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.

/pdf/refractive-index-gas-sensor-based-on-the-tamm-state-in-a-one-26c0xtewzy.pdf

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.

/pdf/ultra-high-sensitive-1d-porous-silicon-photonic-crystal-45cktq3azq.pdf

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

Theoretical investigations of Tamm plasmon resonance for monitoring of isoprene traces in the exhaled breath: Towards chronic liver fibrosis disease biomarkers

https://google.iopscience.iop.org/article/10.1088/1361-6463/abb729/pdf

High performance design for detecting NaI–water concentrations using a two-dimensional phononic crystal biosensor

In this work, a novel design of a highly sensitive two-dimensional fluid/fluid phononic crystal sensor for sensing hydrogen peroxide (H2O2) concentrations up to 75.5% in water is presented. The transmission spectra of the phononic crystal sensor is calculated based on the finite element method (FEM). The host matrix is made from mercury and the inclusions are filled with water. H2O2 with different concentrations have been added in a cavity inside the phononic crystal design. Different resonant modes related to each H2O2 concentration were localized in the center of the phononic band gap. It is predicted that the central frequency of this resonant mode changes as the concentration of the H2O2 alters. The sensor showed high performance and quality factor versus a wide range of H2O2 concentrations. The sensitivity reached up the value of 426 Hz for each 1% change in H2O2 concentration. Also, we obtained a quality factor with the value of 1612 and a figure of merit with the value of 2488. Thereby this sensor can be used as a highly sensitive biosensor for hydrogenates, acidity and all components such as glucose and uric acid in the blood. Finally, obtained simulation results revealed that the proposed H2O2 sensor can be considered as a competitive, prospective, flexible and commercial device for detecting and distinguishing H2O2 concentrations with high efficiency.

Ahmed Mehaney

Papers

Theoretical investigations of Tamm plasmon resonance for monitoring of isoprene traces in the exhaled breath: Towards chronic liver fibrosis disease biomarkers

High performance design for detecting NaI–water concentrations using a two-dimensional phononic crystal biosensor

Two-dimensional phononic crystal sensor for volumetric detection of hydrogen peroxide (H2O2) in liquids

Influence of temperature on the properties of one-dimensional piezoelectric phononic crystals

Numerical optimization of 1D superconductor photonic crystals pressure sensor for low temperatures applications