Main Waveguide Research Articles

Investigation on adiabatic mode evolution in a few-mode optical waveguide

The mode-conversion characteristics of a few-mode optical waveguide based on adiabatic mode evolution are investigated. The mode-conversion efficiency and cross talks of the configuration are found dependent on the position and angle between the assistant waveguide and the main waveguide, and also the size of the assistant waveguide. By setting the bottoms of the two waveguides at the same plane, the symmetry of the configuration can be broken. The configuration is able to convert each mode to a higher order or lower order mode by launching light from different ports. In particular, mode conversion between the two degenerated LP11 modes can be achieved with wide bandwidth.

Multichannel and Binary-Phase All-Optical Control with On-Chip Integrated Subwavelength Plasmonic Waveguides

The control of light with light at a nanometer scale is a fundamental issue in optics. In this study, we demonstrate nanoscale all-optical control of light based on linear optics in an on-chip integrated subwavelength plasmonic waveguide system. The signal intensities of multiple output channels are all-optically manipulated simultaneously in various manners by coupling the fields of a standing wave in the main waveguide to the nearby subwavelength branch waveguides. More importantly, the phase differences between different output channels equal either 0 or π, thereby exhibiting an interesting binary characteristic. This phenomenon provides both phase robustness and switchable features, which significantly facilitate further applications at nanometer scales. As a demonstration, two output channels are used to drive a two-element plasmonic nanoantenna, and the dynamical control of the emission direction of the nanoantenna is successfully presented. The proposed control mechanism displays an ultrafast respo...

Research and development of continous wave 100 kW absorption harmonicfilter in X-band

A gradient leaky-wall waveguide loaded absorbing load filter structure is proposed, which is designed for harmonic suppression in super-high power transmitter of deep-space probe. The attenuation loss characteristics of the filter is analyzed according to the equivalent circuit method, and the massive structure is simulated by the electromagnetic field simulation software. The filter sample which includes one main waveguide, 288 deputy waveguides and 288 absorb loads is processed following the simulating and designing sizes. In order to prevent microwave from leaking and keep good air tightness under the condition of high power, all the components of the filter will be welded together by means of vacuum welding, and then the sample is cleaned ultrasonically. Finally, the filter sample is tested under small signal and large signal separately. According to our test results, the pass band max insertion loss of the filter is 0.3 dB, the min suppression of second harmonic is 75 dB, the min suppression of third harmonic is 50 dB, and the min suppression of fourth harmonic is 35 dB. The measured results show that they are almost the same as the simulation results, and consistent completely with the anticipated. We further conduct the high power experiment on the filter under a large signal of 100 kW, showing that the continuous wave power capacity of the filter can reach up to 100 kW through the power resistance test with the liquid-cooled system. All the test data show that the study and development are very successful. At present, the filer has been applied to a type of ground high power transmitter, and its performances and indicators behave well.

A coupler for parasitic mode diagnosis in an X-band triaxial klystron amplifier

The traditional methods of parasitic mode excitation diagnosis in an X-band triaxial klystron amplifier (TKA) meet two difficulties: limited installation space and vacuum sealing. In order to solve these issues, a simple and compact coupler with good sealing performance, which can prevent air flow between the main and the auxiliary waveguides, is proposed and investigated experimentally. The coupler is designed with the aperture diffraction theory and the finite-different time-domain (FDTD) method. The designed coupler consists of a main coaxial waveguide (for microwave transmission) and a rectangular auxiliary waveguide (for parasitic mode diagnosis). The entire coupler structure has been fabricated by macromolecule polymer which is transparent to microwave signal in frequency range of X-band. The metal coating of about 200 microns has been performed through electroplating technique to ensure that the device operates well at high power. A small aperture is made in the metal coating. Hence, microwave can couple through the hole and the wave-transparent medium, whereas air flow is blocked by the wave-transparent medium. The coupling coefficient is analyzed and simulated with CST software. The coupler model is also included in particle-in-cell (PIC) simulation with CHIPIC software and the associated parasitic mode excitation is studied. A frequency component of 11.46 GHz is observed in the FFT of the electric field of the drift tube and its corresponding competition mode appears as TE61 mode according to the electric field distribution. Besides, a frequency component of 10.8 GHz is also observed in the FFT of the electric field. After optimization of TE61 mode suppression, an experiment of the TKA with the designed coupler is carried out and the parasitic mode excitation at 10.8 GHz is observed through the designed coupler.

Performance Enhancement of Cavity Assisted Photonic Crystal De-Multiplexerin Slow Light Regime

This study first proposes a new version of a photonic crystal based de-multiplexer operating under the slow light regime, secondly analyses the structure numerically to demonstrate de-multiplexing operation and finally studies the impact of light speed on the performance of the proposed structure. The operation wavelength is 1.55 µm. The study indicates that, by adjusting the speed of light, around 0.1C, in the main waveguide and in the output channels’ waveguides, an enhancement in the performance of the de-multiplexer will be gained.

A Quasi-Planar Waveguide Tuner

In this letter, a quasi-planar waveguide tuner is proposed, which is comprised of a main waveguide, three waveguide shorting stubs, and three ridged waveguide shorting stubs. All waveguide stubs are connected to the E-plane of the main waveguide. It can be used to replace the well-known E-H waveguide tuners with a simpler structure, smaller size, and lower fabrication cost. The matching ability is verified by using the quasi-planar tuner to match the discontinuities from an inductive iris and a capacitive iris. The matching results are shown to be the best compared with that of three other conventional tuners, an E-plane tuner, an H-plane tuner, and an E-H tuner. Tested results are also presented.

Determination of third-order elastic moduli via parameters of bulk strain solitons

A method is proposed aimed for determination of the third-order elastic moduli (Murnaghan moduli) based on the estimation of measured parameters of bulk strain solitons in the three main waveguide configurations, a rod, a plate, and a shell. Formulas connecting the third-order moduli of the waveguide material and the parameters of a solitary strain wave (amplitude, velocity, full width at half-maximum) are derived. If the soliton parameters measured in three waveguide types manufactured from the same material are available, determination of the third-order elastic moduli is reduced to the solution of a system of three algebraic equations with a nondegenerate matrix.

Design of Wideband Waveguide Hybrid With Ultra-Low Amplitude Imbalance

We present a design and synthesis procedure for a new 90 ° waveguide hybrid with ultra-low amplitude imbalance. This novel hybrid design is based on Reed's multiple branch waveguide hybrid. The primary feature of this quadrature hybrid design is the introduction of a controllable ripple in the operational band by, firstly changing the heights of the input and output branches and, secondly, by introducing three waveguide-height discontinuity sections placed symmetrically in the main waveguide. This layout allows ultra-low amplitude imbalance over a wide operational band. At the same time, it permits a greater input/output branch height as compared to the Reed's 5-branch waveguide hybrid, which should ease fabrication for short-mm and sub-mm wavelengths. This design concept is demonstrated through a 90 ° waveguide hybrid for the 159-216 GHz band (30% fractional bandwidth). Our simulations indicate that the amplitude imbalance of the hybrid is better than 0.2 dB over the most of the 159-216 GHz band with a phase imbalance better than ±4°. Experimental verification of the hybrid shows excellent agreement with the simulations.

The Electrically Symmetrical E-Plane Waveguide Tee Junction at the Dicke and Altman Planes

The eigenvalue diagram at the Dicke planes of the $E$ -plane tee junction is not unlike that of the $H$ -plane geometry available in the literature. The purpose of this paper is to remedy the situation. It includes an investigation of such a junction loaded with both inductive and capacitive vanes at its symmetry plane. This paper also introduces an alternate definition of the Dicke planes in terms of the location of a piston in the main waveguide, which produces a bandstop response between the other two and that of a similar piston in the side waveguide, which establishes a bandpass between the other two. The electrical symmetrical cases at the Altman and Dicke ports for which the magnitudes of the scattering parameters are those of a symmetrical wye junction are separately realized. Each solution has a distinct eigenvalue diagram, which is symmetric about the real axis. This paper includes the realization and fabrication of one device and is in excellent agreement with the theory. The work is undertaken in WR75 waveguide at a frequency of 13.25 GHz.

Active Multiple Plasmon-Induced Transparency with Graphene Sheets Resonators in Mid-Infrared Frequencies

A multiple plasmon-induced transparency (PIT) device operated in the mid-infrared region has been proposed. The designed model is comprised of one graphene ribbon as main waveguide and two narrow graphene sheets resonators. The phase coupling between two graphene resonators has been investigated. The multimode PIT resonances have been found in both cases and can be dynamically tuned via varying the chemical potential of graphene resonators without optimizing its geometric parameters. In addition, this structure can get multiple PIT effect by equipping extra two sheets on the symmetric positions of graphene waveguide. The simulation results based on finite element method (FEM) are in good agreement with the resonance theory. This work may pave new way for graphene-based thermal plasmonic devices applications.

Submillimeter-Wave 3.3-bit RF MEMS Phase Shifter Integrated in Micromachined Waveguide

This paper presents a submillimeter-wave 500–550-GHz MEMS-reconfigurable phase shifter, which is based on loading a micromachined rectangular waveguide with 9 E-plane stubs. The phase shifter uses MEMS-reconfigurable surfaces to individually block/unblock the E-plane stubs from the micromachined waveguide. Each MEMS-reconfigurable surface is designed so that in the nonblocking state, it allows the electromagnetic wave to pass freely through it into the stub, while in the blocking state, it serves as the roof of the main waveguide and blocks the wave propagation into the stub. The phase-shifter design comprises three micromachined chips that are mounted in the H-plane cuts of the rectangular waveguide. Experimental results of the first device prototypes show that the microelectromechanical system (MEMS)-reconfigurable phase shifter has a linear phase shift of 20 $\mathbf {^{\circ }}$ in ten discrete steps (3.3 bits). The measured insertion loss is better than 3 dB, of which only 0.5–1.5 dB is attributed to the MEMS surfaces and switched stubs, and the measured return loss is better than 15 dB in the design frequency band of 500–550 GHz. It is also shown that the major part of the insertion loss is attributed to misalignment and assembly uncertainties of the micromachined chips and the waveguide flanges, shown by simulations and reproducibility measurements. The MEMS-reconfigurable phase shifter is also operated in an analog tuning mode for high phase resolution. Furthermore, a detailed study has been carried out identifying the reason for the discrepancy between the simulated (90 $\mathbf {^{\circ }}$ ) and the measured (20 $\mathbf {^{\circ }}$ ) phase shift. Comb-drive actuators with spring constant variations between 2.13 and 8.71 N/m are used in the phase shifter design. An actuation voltage of 21.94 V with a reproducibility better than $\mathbf {\sigma }=$ 0.0503 V is measured for the actuator design with a spring constant of 2.13 N/m. Reliability measurement on this actuator was performed in an uncontrolled laboratory environment and showed no deterioration in the functioning of the actuator observed over one hundred million cycles.

High-performance optical waveguide devices using 300 mm Si photonics platform

The Si photonics platform for 300mm SOI wafers has been built up for optical multi-applications. The performance of main optical waveguide devices has been demonstrated. State-of-the-art propagation loss values are obtained for optical waveguides of multi-thickness SOI structures in this platform. The propagation loss is less than 0.5dB/cm at 1.55μm wavelength for 220nm-thick single-mode waveguides with TE-polarization. MMI coupler, AWG and WDM filter showed superior performance for their applications. The 50×50mm2 large Si interposers using photonics electronics convergence technology have been demonstrated. These results indicate that our Si photonics platform is very useful for optical multi-applications.

Effect of lay-up of sub-waveguide on transmission of So mode from main waveguide to sub-waveguides

This paper focuses on transmission characteristics of fundamental symmetric Lamb mode (So) at the junction of a main waveguide and sub-waveguides in composite laminates. Numerical simulations on transmission of So from the main to sub-waveguide revealed that transmission factors of the modes depend on stacking sequence of plies in the waveguides. Experiments were carried out to verify the observations made in numerical simulations. This work gives an insight on the transmission characteristics of So mode while it propagates from a healthy to a delaminated region in a composite laminate.

Electrically symmetric solution of the 3‐port H‐plane waveguide tee junction at the Dicke ports

The tasks of this study are to construct the eigenvalue diagram of the H-plane tee junction, at the Dicke plane which has not been done so far and to introduce a new boundary condition together with a symmetric septum. The new boundary condition introduced here has the magnitudes of the scattering parameters of a symmetric wye junction. The eigenvalue diagram of this junction has a symmetric solution about the real axis of the diagram and has been identified previously. The trial solution adopted in the construction of the Dicke eigenvalue diagram has the reference planes in the main waveguide at the characteristic planes of the junction and that at the side waveguide at a position at which the angle of the reflection coefficient there is 90° out of phase with that of the transmission coefficient between the main and side waveguides. The new junction introduced here has been fabricated experimentally in WR75 waveguide. An Altman junction is separately realised for the first time and constructed.

Generalised asymptotic boundary conditions and their application to composite right/left‐handed rectangular waveguide with double‐ridge corrugations

A generalised form of the asymptotic corrugation boundary conditions (ACBCs) is presented and employed to analyse a composite right/left-handed rectangular waveguide loaded with double-ridge stubs. Enforcing the ACBCs yields the dispersion relation as well as the field distribution in the main waveguide without the need for any sophisticated modal analysis. The asymptotic solution proves to provide accurate results within a wide frequency band. The effect of the various geometrical parameters and the aspect ratios is investigated to determine the range of validity of the ACBCs. The results compared with the full-wave simulations exhibit very good agreement.

A side-illuminated plasmonic planar lens

Planar lens based on nanoscale slits has been demonstrated theoretically and experimentally. In this paper, we propose a 2D model of a similar planar lens but with side-illumination. The lens consists of a main bus waveguide to transport plasmonic wave and grooves functioning as antennas. The shapes and filling materials of the waveguide and grooves are assumed to be invariant in the third direction. The phase retardation needed for wavefront shaping comes from the transverse propagation of the plasmonic wave in the waveguide and the well-designed groove positions. The concept is applied to the design of planar lenses and axicons. The simulation results demonstrate that such structures can work as good diffractive elements. The side-illumination property of such structure enables the potential integration of lens on chip.

A Cross-Guide Waveguide Directional Coupler With High Directivity and Broad Bandwidth

A cross-guide waveguide directional coupler (patent pending) with high directivity and broad bandwidth is proposed in this letter. It consists of two rectangular waveguides (called main waveguide and branch waveguide) crossing at a certain angle and sharing a common broad wall. High directivity is achieved by adding metal inserts in the branch waveguide in the coupling region near the crossed round-ended slots. For verification purpose, a sample coupler has been designed, manufactured and measured. The measured results show that the sample coupler has a directivity greater than 28 dB over the full waveguide bandwidth.

Study the Coupling Characteristics of Line Defects and Point Defects in Photonic Crystals

In order to filter, we use the coupling methods of line defects and point defects in photonic crystals to verity through theories and experimentations, get micro-cavity center frequency and wavelength of the main waveguide frequency resonance, and the same frequency lights will enter micro-cavity. Results show waveguides and micro-cavity can support its modes within in their deficiencies, but defects still can transfer energies through the evanescent coupling, the evanescent coupling is the role of the photonic crystals to the integration of device.

Integrated Guided-Wave Photodiode Using Through-Absorber Quantum-Well-Intermixing

A high-speed, high-saturation power photodiode compatible with a relatively simple monolithic integration process is described. The detector is comprised of an intrinsic bulk absorption layer, an electron drift region, and a field termination layer, and is grown above a main waveguide core comprised of a number of quantum wells, which are used as the active region of a phase modulator. Through-absorber quantum-well-intermixing is used to blue-shift the bandedge of the underlying quantum wells, reducing the optical losses of that material. The detectors demonstrate quantum efficiency, input saturation power, and 3-dB bandwidth of 50 GHz.

Interaction between the fundamental lamb modes and the front edge of a crack in a metallic plate.

Numerical simulations followed by experimental validations were carried out to study the interaction of the fundamental Lamb modes when incident at the front edge of a horizontal crack in a metallic plate. During the interaction, the incident fundamental Lamb mode underwent mode conversion and started propagating in the main and sub-waveguides along with the mode-converted Lamb mode. The amplitude of the mode-converted Lamb mode propagating in the main waveguide was negligible compared with that of the incident wave group. It was found that the amplitude of the transmitted Lamb modes from the main waveguide to the sub-waveguides is nearly the same as the incident wave group's amplitude; wave groups propagating in the thicker sub-waveguides are found to be carrying higher power than their counterparts in the thinner sub-waveguides. Furthermore, it was observed that variation in power coefficients and amplitude-based factors with respect to frequency of excitation were not very significant. Moreover, it was also shown that amplitude of the reflected wave groups in the main waveguide depends on phase velocities of Lamb modes in the main waveguide and sub-waveguides for a given thickness ratio.