Phonon Polariton Modes Research Articles

Surface phonon-polariton enhanced optical forces in silicon carbide nanostructures

The enhanced optical forces induced by surface phonon-polariton (SPhP) modes are investigated in different silicon carbide (SiC) nanostructures. Specifically, we calculate optical forces using the Maxwell stress tensor for three different geometries: spherical particles, slab waveguides, and rectangular waveguides. We show that SPhP modes in SiC can produce very large forces, more than one order of magnitude larger than the surface plasmon-polariton (SPP) forces in analogous metal nanostructures. The material and geometric basis for these large optical forces are examined in terms of dispersive permittivity, separation distance, and operating wavelength.

Near-forward Raman scattering by bulk and surface phonon-polaritons in the model percolation-type ZnBeSe alloy

We study the bulk and surface phonon-polaritons of the Zn0.67Be0.33Se zincblende alloy by near-forward Raman scattering. The short (Be-Se) bond exhibits a distinct percolation doublet in the conventional backscattering Raman spectra, corresponding to a three-mode behavior in total [1×(Zn-Se), 2×(Be-Se)] for Zn0.67Be0.33Se. This offers an opportunity to achieve a refined understanding of the phonon-polariton modes of a zincblende alloy beyond the current two-mode approximation, corresponding to a [1×(Zn-Se), 1×(Be-Se)] description in the present case. The discussion is supported by contour modeling of the Raman signals of the multi-mode bulk and surface phonon-polaritons within the formalism of the linear dielectric response.

Low-Loss, Extreme Subdiffraction Photon Confinement via Silicon Carbide Localized Surface Phonon Polariton Resonators

Plasmonics provides great promise for nanophotonic applications. However, the high optical losses inherent in metal-based plasmonic systems have limited progress. Thus, it is critical to identify alternative low-loss materials. One alternative is polar dielectrics that support surface phonon polariton (SPhP) modes, where the confinement of infrared light is aided by optical phonons. Using fabricated 6H-silicon carbide nanopillar antenna arrays, we report on the observation of subdiffraction, localized SPhP resonances. They exhibit a dipolar resonance transverse to the nanopillar axis and a monopolar resonance associated with the longitudinal axis dependent upon the SiC substrate. Both exhibit exceptionally narrow linewidths (7-24 cm(-1)), with quality factors of 40-135, which exceed the theoretical limit of plasmonic systems, with extreme subwavelength confinement of (λ(res)3/V(eff))1/3 = 50-200. Under certain conditions, the modes are Raman-active, enabling their study in the visible spectral range. These observations promise to reinvigorate research in SPhP phenomena and their use for nanophotonic applications.

Super-Planckian near-field thermal emission with phonon-polaritonic hyperbolic metamaterials

We study super-Planckian near-field heat exchanges for multilayer hyperbolic metamaterials using exact scattering-matrix (S-matrix) calculations. We investigate heat exchanges between two multilayer hyperbolic metamaterial structures. We show that the super-Planckian emission of such metamaterials can either come from the presence of surface phonon-polariton modes or from a continuum of hyperbolic modes depending on the choice of composite materials as well as the structural configuration.

Surface phonon–polaritons in rectangular quantum wires of polar ternary mixed crystals

In this paper, the dispersion relations of surface phonon–polaritons in freestanding rectangular quantum wire systems of polar ternary mixed crystals are derived. The numerical calculations for AlxGa1−xAs and ZnxCd1−xSe quantum wire systems are performed. The results reveal that the frequencies of surface phonon–polariton modes are sensitive to the geometric structures of the quantum wires, the wave-vectors in z-direction, and the compositions of the ternary mixed crystal materials. The effects of the “two-mode” and “one-mode” behaviors of the ternary mixed crystals on the surface phonon–polariton modes are also discussed.

Growth of amorphous carbon and graphene on pulse laser deposited SiC films and their characterization studies

AbstractLaser induced ablation studies have been carried out on formation of amorphous carbon and graphene on SiC thin films with their detailed characterization studies. Pulse laser ablation technique with process parameters such as 248 nm KrF excimer laser, frequency 10 Hz, 200 mJ of laser energy, and chamber pressure of 7 × 10−6 mbar has been used. Films were characterized in detail by grazing incidence X-ray diffraction, Fourier transform infrared, micro-Raman, X-ray reflectivity, Field emission scanning electron microscopic, transmission electron microscope, and Nano-indentation techniques and the results are reported. As deposited SiC film surface is rich in amorphous carbon and the same has been used as the nucleation site for further growth of graphene on SiC films. Film hardness increased from 29 GPa to 37 GPa for SiC film and graphene on SiC film (C-SiC), respectively. These films show bands due to surface phonon polariton mode in the range of 810–840 cm−1 that is a research concern today in nano-photonics area. Further these materials find applications in understanding the laser irradiation effects on SiC based nuclear fusion wall material.

Negative refraction via radiative surface phonon polaritons in a silicon carbide–based multilayer structure

In this letter, we predict that radiative surface phonon polariton (RSPhP) modes, in a multilayer structure consisting of thin-film silicon carbide (SiC) bounded by silicon (Si) and diamond (Di), can be used to achieve negative refraction of mid-infrared light at approximately 11 μm. Dispersion relations, calculated for the Si/SiC/Di structure, show that the RSPhP mode exhibits negative dispersion and couples with incident light. Poynting vector calculations show how the energy flux may be refracted, negatively, in the SiC layer.

Epsilon-Near-Zero Mode for Active Optoelectronic Devices

The electromagnetic modes of a GaAs quantum well between two AlGaAs barriers are studied. At the longitudinal optical phonon frequency, the system supports a phonon polariton mode confined in the thickness of the quantum well that we call epsilon-near-zero mode. This epsilon-near-zero mode can be resonantly excited through a grating resulting in a very large absorption localized in the single quantum well. We show that the reflectivity can be modulated by applying a voltage. This paves the way to a new class of active optoelectronic devices working in the midinfrared and far infrared at ambient temperature.

Surface Phonon Polariton Mediated Thermal Conduction of a Micrometric Glass Waveguide

Calculations of the dispersion relation and of the propagation length of surface phonon-polariton modes in a micrometric glass waveguide have been performed. The dispersion relation was solved in two ranges of frequency where SPP appear in glass. We succeeded in showing a maximal propagation length of 35 μm in a 10 μm radius waveguide with a 1 μm thick wall.

Pulsed terahertz radiation due to coherent phonon-polariton excitation in 〈110〉 ZnTe crystal

Pulsed terahertz (THz) radiation, generated through optical rectification (OR) by exciting 〈110〉 ZnTe crystal with ultrafast optical pulses, typically consists of only a few-cycles of electromagnetic field oscillations with a duration about a couple of picoseconds. However, it is possible, under appropriate conditions, to generate a long damped oscillation tail (LDOT) following the main cycles. The LDOT can last tens of picoseconds and its Fourier transform shows a higher and narrower frequency peak than that of the main pulse. We have demonstrated that the generation of the LDOT depends on both the duration of the optical pulse and its central wavelength. Furthermore, we have also performed theoretical calculations based upon the OR effect coupled with the phonon-polariton mode of ZnTe and obtained theoretical THz waveforms in good agreement with our experimental observation.

Polaritonic Microwave Waves of Inclined Incidence in Some Magnetodielectric Superlattices

This paper concerns a theoretical study of microwave phonon-polaritons excited in a planar magneto-dielectric composite by a plane electromagnetic wave obliquely incident on its surface. The composite consists of alternately spaced piezoelectric and piezomagnetic layers having transverse isotropic properties for both electromagnetic and elastic parameters. Results include direction-dependent dispersion for phase velocity of phonon-polariton modes being excited by the incident electromagnetic wave in the superlattice in consideration here. A peculiar kind of coupling is proved to appear in the system treated, which do not exist in the case of electromagnetic waves propagating along principal symmetry axes. The paper concludes with a short review of available literature data on current and prospective applications of the microwave polaritons.

Berreman mode and epsilon near zero mode

In this paper, we discuss the existence of an electromagnetic mode propagating in a thin dielectric film deposited on a metallic film at the particular frequency such that the dielectric permittivity vanishes. We discuss the remarkable properties of this mode in terms of extreme subwavelength mode confinment and its potential applications. We also discuss the link between this mode, the IR absorption peak on a thin dielectric film known as Berreman effect and the surface phonon polariton mode at the air/dielectric interface. Finally, we establish a connection with the polarization shift occuring in quantum wells.

Thermal Infrared Near-Field Spectroscopy

Despite the seminal contributions of Kirchhoff and Planck describing far-field thermal emission, fundamentally distinct spectral characteristics of the electromagnetic thermal near-field have been predicted. However, due to their evanescent nature their direct experimental characterization has remained elusive. Combining scattering scanning near-field optical microscopy with Fourier-transform spectroscopy using a heated atomic force microscope tip as both a local thermal source and scattering probe, we spectroscopically characterize the thermal near-field in the mid-infrared. We observe the spectrally distinct and orders of magnitude enhanced resonant spectral near-field energy density associated with vibrational, phonon, and phonon-polariton modes. We describe this behavior and the associated distinct on- and off-resonance nanoscale field localization with model calculations of the near-field electromagnetic local density of states. Our results provide a basis for intrinsic and extrinsic resonant manipulation of optical forces, control of nanoscale radiative heat transfer with optical antennas, and use of this new technique of thermal infrared near-field spectroscopy for broadband chemical nanospectroscopy.

Surface phonon polariton characteristics of wurtzite ZnO thin film grown on silicon substrate

AbstractIn this work, p‐polarized far infrared attenuated total reflection (ATR) with Otto configuration technique is employed to study the surface phonon polariton (SPP) characteristics of wurtzite ZnO thin film grown on Si(111) substrate. One prominent dip corresponding to the leaky SPP mode of the ZnO is detected at 532 cm−1. The obtained result is in good agreement with the calculated ATR spectrum simulated based on the transfer matrix formulation. The origin of the observed dip is verified with the surface polariton dispersion curves based on a three anisotropic layer model (air–ZnO–Si). The results also reveal that the real SPP and the interface phonon polariton modes for this studied structure are barely observable experimentally.

Dispersion of Surface and Interface Phonon Polariton Modes in Wurtzite Based Multilayer System

Dispersion of the surface and interface phonon polariton modes in wurtzite based multilayer system is investigated theoretically. In this study, we present a new formulation of the surface polariton (SP) dispersion relation for wurtzite based multilayer system. The expression is derived through solving Maxwell's electromagnetic equations directly by using algebraic manipulation method. The formulation is general and can be applied on any wurtzite layered structures in which the total number of layers in the system is equal or greater than two. In practice, the theory is employed to simulate the SP dispersion curves for several wurtzite layered structures, i.e., vacuum/ZnO, vacuum/ZnO/6H-SiC and vacuum/ZnO/GaN/6H-SiC. The features of these SP dispersion curves are analyzed and discussed in detail. It is shown that the characteristics of layers and the thicknesses of layers in the system have an important influence on the dispersion properties of the surface and interface phonon polariton modes.

Surface and interface phonon polariton characteristics of wurtzite ZnO/GaN heterostructure

Surface and interface phonon polariton modes in wurtzite ZnO/GaN heterostructure on wurtzite 6H–SiC substrate were investigated by a variable angle p-polarized infrared attenuated total reflection spectroscopy. Three dips corresponding to the surface and interface phonon polariton modes were observed; two of the dips that having a lower intensity level of reflectivity were the leaky modes whereas, another one was a real mode. The observations were verified with the surface polariton dispersion curve simulated based on an anisotropy model for a four-layer system. It was shown that the frequencies of leaky modes are predictable by considering the damping of the substrate.

Theoretical investigation of phonon-polariton modes in undoped and ion-doped PPLN crystals

The properties of phonon-polaritons in one-dimensional undoped and ion-doped periodically poled superlattice lithium niobate (PPLN) crystals are studied theoretically. In this paper, we focus on the case that the electric field vector of the electromagnetic wave is parallel to the acoustic propagation vector. The phonon-polaritons are products of the coupling between electromagnetic and acoustic waves of mutually perpendicular propagations. Based on the theory of the phonon-polariton in PPLN, we investigate the phonon-polariton in ion-doped PPLN. The effects of the duty cycle and the impurities upon the properties of phonon-polaritons are discussed in detail. Some potential applications are also discussed.

Studies of surface and interface phonon polariton characteristics of wurtzite ZnO thin film on wurtzite 6H-SiC substrate by p-polarized infrared attenuated total reflection spectroscopy

The surface and interface phonon polariton characteristics of a wurtzite ZnO thin film grown on a wurtzite 6H-SiC substrate are investigated by p-polarized infrared attenuated total reflection spectroscopy. Two absorption dips corresponding to the leaky surface phonon polariton (SPP) mode of ZnO and the interface phonon polariton (IPP) mode of ZnO/6H-SiC are clearly observed at 558 and 916cm−1, respectively. The observations are in good agreement with the results determined from the theoretical surface polariton dispersion curve simulated by means of an anisotropy model. Finally, the effects of the ZnO thin film thickness on the SPP and IPP modes are deduced from the theoretical calculations.

Experimental and theoretical analysis of THz-frequency, direction-dependent, phonon polariton modes in a subwavelength, anisotropic slab waveguide

Femtosecond optical pulses were used to generate THz-frequency phonon polariton waves in a 50 micrometer lithium niobate slab, which acts as a subwavelength, anisotropic planar waveguide. The spatial and temporal electric field profiles of the THz waves were recorded for different propagation directions using a polarization gating imaging system, and experimental dispersion curves were determined via a two-dimensional Fourier transform. Dispersion relations for an anisotropic slab waveguide were derived via analytical analysis and found to be in excellent agreement with all observed experimental modes. From the dispersion relations, we analyze the propagation-direction-dependent behavior, effective refractive index values, and generation efficiencies for THz-frequency modes in the subwavelength, anisotropic slab waveguide.

Surface phonon polariton characteristics of bulk wurtzite ZnO crystal

The surface phonon polariton (SPP) mode of bulk wurtzite (α-) zinc oxide (ZnO) crystal is investigated by means of p-polarized infrared attenuated total reflection (ATR) spectroscopy. From the ATR spectrum, a strong absorption dip corresponds to the SPP mode of bulk α-ZnO is clearly observed at 529 cm −1. The experimental SPP mode showed good agreement with the theoretical SPP mode deduced from the surface polariton dispersion curve generated by the semi-infinite anisotropic crystal model.