Optical Resonator Structures Research Articles

Polarization-selective uncooled infrared sensor with asymmetric two-dimensional plasmonic absorber

A polarization-selective uncooled infrared (IR) sensor was developed based on an asymmetric two-dimensional plasmonic absorber (2-D PLA). The 2-D PLA has an Au-based 2-D periodic dimple structure, where photons can be manipulated by spoof surface plasmon polaritons. Asymmetry was introduced into the 2-D PLA to realize a polarization selective function. Numerical investigations demonstrate that a 2-D PLA with ellipsoidal dimples (2-D PLA-E) gives rise to polarization-dependent absorption properties due to the asymmetric dimple shape. A microelectromechanical systems-based uncooled IR sensor was fabricated using a 2-D PLA-E through complementary metal oxide semiconductor (CMOS) and micromachining techniques. The 2-D PLA-E was formed with an Au layer sputtered on a SiO2 layer with ellipsoidal holes. The dependence of the responsivity on the polarization indicates that the responsivity is selectively enhanced according to the polarization and the asymmetry of the ellipsoids. The results provide direct evidence that a polarization-selective uncooled IR sensor can be realized simply by the introduction of asymmetry to the surface structure of the 2-D PLA, without the need for a polarizer or optical resonant structures. In addition, a pixel array where each pixel has a different detection polarization could be developed for polarimetric imaging using standard CMOS and micromachining techniques.

Enhanced Optical Forces by Hybrid Long-Range Plasmonic Waveguides

Compared with optical resonant structures, current plasmonic waveguides have the advantage of enhancing optical forces in a broad range of wavelengths, but the enhancement can only be maintained for several dozens of microns at 1.55 μm. Here, a hybrid long-range plasmonic waveguide, consisting of two identical dielectric nanowires symmetrically placed on each side of a thin metal film, is proposed for optical forces. Strong optical coupling between the dielectric waveguide mode and long-range plasmonic mode leads to enhanced optical forces on the dielectric nanowire at low input optical power due to the deep subwavelength optical energy confinement. The enhancement can be maintained for distances of 1~2 orders of magnitude larger than that of previous plasmonic waveguides. The deep subwavelength optical confinement as well as enhanced field gradient also allows efficient trapping of single nanoscale particle, while the smaller propagation loss ensures a much larger trapping region at the same input optical power. The present results enable the potential applications of precisely controlling the positions of dielectric nanowires as well as manipulating a single nanoparticle such as a biomolecule and one quantum dot.

Multiphysics simulation for the optimization of optical nanoantennas working as distributed bolometers in the infrared

The electric currents induced by infrared radiation incident on optical antennas and resonant structures increase their temperature through Joule heating as well as change their elec- tric resistance through the bolometric effect. As the thermo-electric mechanism exists throughout a distributed bolometer, a multiphysics approach was adopted to analyze thermal, electrical, and electromagnetic effects in a dipole antenna functioning as a resonant distributed bolometer. The finite element method was used for electromagnetic and thermal considerations. The results showed that bolometric performance depends on the choice of materials, the geometry of the resonant structure, the thickness of an insulating layer, and the characteristics of a bias circuit. Materials with large skin depth and small thermal conductivity are desirable. The thickness of the SiO2 insulating layer should not exceed 1.2 μm, and a current source for the bias circuit enhances performance. An optimized device designed with the previously stated design rules provides a response increase of two orders of magnitude compared to previously reported devices using the same dipole geometry. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI. (DOI: 10.1117/1.JNP.7.073093)

Antenna array connections for efficient performance of distributed microbolometers in the IR

Optical antennas and resonant structures have been extensively investigated due to its potential for electromagnetic detection and energy harvesting applications. However their integration into large arrays and the role of connection lines between individual antennas has drawn little attention. This is necessary if we want to exploit its potential constructively and to enable economical large-scale fabrication. In this contribution we point out some features that an efficient antenna array should address. Experimental measurements on aluminum microbolometers are compared to electromagnetic simulations, it is shown that the finite size of a real array and the interconnection lines interact and affect the global performance.

Phase sensitivity of rotation sensing in coupled resonator waveguides

The dispersion of optical resonator structures can be used to increase the sensitivity of rotation sensing. Using coupled resonator waveguides can realize strong dispersion. In this paper, the transfer matrix method is used to analyze the phase sensitivity of rotation sensing in coupled resonator waveguides, and investigate the influences of resonator arrangement and waveguide parameters on the phase sensitivity. Results show that phase curves and phase sensitivity are dependent on resonator arrangement. The number of resonator and coupling coefficients can influence not only the number and bandwidths of peaks for phase sensitivity of rotation sensing but also the variation of phase sensitivity. However, loss can reduce the phase sensitivity. The results can be used to design the phase sensitivity of coupled resonator waveguides using the resonator arrangement and waveguide parameters, and are beneficial for applications of coupled resonator waveguides in rotation sensing.

Distributed bolometric effect in optical antennas and resonant structures

Universidad Autonoma de San Luis Potosi, Coordinacion para la Innovacion y,Aplicacion de la Ciencia y la Tecnologia, San Luis Potosi, Mexico 78210Abstract. Nanoantennas coupled to nanobolometers have been used as detectors of opticalradiation. They are typically manufactured using two different materials: one for the nano-antenna and another for the nanobolometer. However, those metals used to fabricate nano-antennas also present a bolometric response. Therefore, antenna-coupled detectors using thebolometriceffectdistributedalongthedevicewerecomparedwiththeresultspreviouslyreportedfor nanobolometers coupled with dipole antennas in the infrared regime. We modeled therelevant physical mechanisms and also simulated the simple case of a dipole antenna usinga multi-physics computational tool. The simulation results were compared with experimentalresults. The advantage in performance when using a dedicated material to enhance the bolo-metric effect, is balanced with the easiness of the fabrication of resonant structures involvingonly one material where the bolometric effect is distributed along the device.

Surface morphology of Si layers grown on SiO2

Layers of Si crystals grown on SiO2 surfaces are investigated by scanning tunneling and atomic force microscopy. The deposition of an array of Ge islands on SiO2 surfaces prior to Si growth is found to significantly decrease the concentration of Si crystals and make them more uniform in size. The Si crystals grown at temperatures from 430 to 550°C have a rounded shape of the growing surface. This indicates the presence of a high concentration of threading dislocations and that is confirmed by the observation of dislocation-related photoluminescence in the 1.5μm region. Layers of Si crystals grown on SiO2 are of interest for the fabrication of optical resonant structures for the near-infrared region.

3-dimensional eigenmodal analysis of plasmonic nanostructures

We introduce a 3-dimensional electromagnetic eigenmodal algorithm for the theoretical analysis of resonating nano-optical structures. The method, a variant of the Jacobi-Davidson algorithm, solves the electric field vector wave, or curl-curl, equation for the electromagnetic eigenmodes of resonant optical structures with a finite element method. In particular, the method includes transparent boundary conditions that enable the analysis of resonating structures in unbounded space. We demonstrate the performance of the method. First, we calculate the modes of several dielectric resonator antennas and compare them to theoretically determined results. Second, we calculate the modes of a nano-cuboid and compare them to theoretically determined results. Third, we numerically analyze spherical nanoparticles and compare the result to the theoretical Mie solution. Fourth, we analyze optical dipole antenna configurations in order to assess the method's capability for solving technologically relevant problems.

Modeling and analysis of quadruple optical ring resonator performance as optical filter using Vernier principle

Vernier principle based modeling and analysis of an optical ring resonator structure that includes four asymmetric rings are introduced in this paper to obtain very wide free spectral range (FSR). Delay line signal processing approach in Z-domain modeling is used for analysis of waveguide based novel quadruple optical ring resonator (QORR). Two QORR architectures made of SOI and SiN waveguides have been compared, which produce FSR of 343.4 THz 264.6 THz respectively. Apart from obtaining wider FSR and adequate suppression of spurious interstitial modes close to -30 dB, this work presents group delay and dispersion characteristics for QORR made of materials with different effective refractive indices.

Whispering gallery mode enhanced luminescence from an individual ZnO micro- and nanoscaled optical resonator

A whispering gallery mode optical resonator has been achieved using individual ZnO micro- and nanocolumns. Monochromatic cathodoluminescence images of the ZnO micro- and nanocolumns show that enhanced luminescence intensity is located across the profile of the micro- and nanocolumns, and is mainly attributed to the whispering gallery mode (WGM) enhanced emission. The individual hexagonal ZnO micro- and nanocolumns are regarded as an optical resonator structure. Theoretical calculations and computer simulations based on the finite-difference time-domain suggest that the WGMs are generated in the ZnO micro- and nanocolumns, and these results agree closely with the experimental results.

Pure optical photoacoustic microscopy

The concept of pure optical photoacoustic microscopy(POPAM) was proposed based on optical rastering of a focused excitation beam and optically sensing the photoacoustic signal using a microring resonator fabricated by a nanoimprinting technique. After the refinements of the microring’s working wavelength and in the resonator structure and mold fabrication, an ultrahigh Q factor of 3.0×105 was achieved which provided high sensitivity with a noise equivalent detectable pressure(NEDP) value of 29Pa. This NEDP is much lower than the hundreds of Pascals achieved with existing optical resonant structures such as etalons, fiber gratings and dielectric multilayer interference filters available for acoustic measurement. The featured high sensitivity allowed the microring resonator to detect the weak photoacoustic signals from micro- or submicroscale objects. The inherent superbroad bandwidth of the optical microring resonator combined with an optically focused scanning beam provided POPAM with high resolution in the axial as well as both lateral directions while the axial resolution of conventional photoacoustic microscopy (PAM) suffers from the limited bandwidth of PZT detectors. Furthermore, the broadband microring resonator showed similar sensitivity to that of our most sensitive PZT detector. The current POPAM system provides a lateral resolution of 5 μm and an axial resolution of 8 μm, comparable to that achieved by optical microscopy while presenting the unique contrast of optical absorption and functional information complementing other optical modalities. The 3D structure of microvasculature, including capillary networks, and even individual red blood cells have been discerned successfully in the proof-of-concept experiments on mouse bladders ex vivo and mouse ears in vivo. The potential of approximately GHz bandwidth of the microring resonator also might allow much higher resolution than shown here in microscopy of optical absorption and acoustic propagation properties at depths in unfrozen tissue specimens or thicker tissue sections, which is not now imageable with current optical or acoustic microscopes of comparable resolution.

Optical properties of II-VI colloidal quantum dot doped porous silicon microcavities

In this paper we report on the light emitting properties of mesoporous silicon vertical-cavity optical resonators with II-VI colloidal quantum dots selectively deposited in the cavity layer. Optical resonator structures exhibit reflectivity stop bands of several hundred nanometres and resonant modes with line-widths less than 3.5 nm. The observed modification of spectral and spatial emission properties of the quantum dots and tenfold enhancement at the resonance wavelength is consistent with cavity enhanced spontaneous emission. Using this hybrid fabrication approach we show that narrow band light emitting structures may be fabricated over a broad spectral region in the visible and near-infrared.

Fiber microcoil optical gyroscope

We study the effect of rotation on the propagation of electromagnetic waves in optical microcoil resonator structures. It is shown that the combination of slow-light and conventional propagation mechanisms leads to an enhancement of orders of magnitudes of the Sagnac phase shift and can be used for the realization of highly compact optical rotation sensors and gyroscopes.

Rayleigh superradiance and dynamic Bragg gratings in an end-pumped Bose-Einstein condensate

We study superradiant Rayleigh scattering from a Bose-Einstein condensate (BEC) in a parameter regime where pump depletion and the exchange of photons between the end-fire modes are important. Through experiments and simulations, we show that collective atom-light coupling leads to the self-organized formation of dynamic Bragg gratings within the sample. These gratings lead to an efficient backscattering of pump photons and optical resonator structures within the BEC.

Chromophore-Containing Polymers for Trace Explosive Sensors

The optical properties such as index of refraction and optical absorption of many chromophore-containing polymers are sensitive to the physical and chemical environment to which the polymers are exposed. To demonstrate such applications, chemical sensors to detect trace explosives are presented. The sensors use polymers that contain chromophores whose molecular structure consists of an electron donor and an electron acceptor connected by a charge-transfer bridge of conjugated π-orbital electrons. The polymers used for the trace explosives sensor are not poled, and the chromophores are randomly oriented in the polymer host. Waveguide microring resonator and fiber Bragg grating structures were used in these sensors to enhance the detection sensitivity. Because chromophores undergo photodecomposition under intense ultraviolet radiation, chromophore-containing polymers can be patterned with ultraviolet light to create optical resonator structures in a single photobleaching step. The chemical sensor has shown part-per-billion level sensitivity and good specificity to the vapor, in air, of an explosive simulant 2,4-dinitrotoluene.

Photonic crystals: A platform for label-free and enhanced fluorescence biomolecular and cellular assays

Abstract Photonic crystal surfaces represent a class of resonant optical structures that are capable of supporting high intensity electromagnetic standing waves with near-field and far-field properties that can be exploited for high sensitivity detection of biomolecules and cells. While modulation of the resonant wavelength of a photonic crystal by the dielectric permittivity of adsorbed biomaterials enables label-free detection, the resonance can also be tuned to coincide with the excitation wavelength of common fluorescent tags - including organic molecules and semiconductor quantum dots. Photonic crystals are also capable of efficiently channeling fluorescent emission into a preferred direction for enhanced extraction efficiency. Photonic crystals can be designed to support multiple resonant modes that can perform label free detection, enhanced fluorescence excitation, and enhanced fluorescence extraction simultaneously on the same device. Because photonic crystal surfaces may be inexpensively produced over large surface areas by nanoreplica molding processes, they can be incorporated into disposable labware for applications such as pharmaceutical high throughput screening. In this talk, the optical properties of surface photonic crystals will be reviewed and several applications will be described, including results from screening a 200,000-member chemical compound library for inhibitors of protein-DNA interactions, gene expression microarrays, and high sensitivity of protein biomarkers.

Use of AlInN layers in optical monitoring of growth of GaN-based structures on free-standing GaN substrates

When lattice matched to GaN, the AlInN ternary alloy has a refractive index ∼7% lower than that of GaN. This characteristic can be exploited to perform in situ reflectometry during epitaxial growth of GaN-based multilayer structures on free-standing GaN substrates, by insertion of a suitable Al0.82In0.18N layer. The real-time information on growth rates and cumulative layer thicknesses thus obtainable is particularly valuable in the growth of optical resonant cavity structures. We illustrate this capability with reference to the growth of InGaN∕GaN multiple quantum-well structures, including a doubly periodic structure with relatively thick GaN spacer layers between groups of wells. Al0.82In0.18N insertion layers can also assist in the fabrication of resonant cavity structures in postgrowth processing, for example, acting as sacrificial layers in a lift-off process exploiting etch selectivity between Al0.82In0.18N and GaN.

Engineering the nonlinear phase shift with multistage autoregressive moving-average optical filters

We propose and demonstrate the application of concepts from digital filter design in order to optimize artificial optical resonant structures to produce a nearly ideal nonlinear phase shift response. Multistage autoregressive moving average (ARMA) optical filters (ring-resonator-based Mach-Zehnder interferometer lattices) are designed and studied. The filter group delay is used as a measure instead of finesse or quality factor to study the nonlinear sensitivity for multiple resonances. The nonlinearity of a four-stage ARMA filter is 17 times higher than that of the intrinsic material of the same group delay. We demonstrate that the nonlinear sensitivity can be increased within constant bandwidth by allocating more in-band phase or by using higher-order filter structures and that the nonlinear sensitivity enhancement improves with increasing group delay. We also investigate methods to precompensate the nonlinear response to reduce the occurrence of optical bistabilities. The effect of optical loss, including linear absorption and two-photon absorption, is discussed in postanalysis. In addition, we discuss how the improvement in nonlinear response scales with respect to various filter parameters.

Optical biosensor and scanning probe microscopy studies of cytochrome P450 interactions with redox partners and phospholipid layers

This chapter focuses on nanotechnological methods, such as the optical biosensor technique and scanning probe microscopy (SPM) that enable the effective analysis of the structure-function properties of cytochromes P450 and their redox partners. The combination of the two techniques makes it possible to reveal protein-protein complexes, to measure the kinetic parameters of their formation and decay, and to visualize their spatial structures. In the optical resonant mirror biosensor technique, the nanolayer of protein or lipid under study is deposited onto the surface of the optical resonant structure (prisma-waveguide) at the same time, functions as the measuring cuvette bottom. But the SPM method enables the visualization of protein molecules and their complexes by monitoring (1) an interaction force between the probe tip of the microscope and the molecular surface as the probe tip is scanned across the support with immobilized molecules (atomic force microscopy, AFM) and (2) the tunneling current between the probe tip and the adsorbed molecule (scanning tunneling microscopy, STM).

Growth dynamics of noise-sustained structures in nonlinear optical resonators

The existence of macroscopic noise-sustained structures in nonlinear optics is theoretically predicted and numerically observed, in the regime of convective instability. The advection-like term, necessary to turn the instability to convective for the parameter region where advection overwhelms the growth, can stem from pump beam tilting or birefringence induced walk-off. The growth dynamics of both noise-sustained and deterministic patterns is exemplified by means of movies. This allows to observe the process of formation of these structures and to confirm the analytical predictions. The amplification of quantum noise by several orders of magnitude is predicted. The qualitative analysis of the near- and far-field is given. It suffices to distinguish noise-sustained from deterministic structures; quantitative informations can be obtained in terms of the statistical properties of the spectra.