Input Waveguide Research Articles

Optical refractive index sensor for detection of N2, He and CO2 gases based on square resonance nanocavity in 2D photonic crystal

In this work, the design and simulation of high-sensitivity gas optical sensor (GOS), based on photonic crystals with refractive index different of linear materials is presented. The lattice index is cubic and the dielectric rods are made of silicon and are designed in a square shape. In the proposed optical sensor, three resonance nanocavities are used, the central nanocavity is made of silicon with a refractive index of nSi=2.6, and the sub-nanocavities located in the path of the input waveguide and the output waveguide This optical sensor is able to detection of N2, He and CO2 gases from the air. Numerical simulation results are obtained using two-dimensional FDTD method. The use of three resonance nanocavities and the distances between the dielectric rods increased the sensitivity and quality factor of the structure. The proposed optical sensor has a sensitivity of S = 400 nm/RIU and a quality factor of Q.f = 1080.615, and the power transmission is about TE=100%. The figure of merit is equal to FOM = 258.333 ± 8.333 RIU−1. It is designed to integrate the structure with small dimensions as much as possible. The overall dimensions of the structure are 72.6μm2, which can be easily used in optically integrated circuits.

Design of millimeter wave radar amplification module

In this paper, the millimeter wave radar amplification device is designed using the MWG303 power amplifier chip of Milliway Electronic Technology Co., Ltd. The whole device comprises an input waveguide microstrip transition structure based on Rogers 5880 and an output waveguide microstrip transition structure based on quartz. And waveguide structures such as waveguide turn and waveguide lift, in this design, the waveguide microstrip transition circuit is designed and simulated in the 3D electromagnetic field simulation software HFSS of Ansoft Company, and then the parts are combined, and the micro-assembly test is carried out after CAD processing. The results show that the gain can reaches more than 10dB. The design has the advantages of high gain, good flatness, practical structure and so on.

Ultracompact mode-order converting power splitter for mid-infrared wavelengths using an MMI coupler embedded with oblique subwavelength grating wires

An ultracompact mode-order converting power splitter using a multimode interference (MMI) coupler with subwavelength gratings (SWGs) is proposed for mid-infrared (MIR) wavelength. Two symmetric oblique SWG-wires are embedded in the central input-region that is connected with the input waveguide. As a result, the input TE0 mode is evenly coupled from the input waveguide into the MMI coupler due to the adiabatical mode evolution, and then two desired TE1 modes are formed via self-imaging effect and further guided into the two output channels. Additionally, tapered structures and straight SWG wires are introduced into the two output channels to better obtain the required phase difference for the improvement of converting efficiency. Consequently, both TE0-to-TE1 mode-order converting and power splitting, for the first time, are attained simultaneously in the present single device. Moreover, TE0-to-TE2 power splitting can be readily achieved by flexibly changing the dimensions of the proposed device. Results show that a compact device length of 7μm with an insertion loss (IL) of 0.41 dB, a conversion efficiency (CE) of 99% and a crosstalk (CT) of -19.77 dB is obtained at the wavelength of 2μm; its bandwidth can be enlarged to 220 nm for IL < 0.79 dB and CE> 91%. Besides, fabrication tolerances are addressed and mode propagation profiles are illustrated.

ON USING BENCH MEASURING PIPELINES AS ACOUSTIC LOADS OF PRESSURE PULSATION PROBES

When adjusting the gas turbine engine for operating parameters, taking into account pressure pulsations in the gas generator path, acoustic probes are used with the sensor moving out of the high temperature zone. The input waveguide included in the probe is an acoustically resonating element that significantly distorts the measurement result. Among the various corrective elements for acoustic probes, in practice, a special role is given to non-reflective loads in the form of long lines. During bench tests, it is often advisable for manufacturers to use structures made up of durite hoses with short sections of metal pipelines in addition to long lines. The attached material shows the test results of a model probe with several types of such agreed loads. The possibility of such a solution to increase the accuracy of measuring pressure pulsations in conditions of increased temperatures is shown.

Novel Wavelength Multiplexer Using (N + 1) × (N + 1) Arrayed Waveguide Grating and Polarization-Combiner-Rotator on SOI Platform

We propose an ultra-compact novel wavelength multiplexer employing a ( N + 1) × ( N + 1) arrayed waveguide grating (AWG) and a polarization-combiner-rotator (PCR) on the SOI platform, to realize a multiplexing for 2 N wavelengths with a spacing of Δλ. The ( N + 1) × ( N + 1) AWG works at a bidirectional way to provide two groups of N × 1 wavelength multiplexing with each group having a channel spacing of 2×Δλ, and the central wavelengths of all input channels in one group have a wavelength shift of Δλ with respect to those in the other group. The double channel spacing results in a significant decrease on the footprint of the ( N + 1) × ( N + 1) AWG-based multiplexer compared with a conventional 2 N × 1 AWG multiplexer with the same wavelength spacing Δλ. Due to the fact that a single mode fiber is insensitive to the polarization of input light, if we consider short reach datacom applications such as 100/400 GbE, the two separate multiplexing outputs of the ( N + 1) × ( N + 1) AWG can be combined as one output with one half wavelengths working at TE polarization and the other at TM polarization by employing a low loss and broadband PCR. In the experiment, we demonstrate a 16 × 200 GHz multiplexer based on a 9 × 9 AWG. The experimental results show that the on-chip loss of the fabricated multiplexer is 2.7 dB and the loss uniformity is 0.5 dB. The 1-dB and 3-dB bandwidths are >0.56 nm (i.e., 35% of the wavelength spacing) and >1.1 nm (i.e., 69% of the wavelength spacing), respectively. They can also be further increased by decreasing the gap between adjacent input waveguides at the interfaces of star couplers of the designed AWG without inducing an excess loss. The proposed multiplexer has great potential for application to future super large capacity (> Tb/s) data transmission systems.

Three-dimensional modeling of processes in a traveling-wave tube terahertz range

Mastering the terahertz range promises many opportunities for practical application, in this regard, the problem of optimizing existing and creating new amplifiers and generators operating in this frequency range does not lose its relevance. One of the possible approaches for solving the problem under consideration is provided by electrovacuum electronics, where a traveling wave lamp can be especially noted due to the combination of its characteristics in terms of power and bandwidth. Goal. Creation of a threedimensional model of the device, based on the finite difference time domain (FDTD) method for Maxwell's equations and the cloudin-cell (CIC) method, followed by a series of numerical experiments to study the characteristics of the device with the given electron flow parameters and space configuration interactions. Results. The results of modeling a traveling-wave tube of the O-type in the terahertz range are presented using the example of an amplifier with a retarding structure of the double comb type with a strip electron flow. It is shown that the presented algorithm can be used to simulate processes in a slow-wave structure of a complex type with an input and output waveguide and absorber inserts. The power gain is estimated for a system with an absorber of various lengths, and the absorber length is optimized. Practical significance. The field of application of the proposed model is the study of processes in electrovacuum devices with the aim of both modernizing existing microwave amplifiers and generators in the terahertz range, and developing new devices.

Steam replacement strategy using microwave resonance: A future system for continuous-flow heating applications

This study proposed the replacement of the steam heat exchanger by a novel continuous-flow microwave system. The current microwave heating system has two main drawbacks for continuous-flow applications: higher reflection losses, which reduce the effective microwave power and pose potential safety risks, and an unsteady heating rate, which leads to insufficient heating in a limited time and lower energy conversions. Therefore, we introduced the conceptual design of a novel continuous-flow microwave system for overcoming the specific drawbacks to the largest extent possible. A numerical model of this designed system was developed based on a waveguide-type cavity resonator after fully considering the properties of energy conversion and absorption. Rather than the previous systems, the combined input of waveguides on the E- and H-planes can not only improve over 20% energy utilization, but also facilitate the heating effect of the fluids. Noteworthily, the 45°-tilted waveguides can significantly reduce the reflection losses on the both input direction by enhanced microwave resonance effect, which can further promote the energy efficiency. In addition, the stub tuner was used to match impedance for reducing the application risks. Compared with the traditional steam heating methods, this novel continuous-flow microwave system with higher energy efficiency design is attractive for the dairy industry due to its outstanding electromagnetic responses and cleaner processing.

Starlight coupling through atmospheric turbulence into few-mode fibres and photonic lanterns in the presence of partial adaptive optics correction

ABSTRACT Starlight corrupted by atmospheric turbulence cannot couple efficiently into astronomical instruments based on integrated optics as they require light of high spatial coherence to couple into their single-mode waveguides. Low-order adaptive optics in combination with photonic lanterns offer a practical approach to achieve efficient coupling into multiplexed astrophotonic devices. We investigate, aided by simulations and an experimental testbed, the trade-off between the degrees of freedom of the adaptive optics system and those of the input waveguide of an integrated optic component leading to a cost-effective hybrid system that achieves a signal-to-noise ratio higher than a standalone device fed by a single-mode fibre.

Ultracompact TE0- and TE1-pass/TM0- and TM1-stop dual-mode polarizer for 1.55/2 µm dual-wavelength using silicon-based cross-like hybrid plasmonic waveguides

By leveraging cross-like hybrid plasmonic waveguides (HPWs) and subwavelength gratings, a silicon-based ultracompact T E 0 - and T E 1 - p a s s / T M 0 - and T M 1 -stop dual-mode polarizer for 1.55/2 µm dual-wavelength is proposed and analyzed in detail. The HPWs are located above the bottom Si waveguide to form a hybrid plasmonic silicon nitride waveguide (HPSNW), in which the T E 0 / T E 1 mode is well supported in the bottom Si layer while the T M 0 / T M 1 mode is confined in the S i O 2 / S i 3 N 4 layer of the HPSNW and thus sees high absorption loss at 1.55/2 µm. Accordingly, the T E 0 / T E 1 mode at 1.55/2 µm can directly pass through the device once it is transited from input waveguide to the HPSNW. In contrast, the T M 0 / T M 1 mode at 1.55/2 µm suffers from great mode radiation and mode attenuation, respectively, caused by the modal mismatch and metal absorption, leading to mode blocking. Therefore, a polarizer with dual-mode/dual-wavelength operation is realized for the first time, to the best of our knowledge. Numerical results show that the proposed polarizer has an insertion loss (IL) of 0.37 dB/0.29 dB for the T E 0 / T E 1 mode and an extinction ratio (ER) of 17.3 dB/29.7 dB for the T M 0 / T M 1 mode at 1.55 µm (an IL of 0.42 dB/0.76 dB for the T E 0 / T E 1 mode and an ER of 33.1 dB/23.3 dB for the T M 0 / T M 1 mode at 2 µm) in an ultracompact length of 6.5 µm. The operating bandwidth is up to 630 nm when the ER is over 18.5 dB/19.7 dB and the IL is below 0.52 dB/1 dB for fundamental/first-order mode, indicating an ultrabroadband operation. Additionally, fabrication tolerances of the proposed device are investigated, and electric field evolution is also illustrated.

Ultra-fast all-optical full-adder based on nonlinear photonic crystal resonant cavities

In this paper, a new photonic crystal-based full-adder for the summation of three bits has been proposed. For realizing this device, three input waveguides are connected to the main waveguide. An optical power splitter is placed at the end of this waveguide. Concerning the amount of optical intensity inside this waveguide, two nonlinear resonant cavities transmit the waves toward the correct ports. When the cavities do not drop the optical waves, the splitter guides them toward the output ports. The maximum delay time of the presented structure is around 0.5 ps and shows the fastest response among the reported works. This improvement is obtained due to using the resonant cavities. The time analysis results in a maximum working frequency of 2 THz. Also, designing the structure in 93 µm2 demonstrates that it is more compact than the previous works. The normalized low and high margins are obtained around 10% and 85%, respectively. So, the proposed device is capable of considering optical processing circuits.

Ultracompact silicon polarization splitter-rotator using a dual-etched and tapered coupler.

The polarization splitter-rotator (PSR) plays a significant role in telecom, Datacom, and quantum circuits to meet significant requirements for polarization processing and multiplexing. We design an ultracompact PSR based on a silicon asymmetrical directional coupler (ADC). One waveguide of the ADC is gradually etched in two levels along the coupling region and the S-bend. A trapezoidal taper on the top of the dual-etched waveguide is first formed to satisfy the phase-matching condition for the TM-TE mode conversion, such that the TM mode is cross-coupled from the input waveguide without etching. Then, the etching width gradually increases in the S-bend and the following to achieve a single-mode waveguide for further removal of the residual TM mode. In this way, a high extinction ratio can be achieved for the polarization mode splitting in an ultracompact silicon ADC. For the designed PSR with a total length of about 24 µm, the simulation results reveal that the minimum extinction ratio is greater than 30, 20, or 15 dB within the bandwidth of 33, 100, or 150 nm, respectively, while the maximum polarization conversion loss is less than 0.4, 0.9, or 1 dB.

An Optical Switch Based on Electro-Optic Mode Deflection in Lithium Niobate Waveguide

We propose a 1 × 2 electro-optic miniature optical switch based on mode deflection of lithium-niobate (LN) annealed proton exchange waveguides with microstructured electrodes. Our fabricated device consists of LN waveguides covered with isosceles-triangle-shaped array electrodes, a horn-shaped input waveguide, and two tapered output waveguides. At a driving voltage of 40 V, the two-modes can switch between two output ports with an extinction ratio of 17.39 dB at the wavelength of 1530 nm. The switching speed is 22 ns. This miniature mode switch could find applications in signal processing and high-speed optical communication networks.

Tunable THz and Infrared Plasmonic Filters and Switches Based on Circular Graphene Resonator With 90$^\circ$ Bending of Output Port

Two types of novel graphene-based components, namely, filters and electro-optical switches in guided wave configuration are suggested and analysed. The filters differ from the known ones with collinear orientation of the input and output waveguides by geometry and symmetry. The components consist of a circular graphene disk and two nanoribbons oriented at 90° to each other in the plane of the graphene layer. The graphene elements are placed on a dielectric substrate. We show that change in symmetry leads to a drastic change in the properties of the components. The physical principle of the devices is based on the dipole, quadrupole and hexapole resonances in the graphene disk which define stop-band, pass-band and stop-band frequency characteristics, respectively. A combination of stop-band and pass-band filter properties by shifing the electronic Fermi level allows one to design a switch. Numerical simulations show that the suggested components have very small dimensions, good characteristics and provide a dynamic control of their central frequency via electrostatic gating.

Quantum Engineering Enables Broadband and Robust Terahertz Surface Plasmon-Polaritons Coupler

The in-plane terahertz (THz) surface plasmon polaritons (SPPs) coupler is a key element of THz information transmission and processing. However, existing parallel coupler based on two SPPs waveguides is not robust against perturbations of geometric parameters (arising due to fabrication imperfections) and are limited by the single frequency of operation. In this work, we propose a robust and broadband integrated THz coupler based on the in-plane SPPs waveguides, conducted with the quantum engineering – Stimulated Raman Adiabatic Passage (STIRAP). Our coupler consists of two asymmetric specific curved corrugated metallic structures working as the input and output SPPs waveguides, and one straight corrugated metallic structure functioning as the middle SPPs waveguide. From the theoretical and simulated results, we demonstrate that the SPPs can be efficiently transferred from the input to the output waveguides. Our device is robust against the perturbations of geometric parameters, and meanwhile it manifests broadband performance (from 0.5 THz to 0.8 THz) with a high transmission rate over 70 ${\%}$ . This work represents a step forward for significant improvements in THz sensing, THz imaging, on-chip THz signal processing, and other next-generation THz photonic device.

Bound in continuum states and induced transparency in mesoscopic demultiplexer with two outputs

We investigate the electronic transport in a simple mesoscopic cross structure made of two wires (stubs) grafted at the same point along a quantum waveguide. We show that the structure may exhibit important phenomena such as bound in continuum (BIC) states. These states are transformed into electromagnetically induced transparency (EIT) resonance by detuning slightly the lengths of the stubs. The last phenomenon is used to propose and study a mesoscopic demultiplexer device with an input waveguide and two output waveguides. We give closed-form expressions of the geometrical parameters that allow a selective transfer of a given state in the first waveguide without perturbing the second waveguide. The effect of temperature on the transmission resonances is also examined by using Landauer–Büttiker formula. The analytical results of the dispersion relation and transmission and reflection coefficient are obtained using the Green’s function method.

A side-ported MMI based InP polarization beam splitter

The design of a multimode interference coupler (MMI) based InP polarization beam splitter (PBS) at 1.3 μm wavelength is reported. When the input and output waveguides are placed on the side walls of the PBS MMIs, the PBS can be shortened effectively, while maintaining both low insertion loss (IL) and high extinction ratio (ER). The optimized PBS design is 299 μm in length which is less than 1/3 of the PBS with end ported access ports. At the same time, the ER of the side ported PBS is notably better than the ER of the long end ported PBS.

Optical four-channel demultiplexer based on air-bridge structure and graphite-type ring resonators

A novel an optical four-channel demultiplexer based on a hexagonal lattice shape of embedded air holes in dielectric substrate (air-bridge type) is proposed. Demultiplexing for each channel is obtained by designing the graphite-type ring resonator which consists of small air hole defects in own unit cells. The physical parameters which govern the demultiplexer performance are investigated. It is observed that employing big air hole as a defect in the end of input waveguide enhanced the coupling efficiency between the rings and waveguides. By engineering the refractive index of substrate and size of air holes, the proposed demultiplexer is tuned. The demultiplexer has an average quality factor > 3000 and channel spacing $$\Delta \lambda \le 2\;{\text{nm}}$$ . We showed that big air hole defect in the end of input waveguide is an effective scheme for improving the transmission efficiency and cross talk between channels. The average transmission efficiency and cross talk value are above 98% and − 23 dB, respectively. The total size of proposed structure and its maximum delay time are 289 μm2 and 0.3 ps, respectively. Our demultiplexer has an easy fabrication structure, and it can find key applications for many cores CPU in an on-chip optical network and the dense wavelength demultiplexing in optical integrated circuits.

260‐GHz waveguide module containing an integrated InP HBT amplifier chip

A terahertz integrated amplifier circuit packaged inside a WR-3.4 waveguide is presented. The circuit, fabricated using 250-nm InP technology, contains three amplifier chains each connected to its own input and output waveguide transition pairs. The size of the transition is minimised for the chip to properly fit inside the standard waveguide. The assembled waveguide module shows the peak amplifier gain of 13 dB and 3-dB bandwidth of 32 GHz as its gain is 6.2 dB less than that of an on-wafer amplifier measured using RF probes. The maximum measured output power from the module is 6.5 dBm at 260 GHz compared to 1.4 dBm from single on-wafer amplifier chain.

3-D Printed Wideband Cassegrain Antenna With a Concave Subreflector for 5G Millimeter-Wave 2-D Multibeam Applications

A novel wideband planar Cassegrain beam-former with a three-layered folded parallel plate waveguide geometry is investigated. By replacing the convex subreflector of the conventional design with a concave one, a 20% reduction in the size in boresight direction of the planar Cassegrain beam-former can be achieved, while its operating characteristics are not degraded. The direction of the radiation beam can be adjusted independently in the H- or E-plane by laterally offsetting the feed waveguide or bending the waveguide linking with the metallic flare that operates as a radiating structure. By this means, five Cassegrain subarrays with multiple waveguide inputs and different bending angles are stacked to build a high-gain wideband 2-D multibeam antenna array in the Ka -band, whose 3 dB beams cover angular ranges of ±60° in the E-plane and ±18° in the H-plane. A bandwidth of more than 40%, stable multibeam radiation with cross polarization of less than −25 dB, a gain of higher than 20 dBi, and a radiation efficiency of more than 90% are confirmed experimentally by a metallic 3-D printed subarray. With the compact printable geometry and the good operating performance, the presented 2-D multibeam antenna fed by the planar Cassegrain beam-formers is an attractive candidate for millimeter-wave multiple-input multiple-output (MIMO) applications in the fifth-generation (5G) mobile communications.

Integrated photonics multi-waveguide devices for optical trapping and Raman spectroscopy: design, fabrication and performance demonstration.

We realized integrated photonics multi-waveguide devices for optical trapping and Raman spectroscopy of particles in a fluid. In these devices, multiple beams directed towards the device center lead to a local field enhancement around this center and thus counteract the effect of light concentration near the facets, which is a disadvantage of dual-waveguide traps. Thus, a trapping region is created around the center, where a single particle of a size in a wide range can be trapped and studied spectroscopically, free from the influence of surfaces. We report the design (including simulations), fabrication and performance demonstration for multi-waveguide devices, using our Si3N4 waveguiding platform as the basis. The designed ridge waveguides, optimized for trapping and Raman spectroscopy, emit narrow beams. Multiple waveguides arranged around the central microbath result from fanning out of a single input waveguide using Y-splitters. A second waveguiding layer is implemented for detection of light scattered by the trapped particle. For reliable filling of the device with sample fluid, microfluidic considerations lead to side channels of the microbath, to exploit capillary forces. The interference of the multiple beams produces an array of hot spots around the bath center, each forming a local trap. This property is clearly confirmed in the experiments and is registered in videos. We demonstrate the performance of a 2-waveguide and a 16-waveguide device, using 1 and 3 μm polystyrene beads. Study of the confined Brownian motion of the trapped beads yields experimental values of the normalized trap stiffness for the in-plane directions. The stiffness values for the 16-waveguide device are comparable to those of tightly focused Gaussian beam traps and are confirmed by our own simulations. The Raman spectra of the beads (in this work measured via an objective) show clear peaks that are characteristic of polystyrene. In the low-wavenumber range, the spectra have a background that most likely originates from the Si3N4 waveguides.