Waveguide resonance of subwavelength metallic slits

The transmission characteristics of a metallic film with subwavelength periodic slits are investigated by using the two-dimensional finite-difference time-domain method （2D-FDTD）. Two models are constructed to show the dependance of the transmission spectrum on the slit structure. A sandwiched structure is used to exhibit the contribution of the metallic wall inside slits to the extraordinary high transmission. And a filled slit structure is employed to reflect the relation between the average refractive index inside the slits and the transmission spectrum of the structure. The transmission characteristics of two structures can be explained well with the waveguide resonance theory.

A BIOSENSOR USING COUPLED PLASMON WAVEGUIDE RESONANCE COMBINED WITH HYPERSPECTRAL FLUORESCENCE ANALYSIS

We developed a biosensor that is capable for simultaneous surface plasmon resonance(SPR)sensing and hyperspectral fuores cence analysis in this paper.A symmetrical metal-dielectric slabscheme is employed for the excitation of coupled plasnon waveguide resonance(CPWR)in thepresent work.Resonance bet ween surface plasmon mode and the guided waveguide mode gen-erates narrower full width half-maximum of the refective curves which leads to increased pre.cision for the determination of refractive index over conventional SPR sensors.In addition,CPWR also fers longer surface propagation depths and higher surface electric field strengthsthat enable the excitation of fluorescence with hyperspectral technique to maintain an appreci-able signal-to-noise ratio.The refractive index information obtained from SPR sensing and thechemical properties obt ained through hyperspectral fluorescence analysis confirm each other toexclude false-positive or false-negative cases.The sensor provides a comprehensive understandingof the biological events on the sensor chips.

Resonances Characteristics of Parallel Plate Waveguide Cavities

The influence of air gaps on the response of transmission for a transverse-electric mode parallel-plate waveguide（TE-PPWG） with a single cavity and double cavities has been studied experimentally. As the air gap is larger than the resonant wavelength of high order cavity mode in the single deep grooved waveguide, only the fundamental cavity mode can be excited and single resonance can be observed in the transmission spectrum. Based on above observations, a tunable multiband terahertz（THz）notch filter has been proposed and the variation of air gap has turned out to be an effective method to select the band number. Experimental data and simulated results verify this band number tunability. This mechanical control mechanism for electromagnetic induced transparency（EIT） will open a door to design the tunable THz devices.

Single Photon Scattering in a Pair of Waveguides Coupled by a Whispering-Gallery Resonator Interacting with a Semiconductor Quantum Dot

The single photon scattering properties in a pair of waveguides coupled by a whispering-gallery resonator in- teracting with a semiconductor quantum dot are investigated theoretically. The two waveguides support four possible ports for an incident single photon. The quantum dot is considered a V-type system. The incident direction-dependent single photon scattering properties are studied and equal-output probability from the four ports for a single photon incident is discussed. The influences of backscattering between the two modes of the whispering-gallery resonator for incident direction-dependent single photon scattering properties are also pre- sented.

Efficient Method to Extract Coupling Ratio and Round-trip Loss Parameters of Optical Waveguide Ring Resonator

Based on the measurement of the contrast ratios of the transmission spectra from the throughput and drop ports of ring resonator, an efficient method is proposed to extract the coupling ratio and round-trip loss of the integrated optical waveguide ring resonator. The parameters of a racetrack resonator prepared by ion-exchange technique in K9 optical glass substrate are examined, which demonstrates the validity of this method. The accuracy and applicable range of this method are also discussed.

Entanglement transfer via two arrays of coupled resonator waveguides

We propose a scheme for transferring entanglement through two independent arrays of coupled resonator waveguides, where a three-level atom is embedded in each resonator. We investigate the entanglement dynamics of the transferred state. The influence of initial states and applied lasers on the entanglement sudden death phenomenon is also discussed. Furthermore, we study the dynamics of pairwise quantum correlations measured by the quantum discord.

A High-Sensitivity Refractive-Index Sensor Based on Plasmonic Waveguides Asymmetrically Coupled with a Nanodisk Resonator

A high-sensitivity plasmonic refractive-index sensor based on the asymmetrical coupling of two metal-insulator- metal waveguides with a nanodisk resonator is proposed and simulated in the finite-difference time domain. Both analytic and simulated results show that the resonance wavelengths of the sensor have an approximate linear relationship with the refractive index of the materials which are filled into the slit waveguides and the disk- shaped resonator. The working mechanism of this sensor is exactly due to the linear relationship, based on which tile refractive index of the materials unknown can be obtained from the detection of the resonance wavelength. The measurement sensitivity can reach as high as 6.45 × 10-7, which is nearly five times higher than the results reported in the recent literature [Opt. Commun. 300 （2013） 265]. With an optimum design, the sensing value can be further improved, and it can be widely applied into the biological sensing. Tile sensor working for temperature sensing is also analyzed.

Plasmonic interactions between a perforated gold film and a thin gold film

Based on the finite difference time domain method, we investigated theoretically the optical properties and the plasmonic interactions between a gold film perforated with periodic sub-wavelength holes and a thin gold film. We showed that the plasmon resonant energies and intensities depend strongly on the thicknesses of the two films and the lattice constant. Based on the distributions of normal electric field component Ez, tangential electric field component Ey and total energy, we showed that the optical transmission is due to the collaboration of the localized waveguide resonance, the surface plasmon resonance and the coupling of the fiat-surface plasmon of the two layers.

Enhanced optical transmission through double-layer gold slit arrays

We investigate the relationship between the transmission and the layer distance of double-layer gold slit arrays by using the finite-difference time-domain method. The results show that the transmission properties can be influenced strongly by layer distance. We attribute the two types of resonant modes to surface plasmon resonance and the localised waveguide resonance. We find that the localised waveguide transmission peak redshifts and becomes broader with increasing layer distance D. We also describe and explain the splitting, shift, and degeneration of the surface plasmon resonant transmission peak theoretically. In addition, to clarify the physical mechanism of the transmission behaviours, we analyse the distributions of electric field and total energy for the three transmission peaks with distance D = 45 nm for the double-layer system. Light transporting behaviours are mostly concentrated in the region of the slits as well as the interspaces of the two layers, and for different resonant wavelengths the electric field and energy distributions are different. It is expected that the results obtained here will be helpful for designing subwavelength metallic grating devices.

A proposal for the generation of optical frequency comb in temperature insensitive microcavity

We numerically simulate the generation of an optical frequency comb（OFC） in a microring based on the traditional Si_3N_4 strip waveguide and a temperature compensated slot waveguide.The results show that OFCs are susceptible to temperature with strip waveguide while they can keep stable when temperature changes 10 Kin either low-Q（10-5） or highQ（10-6） microcavity with the well-designed slot waveguide,which has great superiority in practical applications where the temperature drift of the cavity due to the intense pump or surrounding change is unavoidable.

Coupled-resonator-induced transparency in two microspheres as the element of angular velocity sensing

We proposed a two-coupled microsphere resonator structure as the element of angular velocity sensing under the Sagnac effect.We analyzed the theoretical model of the two coupled microspheres,and derived the coupled-resonatorinduced transparency（CRIT） transfer function,the effective phase shift,and the group delay.Experiments were also carried out to demonstrate the CRIT phenomenon in the two-coupled microsphere resonator structure.We calculated that the group index of the two-coupled sphere reaches n_g = 180.46,while the input light at a wavelength of 1550 nm.

Enhanced sum-frequency generation from etchless lithium niobate empowered by dual quasi-bound states in the continuum

The miniaturization of nonlinear light sources is central to the integrated photonic platform,driving a quest for high-efficiency frequency generation and mixing at the nanoscale.In this quest,the high-quality(Q)resonant dielectric nanostructures hold great promise,as they enhance nonlinear effects through the resonantly local electromagnetic fields overlapping the chosen nonlinear materials.Here,we propose a method for the enhanced sum-frequency generation(SFG)from etcheless lithium niobate(LiNbO_(3))by utilizing the dual quasi-bound states in the continuum(quasi-BICs)in a one-dimensional resonant grating waveguide structure.Two high-Q guided mode resonances corresponding to the dual quasi-BICs are respectively excited by two near-infrared input beams,generating a strong visible SFG signal with a remarkably high conversion efficiency of 3.66×10^(-2)(five orders of magnitude higher than that of LiNbO_(3)films of the same thickness)and a small full-width at half-maximum less than 0.2 nm.The SFG efficiency can be tuned via adjusting the grating geometry parameter or choosing the input beam polarization combination.Furthermore,the generated SFG signal can be maintained at a fixed wavelength without the appreciable loss of efficiency by selectively exciting the angle-dependent quasi-BICs,even if the wavelengths of input beams are tuned within a broad spectral range.Our results provide a simple but robust paradigm of high-efficiency frequency conversion on an easy-fabricated platform,which may find applications in nonlinear light sources and quantum photonics.

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.

Photonic phase transition in circuit quantum electrodynamics lattices coupled to superconducting phase qubits

A hybrid quantum architecture was proposed to engineer a localization-delocalization phase transition of light in a two-dimension square lattices of superconducting coplanar waveguide resonators,which are interconnected by current-biased Josephson junction phase qubits.We find that the competition between the on-site repulsion and the nonlocal photonic hopping leads to the Mott insulator-superfluid transition.By using the mean-field approach and the quantum master equation,the phase boundary between these two different phases could be obtained when the dissipative effects of superconducting resonators and phase qubit are considered.The good tunability of the effective on-site repulsion and photon-hopping strengths enable quantum simulation on condensed matter physics and many-body models using such a superconducting resonator lattice system.The experimental feasibility is discussed using the currently available technology in the circuit QED.

Rabi oscillation generation in the microring resonator system with double-series ring resonators

In this paper, a microring resonator(MRR) system using double-series ring resonators is proposed to generate and investigate the Rabi oscillations. The system is made up of silicon-on-insulator and attached to bus waveguide which is used as propagation and oscillation medium. The scattering matrix method is employed to determine the output signal intensity which acts as the input source between two-level Rabi oscillation states, where the increase of Rabi oscillation frequency with time is obtained at the resonant state. The population probability of the excited state is higher and unstable at the optical resonant state due to the nonlinear spontaneous emission process. The enhanced spontaneous emission can be managed by the atom(photon) excitation, which can be useful for atomic related sensors and single-photon source applications.