Bandgap Filter Research Articles

Plasmonic band-gap filter by using tapered waveguide

Plasmonic band-gap filter by using tapered waveguide

Metamaterial inspired electromagnetic bandgap filter for ultra-wide stopband screening devices of electromagnetic interference

Presented here is a reactively loaded microstrip transmission line that exhibit an ultra-wide bandgap. The reactive loading is periodically distributed along the transmission line, which is electromagnetically coupled. The reactive load consists of a circular shaped patch which is converted to a metamaterial structure by embedded on it two concentric slit-rings. The patch is connected to the ground plane with a via-hole. The resulting structure exhibits electromagnetic bandgap (EBG) properties. The size and gap between the slit-rings dictate the magnitude of the reactive loading. The structure was first theoretically modelled to gain insight of the characterizing parameters. The equivalent circuit was verified using a full-wave 3D electromagnetic (EM) solver. The measured results show the proposed EBG structure has a highly sharp 3-dB skirt and a very wide bandgap, which is substantially larger than any EBG structure reported to date. The bandgap rejection of the single EBG unit-cell is better than − 30 dB, and the five element EBG unit-cell is better than − 90 dB. The innovation can be used in various applications such as biomedical applications that are requiring sharp roll-off rates and high stopband rejection thus enabling efficient use of the EM spectrum. This can reduce guard band and thereby increase the channel capacity of wireless systems.

Compact CEBG Filter for High-Frequency Applications With Low Insertion Loss

A compact configurable electromagnetic bandgap (CEBG) filter and a low-loss low-temperature cofired ceramics (LTCCs)-based electromagnetic bandgap (EBG) filter have been proposed. To the best of the authors’ knowledge, this is the minimum size configurable bandpass filter (BPF) ever reported using EBG material. The proposed circuits successfully integrate an integrated passive device (IPD) technique-based high- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> capacitors and LTCC-based built-in capacitors with EBG substrates. The frequencies of the filters can be easily adjusted by controlling the capacitors. For proof-of-concept demonstration purposes, CEBG filters and LTCC-based EBG filters were designed and experimentally validated from the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$C$ </tex-math></inline-formula> -band to the Ku-band. The measurement results demonstrated the filters’ compact size, wide stopband, and reduced insertion loss (IL) as working frequency increases. Four LTCC EBG filters are implemented and fabricated with the highest working frequency of 17 GHz, a minimum IL of 1.91 dB, and a 3-dB fractional bandwidth (FBW) of 3%. The CEBG filter demonstrated a compact size of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.6\times1.35$ </tex-math></inline-formula> mm, a configurable frequency from 6.88 to 13.5 GHz with an almost constant FBW. Insertion losses of the EBG filters reduce as their working frequencies increase which shows an excellent high-frequency application capability of the filters.

Noise mitigation in high-speed PCB applications: experimental verification and validation of electromagnetic band gap filters

Electromagnetic noise (EMI) affects efficiency of a gadget, proximity devices and human beings, necessitating the noise mitigation. Introduction of Electromagnetic Band Gap (EBG) structure in PCB as plane pairs helps for high-speed operations. In this paper, the planar L-bridge embedded pattern-type EBG structure is designed to mitigate the noise. Experimental verification of the designed EBG type with various geometrical parameters is carried out by altering the geometrical parameters of the unit cell with 18 cases. All the cases are simulated for the frequency sweep 0.1–10 GHz. Simulation results are compared with theoretical calculations and measurement results. It is found that they are in good agreement. The depth in noise levels can be efficiently altered by changing air gap, line length and unit cell width. In order to validate the EBG, a continuous plane is considered and found that EBG helps to mitigate the noise level in the higher frequency.

Mismatch in EBG Common-Mode Filters Implemented on PCBs

In this article, impedance mismatch effects on the characteristics of common-mode (CM) electromagnetic bandgap (EBG) filters are studied using three-dimensional (3-D) full-wave numerical simulations. The CM EBG filters considered herein are designed using standard printed circuit board technology and contain either microstrip (MS) differential pairs running above the EBG plane, or stripline (SL) differential pairs running on one of the layers next to the EBG plane. First, the terminations are fixed at 50 Ω, and the effects of the differential line impedance variations on the EBG filter parameters are studied. Overall, the considered variations in the widths of the traces and edge-to-edge separation distances in both the MS and SL structures do not drastically deteriorate the performance of the EBG CM filters. Then impedances of the ports are set different from 50 Ω, and the effects of this mismatch on the baseline SL and MS EBG structures are studied. It is shown that lower port impedances may have significant effect on the characteristics of filters. In addition, baseline EBG filters are cascaded with unmatched four-port load, and this may also deteriorate performance of filters.

Single air-mode resonance photonic crystal nanofiber cavity for ultra-high sensitivity refractive index sensing

We propose a design of series-connected one-dimensional photonic crystal nanofiber cavity sensor (1-D PC-NCS) and one-dimensional photonic crystal nanofiber bandgap filter (1-D PC-NBF). The proposed structure can get a single air mode for refractive index sensing with its extinction ratio of 58.64 dB. It filters out the high order mode and reduces the interaction between signals. By 3D FDTD, the calculated sensitivity is 848.18 nm/RIU (RIU – refractive index unit). Compared with general silicon on-chip nanobeam cavity, the sensitivity is increased by eight times. The additional 1-D PC-NBF will not change the sensitivity and the position of the resonance wavelength. Therefore, the new design we propose addresses the issue of crosstalk, and can be applied to ultra-high sensitivity index-based gas sensing and biosensing without the need for complicated coupling systems.

Highly Sensitive 1 × 8 Parallel Multiplexing of Ultra-Compact Integrated 1D Photonic Crystal Sensor Array Based on Silicon-on-Insulator Platform

We design a $1\times 8$ highly sensitive ultra-compact on-chip integrated sensor array consisting of a $1\times 8$ power splitter, eight one-dimensional photonic crystal slot nanobeam cavities (1DPC-SNCs) connected by additional 1D photonic crystal tapered nanobeam bandgap filters (1DPC-TNBF), and an $8\times 1$ power combiner. The performance of the device is numerically demonstrated by three-dimensional finite-difference-time-domain (3D-FDTD) method. The whole structure is lying on top of a $2~\mu \text{m}$ buried silicon oxide layer, while remaining high sensitivities (over 400 nm/RIU) of the eight sensors, simultaneously. The proposed 1DPC-SNCs can reach a high-quality factor of $3.6\times 10^{5}$ . On account of the additional band-stop filters and the $8\times 1$ power combiner, eight sensing segments interrogated simultaneously by one input and one output port is realized, with the ultra-compact footprint of $64\times 16\,\,\mu \text{m}^{2}$ ( $26\times 16\,\,\mu \text{m}^{2}$ in sensing region). Therefore, this design is a promising platform for realizing large-scale photonic integrated circuits with high integration density, especially for ultra-compact multiple on-chip sensing.

Long-Wavelength Reflecting Filters Found in the Larval Retinas of One Mantis Shrimp Family (Nannosquillidae).

Both vertebrates and invertebrates commonly exploit photonic structures adjacent to their photoreceptors for visual benefits. For example, use of a reflecting structure (tapetum) behind the retina increases photon capture, enhancing vision in dim light [1-5]. Colored filters positioned lateral or distal to a photoreceptive unit may also be used to tune spectral sensitivity by selective transmission of wavelengths not absorbed or scattered bythe filters [6-8]. Here we describe a new category of biological optical filter that acts simultaneously as both a transmissive spectral filter and narrowband reflector. Discovered in the larval eyes of only one family of mantis shrimp (stomatopod) crustaceans (Nannosquillidae), each crystalline structure bisects the photoreceptive rhabdom into two tiers and contains an ordered array of membrane-bound vesicles with sub-wavelength diameters of 153± 5nm. Axial illumination of the intrarhabdomal structural reflector (ISR) invivo produces a narrow band of yellow reflectance (mean peak reflectivity, 572± 18nm). The ISR is similar to several synthetic devices, such as bandgap filters, laser mirrors, and (in particular) fiber Bragg gratings used in optical sensors for awide range of industries. To our knowledge, thestomatopod larval ISR is the first example of a naturally occurring analog to these human-made devices. Considering what is known about these animals' visual ecology, we propose that these reflecting filters may help improve the detection of pelagic bioluminescence in shallow water at night. VIDEO ABSTRACT.

High-sensitivity broad free-spectral-range two-dimensional three-slot photonic crystal sensor integrated with a 1D photonic crystal bandgap filter.

We present a novel high-sensitivity broad free-spectral-range (FSR) two-dimensional three-slot photonic crystal sensor integrated with a 1D photonic crystal tapered nanobeam bandgap filter (1DPC-TNBF) based on thin-film silicon. Designed to lie in the wavelength at around 1550nm, the resonance of the two-dimensional photonic crystal three-slot cavity (2DPC-TSC) shows strong light-matter interaction in the slot region, which enhances the bulk refractive index sensitivity of the sensor significantly. The simulated sensitivity is over 900nm/refractive index unit (RIU). By connecting an additional 1DPC-TNBF to a 2DPC-TSC in series, the high-order modes are suppressed, which means only a fundamental mode exists with a broad FSR over 200nm. Thus, the proposed structure is promising in designing lab-on-a-chip applications, especially in compact parallel-integrated sensor arrays.

Design of freely suspended photonic crystal microfiber cavity sensors array in a general single mode fiber

Abstract We propose a novel design of refractive index (RI) sensor array based on ultrahigh sensitivity one dimensional (1D) photonic crystal microfiber (PCMF) cavities, which is referred as photonic crystal microfiber cavity sensors array (PCMF-CSA). The proposed PCMF-CSA consists of multiple channels connected in parallel. A transmission only containing the fundamental mode (FM) resonance of the PCMF cavity sensor for sensing purpose is created by connecting an additional PCMF bandgap filter to a PCMF cavity sensor in series on each channel. Due to the photonic bandgap (PBG) of the PCMF bandgap filter, the other high-order resonances are filtered out. With proper engineering of the PBG, multiple ultrahigh sensitivity PCMF cavity sensors can be integrated into microarrays without resonance overlap, and be detected simultaneously between a single input optical fiber and a single output optical fiber without the need for complicated coupling systems. The concept was demonstrated with 7-channel PCMF cavity sensor array containing PCMF bandgap filters. By using three-dimensional finite-difference time-domain (3D-FDTD) method, the performance of the device was investigated theoretically. The simulation results showed that the sensors on each channels can be monitored simultaneously from a single output spectrum. The numerical calculated RI sensitivities (S) for each sensing channel of the proposal 7-channel PCMF-CSA as high as 647.33 nm/RIU, 666.67 nm/RIU, 662.00 nm/RIU, 676.00 nm/RIU, 674.67 nm/RIU, 659.33 nm/RIU, 679.99 nm/RIU can be achieved, respectively. The average RI sensitivity as high as 666.57 nm/RIU can be obtained. Moreover, the extinction ratios of all resonant peaks exceed 20.0 dB. The crosstalk of all channels is lower than −24.5 dB. To the best of our knowledge, this is the first silica PCMF sensors array geometry based on conventional single mode fiber (SMF) that features both high Q and S, and thus is potentially a promising platform for ultra-sensitive RI-based gas sensing with high parallel-multiplexing capability.

Design, optimization, and fabrication of mechanical metamaterials for vibration control

Harsh shock and vibration environments are common in engineering applications. Mechanical metamaterials are showing significant potential as candidates for controlling wave propagation and isolating sensitive structural components, but require proper design of their complex microstructures. In this talk we will present time and frequency-domain strategies for Partial Differential Constrained (PDE)-constrained design optimization of locally resonant elastic/acoustic metamaterials. We will present a variety of notch filter resonators and split ring cylinder/sphere geometries that can be easily optimized for wave control applications, along with fabrication details involving multi-material additive manufacturing. A frequency-domain approach will be presented for band-gap or notch filter materials, and a time-domain strategy for transient shock environments. As the metamaterial structures typically involve concentrated masses and elastic connections, an optimization strategy involving 3D simple shapes will be presented. [Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration. With main facilities in Albuquerque, N.M., and Livermore, C.A., Sandia has major R&amp;D responsibilities in national security, energy and environmental technologies, and economic competitiveness.]

A laser-assisted process to produce patterned growth of vertically aligned nanowire arrays for monolithic microwave integrated devices

An experimental process for the fabrication of microwave devices made of nanowire arrays embedded in a dielectric template is presented. A pulse laser process is used to produce a patterned surface mask on alumina templates, defining precisely the wire growing areas during electroplating. This technique makes it possible to finely position multiple nanowire arrays in the template, as well as produce large areas and complex structures, combining transmission line sections with various nanowire heights. The efficiency of this process is demonstrated through the realisation of a microstrip electromagnetic band-gap filter and a substrate-integrated waveguide.

Band-gap tunable dielectric elastomer filter for low frequency noise

In the last decades, diverse materials and technologies for sound insulation have been widely applied in engineering. However, suppressing the noise radiation at low frequency still remains a challenge. In this work, a novel membrane-type smart filter, consisting of a pre-stretched dielectric elastomer membrane with two compliant electrodes coated on the both sides, is presented to control the low frequency noise. Since the stiffness of membrane dominates its acoustic properties, sound transmission band-gap of the membrane filter can be tuned by adjusting the voltage applied to the membrane. The impedance tube experiments have been carried out to measure the sound transmission loss (STL) of the filters with different electrodes, membrane thickness and pre-stretch conditions. The experimental results show that the center frequency of sound transmission band-gap mainly depends on the stress in the dielectric elastomer, and a large band-gap shift (more than 60 Hz) can be achieved by tuning the voltage applied to the 85 mm diameter VHB4910 specimen with pre-stretch Based on the experimental results and the assumption that applied electric field is independent of the membrane behavior, 3D finite element analysis has also been conducted to calculate the membrane stress variation. The sound filter proposed herein may provide a promising facility to control low frequency noise source with tonal characteristics.

Silicon On-chip 1D Photonic Crystal Nanobeam Bandgap Filter Integrated with Nanobeam Cavity for Accurate Refractive Index Sensing

A novel method for integration of high-performance 1-D photonic crystal nanobeam bandgap filter (1-D PC-NBF) and high-sensitivity 1-D PC nanobeam cavity sensor (1-D PC-NCS) is proposed on a monolithic silicon chip. The 1-D PC-NBF consists of a simple 1-D PC nanobeam waveguide, in which the bulk air-hole grating radii are kept the same. The 1-D PC-NCS consists of a common 1-D PC nanobeam cavity, in which the air-hole grating radius is parabolically tapered from center to end. By using the 3-D finite-difference time-domain (3-D-FDTD) method, the proposed 1-D PC-NBF with an effective low-pass bandgap ranging from 1533 to 1785 nm (with width > 250 nm) is demonstrated, where the resonant wavelengths lying in the bandgap are not guided. Then, by connecting an additional 1-D PC-NBF to a 1-D PC-NCS in series, a transmission spectrum only containing the specific fundamental mode of the 1-D PC nanobeam cavity for sensing purposes is created, while the other high-order modes are filtered out. Moreover, the additional 1-D PC-NBF has no influence on the properties (e.g., Q-factor, resonance position, and sensitivity) of the fundamental resonant mode of 1-D PC-NCS. In particular, the footprint of the proposed 1-D PC nanobeam integrated sensor is ultracompact around 0.7 μm × 10 μm, which is improved more than three orders of magnitude compared with the integrated sensor devices based on 2-D PC. Thus, the method presented here is promising to build highly parallel integrated sensor arrays for lab-on-a-chip applications and accurate detections.

A Compact Configurable EBG Filter on PCB

A novel design for configurable electromagnetic bandgap (CEBG) filter on printed circuit board (PCB) is presented. The CEBG filter is implemented in FR4 substrate with surface mounted lumped capacitors. Working frequency of the filter can be controlled by adjusting the value of the capacitor. The CEBG filter is unique in that it creates resonance by introducing a surface mounted capacitor instead of relying on modification of a periodic lattice in the substrate and in that it can cover large frequency range with a compact size. A particular example of a frequency controllable filter is implemented by CEBG process and experimentally demonstrated on the same EBG substrate and with different lumped capacitors. The results show a filter with a size of $2.50\times 3.00\times 1.00$ mm $^{3}$ in PCB achieving performance of an unloaded quality factor (Qu) of 81, an insertion loss (IL) of 3.48 dB at 3.22 GHz, and a Qu of 105, an IL of 2.93 dB at 4.07 GHz using a capacitor of 3.3 and 2.2 pf, respectively.

Coulomb's Law Discretization Method: a New Methodology of Spatial Discretization for the Radial Point Interpolation Method

In this paper, a new particle interaction method based on Coulombs force law has been developed and computationally implemented for performing meshless spatial discretization. The new methodology, which is named Coulombs Law Discretization Method (CLDM), employs an adapted version of the Coulombs vector force equation for obtaining a balanced distribution of nodes in space (equilibrium state), in such a way to achieve high discretization quality of space and complex structures. For this aim, a new quality metrics is introduced. The radial point interpolation method (RPIM) and the uniaxial perfectly matched layers (UPML) are used for solving Maxwell's equations in time domain for 2D problems. The CLDM/RPIM methods are applied to electromagnetic scattering problems and for designing hybrid photonic band-gap filters, based on circular and triangular metallic cylinders. The obtained results are in accordance with analytical solutions.

Dynamically-tunable colloidal band-pass and band-gap filters

We theoretically study particle motion on a periodic array of positive and negative magnetization domains having non-equal widths driven by a multi-frequency magnetic field input signal. Colloidal particles move across the substrate with positive, zero, or negative time-averaged velocity depending on the frequency ratio, the phase difference, and the ratio of the external field strength to the substrate magnetization. Simulations show that particles of a certain size range can either be transported or locally trapped, thereby providing a mechanism for implementing tunable colloidal band-pass and colloidal band-gap filters.

A design method for substrate integrated waveguide electromagnetic bandgap (SIW-EBG) filters

An efficient design method for substrate integrated waveguide electromagnetic bandgap (SIW-EBG) filters is proposed which provides direct dimensional synthesis approach for desired filter objectives without using network representations. The method is applied to the design of an X band SIW-EBG filter and its response is compared with HFSS (high frequency structure simulator) simulations for validation purposes. Fairly good agreement between the results shows the applicability of the proposed method for SIW-EBG filter design.

Ultralight-Trapping Filters With Volume Reflection Holograms

Light trapping is a useful approach for increasing the absorption of thin film photovoltaic (PV) cells. Simple light trapping can be achieved by incorporating a scattering layer on the top and bottom surface of cells and can increase absorption by a factor of 4n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Recently, ultralight trapping using Rugate and 1-D photonic bandgap filters have been proposed to increase light trapping by a factor of 4n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /sin <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> θ, where θ is half of the acceptance angle. In this paper, we present the design of a holographic ultralight trapping filter. The holographic filter can be implemented in large areas at a low cost, which makes it scalable for PV applications. A design is presented that increases the optical path length for near bandgap wavelengths in a thin-film silicon PV cell. The optical path length enhancement is converted to electrical output using the PC-1D simulation software. The short-circuit current for a 10-μm-thick silicon PV cell increases by nearly 14.7% relative to a cell without light trapping.

Transmission spectrum of a dielectric binary multilayered structure with diluted disorder

In this work we investigate the transmission properties of a binary multilayered structure with diluted disorder. This system consists of two interpenetrating sub-sequences. One of them is composed by layers of refractive index na and thickness da, inserted into the odd positions of a stack. The second sub-sequence consists of randomly distributed layers of type A and B, distributed with probability 1−p and p, respectively and inserted into the even sites of the stack. The layer thicknesses were taken to satisfy the Bragg condition nada=nbdb. Using a transfer matrix method, we compute the transmission spectrum, the frequency averaged transmission as a function of the system size and the reduced Lyapunov coefficient for different values of the defect concentration p. For 0<p<1 the system depicts a wide band-gap due to the Anderson localization of the electromagnetic modes promoted by the underlying disorder. However, the diluted character of the disorder implies in the absence of the quarter-wavelength resonant mode within the band-gap that usually appears in random binary structures. This particular feature suggests that binary dielectric structures with diluted disorder shall perform better as a wide band-gap filter than uncorrelated disordered multilayer structures.