Interference Of Evanescent Waves Research Articles

Long Propagating Polaritonic Heat Transfer: Shaping Radiation to Conduction.

Surface phonon polaritons (SPhPs) originate from the coupling of mid-IR photons and optical phonons, generating evanescent waves along the polar dielectric surface. The emergence of SPhPs gives rise to a phase of quantum matter that facilitates long-range energy transfer (100s μm-scale). Albeit of the recent experimental progress to observe the enhanced thermal conductivity of polar dielectric nanostructures mediated by SPhPs, the potential mechanism to present the high thermal conductivity beyond the Landauer limit has not been addressed. Here, we revisit the comprehensive theoretical framework to unify the distinct pictures of two heat transfer mechanisms by conduction and radiation. We first designed our experimental platform to distinguish contributions of two distinct fundamental modes of SPhPs, resulting in far-field radiation and long propagating conduction, respectively, by tuning the configuration of a nanostructured heat channel integrated into the thermometer. We could effectively control the transmission of long-propagating SPhPs to influence the apparent thermal conductivity of the nanostructure. This study reveals the high thermal conductance of 1.63 nW/K by a fast SPhP mode comparable to that by classical phonons, with measurements showing apparent conductivity values of up to 2 W/m·K at 515 K. The origin of the enhanced thermal conductivity was exploited by observing the interference of dispersive evanescent waves by double heat channels. Furthermore, our experimental observations of length-dependent thermal conductance by SPhPs are in good agreement with the revisited Landauer formula to illustrate a polaritonic mode of heat conduction, considering the dispersive nature of radiation not limited to the physical boundaries of a solid object yet directionally guided along the surface.

Wideband Compartment Shielding Technique for Miniaturized Packages Based on Electrically Small Single-Negative Meta-Diaphragm

This article focuses on realizing wideband compartment shielding in the shielding can packages of miniaturized high-speed chip modules and circuits. Because the conventional diaphragms with a low profile are difficult to cope with the high-order mode interference and evanescent wave interference, a new &#x201C;meta-diaphragm,&#x201D; which is based on the single-negative (SNG) metamaterial, is proposed to address these inherent problems. It is demonstrated that benefitting from the large propagation attenuation introduced by the proposed meta-diaphragm, a good shielding performance can be achieved at the first higher order resonance mode. Moreover, by elaborately embedding resistors in the meta-diaphragm, the additional interferences at other resonance frequencies can be significantly suppressed. Furthermore, the structure of the meta-diaphragm is optimized with two approaches: evolving from the single-band SNG structure to the double-band one and integrating with the parasitic patches. The two approaches enable its independent controlling ability at different frequency ranges and enhancement of low-frequency shielding performance. Based on the proposed technique, an experiment is implemented to suppress the resonance-dominated interference between the passive traces in a shielding can. The result agrees well with those from theoretical prediction. The final experimental shielding can&#x2019;s profile and width are 5 and 20 mm, respectively; the meta-diaphragm&#x2019;s profile is only 1.5 mm, i.e., &#x003C; 1/3 of shielding can&#x2019;s profile, and its electrically length is only 3 mm, i.e., <inline-formula> <tex-math notation="LaTeX">$0.1\lambda _{0}$ </tex-math></inline-formula> at 10 GHz, and the measured (simulated) meta-diaphragm can significantly suppress radio frequency interference (RFI) within 10.2&#x2013;17 GHz (10&#x2013;16.9 GHz) and realize <inline-formula> <tex-math notation="LaTeX">$&lt; -33.5$ </tex-math></inline-formula> dB (<inline-formula> <tex-math notation="LaTeX">$&lt; -40$ </tex-math></inline-formula> dB) coupling within 100 kHz&#x2013;18 GHz (dc-to-20 GHz). The miniaturized dimension and wideband results indicate that our proposed technique could meet the compartment shielding requirement of a series of miniaturized packages in the practical radio frequency (RF) chip modules and circuits.

Flexible Evanescent Wave Interference Lithography System for Sub-half-Wavelength Complex Relief Structures Fabrication

Surface microstructures impart various useful properties to objects, for example, improving optical characteristics, wettability, and sliding properties. It is well known that biomimicking relief structures are effective in making such properties arise and have been studied to be applied to various devices. Furthermore, they are expected to be utilized not only for improving a particular property but also for adding more complex functions on a device's surface by fabricating different multi-functional structures on a single surface in the future. However, to begin with, artificially fabricating such biomimicking special functional relief is difficult. One typical feature of biomimicking surfaces is the dual-scale structure, the smaller one of which is less than 200 nm. Moreover, in the case of realizing the more complex devices, it is necessary to fabricate various forms as changing process conditions dynamically. In this study, we proposed and developed a flexible evanescent wave interference lithography system as a novel fabrication method, which allows us to realize the fabrication of sub-half-wavelength complex relief structures. Firstly, we theoretically analyzed the fundamental behavior of the fabricated structure and found that the proposed concept has the potential to realize one of the target complex structures. Secondly, we developed the proposed system with high process flexibility, in which the number of beams, the azimuth angles, and the polarization can be simply manipulated. Finally, we validated the concept of the designed system by some experiments, where we fabricated dual-scale structures with 840-nm and 190-nm fringe patterns simultaneously.

Towards all-optical atom chips based on optical waveguides

Coherent guiding of atoms in two-colour evanescent light fields of two fundamental modes of suspended optical rib waveguides is investigated theoretically. Special attention is paid to waveguides of widths larger than the wavelength of light, which provide better lateral stability of the surface traps and waveguides, and can be used in coherent Bragg beam splitters for matter waves, based on optical gratings formed by interference of evanescent light waves of two crossed optical waveguides. A single-mode regime for evanescent-wave waveguides for atoms is investigated. The general structure and key elements of all-optical atom chips are discussed.

Label-Free Imaging of Single Nanoparticles Using Total Internal Reflection-Based Leakage Radiation Microscopy.

Label-free, fast, and single nanoparticle detection is demanded for the in situ monitoring of nano-pollutants in the environment, which have potential toxic effects on human health. We present the label-free imaging of single nanoparticles by using total internal reflection (TIR)-based leakage radiation microscopy. We illustrate the imaging of both single polystyrene (PS) and Au nanospheres with diameters as low as 100 and 30 nm, respectively. As both far-field imaging and simulated near-field electric field intensity distribution at the interface showed the same characteristics, i.e., the localized enhancement and interference of TIR evanescent waves, we confirmed the leakage radiation, transforming the near-field distribution to far-field for fast imaging. The localized enhancement of single PS and Au nanospheres were compared. We also illustrate the TIR-based leakage radiation imaging of single polystyrene nanospheres with different incident polarizations. The TIR-based leakage radiation microscopy method is a competitive alternative for the fast, in situ, label-free imaging of nano-pollutants.

Fabrication of nano/micro dual-periodic structures by multi-beam evanescent wave interference lithography using spatial beats.

We propose an effective method for fabricating dual-periodic structures using the combination of multi-beam interference lithography and evanescent wave exposure. Four-beam evanescent wave interference lithography (EWIL) is used as a prototype to demonstrate the fabrication feasibility of one-dimensional (1D) micro-grating structures covered with nanodots and two-dimensional microdot structures filled with subwavelength fringes by designing reciprocal lattice vectors of interference fringes. We experimentally fabricated 1D nano-/micro-grating structures with periods of 140 nm and 12.5 µm and microdots filled with subwavelength gratings of 450 nm period by four-beam EWIL. These structures are applicable to superlattice photonic crystals and subwavelength structured surfaces.

Total internal reflection fluorescence pattern-illuminated Fourier ptychographic microscopy

We report a widefield super-resolution (SR) fluorescence microscopy technique termed total internal reflection fluorescence pattern-illuminated Fourier ptychographic microscopy (TIRF-piFPM). It employs pattern-illuminated Fourier ptychography (piFP) under the total internal reflection fluorescence (TIRF) mode, providing a lateral resolution of ∼100 nm, reducing the background level, and correcting unknown optical aberrations. Like the total internal reflection fluorescence structure illuminated microscopy (TIRF-SIM), the illumination field of TIRF-piFPM is modulated by sinusoidal patterns generated by evanescent wave interference. It differs from TIRF-SIM in that TIRF-piFPM reconstructs the SR image by FP iteration. To demonstrate the performance of TIRF-piFPM, we compare it with TIRF-SIM by conducting simulations and experiments and prove that TIRF-piFPM can provide a better result than TIRF-SIM in terms of its robustness to noise and aberration correction ability. In addition, dynamic changes of mitochondria in U2OS cells are captured with a temporal resolution of 2 s, demonstrating its live-cell imaging capability. The addvantages may enable TIRF-piFPM to serve as an alternative to SR fluorescence microscopes in the TIRF family, with promising applications in biological and biomedical imaging.

Measurement of Colloidal Mobility in the Vicinity of a Solid-Liquid Interface based on an Interference of Evanescent Waves

Measurement of Colloidal Mobility in the Vicinity of a Solid-Liquid Interface based on an Interference of Evanescent Waves

Estimation of the Mobility of Colloidal Liquid as Heat Transport Medium with Laser Measurement based on Interference of Evanescent Waves

Estimation of the Mobility of Colloidal Liquid as Heat Transport Medium with Laser Measurement based on Interference of Evanescent Waves

Strong localization of an acoustic wave in a sub-wavelength slot between two plates.

The dispersion relation of the acoustic field in a sub-wavelength slot (its width is smaller than the acoustic wavelength) between two identical plates immersed in an inviscid liquid is theoretically analyzed. Each plate has a phononic crystal structure consisting of periodical grooves drilled in one of outer sides of each plate. It is found that highly localization of acoustic energy can be achieved in the sub-wavelength slot when a traveling acoustic wave is incident upon the slots. The associate physical principle is as follows: The lowest anti-symmetric non-leaky A0 mode of the Lamb wave of each individual thin plate propagating as an evanescent wave extends to the liquid from opposite direction; when the width of the slot is much smaller than the characteristic decay length of the evanescent wave in the liquid, the constructive interference of evanescent waves of the both plates takes place, leading to a strong acoustic field in the slot. This system has potential to serve as an excellent candidate for the ultrasensitive microscopic chemical/biological stimulators and sensors.

Shot noise in systems with semi-Dirac points

We calculate the ballistic conductance and shot noise of electrons through a two-dimensional stripe system (width W ≫ length L) with semi-Dirac band-touching points. We find that the ratio between zero-temperature noise power and mean current (the Fano factor) is highly anisotropic. When the transport is along the linear-dispersion direction and the Fermi energy is fixed at the semi-Dirac point, the Fano factor has a universal value F = 0.179 while a minimum conductivity exists and scales with L1∕2. Along the parabolic dispersion direction, the Fano factor at the semi-Dirac point has a contact-independent limit exceeding 0.9, which varies weakly with L due to the common-path interference of evanescent waves. Our findings suggest a way to discern the type of band-touching points.

Optical and holographic properties of nano-sized As2S3 films

The theoretical background as well as the experimental results of evanescent wave holographic recording with grating periods of 3.2, 0.88 and 0.37μm (spatial frequencies of 310mm−1, 1140mm−1 and 2700mm−1) in nano-sized As2S3 films with thicknesses of 29nm, 15nm and 10nm are presented. The grating recording has been performed using the interference of surface-propagating evanescent waves, created by total internal light reflection. The maximum diffraction efficiency of 5.6×10−3% has been achieved for grating period of 0.88μm and sample thickness of 15nm. Besides, the optical characteristics as refractive index n and extinction coefficient k of the films studied have been determined from spectrophotometric measurements in 250–650nm wavelength region. Furthermore, drawing a connection to our previous morphological investigations, the existence of a strong relationship between microstructure, optical and holographic behavior of nano-sized As2S3 films has been revealed. On this basis the possibility of applying the evanescent – wave holography as a useful nano-tool for studying structures and different phenomena at nanometer scale has been outlined.

Near-field light focusing by a slit array in a planar metal film with nonuniform slit dielectric material

We study the interference of evanescent electromagnetic waves generated from multi-slits in a metal film and demonstrate the anomalous bending of light at infrared frequencies due to negative refraction. We also calculate the diffraction of an incident plane electromagnetic waves by a metallic film with an arbitrary linear array of slits, slit separation, and slit dielectric material. In contrast to a double-convex shaped quartz lens, we show that a planar metallic film with a one-dimensional slit array can also focus polarized light in the near-field region when either the slit width or the slit dielectric material becomes spatially nonuniform.

ELECTRONIC STATES AND LOCAL DENSITY OF STATES NEAR GRAPHENE CORNER EDGE

We study that stability of edge localized states in semi-infinite graphene with a corner edge of the angles 60°, 90°, 120° and 150°. We adopt a nearest-neighbor tight-binding model to calculate the local density of states (LDOS) near each corner edge using Haydock's recursion method. The results of the LDOS indicate that the edge localized states stably exist near the 60°, 90°, and 150° corner, but locally disappear near the 120° corner. By constructing wave functions for a graphene ribbon with three 120° corners, we show that the local disappearance of the LDOS is caused by destructive interference of edge states and evanescent waves.

Interferometric lithography for nanoscale feature patterning: a comparative analysis between laser interference, evanescent wave interference, and surface plasmon interference

In this paper, we experimentally demonstrate and compare single-exposure multiple-beam interference lithography based on conventional laser interference, evanescent wave interference, and surface plasmon interference. The proposed two-beam and four-beam interference approaches are carried out theoretically and verified experimentally, employing the proposed configurations so as to realize the patterning of one- and two-dimensional periodic features on photoresists. A custom-fabricated grating is employed in the configuration in order to achieve two- and four-beam interference.

Projection lithography below lambda/7 through deep-ultraviolet evanescent optical imaging

An approach is presented to allow for imaging down to 26 nm using 193 nm projection reduction lithography together with evanescent wave optical effects at the imaging plane. The physical limitations of imaging imposed by the refractive indices of the materials were surpassed through the interference of evanescent waves at near fields. This has allowed for the imaging into photoresist of half-pitch resolution below lambda/7. A special situation where imaging at a system numerical aperture above the resist refractive index is discussed. Lithography results are shown using image media including air, water, and a high refractive index fluid together with a systematic gauge control to determine gap requirements and tolerances to achieve adequate image contrast into the resist. Gauging methods include both optical and mechanical approaches to achieve nanometer level gap control. It is found that gap depths as large as 50 nm can be tolerated using this approach, well beyond the levels associated with alternative high resolution approaches such as those using surface plasmons.

Approach of enhancing exposure depth for evanescent wave interference lithography

Theoretically evanescent wave lithography can achieve the feature size with dimensions less than one fifth of the wavelength of irradiation source, it can meet the resolution of the nano-grating. However, according to the theoretical calculation and the experimental results, the amplitude of evanescent wave away from the surface of the medium decays exponentially, it will cause short exposure depth, low contrast in photoresist so that the pattern is unable to transfer accurately to the substrate. In this paper, in order to explore the possibility for fabricating large-area nano-grating by interference lithography, we try to enhance the exposure depth of the evanescent interference lithography based on the Surface Plasmon Polarization (SPP) near-field technologies. The theoretical analysis and parameters optimization show that the improving interference lithography technology can be used to fabricate the grating with 60 nm feature size.

2D dark optical surface lattice with an efficient intensity-gradient cooling of atoms by evanescent wave interference

We propose a novel scheme to form a 2D dark optical surface lattice (DOSL) for cold atoms on the surface of the dense flint glass by using two sets of blue-detuned evanescent wave interference fields and a blue-detuned evanescent wave field. In the 2D DOSL, cold atoms will be trapped in the vicinity of minimum intensity and suffered the minimal light shift as well as the lowest coherence loss. The total potential and trap-depth of the individual optical micro-trap in the 2D DOSL are high enough to trap cold atoms (T=120μK) released from the standard magneto-optical trap (MOT), and atoms trapped in the 2D DOSL can be cooled to several μK with the efficient intensity-gradient Sisyphus cooling. The lattice constant of the DOSL can be controllable by changing the incident angles of lights.

2D array of surface optical micro-traps by evanescent wave interference

We propose a novel scheme to form a 2D surface array of optical micro-traps of cold atoms by using two sets of far red-detuned evanescent wave interference and a blue-detuned evanescent wave. The optical potentials of the 2D surface array of optical micro-traps are high enough to trap cold atoms released from the standard magneto-optical trap，and 87Rb atoms trapped in the array of optical micro-traps can be cooled to 2.56μK with efficient intensity-gradient Sisyphus cooling. Our study shows that the proposed 2D surface array of optical micro-traps can be used in atomic physics，atomic optics, quantum optics and so on.

Evanescent wave interference lithography for surface nano-structuring

Surface nano-structuring on photoresist beyond the diffraction limit has been investigated by using total internal reflection induced evanescence wave interference with a Lloyd's mirror. The size of the patterns can be down to 80 nm with the incident laser wavelength, λ, of 325 nm, less than λ/4 resolution. This may be attributed to laser induced evanescent wave, which has a shorter wavelength than that of the incident laser in air. The energy distribution of evanescent wave interference patterns was studied theoretically. It shows good agreement with the experiments. This technique can be used to improve traditional laser interference lithography to get smaller feature sizes with a simple modification by putting a prism in front of the sample only.