We investigated surface waves guided by the boundary of a semi-infinite layered metal-dielectric nanostructure cut normally to the layers and a semi-infinite dielectric material. Using the Floquet-Bloch formalism, we found that Dyakonov-like surface waves with hybrid polarization can propagate in dramatically enhanced angular range compared to conventional birefringent materials. Our numerical simulations for an Ag-GaAs stack in contact with glass show a low to moderate influence of losses.
We investigate spatial-dispersion properties of hybrid surface waves propagating in the boundary of a semi-infinite
layered metal-dielectric nanostructure. Electromagnetic fields can be dramatically affected by a nonlocal optical
response of the plasmonic lattice. We demonstrate that the use of the so called effective medium approximation
(EMA) is not justified if the thickness of a metallic layer becomes of the order of the metal skin depth. We
compare the results obtained by means of EMA with computer solutions of Maxwell's equation, including losses
in the metal.
This paper reviews the main properties and applications of nanomembrane-based plasmonic structures, including some results presented here for the first time. Artificial nanomembranes are a novel building block in micro- and nanosystems technologies. They represent quasi-two-dimensional (2D) freestanding structures thinner than 100 nm and with giant aspect ratios that often exceed 1,000,000. They may be fabricated as various quasi-2D metal-dielectric nanocomposites with tailorable properties; they are fully symmetric in an electromagnetic sense and support long-range surface plasmon polaritons. This makes nanomembranes a convenient platform for different plasmonic structures such as subwavelength plasmonic crystals and metamaterials and applications such as plasmon waveguides and ultrasensitive bio/chemical sensors. Among other advantages of nanomembrane plasmonics is the feasibility to fabricate flexible, transferable plasmonic guides applicable to different substrates and dynamically tunable through stretching. There are various approaches to multifunctionalization of nanomembranes for plasmonics, including the use of transparent conductive oxide nanoparticles, but also the incorporation of switchable ion channels. Since the natural counterpart of the artificial nanomembranes are cell membranes, the multifunctionalization of synthetic nanomembranes ensures the introduction of bionic principles into plasmonics, at the same time extending the toolbox of the available nanostructures, materials and functions.
We used an exact analytical approach to investigate the electromagnetic wave propagation across an isotropic metamaterial composite with i. a sinusoidally periodic gradient of the real parts of the effective permittivity and permeability, ii. spatially uniform imaginary parts of the effective permittivity and permeability, and iii. spatially uniform impedance. The real part of the effective refractive index can be positive and negative along the direction of nonhomogeneity. A remarkably simple direct solution for the field distribution was obtained.
We studied the propagation of plasmonic modes along planar multilayer metal-dielectric structures with finite number of bi-layer unit cells. The dispersion relations for various investigated waveguide structures with the multilayer core and symmetric or asymmetric cladding have been analyzed. In the case of symmetric metallic cladding we have found both TE and TM modes within the light cone, while TM modes only exist outside the light cone. Both symmetric and asymmetric dielectric claddings support modes outside the light cone and of TM-polarization only. Formation of photonic bands and gaps, the structure of their edge lines, and the behavior of modes that cross the edge lines has been investigated. In the subwavelength regime, we have found ordinary surface plasmon polariton dispersion in the forbidden gap that is created via coalescence of the two modes that cross the neighboring band-gap edges. One of those modes can exhibit negative group velocity.
We analyzed the intrinsic noise of plasmonic sensors caused by the adsorption-desorption of gaseous analytes on the
sensor surface. We analyzed a general situation when there is a larger number of different species in the environment.
We developed our model and applied it to calculate various analyte mixtures, including some environmental pollutants,
toxic and dangerous substances. The spectral density of mean square refractive index fluctuations follows a dependence
similar to that of generation-recombination noise in photodetectors, flat at lower frequencies and sharply decreasing at
higher. Some of the calculated noise levels are well within the detection range of conventional surface plasmon
resonance sensors. One of the obvious conclusions is that AD noise may be an important limiting factor in monitoring
process kinetics by nanoplasmonic sensors. An AD noise peak is observed in temperature dependence of mean square
refractive index fluctuations, thus sensor operating temperature may be optimized to obtain larger signal to noise ratio. A
significant property of AD noise is its increase with the plasmon sensor area decrease, which means that it will be even
more pronounced in modern nanoplasmonic devices. Our consideration is valid both for conventional surface plasmon
resonance devices and for general nanoplasmonic devices. This research could be of importance in diverse areas such as
environmental sensing, homeland security, forensic applications, life sciences, etc.
KEYWORDS: Sensors, Infrared detectors, Microelectromechanical systems, Infrared sensors, Solids, Thermography, Temperature metrology, Mechanical sensors, Infrared radiation, Signal to noise ratio
The ultimate performance of modern mechanical sensors based on bimaterial cantilevers significantly lags behind the
maximum values as limited by thermal fluctuations. Even more, the signal-to-noise ratios of novel MEMS sensors fall
behind the characteristics of the previous generations of mechanical sensors fabricated by macroscopic production
technologies. In this paper we present for the first time a comparative analysis of the ultimate detection limits of MEMS
sensors based on bimaterial cantilever displacement and detectors based of longitudinal elongation of an equivalent
cantilever. The starting point of our analysis was a definition of the correspondence between the transversal
displacement of a bimaterial cantilever and the longitudinal elongation of the equivalent simple cantilever. These two
structures generally cannot be directly compared, since the bimaterial cantilever displacement depends on 14 variables,
while the longitudinal elongation of the simple cantilever depends on 7 parameters only. However, we show that under
certain conditions a full correspondence can be established between the parameters of these two structures. The
expansion coefficient is used here in its general sense to describe the linear length change as a function of a given
external variable, for instance temperature, analyte concentration, photonic flux, etc.
We considered figures of merit for chemical and biological sensors based on plasmonic structures and utilizing adsorption/desorption mechanism. The operation of these devices in general is limited by noise determining the minimum detectable refractive-index change. We dedicated our work to the intrinsic noise mechanisms connected with the plasmonic process itself. In contrast, most of the available literature is almost exclusively dedicated to the external noise sources (illumination source and photodetector). Reviewing the refractive-index fluctuations caused by thermal, adsorption-desorption and 1/f noise, we observed a striking analogy between the qualitative behavior of noise in (nano)plasmonic devices and that in semiconductor infrared detectors. The power spectral densities for noise in both of these have an almost identical shape; the adsorption-desorption noise corresponds to generation-recombination processes in detectors, while the other two mechanisms exist in the both types of the devices. Thus the large and mature existing apparatus for infrared detector noise analysis may be applied to the plasmonic sensors. Based on the observed analogy, we formulated the noise-equivalent refractive-index and the specific detectivity as the figures of merit to analyze the ultimate performance of plasmon sensors. The approach is valid for conventional surface plasmon resonance sensors, but also for nanoplasmonic and metamaterial-based devices.
We investigate the thermal antenna behavior of emissive/absorptive substrates coated by passive optical multilayer systems
that contain negative refractive index metamaterials (NIM). Spectral and angular distributions of the thermal radiation
emittance for periodic defect-containing multilayer with NIM is addressed. We analyze realistic finite structures and took
into account dispersion and losses in the NIM part. The application of NIM-containing 1D structures offers new degrees
of freedom for the design, thus opening a path to obtain spectrally and spatially selective thermal emitters that could lead
to improvements in the existing systems for thermal radiation control.
We propose a single-chip multicolor photodetector for micrometers range based on a linear IR semiconductor detector array with an integrated 1D photonic bandgap (PBG) filter. A wedge- shaped defect slab is introduced into the filer instead of one of the layers. The bandgap of the photonic crystal coincides with the spectral sensitivity range of the photodetector array, while the built-in defect gives a transmission peak within the same range. The defect thickness varies along the array length and thus shifts the transmission peak wavelength. The optimized photonic bandgap filter including defect is designed using the transfer matrix method. The peak frequency is tuned by choosing the geometrical parameters of the wedge-shaped defect. In our experiments, thin alternating Si and SiO2 films are sputtered onto the array surface, thus forming a 1D PBG structure. The defect is fabricated by gradually changing the middle Si layer thickness over the width of the array. Its wedge-forming is performed by micromachining or, alternatively, by in-situ oblique deposition within the sputtering system and, possibly, subsequent chemomechanical polishing. The characteristics of the finished PBG structure are measured using an IR spectrophotometer. An increase of the number of PBG layers improves the confinement of transmission peaks and thus decreases the crosstalk between the array elements. Although our multicolor detector is designed for the (3-5) micrometers atmospheric window, it can be straightforward redesigned for any other optical range.
In this paper we propose a silicon UV flame detector for combustion systems. In gas burners the relative intensity of flame radiation is dominant in the UV region. In the visible and IR regions the relative intensity of radiation of the incandescent surfaces is several orders of magnitude greater than the gas flame radiation intensity. Therefore it is required that the flame detector has a much greater sensitivity in the UV region. The propose detector is formed on n-type silicon on isolator wafer. In order to suppress sensitivity in the visible and the IR regions, the absorption region of the detector is greatly reduced, and a UV filter utilizing photonic crystal is designed. The p-n junctions are formed by very shallow diffusion of impurities. The contacts are made after the deposition of a thin oxide layer. The UV filter is then sputtered on the detector surface. The filter consists of a thin silver film, and a 1D photonic crystal made of twelve pairs of NaF/Y2O3 layers. The photonic band gaps of the crystal should suppress the propagation of the light with wavelengths greater than 0.35 micrometers . For the detector active area of 5 mm2, the thickness of the silver layer of 0.13 micrometers and a dark current of 1 nA, the noise equivalent power at 0.32 micrometers is 4.23 10-13 W/Hz1/2. The calculated flame signal to total signal ratio is 0.52.
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