Beam Waveguide Research Articles

On the integrability aspects of nonparaxial nonlinear Schrödinger equation and the dynamics of solitary waves

The integrability nature of a nonparaxial nonlinear Schrödinger (NNLS) equation, describing the propagation of ultra-broad nonparaxial beams in a planar optical waveguide, is studied by employing the Painlevé singularity structure analysis. Our study shows that the NNLS equation fails to satisfy the Painlevé test. Nevertheless, we construct one bright solitary wave solution for the NNLS equation by using the Hirota's direct method. Also, we numerically demonstrate the stable propagation of the obtained bright solitary waves even in the presence of an external perturbation in a form of white noise. We then numerically investigate the coherent interaction dynamics of two and three bright solitary waves. Our study reveals interesting energy switching among the colliding solitary waves due to the nonparaxiality.

Tunable Microwave Photonic Filter Based on LNOI Polarization Beam Splitter and Waveguide Grating

A tunable microwave photonic filter (MPF) based on a polarization beam splitter (PBS) and waveguide grating true-time delay line (TTDL) is proposed and demonstrated experimentally. Taking advantage of the high birefringence property of lithium niobate (LN), the PBS is achieved by a simple structure in a short length. The TTDL consists of an LNOI waveguide grating and flexible electrodes covering along the grating. Owing to the electro-optic effect of LN, a wide tuning range and high tuning accuracy of delay time can be achieved simply by controlling the charging position of the electrodes. With the proposed PBS and TTDL, the MPF exhibits low drive voltage, low power consumption, and high response rate in a simple construction.

Fine tuning of quantum particle plasmon

It is of recent interest to study plasmonics of metallic and semiconductor particles that are so small that carriers in the conduction band are separated at discrete subbands due to quantum confinement. These small metallic and semiconductor particles are referred as quantum particles in the present work. The modifications of plasmons of quantum particles are studied in the framework of an electron-in-a-box model with an every-electron-count computational scheme. The quantum size effects are incorporated into the classic description of small particle plasmons with the emphasis on intra-subband fluctuations caused by the quantum confinement. The carrier redistribution at subbands is related to the environmental temperature via Fermi-Dirac distribution. Numerical results have shown that the frequency, the strength, and the shape of the plasmons are modified as a function of both particle size and temperature. The discovery suggests potential applications to tune the plasmonics of quantum particles externally and to calibrate the particle properties accounting to plasmonics. It is proposed that the environmental temperature can be conveniently controlled by evanescent light concentration, such as, laser beams in a slot waveguide.

High Voltage Monitoring with a Fiber-Optic Recirculation Measuring System

Optical technologies for measuring electrical quantities have unique properties and significant advantages in the high-voltage electric power industry; for example, the use of optical fibers ensures the high stability of measuring equipment to electromagnetic interference and galvanic isolation of high-voltage sensors; external electromagnetic fields do not influence the data transmitted from optical sensors via fiber-optic communication lines; problems associated with ground loops are avoided, and there are no side electromagnetic radiation or cross-coupling between the channels. The structure and operation principle of a quasi-distributed fiber-optic recirculation system for monitoring high voltages are presented. The sensitive element of the system is a combination of a piezoceramic tube with an optical fiber beam waveguide where the inverse transverse piezoelectric effect occurs. The electrical voltage measurement principle is based on recording the change in the recirculation frequency under the applied voltage influence. When the measuring sections are arranged in ascending order of the measured effective voltages relative to the receiving-transmitting unit, a relative resolution of 0.30–0.45% for the PZT-5H and 0.8–1.2% for the PZT-4 is achieved in the voltage range of 20–150 kV.

Caustic and Weakly Diverging Beams in Horizontally Inhomogeneous Oceanic Waveguides

Using approximate analytical calculations based on the WKB and adiabatic approximations for the mode representation of the field, as well as numerical simulation based on the theory of adiabatic modes, geometric acoustic approximation, and the parabolic equation method, the patterns of the formation and propagation of caustic and weakly diverging acoustic beams in a horizontally inhomogeneous refractive oceanic waveguide are studied. The horizontal distance regions are determined at which the dependences of the acoustic field intensity on the horizontal distance typical of caustic and weakly diverging beams are retained. The study considers the processes involved in reformation of caustic and weakly diverging beams in an oceanic waveguide with increasing water layer depth and constant sound speed profile, which near the source characterized an underwater sound channel open toward the bottom. The conditions are formulated for an effectively matched transition of shallow-water waveguide modes refracted in the thermocline and interacting with the bottom to purely refracted modes of the underwater sound channel in a relatively deep water part of the oceanic waveguide.

Updated Fast Solution for Quasi-Optical Beam Waveguides With Tilted FFT Beam Propagator

An updated fast solution in modeling quasi-optical beam waveguides is reported, where several mirror reflectors are utilized for the beam transformation. The fast Fourier transform Poynting vector ray tracing between virtual apertures (FFT-PVVAs) algorithm has been introduced and applied in modeling the reflected beam, based on the FFT-accelerated beam propagator between parallel apertures, and the Poynting vector ray tracing for the mirror reflection. However, for designing and optimizing a beam path with multireflectors, it is desired that the accumulated precision loss due to the Poynting vector ray tracing can be further reduced. As a modification, angular spectrum transform-based beam propagator between oblique apertures is introduced, so as to reduce the ray tracing path length. The improved method is named as FFT-PVVA-tilted propagation (FFT-PVVA-TP). As validation, beam propagation in a four-mirror beam waveguide is simulated by FFT-PVVA, FFT-PVVA-TP, and physical optics integration. Numerical results suggest that FFT-PVVA-TP provides clearly better accuracy after four times of beam reflection.

Temporal response of polymer waveguide beam scanner with thermo-optic phase-modulator array.

Solid-state light detection and ranging, capable of performing beam scanning without using any mechanical moving parts, requires a phase-modulator array. Polymers facilitate the fabrication of efficient phase modulators with low drive power, owing to their high thermo-optic (TO) effect and low thermal conductivity. We designed and fabricated a polymeric phase-modulator array and analyzed the temporal response of the TO phase modulator. The frequency response of the phase modulator was measured for a Mach-Zehnder interferometer (MZI), and the transfer function was modeled in terms of multiple poles and zeros. The frequency response of a fabricated beam-scanning device incorporating the TO phase modulator was also measured. The temporal response of the beam scanner was confirmed to coincide well with that of the MZI modulator. The device exhibited a fast rise time of 12 ms, accompanied by slight power variations appearing for a long period (over hundreds of seconds), which originated from the inherent viscoelastic effect of the polymer materials.

A Design of Microfluidic Chip with Quasi-Bessel Beam Waveguide for Scattering Detection of Label-Free Cancer Cells.

Light scattering detection in microfluidic chips provides an important tool to identify cancer cells without any label processes. However, forward small-angle scattering signals of cells, which are related to their sizes and morphologies, are hard to be detected accurately when scattering angle is less than 11° in microfluidic chips by traditional lighting design due to the influence of incident beam. Therefore, cell's size and morphology being the golden standard for clinical detection may lose their efficacy in recognizing cancer cells from healthy ones. In this article, a novel lighting design in microfluidic chips is put forward in which traditional incident Gaussian beam can be modulated into quasi-Bessel beam by a microprism and waveguide. The quasi-Bessel beam's advantages of nondiffraction theoretically make forward scattering (FS) detection less than 11° possibly. Our experimental results for peripheral blood lymphocytes of human beings and cultured HeLa cells show that the detection rates increase by 47.87% and 46.79%, respectively, by the novel designed microfluidic chip compared to traditional Gaussian lighting method in microfluidic chips. © 2019 International Society for Advancement of Cytometry.

Integrated photonic tunable basic units using dual-drive directional couplers.

Photonic integrated circuits based on waveguide meshes and multibeam interferometers call for large-scale integration of Tunable Basic Units (TBUs) that feature beam splitters and waveguides. This units are loaded with phase actuators to provide complex linear processing functionalities based on optical interference and can be reconfigured dynamically. Here, we propose and experimentally demonstrate, to the best of our knowledge, for the first time, a thermally actuated Dual-Drive Directional Coupler (DD-DC) design integrated on a silicon nitride platform. It operates both as a standalone optical component providing arbitrary optical beam splitting and common phase as well as a low loss and potentially low footprint TBU. Finally, we report the experimental demonstration of the first integrated triangular waveguide mesh arrangement using DD-DC based TBUs and provide an extended analysis of its performance and scalability.

Dynamics of space- and time-modulated metastructures

Topology has recently emerged as a principle governing unique wave transport phenomena through interface or edge modes that are impurity-immune and potentially unidirectional. In this context, this presentation illustrates the effect on dispersion topology of modulations of properties in space and time. The two modulation strategies are shown to lead to dual phenomena, which can be described by interchanging frequency and wavenumber, and that manifest themselves as gaps enabling frequency/wavenumber-selective wave manipulation. Time modulation produces narrowband tunable reflection at a frequency determined by the modulation, which is illustrated on a beam waveguide with switching negative impedance piezoelectric shunts. Adiabatic, or slow, space modulation of the stiffness properties of a plate structure drives the transition from a localized state at one boundary, to a bulk state and, finally, to another localized state at the opposite boundary. The presented investigations suggest the application of modulation strategies for single-port tunable filtering devices that may be implemented in acoustic, mechanical or photonic platforms. Moreover, the considered experimental platforms allow the exploration of various unique properties associated with time and/or space modulation, including filtering, frequency conversion, non-reciprocity, and topological pumping for wave redirection.Topology has recently emerged as a principle governing unique wave transport phenomena through interface or edge modes that are impurity-immune and potentially unidirectional. In this context, this presentation illustrates the effect on dispersion topology of modulations of properties in space and time. The two modulation strategies are shown to lead to dual phenomena, which can be described by interchanging frequency and wavenumber, and that manifest themselves as gaps enabling frequency/wavenumber-selective wave manipulation. Time modulation produces narrowband tunable reflection at a frequency determined by the modulation, which is illustrated on a beam waveguide with switching negative impedance piezoelectric shunts. Adiabatic, or slow, space modulation of the stiffness properties of a plate structure drives the transition from a localized state at one boundary, to a bulk state and, finally, to another localized state at the opposite boundary. The presented investigations suggest the application of mo...

About Azimuthal Acceleration of the Electrons by Azimuthal Surface Waves in a Dielectric-Lined Circular Waveguide With Two Thin Annular Rotating Electron Beams

Considering two annular rotating electron beams in a dielectric-lined waveguide, the frequency spectrum of the azimuthal waves and their field profile distribution are investigated. The charged particle acceleration due to the tangential component of the electric field is simulated. The simulation is carried out for important factors, such as the electron energy gain (acceleration gradient) and the deflection angle in two different vacuum regions (the core and clad of the dielectric waveguide). The graphs of the mentioned parameters versus the traveled distance by the electron are presented, and they are compared with each other. It is found that in some cases, the tangential acceleration of the charged particle in the clad of the cylindrical waveguide can be more effective.

Exceptional points of any order in a single, lossy waveguide beam splitter by photon-number-resolved detection

Exceptional points (EPs) are degeneracies of non-Hermitian operators where, in addition to the eigenvalues, corresponding eigenmodes become degenerate. Classical and quantum photonic systems with EPs have attracted tremendous attention due to their unusual properties, topological features, and an enhanced sensitivity that depends on the order of the EP, i.e. the number of degenerate eigenmodes. Yet, experimentally engineering higher-order EPs in classical or quantum domains remains an open challenge due to the stringent symmetry constraints that are required for the coalescence of multiple eigenmodes. Here we analytically show that the number-resolved dynamics of a single, lossy, waveguide beamsplitter, excited by $N$ indistinguishable photons and post-selected to the $N$-photon subspace, will exhibit an EP of order $N+1$. By using the well-established mapping between a beamsplitter Hamiltonian and the perfect state transfer model in the photon-number space, we analytically obtain the time evolution of a general $N$-photon state, and numerically simulate the system's evolution in the post-selected manifold. Our results pave the way towards realizing robust, arbitrary-order EPs on demand in a single device.

Liquid Crystal Beam Steering Devices: Principles, Recent Advances, and Future Developments

Continuous, wide field-of-view, high-efficiency, and fast-response beam steering devices are desirable in a plethora of applications. Liquid crystals (LCs)—soft, bi-refringent, and self-assembled materials which respond to various external stimuli—are especially promising for fulfilling these demands. In this paper, we review recent advances in LC beam steering devices. We first describe the general operation principles of LC beam steering techniques. Next, we delve into different kinds of beam steering devices, compare their pros and cons, and propose a new LC-cladding waveguide beam steerer using resistive electrodes and present our simulation results. Finally, two future development challenges are addressed: Fast response time for mid-wave infrared (MWIR) beam steering, and device hybridization for large-angle, high-efficiency, and continuous beam steering. To achieve fast response times for MWIR beam steering using a transmission-type optical phased array, we develop a low-loss polymer-network liquid crystal and characterize its electro-optical properties.

Self-similar solitons in optical waveguides with dual-power law refractive index

We consider the propagation of optical beams in an inhomogeneous nonlinear waveguide whose refractive index exhibits a dual power law dependence on the electric field amplitude. Self-similar evolution of the beams is studied within the framework of a generalized nonlinear Schrödinger equation with distributed diffraction, dual power-law nonlinearity, and gain or loss. The propagation properties and formation conditions of self-similar solitons in such a waveguide is studied by means of an improved homogeneous balance principle and an extended hyperbolic function method. A variety of new self-similar bright solitons are found and their characteristics are explored in terms of the inhomogeneous material parameters. A class of self-similar kink solitons is also identified, featuring another type of the self-similar evolution in the nonlinear waveguide. Dynamical behaviors of these self-similar structures are studied for a periodic distributed amplification system. It is shown that the parameters associated with the group velocity enable one to control the self-similar wave structure and dynamical behavior more efficiently, while the gain parameter affects just the evolution of the self-similar soliton’s peak. Unlike the case of homogeneous dual power-law materials, soliton structures in inhomogeneous systems show novel and interesting features due to their distributed parameters which allow effective control of their dynamics.

High gain substrate integrated waveguide beam scanning antenna with sub‐array elements

A method to enhance the gain of substrate integrated waveguide (SIW) beam scanning antenna is proposed in this article. 2 × 2 SIW cavity-backed sub-arrays are employed in array design. The antenna is constructed on two layers. The top layer places four SIW cavity-backed sub-arrays as radiating elements and the bottom layer is an SIW transmission line to feed the sub-arrays. Beam scanning feature can be obtained due to the frequency dispersion. Moreover, through separating radiators to the other layer and using 2 × 2 SIW cavity-backed sub-arrays as radiating parts, the antenna gain is improved significantly. For a linear array, 4.1 to 6.8 dB gain enhancement is achieved compared to a conventional SIW beam scanning antenna with the same length. Then, the linear array is expanded to form a planar array for further gain improvement. A 64-element planar beam scanning array is designed, fabricated, and tested. Experimental results show that the proposed planar array has a bandwidth from 18.5 GHz to 21. 5 GHz with beam scanning angle from −5° to 11.5° and gain in the range of 20.5 to 21.8 dBi. The proposed high gain beam scanning antennas have potential applications in radar detection and imaging.

Highly directive 3D‐printed dual‐beam waveguide slotted antennas for millimeter‐wave applications

AbstractA highly directive 3D‐printed dual beam waveguide slotted antennas designed at 28 GHz are presented in this work. By having dual‐beam directional pattern, the coverage area can be doubled. The performance of dual‐beam waveguide slotted antennas is investigated with new metal 3D printing technique. The slots are basically designed at half wavelength dimension and distance with symmetrical and asymmetrical offset to form different phase radiations. The longitudinal slotted arrays are implemented on both side of the waveguide broad walls, thus enabling the dual beams on the antenna. The proposed antennas are simulated using computer simulation technology software and fully metal printed using EOS M280 machine. The simulated performance is validated experimentally using network analyzer measurement. The dimensional tolerance and surface roughness are profiled in this work. A good match better than 10 dB is achieved. The antennas are proposed for three‐dimensional beamforming in millimetre wave applications.

Generation of THz radiation by sequence of ring beams in multilayer dielectric waveguide

In this paper, we describe a new type of a THz radiation source in a multilayer dielectric waveguide based on the Vavilov-Cerenkov radiation created by a sequence of electron ring beams. We present parameters of the sequence needed for generation of TM03 with frequency of 531.2 GHz in result radiation and results of beam dynamics calculation. Also, we discuss the degree of monochromaticity and spectrum of the THz radiation.

Two-dimensional silicon annular photonic crystals for realizing polarization-independent unidirectional transmission

Optical diode is a device that can realize unidirectional transmission of light. Its function is similar to that of an electronic diode. It has important applications in the field of optoelectronic integration and all-optical communications. Unidirectional wave transmission requires either time-reversal or spatial inversion symmetry breaking. The magneto-optical effect and optical nonlinearity are usually utilized to break the time-reversal symmetry and obtain the unidirectional transmission. However, these schemes all need high light intensity or magnetic field strength to be realized, and limit the usage. Therefore, spatial inversion symmetry breaking is highly desirable because of totally linear materials under low intensities. Quit a lot of researchers have designed optical diodes based on the photonic crystals and achieved unidirectional transmission for TE-like or TM-like light. The early design realized light unidirectional transmission by PC structures for only one polarization state (TE-like or TM-like incident light). It limits the application for the high integration and reconfigurable optical interconnection. The structure which can achieve unidirectional transmission for both TE and TM polarizations needs to be designed. The annular PCs have been verified to realize polarization-independent phenomena, such as beam splitting, self collimation and waveguide. In this paper, an annular PC is proposed. The plane wave expansion method is used to calculate band structures. The results show that it exhibits a significant directional band gap for both TE and TM mode. Then, the triangular annular PC is constructed, and its transmission spectra and field distributions are calculated by the finite-different time-domain method. It is found that the structure can realize the polarization-independent unidirectional transmission, but the forward transmissivity is too low (about 20%). Moreover, another smaller size annular PC is further introduced to form annular PC heterojunction, which effectively improves the polarization-independent unidirectional transmission performance and the forward transmissivity has doubled. Through the adjustment of the interface structure, the forward transmissivity is further increased. The optimized annular PC heterostructure can realize polarization-independent unidirectional transmission, and the forward transmissivity reaches 44%. The heterostructure can be used to fabricate polarization-independent optical diode, and may have potential applications in complex all-optical integrated circuits.

Gain Enhancement for Circularly Polarized SIW Frequency Beam Scanning Antenna Using a Phase-Correcting Grating Cover

A planar circularly polarized (CP) frequency beam scanning Fabry-Perot resonator antenna (FPRA) with enhanced gain property is presented in this paper. The antenna consists of two layers. The CP substrate integrated waveguide (SIW) beam scanning leaky-wave antenna (LWA) is used as the feeding antenna. It provides good impedance matching and stable radiation pattern over the working band. Then, partially reflecting surface (PRS) layer is introduced to improve the gain property by using a single substrate with metal patches array printed on both top and bottom surfaces. After comparisons among four patch types, circular patch type is chosen. It is an ideal choice for CP antenna because of its completely symmetrical structure along φ-plane and gentler phase slope. Parameter analysis is made for better understanding of the working principle. Finally, the antenna is fabricated and measured for verification. It shows that the main beam scans from -38° to 28° within the operating frequency band from 9.1 to 14.6 GHz (or 47.8%). The 3-dB axial ratio (AR) bandwidth is from 10.2 to 13.5 GHz (or 28.7%). Maximum gain is 14.6 dBic, and 3-dB gain bandwidth is from 11 to 14 GHz (or 26.1%). Gain enhancement of about 3.3 ~ 6 dB is achieved, compared with the unloaded type. Due to the advantages of high gain, CP beam-scanning capability, and easy fabrication, this method is a good option to design antennas in wireless communication and radar systems.

Beam dynamics in quadratically nonlinear waveguides with gain and losses

A propagation of optical beams in active waveguides with quadratic nonlinearity is considered. It is shown that gain in one harmonic can compensate losses in the other harmonic. As a result of this process, stationary beams can be formed in the system. Exact solutions for stationary modes of a single waveguide are obtained, and their stability is analyzed. A possibility of the Hopf bifurcation that results in emergence of stable periodic regimes in a monomer is demonstrated. Stationary solutions are also found for a dimer with identical waveguides and a dimer with parity-time symmetry. The stability analysis demonstrates that stable beams exist in a wide range of the system parameters.