the concept of the soft reflections, and to check the analytically calculated field distributions both in good agreement with experiments. Specially we obtain stronger sound enhancement than in linearly chirped crystals. This sound enhancement could motivate applications in energy harvesting, e.g., to increase the efficiency of detectors and absorbers.
TL;DR: A theoretical model based on the coupled mode theory is developed and observed strong asymmetric Fano resonances are observed and the degree of asymmetry can be tuned through the positions of the input and output fibers.
Abstract: Silicon nitride (Si3N4) optical ring resonators provide exceptional opportunities for low-loss integrated optics. Here we study the transmission through a multimode waveguide coupled to a Si3N4 ring resonator. By coupling single-mode fibers to both input and output ports of the waveguide we selectively excite and probe combinations of modes in the waveguide. Strong asymmetric Fano resonances are observed and the degree of asymmetry can be tuned through the positions of the input and output fibers. The Fano resonance results from the interference between modes of the waveguide and light that couples resonantly to the ring resonator. We develop a theoretical model based on the coupled mode theory to describe the experimental results. The large extension of the optical modes out of the Si3N4 core makes this system promising for sensing applications.
TL;DR: In this article, a high contrast all-optical controllable switch and router based on two cross-waveguide-based nonlinear photonic crystal switches and a T-branch waveguide is presented.
Abstract: We present a new high-contrast all-optical controllable switch and router, which is based on two cross-waveguide-based nonlinear photonic crystal switches and a T-branch waveguide. We show that by applying a proper state of control signals (a controlled switching mechanism), the input power can be routed to any of the two output ports. The operation of the proposed device is investigated through the use of analytical and numerical methods.
TL;DR: In this paper, the authors report temporal and spectral domain observation of regenerative oscillation in monolithic silicon heterostructured photonic crystals cavities with high quality factor to mode volume ratios (Q/V).
Abstract: We report temporal and spectral domain observation of regenerative oscillation in monolithic silicon heterostructured photonic crystals cavities with high quality factor to mode volume ratios (Q/V). The results are interpreted by nonlinear coupled mode theory (CMT) tracking the dynamics of photon, free carrier population, and temperature variations. We experimentally demonstrate effective tuning of the radio frequency tones by laser-cavity detuning and laser power levels, confirmed by the CMT simulations with sensitive input parameters.
TL;DR: In this article, the structural symmetry required for long-range surface plasmon-polariton modes to take place is examined and mapped to asymmetric plasmanic structures.
Abstract: The structural symmetry required for long-range surface-plasmon-polariton modes to take place is examined and mapped to asymmetric plasmonic structures. This study leads to a design methodology that facilitates the realization through systematic design of long-range modes in any asymmetric hybrid plasmonic waveguide (AHPW). Examining the modal behavior of an AHPW reveals that field symmetry on either side of the metal is the only necessary condition for plasmonic structures to support long-range propagation. We report that this field symmetry condition can be satisfied irrespective of asymmetry in a waveguide structure, material, or even field profile. The structure is analyzed using the coupled mode theory, transfer matrix method, and finite-difference time-domain method. The AHPW supports high-loss antisymmetric and long-range symmetric supermodes. Dispersion of these supermodes with respect to waveguide dimensions display similar anticrossing characteristics to those obtained in two coupled harmonic oscillators, where the propagation losses display peaks and troughs in the vicinity of the anticrossing region. To place the work in perspective, an AHPW with a width of 200 nm was found to support a long-range supermode with a subwavelength mode area of 0.23 μm2 and propagation loss of 0.025 dB·μm−1 at the wavelength of 1550 nm, providing a radically improved attenuation confinement trade-off compared with other common types of plasmonic waveguides.
TL;DR: The behavior of this coupled system, based on the coupling between its dielectric and cavity modes, is studied and closed form expressions for the fields of the coupled system are proposed.
TL;DR: High sensitivity splitting mode sensors are theoretically demonstrated showing, as an example, a strain sensitivity improvement of at least one order of magnitude over the state-of-the-art.
Abstract: In this paper, we report on theoretical investigation of split mode resonant sensors based on fiber Bragg grating (FBG) ring resonators and π-shifted fiber Bragg grating (π-FBG) ring resonators. By using a π-shifted Bragg grating ring resonator (π-FBGRR) instead of a conventional fiber Bragg grating ring resonator (FBGRR), the symmetric and antisymmetric resonance branches (i.e., the eigen-modes of the perturbed system) show peculiar and very important features that can be exploited to improve the performance of the fiber optic spectroscopic sensors. In particular, the π-FBGRR symmetric resonance branch can be taylored to have a maximum splitting sensitivity to small environmental perturbations. This optimal condition has been found around the crossing points of the two asymmetric resonance branches, by properly choosing the physical parameters of the system. Then, high sensitivity splitting mode sensors are theoretically demonstrated showing, as an example, a strain sensitivity improvement of at least one order of magnitude over the state-of-the-art.
TL;DR: The design and fabrication of cascade-coupled racetrack resonators based on the Vernier effect are presented and experimental spectra of Vernier architectures were demonstrated for the first time in the mid-infrared with insertion loss lower than 1 dB and maximum interstitial peak suppression of 10 dB.
Abstract: In this paper we report the experimental demonstration of racetrack resonators in silicon-on-insulator technology platform operating in the mid-infrared wavelength range of 3.7-3.8 μm. Insertion loss lower than 1 dB and extinction ratio up to 30 dB were measured for single resonators. The experimental characterization of directional couplers and bending losses in silicon rib waveguides are also reported. Furthermore, we present the design and fabrication of cascade-coupled racetrack resonators based on the Vernier effect. Experimental spectra of Vernier architectures were demonstrated for the first time in the mid-infrared with insertion loss lower than 1 dB and maximum interstitial peak suppression of 10 dB.
TL;DR: Using coupled mode theory, an extremely high transmission contrast is demonstrated in an all-optical diode in L-shaped photonic crystal waveguide that uses the multistability of single nonlinear Kerr microcavity with two dipole modes.
Abstract: A design of all-optical diode in L-shaped photonic crystal waveguide is proposed that uses the multistability of single nonlinear Kerr microcavity with two dipole modes. Asymmetry of the waveguide is achieved through different couplings of the dipole modes with the left and right legs of the waveguide. Using coupled mode theory we demonstrate an extremely high transmission contrast. The direction of optical diode transmission can be controlled by power or frequency of injected light. The theory agrees with the numerical solution of the Maxwell equations.
TL;DR: A photonic crystal slab-based 1 × 3 power splitter with high output transmission and equal power distribution is proposed by cascading an asymmetric 1 × 2 powersplitter and a symmetric 1 → 2 power splitters with flexible structural defects.
Abstract: We propose a photonic crystal slab-based 1 × 3 power splitter with high output transmission and equal power distribution It is designed by cascading an asymmetric 1 × 2 power splitter and a symmetric 1 × 2 power splitter Desired equal power splitting is achieved by introducing and optimizing the splitting region of the 1 × 2 power splitters with flexible structural defects Simulations were carried out by using 3-D Finite Difference Time Domain method showing equal normalized power distributions of 296%, 289% and 305% at 1550 nm optical wavelength In addition, equal power splitting also takes place at 1561 nm