Waveguide Dimensions Research Articles

Highly efficient, modal phase-matched second harmonic generation in a double-layered thin film lithium niobate waveguide.

In this contribution, we numerically investigate second harmonic generation in double-layered lithium niobate on the insulator platform by means of the modal phase matching. The modal dispersion of the ridge waveguides at the C waveband of optical fiber communication is calculated numerically and analyzed. Modal phase matching can be achieved by changing the geometric dimensions of the ridge waveguide. The phase-matching wavelength and conversion efficiencies versus the geometric dimensions in the modal phase-matching process are investigated. We also analyze the thermal-tuning ability of the present modal phase matching scheme. Our results show that highly efficient second harmonic generation can be realized by the modal phase matching in the double-layered thin film lithium niobate ridge waveguide.

Topological magnon modes of a chain of magnetic spheres in a waveguide

We study topological features of a bipartite chain of magnetic spheres embedded in a rectangular metallic waveguide. The coherently coupled chain via the waveguide mode can host two topologically distinct phases identified by the Zak phase. A finite chain supports a pair of doubly degenerate topological edge states within the gap when the intercoupling dominates over the intracoupling, demonstrating that despite the strong coupling to the waveguide mode, the bulk-edge correspondence still holds. The nontrivial (trivial) topological phase is determined by the intracell and intercell coupling of magnetic spheres which depend on the separation, the external magnetic inductions, and the waveguide dimensions. Magnetically tunable topological magnon modes may enable unprecedented topological photonic devices.

СУМАТОР ПОТУЖНОСТЕЙ НА БАЗІ КВАЗІОПТИЧНОГО ВІДКРИТОГО РЕЗОНАТОРА ЯК ВИСОКОСТАБИЛЬНИЙ ГЕНЕРАТОР ТЕРАГЕРЦЕВОГО ДІАПАЗОНУ

The efficiency of excitation of the axial-asymmetric vibration TEM10q in a quasioptical open resonator of the power combiner (ORSM) by means of the TE20 waveguide wave is investigated. Based on the theory of mirror antennas, the efficiency of excitation of TEM10q oscillations in a hemispherical resonator using a rectangular waveguide with a cross-section in which the TE20 wave propagates is estimated. Based on the calculations, it was concluded that about 87% of the power supplied to the resonator via the waveguide is used to excite the oscillation under consideration. Therefore, such a resonant system should have good selective properties. Additional studies were conducted to confirm this. It was established that with coordinated excitation of oscillations in the VRSP, the latter has angular and frequency spectrum selection. With the correct selection of the transverse dimensions of a rectangular waveguide with a TE20 wave, located in the center of a VRSP flat mirror, the latter will have a single-frequency response in a wide frequency band and a high power stacking factor in the terahertz range can be provided. When placing the sources in each of the two rectangular waveguides that pass into the emitters of the above dimensions, we will get a power adder based on a hemispherical VRSP. An electrodynamic system of two rectangular waveguides of certain cross-sectional dimensions is proposed and investigated, which allows adjusting the amount of coupling between the sources and the resonator. For this purpose, an E-polarized wire diffraction grating is located on the VRSP flat mirror, changing the period of which regulates the connection of the resonator with the sources. It was found that by choosing the parameters of one-dimensional diffraction gratings (E-polarization) in the openings of the communication elements, it is possible to ensure any predetermined connection of individual sources with a resonant volume. Experimental studies of VRSP at a frequency of 130 GHz were carried out. The measured power at its output was within (10...13 dBm), which corresponds to the efficiency of power assembly k=0.76. The results of the conducted research allow us to draw a conclusion about the prospects of using the developed VRSP in highly stable generators of the terahertz range.

A New Design for Enhancing Highly Sensitive Interferometer Biosensor Using a Silicon Rib Waveguide

In this paper, we have proposed a new design, to enhance and simulate a Highly Sensitive Mach-Zehnder Interferometer (MZI) Biochemical sensing platform using a Silicon Rib Waveguide. We considered two different MZI configurations: the first one with an S-bend & Y-junction and the second with an angular Y-junction. We determined the critical cut-off radius and the critical cut-off angle for the S-bend & Y-junction and the angular Y-junction configurations respectively. Based on the analyses of the evanescent field intensity, the mode polarization and cross section dimensions of the Silicon Rib waveguide are optimized using beam propagation method. The critical parameters of the design are calculated to ensure minimal optical losses and a new sensitivity value of 308 dB/RIU with a detection limit of 10-7, which shows the ability of the structure to produce biosensor.

Hybrid Image Graphene Polaritons with Extremely Confined Mode and Field Enhancement in the Terahertz Regime

AbstractGuiding terahertz waves below the diffraction limit of light typically excite graphene plasmons (GPs). However, the mode confinements of conventional GPs using graphene–dielectric interfaces are limited. To further squeeze the optical mode sizes, a graphene–dielectric–metal (GDM) configuration supporting an image graphene plasmon (IGP) has been reported recently through the plasmon interactions in a graphene sheet and its mirror image inside a metal with out‐of‐phase charge oscillations. This study proposes a waveguide structure consisting of a cylindrical dielectric wire over a GDM to achieve an ultraconfined mode area by coupling a dielectric waveguide and an IGP mode. Furthermore, this work examines the dependence of waveguide dimensions and material properties on the mode characteristics of the proposed hybrid IGP (HIGP). This HIGP achieves plasmon wavelengths 20 times shorter and normalized propagation lengths twice longer than GPs, accompanying a mode size of 3 × 10−8A0, where A0 is the diffraction‐limited mode area. Moreover, the simple structure makes the HIGP easy to be verified experimentally. This work demonstrates that the HIGP delivering strong light–matter interactions at extremely compact dimensions can be exploited for building highly integrated, enhanced nonlinear, high‐resolution sensing and imaging THz devices.

Hybrid integration of chipscale photonic devices using accurate transfer printing methods

Transfer printing is becoming widely adopted as a back-end process for the hybrid integration of photonic and electronic devices. Integration of membrane components, with micrometer-scale footprints and sub-micron waveguide dimensions, imposes strict performance requirements on the process. In this review, we present an overview of transfer printing for integrated photonics applications, covering materials and fabrication process considerations, methods for efficient optical coupling, and high-accuracy inter-layer alignment. We present state-of-the-art integration demonstrations covering optical sources and detectors, quantum emitters, sensors, and opto-mechanical devices. Finally, we look toward future developments in the technology that will be required for dense multi-materials integration at wafer scales.

High-Performance Pockels Effect Modulation and Switching in Silicon-Based GaP/Si, AlP/Si, ZnS/Si, AlN/3C-SiC, GaAs/Ge, ZnSe/GaAs, and ZnSe/Ge Superlattice-On-Insulator Integrated Circuits.

We propose new a Si-based waveguided Superlattice-on-Insulator (SLOI) platforms for high-performance electro-optical (EO) 2 × 2 and N × M switching and 1 × 1 modulation, including broad spectrum and resonant. We present a theoretical investigation based on the tight-binding Hamiltonian of the Pockels EO effect in the lattice-matched undoped , , , , , , and wafer-scale short-period superlattices that are etched into waveguided networks of small-footprint Mach-Zehnder interferometers and micro-ring resonators to yield opto-electronic chips. The spectra of the Pockels r33 coefficient have been simulated as a function of the number of the atomic monolayers for “non-relaxed” heterointerfaces. The large obtained r33 values enable the SLOI circuit platforms to offer a very favorable combination of monolithic construction, cost-effective manufacturability, high modulation/switching speed, high information bandwidth, tiny footprint, low energy per bit, low switching voltage, near-IR-and-telecom wavelength coverage, and push-pull operation. By optimizing waveguide, clad, and electrode dimensions, we obtained very desirable values of the VπL performance metric, in the range of 0.062 to 0.275 V·cm, portending a bright future for a variety of applications, such as sensor networks or Internet of Things (IoT).

Phase regeneration of 8PSK signal using phase-sensitive amplification based on an organic-Ge hybrid waveguide.

We numerically demonstrate the phase regeneration of eight-phase-shift keying (8PSK) in an organic-Ge hybrid waveguide with 10µm length. Through filling graphene oxide with a high Kerr coefficient and engineering of waveguide dimensions, an ultrahigh nonlinear coefficient with 5.86×106W-1m-1 is attained at 1550 nm. The phase regeneration of 8PSK signal is achieved by using phase-sensitive amplification of the dual-conjugated-pump degenerate four-wave mixing scheme. The error-vector magnitude (EVM), optical signal-to-noise ratio, as well as constellation diagrams of 8PSK signal are also used to evaluate the phase regeneration capacity quantitatively. A reduction of EVM from 39.25% to 1.34% for 8PSK signal is found. The results show great phase regeneration and noise-squeezing ability, which indicate that such a phase-sensitive amplifier of a waveguide can find critical promising applications in all-optical signal processing.

Space charge waves in a two-dimensional electron gas

This paper uses field theory to derive the exact dispersion relation of space charge waves in a two-dimensional electron gas (2DEG) located in a dielectric or a dissimilar dielectric waveguide. It is found that the dispersion of a 2DEG can be modeled accurately using the free-electron sheet model, which is further confirmed by the almost identical polarizability of a 2DEG and of a free-electron sheet with zero drift velocity. Transitions among the well-known 2DEG dispersion, the beam mode in vacuum electronics, and Gould–Trivelpiece mode in plasma physics are demonstrated by varying the 2DEG density and direct current drift velocity. The effects of waveguide dimensions are also presented. Our method is general and can be applied to find the dispersion relation of 2DEG with arbitrary drift velocity (governed by electric field and scattering) in more complex circuits. Our study provides insight into the design of electromagnetic wave devices and circuits involving a 2DEG.

Mitigating indistinguishability issues in photon pair sources by delayed-pump intermodal four wave mixing.

Large arrays of independent, pure and identical heralded single photon sources are an important resource for linear optical quantum computing protocols. In the race towards the development of increasingly ideal sources, delayed-pump intermodal four wave mixing (IFWM) in multimode waveguides has recently emerged as one of the most promising approaches. Despite this, fabrication imperfections still spoil the spectral indistinguishability of photon pairs from independent sources. Here we show that by tapering the width of the waveguide and by controlling the delay between the pump pulses, we add additional spectral tunability to the source while still inheriting all the distinctive metrics of the IFWM scheme. This feature is used to recover spectral indistinuishability in presence of fabrication errors. Under realistic tolerances on the waveguide dimensions, we predict >99.5% indistinguishability between independent sources on the same chip, and a maximum degradation of the heralded Hong-Ou-Mandel visibility <0.35%.

Analysis of Optical Losses in Polymer Optoelectronic Bus of a New Generation Printed Circuit Boards

The article considers individual factors of loss growth in polymer planar optical waveguides, which are included in the composition of optical-electronic buses, introduced in perspective new generation printing boards. The article proposes several approaches to reducing losses in optical radiation, which include losses at the end of the optical waveguide and the light transition to the input/output element of the optoelectronic bus of the printed circuit board. According to the results of modelling the modal structure of a polymer planar optical waveguide, made from a polymer material, polydimethylsiloxane (PDMS), in the software environment of Comsol Multiphysics, the dimensions of the core optical waveguide are determined, providing a single-mode structure of an optical waveguide. A measuring stand was developed and assembled for calculating the transmission losses in polymer planar optical waveguides of the optoelectronic bus of a printed circuit board, which meets the requirements of IEC 62596-2: 2017. The minimum measured loss in the manufactured polymer planar optical waveguides was 20 dB, which corresponds to foreign analogues of the optical-electronic bus of the printed circuit board.

Scalable and Robust Photonic Integrated Unitary Converter Based on Multiplane Light Conversion

Optical unitary converter (OUC) that can convert a set of N mutually orthogonal optical modes into another set of arbitrary N orthogonal modes is expected to be the key device in diverse applications, including the optical communication, deep learning, and quantum computing. While various types of OUC have been demonstrated on photonic integration platforms, its sensitivity against a slight deviation in the waveguide dimension has been the crucial issue in scaling N. Here, we demonstrate that an OUC based on the concept of multi-plane light conversion (MPLC) shows outstanding robustness against waveguide deviations. Moreover, it becomes more and more insensitive to fabrication errors as we increase N, which is in clear contrast to the conventional OUC architecture, composed of 2 $\times$ 2 Mach-Zehnder interferometers. The physical origin behind this unique robustness and scalability is studied by considering a generalized OUC configuration. As a result, we reveal that the number of coupled modes in each stage plays an essential role in determining the sensitivity of the entire OUC. The maximal robustness is attained when all-to-all-coupled interferometers are employed, which are naturally implemented in MPLC-OUC.

A Study of Wave Confinement and Optical Force in Polydimethlysiloxane-Arylazopyrazole Composite for Photonic Applications.

A refractive index of dielectrics was modified by several methods and was known to have direct influence on optical forces in nanophotonic structures. The present contribution shows that isomerization of photoswitching molecules can be used to regulate refractive index of dielectrics in-situ. In particular, spectroscopic study of a polydimethylsiloxane–arylazopyrazole (PDMS–AAP) composite revealed that refractive index of the composite shifts from 2.0 to 1.65 in trans and cis states, respectively, of the embedded AAP. Based on this, a proposition is made for a waveguide structure, in which external UV/Vis source reversibly regulates the conformation of the PDMS–AAP core. Computational study is performed using Maxwell’s equations on buried waveguide structure. The simulation, implemented in PYTHON, sequentially utilizes empirical refractive indices of the composite in the isomeric states in lieu of regulation by a source. The simulation revealed highly confined wave propagations for injected signals of 340 and 450 nm wavelengths. It is observed that the cis state suppresses higher order mode when propagating UV wavelength but allows it for visible light. This modal tuning demonstrated that single mode can be selectively excited with appropriate waveguide dimensions. Further impact of the tuning is seen in the optical force between waveguide pair where the forces shift between attractive and repulsive in relation to the isomeric state of the PDMS–AAP core. These effects which stem from the adjustment of refractive index by photoisomerization suggests that in-situ regulation of index is achievable by successful integration of photoswitching molecules in host materials, and the current PDMS–AAP composites investigated in this study can potentially enhance nanophotonic and opto-mechanical platforms.

Slot Line Waveguide Induced Magnetization Dynamics of Perpendicularly Magnetized La-YIG Thin Film

We study the magnetization dynamics in La-doped yttrium iron garnet thin film induced by a slot line waveguide with the magnetic field applied perpendicular to the plane. The magnetization dynamics depend significantly on the slot line waveguide dimensions, particularly the number of excitation conditions increases with the enlargement of linewidth and the gap between the lines. Such an increase is not observed when the magnetic field is applied to the film plane. The excitation is caused by the interaction between the local magnetization dynamics around the line and the spin waves coming from the other side of the line. Forward volume magnetostatic spin waves are emitted when the magnetic field is applied perpendicular to the film. Their magnetic field dependence of the wavelength change is very gradual, allowing the satisfaction of the resonance condition to be much easier than the in-plane magnetized film.

Highly Sensitive Refractive Index-Based Sensor for DNA Hybridization Using Subwavelength Grating Waveguide

A biosensor for detecting DNA hybridization via refractive index sensing has been demonstrated using a subwavelength grating (SWG) waveguide. Waveguide dimensions are selected by parametric optimizations to increase the mode-analyte overlap with considerations of typical silicon-on-insulator fabrications technology. DNA layer is added with a linker layer on silicon pillars of the SWG waveguide to optimize and detect the DNA hybridization. Some essential characteristics such as mode overlap factor, change in effective refractive index, waveguide sensitivity, and shift in resonance wavelength are computed for the different dimensional parameters of the SWG waveguide in DNA hybridization along with mode field intensity and normalized power using the finite element method. The DNA hybridization is shown by variation in normalized power of interacting light in cladding region of the waveguide for 0% to 100% fractional change of dsDNA and ssDNA. Waveguide sensitivity, shift in resonance wavelength, device sensitivity, and intrinsic limit of detection are obtained to ∼ 0.157, 7.01, 605 nm/RIU, and 1.30 × 10−4 RIU, respectively, for the optimized structure of SWG waveguide in sensing of DNA hybridization, which could be suitable aspects for detecting DNA hybridization.

Triangular Shape Hybrid Metal-Insulator-Metal Plasmonic Waveguide for Low Propagation Loss at Deep Subwavelength

The triangular shape based hybrid metal-insulator-metal plasmonic waveguide, to achieve the low propagation loss at deep-subwavelength, has been proposed, and analyzed for the optical properties of the fundamental mode, such as normalized effective mode area, propagation length, etc., at <inline-formula><tex-math notation="LaTeX">$1550{\rm{\ nm}}$</tex-math></inline-formula> of working wavelength. Due to the triangular type of high-index regions, the light is primarily confined at its tip-points, i.e., within the low-index materials. This type of waveguide structure can essentially provide the remarkably low propagation loss at deep subwavelength. The optical performance of fundamental hybrid mode is analyzed, by altering the waveguide dimensions, including the angle of triangular-shape high-index layer. Further, the investigation of mode character helps to understand the mode behavior of the proposed waveguide. The simulation results have established that the propagation length of fundamental hybrid mode of the presented waveguide can be achieved as &#x223C; 279.7 &#x03BC;m, with the normalized effective mode area of <inline-formula><tex-math notation="LaTeX">$\sim \ 0.4842$</tex-math></inline-formula>, at <inline-formula><tex-math notation="LaTeX">$w= 200\ nm$</tex-math></inline-formula>, <inline-formula><tex-math notation="LaTeX">${h_{si}} = \ 300\ nm$</tex-math></inline-formula>, <inline-formula><tex-math notation="LaTeX">${h_g} = \ 10\ nm$</tex-math></inline-formula>, and <inline-formula><tex-math notation="LaTeX">${h_m} = \ 100\ nm$</tex-math></inline-formula>; however, with other waveguide dimensions, <inline-formula><tex-math notation="LaTeX">${L_p}$</tex-math></inline-formula> has been achieved as, <inline-formula><tex-math notation="LaTeX">$ &gt; 700\ \mu m.$</tex-math></inline-formula> Further, the analysis on coupling length <inline-formula><tex-math notation="LaTeX">$( {{L_c}} ),$</tex-math></inline-formula> between the two nearby and similar type of the proposed waveguides, have been accomplished, and <inline-formula><tex-math notation="LaTeX">${L_c} &gt; 2500\ \mu m$</tex-math></inline-formula> has been attained for the waveguide separation, and width respectively of <inline-formula><tex-math notation="LaTeX">$800\ nm$</tex-math></inline-formula>, and <inline-formula><tex-math notation="LaTeX">$200\ nm$</tex-math></inline-formula>. Moreover, the phases of fabrication process, along with the tolerance issues in fabricating the tip-points of high-index regions, have been discussed for the proposed waveguide structure. The waveguide structure proposed in this work can be fundamentally effective for the proposal of various nano-photonic components, such as power splitter, directional coupler, etc.

Material Relative Permittivity Determination From the Inhomogeneous Transmission-Line Secondary Parameters

After further transmission line technique investigation, we propose a new approach to material characterization based on the combination of the propagation constant and the characteristic impedance of the transmission-line. Three main elements constitute the approach novelty’s root: the determination of the propagation constant without using the eigenvalue principle, the improved mathematical expression of the characteristic impedance, and the automatically corrected coefficient. The two-line technique is based on three required measures, where the most extended fixture is partially filled with the specimen to be tested. As a result, the discontinuities caused by the geometric change of access interfaces and the waveguide dimensions have been solved. The characteristic impedance is determined straight and amended by a third polynomial function degree. The polynomial function and the amended correction coefficient determination are the facilitation parameters of the new approach technique. This new method allows the extraction of the material’s complex relative permittivity. The procedure has been validated with the Rogers RO4003C, Alumina 99.6%, and Vinifera (based on the dielectric materials available in our laboratory) through the microstrip fixture in the scanned frequency (0.08 – 8) GHz by extracting its electric intrinsic parameters. The dielectric constants range from 1.1–10.4, where the thicknesses are 1.54 mm, 2.067 mm, and 1.078 mm have been used. Two identical microstrip test cells with the same geometric dimensions but various lengths have been manufactured. That promotes the feasibility of two measures simultaneously.

Quad-Port MIMO Filtenna With High Isolation Employing BPF With High Out-of-Band Rejection

A quad-port multiple-input multiple-output (MIMO) filtenna with compact dimensions of <inline-formula> <tex-math notation="LaTeX">$50\times50$ </tex-math></inline-formula> mm² is arranged. In this MIMO filtenna, each element is placed orthogonal to its adjacent one to enhance the isolation. The MIMO element is configured based on the novel COVID-19 virus shape with a co-planar waveguide (CPW) feeding structure and dimensions of <inline-formula> <tex-math notation="LaTeX">$17\times22$ </tex-math></inline-formula> mm². The element bandwidth ranges from 3.3 GHz to more than 60 GHz. Three frequency notches are designed at 3.5 GHz for WiMAX, 5.5 GHz for WLAN, and 8.5 GHz for X-band applications. A bandpass filter (BPF) with high out-of-band rejection is used as a decoupling structure (DS) to improve the isolation to more than 30 dB across most of the bandwidth. The BPF is designed based on LC lumped elements, and then implemented using planar strip lines. The proposed MIMO filtenna system provides an impedance bandwidth of 2.4&#x2013;18 GHz, a peak gain of 5 dBi, and an envelope correlation coefficient (ECC) less than 0.00021. In turn, channel capacity loss does not exceed 0.2. The MIMO filtenna is fabricated and measured showing a good agreement between the measured and simulated results.

On-chip stimulated Brillouin scattering in As[formula omitted]S[formula omitted] waveguides with soft claddings of Benzocyclobutene

On-chip stimulated Brillouin scattering (SBS) can be implemented with arsenic trisulfide (As2S3) waveguides and benefits various applications of microwave photonic, signal processing and sensing. While stiff top-claddings of silica on the waveguides can help to enhance the opto-acoustic interaction in SBS, the soft cladding can facilitate the realization of narrow linewidth Brillouin lasers. Herein, we systematically study the on-chip SBS characteristics of the ridge As2S3 waveguides with soft claddings of Benzocyclobutene (BCB). Specifically, an optical propagation loss lower than 0.2 dB/cm and a Brillouin gain coefficient of approximately 300 m−1 W−1 at the Brillouin frequency of 7.70 GHz have been demonstrated. In particular, the linewidth of the Brillouin gain spectrum is broadened to be about 60 MHz. The influence of waveguide width on the SBS properties is systematically studied and the mostly-concerned linewidth broadening effect with respect to different waveguide dimensions has been found to be negligible. As an application of the fabricated BCB-cladded As2S3 waveguide, we have demonstrated the microwave bandpass filter with a suppression ratio of up to 23 dB. The As2S3 waveguides with BCB claddings may provide an effective and economic platform for on-chip SBS applications, such as integrated notch filter, Brillouin amplifiers, Brillouin lasers.

Metallic waveguide transmitarrays for dual-band multibeam terahertz antennas

A metallic waveguide transmitarray antenna (MWTA) is proposed to attain dual-band multibeams with high gain in the terahertz (THz) range, which is realized by independently controlling the phases of the two bands with orthogonal polarizations simultaneously. The phase distribution of each polarization on the MWTA for attaining the corresponding multibeam radiation pattern is calculated by using the Gerchberg–Saxton algorithm based on Fresnel diffraction theory. Furthermore, the phase delay of each unit cell is adjusted by varying the waveguide dimension to achieve the corresponding phase distributions. As a proof of concept, a dual-band MWTA with a diameter of 48 mm is designed and simulated to transform plane waves into triple beams at 0.14 THz and dual beams at 0.1 THz, respectively. Their peak gains are ∼30 and ∼28 dBi and the aperture efficiencies are 67% and 56%, respectively. Their 1 dB gain bandwidths can reach 10 GHz (136.5–146.5 GHz) and 11 GHz (94.7–105.6 GHz), respectively. The measured far-field results agree well with the simulations. The proposed dual-band THz antennas are very promising for applications in wireless and satellite communications.