Resonant Transmission Of Light Research Articles

(Invited) Enhancement of Light Emission in Luminescent Structures within Nano-Arrays

Nanostructures can dramatically alter the light emission in luminescent structures by strongly altering the photonic densities of states at the location of the luminescent emitter. We describe and develop two complementary platforms that tailor luminescent emission through i) quantum dots in nanocup arrays and ii) corrugated nanoarrays in organic light-emitting structures.We fabricated nanocup arrays with pitch ~750 nm by replica molding in polymer molds. A thin non-conformal gold film was sputter-deposited on the polymer film with angle-directed deposition. The gold film was continuous with a variation of spatial thickness, with the film being optically thin at the bottom of the nanocup [1]. Optical measurements revealed an extraordinary optical transmission (EOT) peak at a wavelength slightly smaller than the pitch. Although no holes were etched in the film the optically thin metal at the bottom allowed resonant light transmission. This is a simple pathway to fabricate large area (>cm2) nano-arrays with EOT without expensive lithography which limits such nano-arrays to very small areas. Quantum dots were embedded in these nanoarrays and revealed a marked reduction of photo-luminescence lifetime by ~4 compared to the control samples, when the emitting wavelength was tuned to the optical resonance of the nanoarray. Scattering matrix and FDTD simulations both show an enhancement of the field by a factor >100. The optically enhanced field in nanocups enhanced the spontaneous emission of embedded quantum dots. The simulated Purcell factor is enhanced by >80 at the bottom of the nanocup, and by a factor of 3-15 averaged over the nanocup height, in agreement with measured photoluminescence lifetimes that decreased by a factor of ~4 for a quantum dot ensemble.We also study and simulate light emission from organic light emitting diodes (OLEDs) -where only 20% of the light is emitted to air and remainder (~80%) is trapped as internally waveguided modes and surface plasmon modes at the cathode-organic interface. We develop rigorous scattering matrix simulations [2] to demonstrate the emission of light can be increased by enhancement factors >3, when the OLEDs are integrated with periodic nanoarrays. The emissive region conformally follows the periodicity of the nano-array. The periodic nanostructures diffract trapped waveguided modes and plasmonic modes to the air cone and are a pathway to achieving light outcoupling efficiencies exceeding 60%. The predicted dependence of the outcoupled light emission on the pitch and height of the nano-arrays will be presented. Acknowledgements: Partially supported by NSF grants CMMI-1265844 and CMMI-170648.

Thin-Film Frustrated Total Internal Reflection Filter with Plasmonic Nanoparticle Inclusions in the Layers

The influence of plasmonic nanoparticles embedded in the central and side layers of the frustrated total internal reflection filter on the resonant transmission of light is analyzed. It is shown that the frequency dispersion causes the splitting of the filter bandwidth and the angular splitting of the incident beam into several output beams.

Resonant optical transmission through the sub-wavelength air-hole arrays in a gold thin film for sensing applications

We have investigated numerically the optical spectral properties of resonant transmission of light through sub-wavelength air-holes in a gold thin film by using the finite element method. The enhanced transmission can be comprehended in the light of interfering surface-wave-like modes propagating in the sub-wavelength air-holes. The effects of geometrical and material properties of the sub-wavelength air-holes in the transmission spectrum were characterized. The proposed structure can be operated as refractive index (RI) sensor with a sensitivity of 524.8 nm/RIU (RIU = refractive index unit) ranging from the visible to the near-infrared. This feature provides a remarkable scheme of nanoscale sensing for the RI variations of the environmental media such as applications in liquid and gas sensing.

Optical-bistability-enabled control of resonant light transmission for an atom-cavity system

The control of light transmission through a Fabry-Perot cavity containing atoms is theoretically investigated, when the cavity mode beam and an intersecting control beam are both close to specific atomic resonances. A four-level atomic system is considered and its interaction with the cavity mode is studied by solving for the time dependent cavity field and atomic state populations. The conditions for optical bistability of the atom-cavity system are obtained in steady state limit. For an ensemble of atoms in the cavity mode, the response of the intra-cavity light intensity to the intersecting resonant beam is understood for stationary atoms (closed system) and non-static atoms (open system). The open system is modelled by adjusting the atomic state populations to represent the exchange of atoms in the cavity mode, with the thermal environment. The solutions to the model are used to qualitatively explain the observed steady state and transient behaviour of the light in the cavity mode, in Sharma et. al. [1]. The control behaviour with three- and two-level atomic systems is also studied, and the rich physics arising out of these systems, for closed and open atomic systems is discussed.

Resonant transmission of light in chains of high-index dielectric particles

We study numerically, analytically and experimentally the resonant transmission of light in a waveguide formed by a periodic array of high-index dielectric nanoparticles with a side-coupled resonator. We demonstrate that a resonator with high enough Q-factor provides the conditions for the Fano-type interference allowing to control the resonant transmission of light. We suggest a practical realization of this resonant effect based on the quadrupole resonance of a dielectric particle and demonstrate it experimentally for ceramic spheres at microwaves.

Diffusive Propagation of Exciton-Polaritons through Thin Crystal Slabs.

If light beam propagates through matter containing point impurity centers, the amount of energy absorbed by the media is expected to be either independent of the impurity concentration N or proportional to N, corresponding to the intrinsic absorption or impurity absorption, respectively. Comparative studies of the resonant transmission of light in the vicinity of exciton resonances measured for 15 few-micron GaAs crystal slabs with different values of N, reveal a surprising tendency. While N spans almost five decimal orders of magnitude, the normalized spectrally-integrated absorption of light scales with the impurity concentration as N1/6. We show analytically that this dependence is a signature of the diffusive mechanism of propagation of exciton-polaritons in a semiconductor.

Optical control of resonant light transmission for an atom-cavity system

We demonstrate the manipulation of transmitted light through an optical Fabry-Perot cavity, built around a spectroscopy cell containing enriched rubidium vapor. Light resonant with the $^{87}$Rb D$_{2}$ ($F=2/F=1$) $\leftrightarrow F'$ manifold, is controlled by transverse intersection of the cavity mode by another resonant light beam. The cavity transmission can be suppressed or enhanced depending on the coupling of atomic states due to the intersecting beams. The extreme manifestation of cavity mode control is the precipitious destruction (negative logic switching) or buildup (positive logic switching) of the transmitted light intensity, on intersection of the transverse control beam with the cavity mode. Both the steady state and transient response are experimentally investigated. The mechanism behind the change in cavity transmission is discussed in brief.

Experimental Demonstration of Reduced Light Absorption by Intracavity Metallic Layers in Tamm Plasmon-based Microcavity

We demonstrate experimentally a microcavity based on SiO2/TiO2 with two gold layers directly attached to the central base of the microcavity. The design of optical modes based on the peculiarities of Tamm plasmons provides reduced absorption due to the fixing of the node of the electric field of optical mode to metallic layers. Experimentally measured reflection and transmission spectra exhibits three features, corresponding to three hybrid modes of the microcavity. The widths of spectral features confirm that absorption of light by metallic layers is vanishing for optimized mode. The latter is confirmed by resonant transmission of light through the structure. In case of the laser structure, two intracavity metallic layers could serve as contacts for electrical pumping.

Resonant transmission of light through ZnO nanowaveguides in a silver film

Abstract

Enhancement of Faraday effect in one-dimensional magneto-optical photonic crystal including a magnetic layer with wavelength dependent off-diagonal elements of dielectric constant tensor

Optical and magneto-optical properties of one-dimensional magneto-optical photonic crystal (1-D MPC) prepared by the sol–gel dip-coating method, including a magnetic defect layer composed of mixture of CoFe2O4 and SiO2, are investigated from both the experimental and theoretical standpoints. The resonant transmission of light was observed around 570nm in the photonic band gap. The Faraday rotation angle θF showed two maxima at 490 and 640nm, and the wavelength dependence of θF above 760nm was similar to that of the CoFe2O4+SiO2 single-layer film. The two maxima of θF are attributed to the enhanced Faraday rotation of nonmagnetic TiO2 layers in the cavity structure and that in magnetic CoFe2O4+SiO2 layer through the light localization in MPC. The maximum value of θF due to the magnetic CoFe2O4+SiO2 layer in the MPC was 22-times larger than that in the single-layer film. The simulation study of MPC with CoFe2O4+SiO2 magnetic defect layer, based on the matrix approach method, showed that the resonant light transmission was accompanied by the localization of electric field, and large enhancement of θF appeared at different wavelengths so as to agree with the experimental features. This can be explained in terms of the wavelength dependent off-diagonal components of the dielectric constant tensor in addition to the large extinction coefficient in the CoFe2O4+SiO2 magnetic defect layer.

Grating coupler integrated photodiodes for plasmon resonance based sensing

In this work, we demonstrate an integrated sensor combining a grating-coupled plasmon resonance surface with a planar photodiode. Plasmon enhanced transmission is employed as a sensitive refractive index (RI) sensing mechanism. Enhanced transmission of light is monitored via the integrated photodiode by tuning the angle of incidence of a collimated beam near the sharp plasmon resonance condition. Slight changes of the effective refractive index (RI) shift the resonance angle, resulting in a change in the photocurrent. Owing to the planar sensing mechanism, the design permits a high areal density of sensing spots. In the design, absence of holes that facilitate resonant transmission of light, allows an easy-to-implement fabrication procedure and relative insensitivity to fabrication errors. Theoretical and experimental results agree well. An equivalent long-term RI noise of 6.3 × 10(-6) RIU/√Hz is obtained by using an 8 mW He-Ne laser, compared to a shot-noise limited theoretical sensitivity of 5.61 × 10(-9) RIU/√Hz. The device features full benefits of grating-coupled plasmon resonance, such as enhancement of sensitivity for non-zero azimuthal angle of incidence. Further sensitivity enhancement using balanced detection and optimal plasmon coupling conditions are discussed.

Polariton-polariton interaction constants in microcavities

Resonant transmission of light through a microcavity in the strong coupling regime is used to estimate the strength of the interaction between polaritons with parallel $({\ensuremath{\alpha}}_{1})$ or antiparallel $({\ensuremath{\alpha}}_{2})$ spins. The ratio ${\ensuremath{\alpha}}_{2}/{\ensuremath{\alpha}}_{1}$ is found to be strongly dependent on the detuning between exciton and photon modes. From negative to zero detuning it changes from about 0 to less than $\ensuremath{-}1$. Our observations indicate that at certain conditions the polaritons might rather condense in the real space than form a Bose-Einstein condensate. We analyze theoretically different mechanisms of polariton-polariton interaction including the mean-field electrostatic interaction, the direct exchange interaction, the Van-der-Waals interaction and the indirect exchange interaction via dark exciton and biexciton states.

Fiber-coupled semiconductor waveguides as an efficient optical interface to a single quantum dipole

We theoretically investigate the interaction of a single quantum dipole with the modes of a fiber-coupled semiconductor waveguide. Through a combination of tight modal confinement and phase-matched evanescent coupling, we predict that approximately 70% of the dipole's emission can be collected into a single-mode optical fiber. We further show that the dipole strongly modifies resonant light transmission through the system, with a change of over 1 order of magnitude for an appropriate choice of fiber-waveguide coupler geometry.

Resonant transmission of light through surface plasmon structures

Plasmonics enables the realization of new optical components. Here, we report yet another plasmonic component based on a pair of surfaces displaying grating coupled plasmon enhanced transmission. We observe high quality factor transmission peaks as high as 100 through our plasmonic filter based on gratings obtained directly from optical storage disks. Wavelength and polarization dependent transmission is also demonstrated in the visible and infrared portions of the spectrum. The resonance wavelength of this filter can be tuned by simply changing the angle of incidence. Numerical calculations agree well with measurements. Our work can open up directions toward disposable optical components such as filters and polarizers.

Resonance tunnelling of photons through multiple-well structures in two- dimensional photonic crystals with various well-media

Resonant transmission of light through multiple well structures is investigated by the R-matrix algorithm. The structure consists of the two-dimensional photonic crystal barrier series with homogeneous transparent media in between. We find that the transmission probability displays a typical pattern in the propagation forbidden band, which shows n-fold peak splitting in an n-well system. A higher permittivity value of the transparent well-medium results in denser resonance peaks with frequencies shifted towards the red and furthermore the number of peaks can be greatly suppressed when the normal well-medium is replaced by left-handed materials. We observe a new distortion of resonance-peak splitting with alternately placing the normal and the left-handed media in two wells completely different from the distortion induced by the asymmetry of well-width with the same kind of well-media in both wells. Based on analytical calculation of the transmission probability in one-dimensional photonic-crystal wells the new observation is understood as a result of destructive interference in the left-handed and normal well-media. Since the numerical calculations are carried out for the two-dimensional crystal system with practical photonic-crystal parameters, it is expected that the predictions can be verified by experiments.

Coupled-resonator-induced reflection in photonic-crystal waveguide structures

We study the resonant transmission of light in a coupled-resonator optical waveguide interacting with two nearly identical side cavities. We reveal and describe a novel effect of the coupled-resonator-induced reflection (CRIR) characterized by a very high and easily tunable quality factor of the reflection line, for the case of the inter-site coupling between the cavities and the waveguide. This effect differs sharply from the coupled-resonator-induced transparency (CRIT)--an all-optical analogue of the electromagnetically-induced transparency--which has recently been studied theoretically and experimentally for the structures based on micro-ring resonators and photonic crystal cavities. Both CRIR and CRIT effects have the same physical origin which can be attributed to the Fano-Feshbach resonances in the systems exhibiting more than one resonance. We discuss the applicability of the novel CRIR effect to the control of the slow-light propagation and low-threshold all-optical switching.

Semi-analytical method for light interaction with 1D-periodic nanoplasmonic structures

We present a detailed description of a computationally efficient, semi-analytical method (SAM) to calculate the electomagnetic field distribution in a 1D-periodic, subwavelength-structured metal film placed between dielectric substrates. The method is roughly three orders of magnitude faster than the finite-element method (FEM). SAM is used to study the resonant transmission of light through nanoplasmonic structures, and to analyze the role of fundamental and higher-order Bloch surface plasmons in transmission enhancement. The method is also suitable for solving the eigenvalue problem and finding modes of the structure. Results obtained with SAM, FEM, and the finite-difference time-domain method show very good agreement for various parameters of the structure.

Resonant transmission of light through finite arrays of slits

Finite-size effects associated with the phenomenon of extraordinary optical transmission are theoretically addressed. We analyze the $N$ dependence of the transmission resonances appearing in one-dimensional periodic arrays of $N$ slits. For the transmission resonances located close to the period of the array, it is found that the evolution is controlled by the width of the slits. This parameter completely governs the electromagnetic coupling between slits that, in turn, is the key actor in the formation of the collective surface electromagnetic mode responsible for the enhanced transmission. On the contrary, the transmission process associated with the excitation of waveguide resonances inside the slits is almost independent of the number of slits perforated on the metallic film.

Low-threshold bistability of slow light in photonic-crystal waveguides

We analyze the resonant transmission of light through a photonic-crystal waveguide side coupled to a Kerr nonlinear cavity, and demonstrate how to design the structure geometry for achieving bistability and all-optical switching at ultralow powers in the slow-light regime. We show that the resonance quality factor in such structures scales inversely proportional to the group velocity of light at the resonant frequency and thus grows indefinitely in the slow-light regime. Accordingly, the power threshold required for all-optical switching in such structures scales as a square of the group velocity, rapidly vanishing in the slow-light regime.

Resonant light transmission through a nanohole in a metal film

The maximum wavelength at which light can propagate through a rectangular hole in a metal is dramatically increased due to the existence of surface-plasmon (SP) waves along the edges of the hole. For example, a 15-nm-wide hole in silver can have a cutoff wavelength more than double that of a perfect electric conductor. Furthermore, we show that there is a Fabry-Pe/spl acute/rot (FP) resonance for light transmission close to the cutoff wavelength, which gives a peak in the transmission. Impedance mismatch between the hole and free space provides the reflection required for the FP resonance. Due to the SPs in the hole, the reflection coefficient is typically larger in amplitude and has a smaller phase-shift than what has previously been observed in microwave systems. Our findings using analytic theory, finite-difference mode calculations, and finite-difference time-domain simulations agree well with recent experiments on the transmission through subwavelength rectangular holes. The transmission resonances found in a single subwavelength hole are of interest to nanolithography, biosensors, subwavelength microscopy, and photonic integrated circuits.