Controlling thermal transport has become relevant in recent years. Traditionally, this control has been achieved by tuning the scattering of phonons by including various types of scattering centres in the material (nanoparticles, impurities, etc). Here we take another approach and demonstrate that one can also use coherent band structure effects to control phonon thermal conductance, with the help of periodically nanostructured phononic crystals. We perform the experiments at low temperatures below 1 K, which not only leads to negligible bulk phonon scattering, but also increases the wavelength of the dominant thermal phonons by more than two orders of magnitude compared to room temperature. Thus, phononic crystals with lattice constants ≥1 μm are shown to strongly reduce the thermal conduction. The observed effect is in quantitative agreement with the theoretical calculation presented, which accurately determined the ballistic thermal conductance in a phononic crystal device.

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Engineering thermal conductance using a two-dimensional phononic crystal

The feasibility of tuning the band structure of phononic crystals is demonstrated by employing magnetostrictive materials and applying an external magnetic field. Band structures are calculated with a plane wave expansion method that accounts for coupling between the elastic behavior and the magnetic field through the development of elastic, piezomagnetic, and magnetic permeability effective tensors. We show the contactless tunability of the absolute band gaps of a two-dimensional phononic crystal composed of an epoxy matrix and Terfenol-D inclusions. The tunable phononic crystal behaves like a transmission switch for elastic waves when the magnitude of an applied magnetic field crosses a threshold.

Tunable magnetoelastic phononic crystals

Gas sensors are important in many fields such as environmental monitoring, agricultural production, public safety, and medical diagnostics. Herein, Tamm plasmon resonance in a photonic bandgap is used to develop an optical gas sensor with high performance. The structure of the proposed sensor comprises a gas cavity sandwiched between a one-dimensional porous silicon photonic crystal and an Ag layer deposited on a prism. The optimised structure of the proposed sensor achieves ultra-high sensitivity (S = 1.9×105 nm/RIU) and a low detection limit (DL = 1.4×10−7 RIU) compared to the existing gas sensor. The brilliant sensing performance and simple design of the proposed structure make our device highly suitable for use as a sensor in a variety of biomedical and industrial applications.

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Refractive index gas sensor based on the Tamm state in a one-dimensional photonic crystal: Theoretical optimisation.

Porous silicon one-dimensional photonic crystals (PSi-1DPCs) are capable of sensing solutions and liquids based on the smallest variation of the refractive indices. In the present work, we present a novel metal/PSi-1DPC as a liquid sensor based on Tamm/Fano resonances. The operating wavelength range is from 6.35 to 9.85 μm in the mid-infrared (MIR) spectral region. Different metals (Al, Ag, Au, and Pt) are attached to the top surface of the PSi-1DPCs structure to show Tamm/Fano resonances more clearly. To the best of our knowledge, it is the first time that Tamm/Fano resonances exhibit simultaneously in PSi-1DPCs within the same structure. The reflection spectra were calculated for the metal/PSi-1DPC structure by using the transfer matrix method (TMM) and the Bruggeman’s effective medium approximation (BEMA). The simulations show that the Tamm/Fano resonances are red-shifted towards the higher wavelengths with increasing the refractive index of the pores. The Ag/PSi-1DPC sensor showed the highest performance. Its sensitivity can be reached to the value 5018 nm/RIU with a high-quality factor of about 2149.27. We predict the proposed sensors can be easily fabricated and we expect them to show higher performance than other reported sensors of this type. Therefore, it will be of interest in the field of optical sensing in different fields.

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Ultra-high sensitive 1D porous silicon photonic crystal sensor based on the coupling of Tamm/Fano resonances in the mid-infrared region

Photonic sensing is a new technology and accurate measurement for biosensing applications. The present work has been proposed blood sugar biosensor in the visible region by using a defective one-dimensional photonic crystal (1D-PC). The structure adopted is Air/(SiO2/Si)^5/SiO2/D/SiO2/(SiO2/Si)^5/ SiO_2substrate. The defect layer (D) is filled with blood sugar solution with different concentrations. The transmission spectrum was calculated numerically by using the transfer matrix method (TMM). The thickness of the defect layer and incident angle has been optimized to achieve the best performance of the sensor. The localization of defect mode shifts to a longer wavelength with increasing the defect layer thickness. In addition to increase the incident angle from θ_0=0 to θ_0=90 degree, the defect peak was shifted towards the short wavelength region. The optimized value of our structure demonstrates high sensitivity for the blood sugar (S = 1100 nm/RIU) in range of concentration C=0 to C=500 mg/dl, more enhancement of the quality factor (about 3.755*106) and very low detection limit (DL=10^(-8) RIU) are achieved. These results indicate that the proposed structure has higher performance as a blood sugar sensor than many previously reported data.

https://iopscience.iop.org/article/10.1088/1402-4896/ab53f5/pdf

Theoretical study of hybrid multifunctional one-dimensional photonic crystal as a flexible blood sugar sensor

In this research, the photonic and phononic response of one-dimensional multilayer phoxonic crystals (PxCs) with normal incident of electromagnetic and acoustic waves is discussed. The presented design can work as a highly sensitive sensor for measuring three binary alcohol/water mixtures (i.e., 1-propanol/water, ethanol/water, and methanol/water) for a wide range of concentrations. The PxC sensor is able to detect small changes in the refractive index and longitudinal sound velocity of the alcohol/water mixture with initially neglecting the acousto-optical interaction. The sensor design is a defective structure as [$({\rm Si}/{\rm SiO}_2)^4 (\rm mixture\;wt. \%) {({{\rm SiO}_2}/{\rm Si})^4}$(Si/SiO2)4(mixturewt.%)(SiO2/Si)4]. Also, we studied the effects of changing mixture concentrations from 0 wt. % to 100 wt. % on the physio-chemical parameters and resonant mode frequency. In our results, we have achieved high performance for the three alcohol mixtures in both phononic and photonic sensors especially for low concentrations. For example, in the photonic sensor we obtained sensitivity, $Q$Q value, and figure of merit of 873 nm/RIU, 755, and ${290}\;{{\rm RIU}^{ - 1}}$290RIU−1, respectively, for methanol of concentration 10% in water. The phononic sensor showed higher results compared with the photonic sensor, as for ethanol with concentration 26.8% in water we obtained sensitivity, $Q$Q value, and figure of merit of ${37}\;{{\rm MHz/ms}^{ - 1}}$37MHz/ms−1, 1604, and ${8.4}\;{({\rm m/s})^{ - 1}}$8.4(m/s)−1, respectively. The proposed structure has different merits: operation at high temperatures, compact size, ease of fabrication, and feasibility of alcohol detection with two different methods that could be used in many chemical applications.

Determination of 1-propanol, ethanol, and methanol concentrations in water based on a one-dimensional phoxonic crystal sensor

Based on the transfer matrix method (TMM) and Bloch theory, the interaction of elastic waves (normal incidence) with 1D phononic crystal had been studied. The transfer matrix method was obtained for both longitudinal and transverse waves by applying the continuity conditions between the consecutive unit cells. Dispersion relations are calculated and plotted for both binary and ternary structures. Also we have investigated the corresponding effects on the band gaps values for the two types of phononic crystals. Furthermore, it can be observed that the complete band gaps are located in the common frequency stop-band regions. Numerical simulations are performed to investigate the effect of different thickness ratios inside each unit cell on the band gap values, as well as unit cells thickness on the central band gap frequency. These phononic band gap materials can be used as a filter for elastic waves at different frequencies values.

Enhancement of phononic band gaps in ternary/binary structure

In this work, a one-dimensional porous silicon carbide phononic crystal (1D-PSiC PnC) sandwiched between two rubber layers is introduced to obtain low frequency band gaps for the audible frequencies. The novelty of the proposed multilayer 1D-PnCs arises from the coupling between the soft rubber, unique mechanical properties of porous SiC materials and the local resonance phenomenon. The proposed structure could be considered as a 1D acoustic Metamaterial with a size smaller than the relevant 1D-PnC structures for the same frequencies. To the best of our knowledge, it is the first time to use PSiC materials in a 1D PnC structure for the problem of low frequency phononic band gaps. Also, the porosities and thicknesses of the PSiC layers were chosen to obtain the fundamental band gaps within the bandwidth of the acoustic transducers and sound suppression devices. The transmission spectrum of acoustic waves is calculated by using the transfer matrix method (TMM). The results revealed that surprising low band gaps appeared in the transmission spectra of the 1D-PSiC PnC at the audible range, which are lower than the expected ones by Bragg’s scattering theory. The frequency at the center of the first band gap was at the value 7957 Hz, which is 118 times smaller than the relevant frequency of other 1D structures with the same thickness. A comparison between the phononic band gaps of binary and ternary 1D-PSiC PnC structures sandwiched between two rubber layers at the micro-scale was performed and discussed. Also, the band gap frequency is controlled by varying the layers porosity, number and the thickness of each layer. The simulated results are promising in many applications such as low frequency band gaps, sound suppression devices, switches and filters.

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Locally Resonant Phononic Crystals at Low frequencies Based on Porous SiC Multilayer

In this work, we have introduced a comprehensive study concerning with the effects of some physical parameters on the dispersive properties of 1D phononic crystal (PnC). We have treated the propagation of elastic (in-plane) waves incident normally on 1D PnC. Based on the transfer matrix method, the reflection coefficients are calculated and plotted for the plane waves. We have studied many physical parameters effects on the properties of PnCs such as type of surrounding material, type of composites materials, temperature and propagation of waves in defect structures. Also the phenomenon of local resonance was discussed in this survey. These results can be useful in many applications such as sound suppressions and temperature sensor materials.

Ahmed Mehaney

Papers

Ultra-high sensitive 1D porous silicon photonic crystal sensor based on the coupling of Tamm/Fano resonances in the mid-infrared region

Determination of 1-propanol, ethanol, and methanol concentrations in water based on a one-dimensional phoxonic crystal sensor

Enhancement of phononic band gaps in ternary/binary structure

Locally Resonant Phononic Crystals at Low frequencies Based on Porous SiC Multilayer

Study of physical parameters on the properties of phononic band gaps