Waveguide Parameters Research Articles

Cadmium telluride waveguide for coherent MIR supercontinuum generation covering 3.5-20 µm.

The mid-infrared (MIR) wavelength coincides with various molecular resonances. In particular, a 13-20 µm wavelength window has fingerprints of unique groups such as organometallic, halogenated, and aromatic bonds. In this work, for the first time, to the best of our knowledge, an on-chip supercontinuum generation (SCG) source based on cadmium telluride (CdTe)/ cadmium sulfide (CdS)/ silicon heterostructure is proposed to extend the on-chip SCG beyond 13 µm (spanning 3.5 to 20 µm). CdTe has an ultra-broad transparent spectral range up to 25 µm, and almost the largest third-order nonlinear coefficient (n2∼ 5×10-17 m2/W at 1.55 µm, 1.3×10-17 m2/W at 9 µm, several times larger than that of silicon) among the MIR materials, making CdTe an excellent candidate for long-wavelength MIR on-chip SCG. The waveguide structure is designed with CdS as the intermediate cladding layer to achieve a low waveguide loss and high mode confinement. A large-core CdTe waveguide is tailored to generate a low and flat dispersion (< 30 ps/nm/km) in a spectral range spanning from 5 to 20 µm, while balancing the large effective nonlinearity and the convenience of coupling. The simulation results solved by the nonlinear Schrödinger equation manifest that the engineered large cross-section waveguide with only 2.5-mm propagation distance broadens the MIR spectrum covering 3.5 to 20 µm pumped by a 9 µm femtosecond laser. Moreover, it is found that good coherence is achieved from the designed MIR waveguide, before severe soliton fission breaks the temporal profile. 5-fold self-compression of the pump pulse down to 1.6 optical cycles is observed while propagating inside the CdTe waveguide. The detailed simulation of the CdTe/CdS/Si waveguide design with the various waveguide parameters, polarizations, pump wavelengths, and pump power are provided. With the SC spectrum covering almost the entire fingerprint regime and the excellent coherence generated from the designed CdTe waveguide, it provides abundant new opportunities for MIR microphotonics.

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.

Tunable generation and propagation of vortex beams in a photonic chip

We used a direct laser writing technique to build annular waveguides inside a glassy blade. These waveguides have shown the capability of generating orbital angular momentum beams with different topological charges in the same structure. Here we demonstrate that, after choosing suitable waveguide parameters, one may tune the topological charge of a beam just by tilting the input wavefront. This work opens opportunities for optical communications using spatial degrees of freedom multiplexed beams and for generation of tunable angular momentum at the microscale for integrability of lab on chips.

3D-printed sound absorber considering ventilation.

To reduce the noise in a ventilated system, three-dimensional (3D)-printed sound absorbers, based on multiple spiral waveguides, are proposed in this letter. A waveguide unit consists of a fixed-length cylindrical straight tube and a certain number of spiral tubes. The geometrical parameters of the spiral waveguides can be flexibly regulated, aided by the 3D digital modeling method to control the phase of the sound wave. Experimental results show that the proposed sound absorber can obtain the sound transmission loss (STL) about 9.6 dB in a frequency range of 300-1250 Hz with an 18% ventilation ratio.

Nonlinear loss characterization of continuous wave guiding in silicon wire waveguides

Accurate propagation loss characterization of silicon waveguides is increasingly demanded for silicon-photonics-(Si-Ph) applications with high-power continuous-wave-(CW) light sources. We report on nonlinear loss parameters of silicon wire waveguides for 1.31 μm wavelength CW light extracted from transmission data measured for different lengths and polarizations. Such parameters were, so far, unavailable, although they are required for accurately modeling Si-Ph optical circuits. More-than-ten-times enhancement of two-photon absorption from prior results for short pulse light was observed at power densities ranging up to 4.7 × 1011 W m−2 while free carrier absorption was suppressed. We estimate the nonlinear loss of the waveguides using the parameter values obtained.

Dispersion Analysis and Material Property Identification of a Circular Piezoelectric Ridge Waveguide

Abstract This study investigates the dispersive properties of ridge waves that travel circumferentially around piezoelectric circular ridge waveguides and investigates their resonant modes. Based on the variable separation method and Hamilton's principle, the displacement of ridge waveguides is represented as the product of a cross-sectional coordinate-dependent function and the propagator along the circumference of a circular ridge waveguide. The dispersion curves of the flexural waves and resonant frequencies corresponding to ridge waveguides are solved numerically by applying the bidimensional finite element method (Bi-d FEM) and using the three-dimensional (3D) ansys package. The estimated impedance curves are compared with the predicted dispersion curves of waves from ridge waveguides to validate the proposed numerical approach. The elastic constants of the circular piezoelectric ridge waveguide are determined through an inverse scheme that is based on the modified simplex method. The numerical and experimental results show that by using the modified simplex method to inverse calculate the elastic constants and geometric parameters of the piezoelectric circular ridge waveguides, a good degree of accuracy and sensitivity can be achieved.

Direct (3+1)D laser writing of graded-index optical elements

We propose single-step additive fabrication of graded-index optical elements by introducing the light exposure as the additional dimension to three-dimensional (3D) laser writing, hence (3 + 1)D writing. We use a commercial printer and photoresist to realize the proposed single-step fabrication method that can be swiftly adopted for research and engineering. After presenting the characterization of the graded-index profiles via basic structures, we demonstrate two different optical devices: volume holograms that are superimposed using angular and peristrophic multiplexing, and optical waveguides with well-defined refractive index profiles. In the latter, we precisely control the propagating modes via tuning the (3 + 1)D-printed waveguide parameters and report step-index and graded-index core–cladding transitions.

Re-analysis of single-mode conditions for thin-film lithium niobate rib waveguides

Single-mode waveguide devices are necessary in photonic integrated circuits. Previous studies on the single-mode conditions (SMCs) of the thin film lithium niobate (TFLN) either only focus on wire waveguide, or lack comprehensive discussions on the influence of the rib waveguide with different cross-section area at a certain height. In this paper, a systematical study on the SMCs of rib waveguide based on TFLN is carried out by using finite difference method (FDM). By comparing the effective refractive index between the first-order mode in the central rib region and the fundamental mode in the slab waveguide, and the fraction of the mode power flux between the TFLN rib region and the whole waveguide region, the SMCs in the central rib region are analyzed in terms of geometric parameters of the TFLN rib waveguide. The simulation results suggest that no single equation could meet the SMCs of different waveguide structures simultaneously in a small TFLN with the height no more than 900 nm. Ultimately, new approximate expressions as functions of rib-waveguide width and etching depth are proposed to precisely describe the single-mode condition at these dimensions.

An analytical model for predicting the shielding effectiveness and resonances of a lossy enclosure with apertures

In this paper, an improved analytical model is presented to predict the shielding effectiveness (SE) and resonances of an apertured enclosure composed of the material of finite conductivity. In the model, the modified parameters of the rectangular waveguide are introduced to deal with the lossy enclosure with apertures, which can consider the effects of wall loss on the SE. Firstly, according to the circuit theory and electromagnetic topology (EMT) theory, the lossy enclosure is modeled as the circuit model and signal flow graph, respectively. Then, the electric field components at the monitor point can be obtained; hence, the SE can be predicted accurately. Finally, the presented model is utilized to analyze the effects of various parameters and conditions on the SE. The validity of the presented model is verified by the CST through several cases, showing that the lossy enclosure is feasible to damp all the resonant modes.

Seasonal Variation of the D‐Region Ionosphere: Very Low Frequency (VLF) and Machine Learning Models

AbstractThe D‐region ionosphere (6090 km) plays an important role in long‐range communication and response to solar and space weather; however, it is difficult to directly measure with currently available technology. Very low frequency (VLF) radio remote sensing is one of the more promising approaches, using the efficient reflection of VLF waves from the D‐region. A number of VLF beacons can therefore be turned into diagnostic tools. VLF remote sensing techniques are useful and can provide global coverage, but in practice have been applied to a limited area and often on only a small number of days. In this work, we expand the use of a recently introduced machine learning based approach (Gross &amp; Cohen, 2020, https://doi.org/10.1029/2019JA027135) to observe and model the D‐region electron density using VLF transmitting beacons and receivers. We have extended the model to cover nighttime in addition to daytime, and have applied it to track D‐region waveguide parameters, h’ and , over 400 daytimes and 150 nighttimes on up to 21 transmitter‐receiver paths across the continental US. Using an exponential fit, h’ represents the height of the ionosphere and represents the slope of the electron density. Using this data set, we quantify diurnal, daily and seasonal variations of the D‐region ionosphere for both daytime and nighttime D‐region ionosphere. We show that our model identifies expected variations, as well as producing results in line with other previous studies. Additionally, we show that our daytime predictions exhibit a larger autocorrelation at higher time lags than our nighttime predictions, indicating a model with persistence may perform better.

Simulation and Experimental Verification of the Thermal Behaviour of Self-Written Waveguides

In this work, we investigated the optical response of a self-written waveguide (SWW) in detail by heating the structure from room temperature up to 60 °C. Previous results indicated a decrease in the optical transmission with increasing temperature for certain waveguide parameters. Based on new experimental measurements, we have identified material parameters resulting in opposite behaviour. An experimental setup was conceived to verify these results. Hereby, we were able to show that we can adjust material parameters such as refractive index and the corresponding density of the material by adapting the curing time applied during the fabrication of the waveguides. This, in turn, affects the material’s response during the heating process. We showed that a limitation of the external curing time changes the internal conditions of the SWW and the cladding in a manner that the numerical aperture increases with the temperature, which subsequently also results in an increase in the optical transmission. In this study, we explain this unexpected behavior of the SWW and point towards possible future applications.

Footprint Analysis of CMOS Compatible Silicon-on-Insulator Based Photonic Waveguides

Aim: Establish the efficient footprint size, i.e., the total substrate width of photonic waveguides (Ridge, Rib, and Slot) under the fundamental mode propagation constraints. Objective: By varying the total substrate width for all photonic waveguides (Ridge, Rib, and Slot) with respect to four major waveguide parameters, namely effective refractive index, propagation loss, propagation length, and confinement percentage, the converged values of these waveguide parameters have to be obtained. Methods and Materials: The Finite Element Method (FEM) based simulations, using the COMSOL Multiphysics, have been used to study the modal characteristics of photonic waveguides to achieve their efficient footprint size. Results: The total substrate widths have been obtained for all four parameters and considering the impact of all these waveguide parameters simultaneously, the efficient total substrate width has been recognized as 2500 nm, 4000 nm, and 3000 nm, respectively, for Ridge, Rib, and Slot waveguides. Conclusion: The efficient waveguide footprints, i.e., the total substrate widths for the three photonic waveguides, namely Ridge, Rib and Slot waveguides have been established.

Performance analysis of different slot waveguide structures for evanescent field based gas sensor applications

Slot waveguide has emerged as a potential candidate for the design of evanescent field absorption based photonic gas sensors, etc. In this paper, three different slot waveguide structures, i.e., conventional slot, partial-strip-loaded slot, and full-strip-loaded slot waveguides have been explored, to analyze their sensing performance for methane gas. In anticipation of improvement in evanescent field ratio in slot region, and hence, the sensing capabilities of the gas sensor, the slot waveguide structures have been designed by depositing the germanium layer over the calcium fluoride in different manners. Several waveguide parameters, such as evanescent field ratio, propagation loss, and sensitivity have been considered for the analysis and comparison of the presented slot waveguide structures, by varying the arm-width and thickness of germanium layer. Simulation results have demonstrated that the full-strip-loaded slot waveguide has the superior performance, in terms of higher evanescent field (28%), and higher sensitivity (73.76 L/Mol), which is closely followed by the partial-strip-loaded slot waveguide, for a target value of propagation loss (3 dB/cm). However, the conventional slot waveguide provides slightly larger optimum waveguide length (0.86 cm), as compared to other presented slot waveguides.

Investigation of the dependence of the field energy in a low conductive fiber optic with a gradient profile of the refractive index

A circular, cross-sectionally low conductive fiber optic with a power-law profile of the refractive index is considered. A general solution for the field inside the fiber is obtained for the single-mode operation. In the first approximation, the analytical expression for the field and energy inside the fiber for any power-law profile is obtained. The dependences of energy on the waveguide parameter for the second-and third-degree profiles of the refractive index expression are plotted. It is shown that in this approximation, the energy grows as the waveguide parameter increases up to a particular value of the parameter, after which the growth for the second and third powers changes places.

Bumbung Gelombang Lingkaran Susun Untuk Aplikasi RF Energy Harvesting pada GSM 1800 MHz

Mobile device for mobile communication, especially GSM communication is one of the most important thing in our daily activities. A massive mobilty and connectivity to make sure everyone is connected to each other is necessary. In a same time, electrical power needs will increase in order to support the increasingly rapid exchange of information. In this research shown the result of circular waveguide array mode TM01 measurement for RF energy harvesting application at frequency GSM 1800 MHz – 1900 MHz. Design of circular waveguide array through parameter study developed an optimum result, return loss at frequency centre 1850 MHz. Realization of this design is measured in unechoic chamber for minimizing a reflected wave from the ambient, so it called an ideal area for waveguide parameter measurement. The measurement results return loss at freuquency 1840 MHz

Factors influencing the microwave propagation performance of different types of materials

This paper focuses on studying and comparing specific various types of materials which are Silica glass ( ), , Titanium oxide ( ), Graphene ( ), Silicon ( ), Gallium arsenide ( ), and Chromium oxide ( ). It deals with single layer of each previous material in dielectric slab waveguide. Moreover, it studies and compares the effects of a microwave frequency ( ) of the applied electromagnetic waves on TE-modes under assumption of using a constant value of materials thicknesses. It was clearly shown that waveguide parameters of different materials are different depending on its structure and its refractive index. Results and discussion section demonstrates overall comparing among these seven different materials.

Point spread function of a four-wave radiation converter in a multimode waveguide with Kerr nonlinearity

An expression is obtained for the point spread function of a four-wave radiation converter in a multimode waveguide with Kerr nonlinearity, taking into account the transfer of energy from the object wave to the signal wave and vice versa. For single-mode pump waves, the presence of «generation» points is shown and conditions are found on the waveguide parameters, characteristics of the interacting waves, under which the «generation» condition is realized. In the vicinity of the «generation» points, the shape of the point spread function is determined by one of the waveguide modes, the number of which coincides with the number of the pump wave mode. For a four-wave radiation converter in a waveguide with infinitely conducting surfaces, the quality of the wavefront conjugation near the second «generation» point coincides with the quality of the wavefront conjugation at a low reflection coefficient. For a four-wave radiation converter in a parabolic waveguide near the second and next «generation» points, the shape of the point spread function is determined by one of the waveguide modes.

Waveguide phase shifter based on controlled metamaterial

The paper present study of the opto-controlled metamaterial integrated into the waveguide design to control the phase of the flowing electromagnetic wave. A change in the metamaterial characteristics occurs when we switching nodes of a system consisting of thin metal conductors. In the course of the study a computer simulation of an electrodynamic system was carried out. It consists of a waveguide with dimensions of 26.4x10.62x200 mm and a metamaterial integrated into the structure, as a result of which, the flowing electromagnetic wave images, phase graphs S21 of the waveguide parameters were obtained.

Structural Health Monitoring of Walking Dragline Excavator Using Acoustic Emission

The article is devoted to the organization of the structural health monitoring of a walking dragline excavator using the acoustic emission (AE) method. Since the dragline excavator under study is a large and noisy industrial facility, preliminary prospecting researches were carried out to conduct effective control by the AE method, including the study of AE sources, AE waveguide, and noise parameters analysis. In addition, AE filtering methods were improved. It is shown that application of the developed filtering algorithms allows to detect AE impulses from cracks and defects against a background noise exceeding the useful signal in amplitude and intensity. Using the proposed solutions in the monitoring of a real dragline excavator during its operation made it possible to identify a crack in one of its elements (weld joint in a dragline back leg).

Quantitative analysis and optimization design of the segmented planar integrated optical imaging system based on an inhomogeneous multistage sampling lens array.

The non-uniformity of the lens array in the segmented planar integrated optical imaging system has not been studied. We design an inhomogeneous multistage sampling lens array based on a hierarchical multistage sampling lens array of the segmented planar integrated optical imaging system by changing the radius of the lenslet for frequency-selective sampling to optimize the design of the UV spatial frequency distribution. The signal transfer model of the proposed imaging system was established considering the radius of the lenslet and key waveguide parameters. Simulation results show that the proposed system produces better imaging quality owing to the selective sampling of frequency. Compared with the homogeneous multistage sampling lens array (radius of 1.8 mm), the optimal radius parameters of the inhomogeneous multistage sampling lens array are given for the same longest lens array length. Detailed calculations of the parameters of the waveguide connected to the lens array were performed. Our results provide a theoretical basis for the optimal design and process of a new segmented planar integrated optical imaging system.