Dielectric Prism Research Articles

Achieving a comparable transverse magneto-optical Kerr effect by spin–orbit field driven magnetoplasmonic

In this study, we propose and simulate a magnetoplasmonics heterostructure that utilizes spin–orbit fields to generate an internal magnetic field and create a significant magneto-optical effect. Our approach offers a new way to overcome the challenges of using permanent magnets or magnetic coils in conventional magnetoplasmonics, such as high-power consumption and non-scalability. We demonstrate that it is possible to create an appropriate amount of magnetic field using spin–orbit fields induced by the spin-Hall effect, such that the consumption power becomes reasonable and the dimensions could be miniaturized. This approach will be an important development in the field of magneto-optics, as it can lead to enhanced transverse magneto-optical Kerr effect in the present of surface plasmon polaritons. The proposed nanostructure consists of a ferromagnetic film adjacent to a heavy metal layer, both sandwiched between two noble metal films, and deposited on a dielectric prism. The strength of the Kerr signal strongly depends on the thickness of the ferromagnetic layer, with the maximum effect observed at a thickness of 5nm. This concept has potential for various nanophotonic and spintronic applications, particularly for developing high-speed active plasmonic devices for ultrafast light modulation.

Modulation of classical non-separability of vector vortex beams using Brewster effect

The vector vortex beams are generated by the superposition of two orthogonal orbital angular momentum (OAM) beams having orthogonal polarization states using a stable common path technique. The degree of non-separability of the generated vector vortex beams is controlled by changing the input polarization state and Brewster effect using a dielectric prism. We have estimated the linear entropy (SL) of the classical non-separable beams by measuring the reflection coefficients for different input polarization states at each rotation angle of the prism. The shifting of the peak value of SL for different input polarization states at the particular rotation angles of the prism is observed. The usefulness of the proposed scheme is demonstrated in sensing the refractive index variations of the prism.

Dielectric elastomer-driven liquid prism enabling two-dimensional beam control

In this paper, a dielectric elastomer (DE)-driven liquid prism enabling two-dimensional beam control is proposed. The proposed liquid prism consists of a flexible driver and a liquid cavity. The glass plate is driven by DE to change the tilt angle of the liquid-solid interface for beam steering and field of view (FOV) tuning. The maximum optical deflection angle of 8.13° and response time of 76.77 ms were measured, the variable FOV capability was also verified. The proposed liquid prism can be used in beam modulation, microscope systems.

Radio frequency discharge apparatus for studying spin transfer from solid surfaces to metastable helium gas

We developed a radio frequency discharge apparatus for He gas to investigate the spin states of metastable helium (He*) interacting with solid-state surfaces. Our apparatus consisted of a stainless steel vacuum chamber, in which a coil produced He* by discharging introduced He gas. The spin states of the He* were detected using optical pumping and probing techniques. The chamber was designed to accommodate various solid-state samples. We measured the He* polarization produced at a dielectric prism surface by total internal reflection of the circularly polarized pumping light. Our apparatus can be used to investigate possible spin transfer from various solid surfaces to He* atoms.

Artificial dielectric beam-scanning prism for the terahertz region

We design and fabricate an artificial dielectric prism that can steer a terahertz beam in space and experimentally investigate its behavior. The artificial dielectric medium consists of a uniformly spaced stack of metal plates, electromagnetically equivalent to an array of parallel-plate waveguides operating in tandem. At an operating frequency of 0.3 THz, we observe a maximum beam deflection of 29°, limited by the precision of the available spacers. Spring-loading the spacers between the plates allow us to scan the beam continuously and dynamically over a range of 5°. The measured beam intensity maps at the input and output of the device reveal very good Gaussian beam quality and an estimated power efficiency of 71%. As a possible real-world application, we integrate the prism into the path of a free-space terahertz communication link and demonstrate unimpaired performance.

GENERAL SOLUTION OF THE EXCITATION PROBLEM OF A SYMMETRIC FLAT DIELECTRIC STRUCTURE BY PLANE ELECTROMAGNETIC WAVES

General solution of the excitation problem of a symmetric flat dielectric structure by two laser pulses is obtained. The symmetrical geometry consists of two dielectric prisms separated by a vacuum channel for electron acceleration (so called “sandwich”). Each prism can be illuminated with a separate laser pulse; electric filed amplitudes of pulses can differ. The general solution consist from a symmetric distribution and asymmetric one of a longitudinal electric field across the vacuum channel. In the case of a general solution, the effect of the asymmetric part on the total amplitude of the accelerating and defocusing fields is also analyzed. We determined also conditions when a symmetric or asymmetric solution only is realized. For these cases, the obtained analytical solutions are compared with results of full time-domain numerical simulations of bilateral excitation of dielectric prisms with laser pulses.

High-Bunch-Charge and High-Energy-Gain Inverse-Cherenkov Particle Accelerator With Prebunched Beam

Dielectric laser accelerator (DLA) is a promising candidate for next-generation on-chip particle accelerator. However, practical applications of DLA to date have been restricted due to low accelerated bunch charge and low energy gain, especially for subrelativistic particles. To break through these limitations, here we propose a multistage DLA scheme with inverse Cherenkov effect. The first stage, formed by a pair of symmetric dielectric prisms, is to prebunch a long (tens to hundreds of laser-wavelengths) electron beam with relatively high bunch charge (several to tens of femto-coulombs) via velocity bunching. The subsequent stages, consisting of pairs of dielectric prism stacks, are to fulfill cascade acceleration of the prebunched beam. The synchronization of subrelativistic particles with laser field is realized via adjusting the prism angles in each stack. With theoretical analyses and simulations, we obtain an energy gain of more than 400 keV for an electron beam with initial energy of 100 keV. Compared with that of a non-prebunched beam, the accelerated bunch charge of a prebunched beam is more than four times higher. This proposed scheme affords an effective way of developing an on-chip particle accelerator with high energy gain and high bunch charge.

Comparison of geometric optics and «aperture» methods for calculation of the electromagnetic radiation caused by charged particles flying by dielectric objects

Calculation of the electromagnetic field exited by a charged particle flying close to dielectric object is one of the important problems of charged particle radiation theory. In some cases, geometric optics area is preferable for calculations. In the article, two methods of solution of such problem with dielectric prism possessing large size (in comparison with the wavelength under consideration) are considered. One of them is based on geometric optics method, another one is based on asymptotics of «aperture» integrals. It is shown that, in geometric optics area, the first method has a series of advantages. For example, ray tube cross-section expression obtained within geometric optics method allows one to find caustics or to show their abscence, which is demonstrated in the article for three objects of various shapes.

Cumulative ejection of terahertz radiation from a laser-driven magnetized plasma

We propose a scheme for efficient directional emission of laser-driven wakefields from a magnetized plasma. In the scheme, a laser–plasma interaction region is sandwiched between a pair of dielectric prisms of total internal reflection. The wakefields, propagating in the plasma at different angles to the laser beam, are cumulated by the prisms and radiated to free space in the direction of the laser beam. For magnetic fields <100 T, a 50-fs laser pulse with 1-J energy can generate long lasting (hundreds of ps) multicycle terahertz radiation with mJ-level energy. For a 500-T field, the laser pulse can generate terahertz bursts with a uniform spectrum in the ∼7–14 THz interval with ten-mJ-level energy.

Scalable optical-to-terahertz converter with a prism-coupled plane-parallel lithium niobate plate.

A nonlinear optical converter of femtosecond laser pulses to terahertz radiation, which combines the tilted-pulse-front pumping and prism coupling techniques, is proposed and experimentally tested. In contrast to the conventional tilted-pulse-front scheme with a prism-shaped LiNbO3 crystal, the converter consists of a plane-parallel LiNbO3 plate sandwiched between two dielectric prisms. One prism is used to couple the pump beam into the LiNbO3 plate, another prism couples the generated terahertz radiation out of the plate. The proposed scheme enables scaling to large-diameter LiNbO3 wafers and large-aperture high-energy pump laser beams resulting in generation of strong terahertz fields. In a proof-of-principle experiment with a 1-mm thick, small size (1 × 2 cm2) LiNbO3 plate pumped by a mJ-class laser, the conversion efficiency comparable to that of the conventional scheme (∼0.1%) was demonstrated.

Enhanced quadrupole effects for atoms in surface spiral beams with a thin dielectric waveguide

Recently, some physical research has recognized the coupling of optical phase singularity light with quadrupole-active atomic transitions. We show that a Laguerre-Gaussian beam, when completely internally reflected at the dielectric/vacuum interface, can generate a well-defined surface spiral beam with a two-dimensional intensity distribution confined to a sub-wavelength region near the interface outside of the dielectric. The quadrupole interaction has been shown to be significantly enhanced in the case of coating the planar surface of a dielectric prism using multilayer dielectric thin films of different thicknesses. The mechanical action on the atom due to the optical forces characterized by optical quadrupole transitions could greatly facilitate the revolution of optical manipulation of neutral atoms along the dielectric/vacuum interface. The typical optical quadrupole potential, evaluated for the atomic transition, corresponds to λ=675.0nm with ΓQ=7.8×105s-1, in Cesium atoms, which is a dipole-forbidden but quadrupole-allowed transition. The parameters used to compute the optical quadrupole potential are similar to those in recent experiments. The factors controlling the general enhancement are pointed out and discussed.

THz-driven dielectric particle accelerator on chip.

Recently, terahertz (THz)-driven particle accelerators have drawn increasing attention. The development of high-energy-gain THz accelerators on chip has been a challenge. Here we propose a concept of an on-chip THz-driven particle accelerator that uses few-cycle THz pulses to drive dielectric prisms. It avoids the serious waveguide dispersion of previous THz linacs based on dielectric lined waveguides and enhances the electron-energy gain. In addition, we propose to use prism stacks to overcome the asynchronization effect when accelerating low-energy particles, by which a longer acceleration length with even higher energy gain can be realized. Compared with the available on-chip dielectric laser accelerators, the proposed scheme avoids serious dielectric dispersion and enhances accelerated bunch charge. Hence, it promises an attractive particle accelerator on chip.

Angular deviations: from a cubic equation to a universal closed formula to determine the peak position of reflected and (upper) transmitted beams

Angular deviations and lateral displacements are optical effects widely investigated in literature. In this paper, by using the Taylor expansion of the Fresnel coefficients, we obtain an analytic expression for the beam reflected by and (upper) transmitted through a dielectric prism. These analytical approximations lead to a cubic equation which allows to determine the angular deviations of the optical beams. Near the Brewster angles, under specific conditions, we obtain a universal formulation for the cubic equation. Its explicit solution determines the peak position of the reflected and (upper) transmitted beams. The universal solution could be of great utility in future experimental implementations. The analytic results show an excellent agreement with the numerical calculation and the analytic expressions given for the reflected and (upper) transmitted beams should play an important role in the weak measurements analysis.

The photonic nanojets formation by two-dimensional microprisms

Using the finite difference method implemented in the COMSOL Multiphysics software package, the focusing of laser radiation by dielectric prisms with a triangular profile was numerically investigated. It was shown that two-dimensional triangular prisms make it possible to focus light in free space into spots with dimensions smaller than the scalar diffraction limit. In particular, a silica glass prism with a base width of 60 μm and a height of 28.5 μm forms a photonic nanojet with a maximum intensity of 6 times the intensity of the incident radiation and a width of FWHM=0.38λ. A prism from barium titanate with a base width of 60 μm and a height of 20 μm allows to obtain a photonic nanojet with the same width (0.38λ) and a maximum intensity 5 times the intensity of the incident radiation. The size of the focal spot can be reduced further if the height of the prism is selected so that the maximum intensity is located inside the material of the prism. For example, a barium titanate prism with a height of 21 μm and a base width of 60 μm forms a focal spot with a width of FWHM=0.25λ.

Laser planar trapping

We investigate the phenomenon of the transverse breaking of symmetry of Gaussian lasers transmitted through dielectrics, showing for which incidence conditions and beam parameters it can be observed in optical experiments. The numerical analysis, done by using the integral form of the transmitted beam at the lower interface of a dielectric prism, shows, for incidence approaching the critical region, a laser planar trapping. By using an analytic approximation for the intensity of lower transmitted beam, we model the wave front curvature by a closed expression which depends on the refractive index, on the geometrical properties of the dielectric block, and, finally, on the incidence angle of the incoming beam. The analytic formula shows an excellent agreement with the numerical analysis and it could be useful in future experimental implementations.

Effect of sulfosalt and polymers on performance parameter of SPR biosensor

The aim of the paper is to see the influence of Franckeite on the sensing application of SPR based biosensor. Franckeite is an emerging (2D) material from sulfosalt family having naturally presented spontaneously vander Waals (vdW) Heterostructure. We have investigated and carried out detailed analysis to design the high-performance biosensor by exploiting the unique properties of Franckeite. The performance of the biosensor is quantified in terms of Sensitivity and other performance parameters. Proposed work is theoretical where we have proposed a surface plasmon resonance (SPR) biosensor in combination of the nanosheets of (Bimetallic layer + Franckeite + TMDC + BP) in order to enhance the sensitivity. It’s also shown in the paper that by sandwiching a buffer (polymer) with low refractive index (close to water) between metal layer (Au in this case) and dielectric medium prism, the value of FWHM reduced dramatically and significant enhancement observed in FOM (100RIU−1) and detection accuracy (2.38 deg−1). We have also illustrated the concept of long range –SPR (LRSPR) in this paper by giving the comparative analysis of different polymers. As an air-stable 2D material, we expect that 2D Franckeite Nano sheets could have potential applications in the field of chemical as well as biosensing application in the future.

Symmetry analysis and multipole classification of eigenmodes in electromagnetic resonators for engineering their optical properties

The resonator is one of the main building blocks of a plethora of photonic and microwave devices from nanolasers to compact biosensors and magnetic resonance scanners. The symmetry of the resonators is tightly related to their mode structure and multipole content which determines the linear and non-linear response of the resonator. Here, we develop the algorithm for the classification of eigenmodes in resonators of the simplest shapes depending on their symmetry group. For each type of mode, we find its multipole content. As an illustrative example, we apply the developed formalism to the analysis of dielectric triangular prism and demonstrate the formation of high-Q resonances originated due to suppression of the scattering through the main multipole channel. The developed approach one to engineer, predict, and explain scattering phenomena and optical properties of resonators and meta-atmos basing only on their symmetry without the need for numerical simulations and it can be used for the design of new photonic and microwave devices.

Phenomenon of Frustrated Total Internal Reflection in the Near-Field Interference Microwave Sounding

A new approach is proposed in solving the problems of active near-field microwave probing of materials, objects and media. According to this approach, the probing near field is formed as a result of overlapping of the evanescent fields generating under the conditions of a frustrated total internal reflection in the gap between the major faces of two right-angle dielectric prisms. An object under study placed into this gap exerts a noticeable influence on the reflected radiation characteristics. On this basis, one can not only perform the object quality diagnostics, but also obtain the data on its material parameters. A schematic design of a nearfield interference microwave microscope is described, which implements the proposed approach. The results of test measurements under the conditions of diagnostics of metalized strips with breaks are presented.

Dark state atom mirrors based on artificial gauge fields created by surface optical vortices

We propose the construction of an atom mirror for cold three-level atoms in a dark state where the forces, responsible for the atomic reflection, are provided by artificial gauge fields. These fields are created from the total internal reflection of optical vortex beams with Gaussian intensity profiles at the interface of a dielectric prism and vacuum. We investigate the role of the photon angular momentum in the magnitude of these fields and consequently on the efficiency of atomic reflection.

Radiation of a charge moving along the boundary of dielectric prism

Radiation generated by a charge moving along one of the prism borders is analyzed. The size of the object is assumed to be much larger than the wavelengths under consideration. We calculate the wave field outside the target using the ``aperture method'' which is applicable for any distances from the prism. We obtain the particular form of Stratton-Chu formulas for the case of the prism and develop an algorithm for the calculation of the radiation field outside the prism. Typical numerical results are demonstrated and discussed.