Mid-infrared Metasurface Research Articles

Quasi-bound states in the continuum with stable dual-resonance wavelengths in mid-infrared metasurface for ultrasensitive refractive index sensing and molecular vibrations of strong coupling

In this paper, a dual-resonances mid-infrared all-dielectric metasurface sensor based on asymmetric cross dimer, which is driven by quasi-bound states in the continuum (QBIC), is proposed and investigated. The metasurface sensor maintains the total permittivity constant when the asymmetric parameter is adjusted, thereby ensuring the stability of the QBIC resonance wavelengths, which exhibit Q-factors of 6351 and 13561, respectively. The multiple decompositions and electromagnetic field distributions reveal that the toroidal dipole is the dominant component of the dual-resonance modes. The sensitivities to the refractive index are 3559 nm/RIU and 1146 nm/RIU, with corresponding figures of merit of 4449 RIU−1 and 2453 RIU−1, respectively. Further numerical simulations have demonstrated a strong coupling phenomenon between the QBIC and the molecular vibrations of polymethyl methacrylate (PMMA), resulting in a significant enhancement of the infrared absorption signal. With the 50-nm-thick PMMA layer, the enhancement of molecular signal is 90.614%.

Plasmonic Anapole Mode in a Mid-Infrared Metasurface with Improved Quality Factor

Plasmonic Anapole Mode in a Mid-Infrared Metasurface with Improved Quality Factor

Self-similar ring element array develop for Fano response as mid-infrared: Liver cancer study

the mid-infrared metasurfaces play an important in optical applications including sensing and having Fano response is a benefit in this field for many goals including biosensing. So, these points are considered in this study and self-similar Plasmonic metasurface is suggested for sensing application. The suggested structure has a symmetrical formation but non-similar elements are considered to raise the Fano response. The structure contains five rings while the central one has a larger dimension than the four elements surrounding the central ring as an array of rings. The interaction of bright modes for both elements of the central ring and the array elements makes the Fano response at 1850 and 1910 nm while the single central ring has resonance at 1910 nm and the array rings have resonance at 1850 nm. The interaction of the element enhances the Q-factor of both resonances. The Full-wave method finite integrated technique (FIT) is used for modeling as a time domain method and the couple mother theory (CMT) is used for the analytical model. This metasurface is implemented as a sensor for detecting material under test and the sensitivity of the sensor is obtained 282 nm/RIU (Refractive Index Unit). Finally, the tissue of the liver as healthy and cancer cells are considered for examining the quality of the sensor.

Ge3Sb2Te6-based mid-infrared metasurfaces for polarization control and wavefront steering

Benefiting from excellent properties in wavefront control, germanium antimony telluride (GeSbTe)-based photonic devices provide new opportunities for manipulating electromagnetic wave. In this paper, Ge3Sb2Te6 meta-atoms are presented to realize polarization switching for mid-infrared wave through the state transition from the crystalline Ge3Sb2Te6 to the amorphous Ge3Sb2Te6. When the crystalline Ge3Sb2Te6 is involved, the proposed meta-atoms with 90° phase shift achieve high-efficiency polarization conversion and 360° phase coverage. As Ge3Sb2Te6 is changed to the amorphous state, phase coverage drops to only 36°, and most of the cross-polarized wave vanishes. Using these designed meta-atoms, three metasurfaces are implemented at 76.5 THz. Firstly, a gradient metasurface is constructed, and it dynamically switches between specular reflection and anomalous reflection. Next, a reflective metalens is proposed to realize switching between focusing and defocusing under different states of Ge3Sb2Te6. Lastly, a focused vortex beam is presented to reconstruct the mode of orbital angular momentum (OAM). All designs realize the switching between cross-polarization and co-polarization. Our work could have possible applications in fields such as mid-infrared switching, focusing, and wireless communication.

Electrical Phase Modulation Based on Mid‐Infrared Intersubband Polaritonic Metasurfaces

Electrically reconfigurable metasurfaces that overcome the static limitations in controlling the fundamental properties of scattered light are opening new avenues for functional flat optics. This work proposes and experimentally demonstrates electrically phase-tunable mid-infrared metasurfaces based on the polaritonic coupling of Stark-tunable intersubband transitions in semiconductor heterostructures and electromagnetic modes in plasmonic nanoresonators. In the applied voltage range of -3 to +3V, the local phase tuning of the light reflects from the metasurface, which enables the electrical control of the polarization state and wavefront of the reflected wave. Electrical beam polarization control, electrical beam diffraction control, and electrical beam steering are experimentally demonstrated as applications for local phase tunability. The proposed electrically tunable metasurfaces can easily tune the operating wavelength and function at relatively low voltages, which will enable various applications in the mid-infrared region.

Downhole FT-MIR Spectrometer Using Perfect Metasurface Absorber

Realization of “Fourier transform infrared (FT-IR) on a chip” holds the potential of a disruptive technology for downhole chemical analysis within the oil and gas industry. One of the critical obstacles to downhole integration though has been the cooling requirements of conventional technologies. Here, we report the design and numerical analysis of an uncooled miniaturized Fourier transform mid-infrared (FT-MIR) spectrometer compatible with downhole thermal environments, enabled by a broadband mid-infrared metasurface detector/source combination derived from a geometric inversion of a set of conformal mapping contours. The metasurface is numerically found to exhibit a near-zero index metamaterial (NZIM) behavior with absorption characterized by surface plasmon resonances confined to the ultrathin ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula> /300) metasurface plane, making the absorption properties of the microbolometer design much less sensitive to the remaining support structure than in typical designs. This feature allows the metasurface to be integrated on a single VO2 substrate operated at elevated downhole temperatures that coincide with the metal–insulator transition region. Within this transition region, the VO2 material exhibits enhanced thermometric properties, enabling an uncooled microbolometer design with predicted maximum detectivity <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${D}^{*} = 1.5\times {10}^{{10}}\,\,\text {cm} \sqrt {\text {Hz}}/\text {W}$ </tex-math></inline-formula> and noise equivalent difference temperature (NEDT) of 1 mK at a modulation frequency of 500 Hz. These parameters approach entry-level lab FT-MIR spectrometers and could represent a significant step in deploying mid-infrared spectroscopy into oilfield downhole logging applications.

Thermally switchable, bifunctional, scalable, mid-infrared metasurfaces with VO2 grids capable of versatile polarization manipulation and asymmetric transmission

We conceptualized three-array scalable bifunctional metasurfaces comprising only three thin strip grids and numerically determined their characteristics in the mid-infrared spectral regime for switchable operation scenarios involving polarization manipulation and related diodelike asymmetric transmission (AT) as one of two functionalities. A few or all of the grids were taken to be made of VO2, a bifunctionality-enabling phase-change material; there are no layers and/or meta-atoms comprising simultaneously both metal and VO2. For each proposed metasurface, two effective structures and, therefore, two different functionalities exist, corresponding to the metallic and insulating phases of VO2. The achieved scenarios of functionality switching significantly depend on the way in which VO2 is incorporated into the metasurface. Switchable bands of polarization manipulation are up to 40 THz wide. The AT band can be modulated when Fabry–Perot (anti-) resonances come into play. Besides, transmission regimes with the cross-polarized component insensitive to VO2 phase change are possible, as well as the ones with all co- and cross-polarized components having the same magnitude for both linear polarizations of the incident wave.

Controlled and tunable plasmon-induced transparency based on graphene metasurfaces in atmospheric windows

Considering the development of plasmon-induced transparency functional devices and the research value of the atmospheric windows in many civilian and military applications, we propose a mid-infrared metasurface composed of a multilayer elliptical graphene and two graphene strips that can generate PIT, and the PIT can be dynamically tuned in the range of 3.67 μm–9.53 μm beyond monolayer graphene. The numerical results from Finite-Difference Time-Domain (FDTD) method are consistent with the analytical results from Lorentz oscillator theory. In addition, we can control the generation and vanishment of the PIT by changing the polarization of the source, achieving a triple-frequency asynchronous switch, and the performance index indicates that the modulation depth is maintained at about 90% at a relatively high Fermi energy level. Our work achieves a dynamically tunable and controllable PIT for applications including filters and optical switches in atmospheric windows.

Principles and application progress of mid-infrared metasurfaces in imaging and detection (Invited)

Principles and application progress of mid-infrared metasurfaces in imaging and detection (Invited)

Topological phonon-polariton funneling in midinfrared metasurfaces.

Topological photonics offers enhanced control over electromagnetic fields by providing a platform for robust trapping and guiding of topological states of light. By combining the strong coupling between topological photons with phonons in hexagonal boron nitride (hBN), we demonstrate a platform to control and guide hybrid states of light and lattice vibrations. The observed topological edge states of phonon-polaritons are found to carry nonzero angular momentum locked to their propagation direction, which enables their robust transport. Thus, these topological quasiparticles enable the funneling of infrared phonons mediated by helical infrared photons along arbitrary pathways and across sharp bends, thereby offering opportunities for applications ranging from Raman and vibrational spectroscopy with structured phonon-polaritons to directional heat dissipation.

Wafer-Scale Functional Metasurfaces for Mid-Infrared Photonics and Biosensing.

Metasurfaces have emerged as a breakthrough platform for manipulating light at the nanoscale and enabling on-demand optical functionalities for next-generation biosensing, imaging, and light-generating photonic devices. However, translating this technology to practical applications requires low-cost and high-throughput fabrication methods. Due to the limited choice of materials with suitable optical properties, it is particularly challenging to produce metasurfaces for the technologically relevant mid-infrared spectral range. These constraints are overcome by realizing functional metasurfaces on almost completely transparent free-standing metal-oxide membranes. A versatile nanofabrication process is developed and implemented for highly efficient dielectric and plasmonic mid-infrared metasurfaces with wafer-scale and complementary metal-oxide-semiconductor (CMOS)-compatible manufacturing techniques. The advantages of this method are revealed by demonstrating highly uniform and functional metasurfaces, including high-Q structures enabling fine spectral selectivity, large-area metalenseswithdiffraction-limited focusing capabilities, and birefringent metasurfaces providing polarization control at record-high conversion efficiencies. Aluminum plasmonic devices and their integration into microfluidics for real-time and label-free mid-infrared biosensing of proteins and lipid vesicles are further demonstrated. The versatility of this approach and its compatibility with mass-production processes bring infrared metasurfaces markedly closer to commercial applications, such as thermal imaging, spectroscopy, and biosensing.

Hyperbolic surface wave propagation in mid-infrared metasurfaces with extreme anisotropy

Hyperbolic metasurfaces are characterized by an extreme anisotropy of their effective conductivity tensor, which may be induced at visible frequencies by sculpting metals at the subwavelength scale. In this work, we explore practical implementations of hyperbolic metasurfaces at mid-infrared wavelengths, exploiting devices composed of metals and high-index semiconductor materials, which can support the required field confinement and extreme anisotropy required to realize low loss hyperbolic surface waves. In particular, we discuss the role of broken symmetries in these hybrid metasurfaces to enable large and broadband hyperbolic responses spanning the entire mid-infrared wavelength range (3–30 μm). Our findings pave the way to the development of large scale nanophotonic devices to manipulate mid-infrared light, with applications in nonlinear optics due to the high field confinement, light routing at the nanoscale, thermal control and management, and sub diffraction imaging.

Transmissive mid-infrared achromatic bifocal metalens with polarization sensitivity.

Metasurfaces have shown great potential in versatile areas such as vortex-beam generators, metalenses, holograms and so on. However, chromatic error hinders metasurfaces, especially metalenses, from wider applications. In this paper, we demonstrate a novel design for a transmissive mid-infrared achromatic bifocal metalens with polarization sensitivity. The compensation phase is used to eliminate the chromatic aberration. Simulation results show that, over a continuous waveband from 3.9 to 4.6µm, the focal length only changes by 2.26% with an average focusing efficiency of about 18%. This work can push the practical application of mid-infrared metasurfaces.

Giant midinfrared nonlinearity based on multiple quantum well polaritonic metasurfaces

AbstractUltrathin engineered metasurfaces loaded with multiple quantum wells (MQWs) form a highly efficient platform for nonlinear optics. Here we discuss different approaches to realize mid infrared metasurfaces with localized second-harmonic generation based on optimal metasurface designs integrating engineered MQWs. We first explore the combination of surface lattice resonances and localized electromagnetic resonances in nanoresonators to achieve very large field concentrations. However, when we consider finite size effects, the field enhancement drops significantly together with the conversion efficiency. To overcome this shortcoming, we explore nonetched L-shaped dielectric nanocylinders and etched arrow-shaped nanoresonators that locally support multiple overlapped resonances maximizing the conversion efficiency. In particular, we show the realistic possibility to achieve up to 4.5% efficiency for a normal incident pump intensity of 50 kW/cm2, stemming from inherently local phenomena, including saturation effects in the MQW. Finally, we present a comparison between pros and cons of each approach. We believe that our study provides new opportunities for designing highly efficient nonlinear responses from metasurfaces (MSs) coupled to MQW and to maximize their impact on technology.

Metamaterial-enhanced infrared attenuated total reflection spectroscopy.

The use of Fourier transform infrared spectroscopy with attenuated total reflection (FTIR-ATR) allows solid or liquid samples to be characterised directly without specific sample preparation. In such a system, the evanescent waves generated through total internal reflection within a crystal interact with the sample under test. In this work we explore the use of a mid-infrared metasurface to enhance the interaction between molecular vibrations and the evanescent waves. A complementary ring-resonator structure was patterned onto both silicon and SiO2/Si substrates, and the spectral properties of both devices were characterised using a FTIR-ATR system. Minima in reflectance were observed corresponding to the resonance of the metasurface on the silicon substrate, and to the hybrid resonance of phonon modes and metasurface resonances on the SiO2/Si substrate, in good agreement with simulations. Preliminary experiments were undertaken using mixtures containing trace amounts of butyl acetate diluted with oleic acid. Without the use of a metasurface, the minimum concentration of butyl acetate that could be clearly detected was 10%, whereas the use of the metasurface on the SiO2/Si substrate allowed the detection of 1% butyl acetate. This demonstrates the potential of using metasurfaces to enhance trace chemical detection in FTIR-ATR systems.

Passive temperature control based on a phase change metasurface

In this paper, a tunable mid-infrared metasurface based on VO2 phase change material is proposed for temperature control. The proposed structure consisting of a VO2/SiO2/VO2 cavity supports a thermally switchable Fabry-Perot-like resonance mode at the transparency window of the atmosphere. Theoretically, the radiative cooling power density of the proposed metasurface can be switched to four-fold as the device temperature is below/above the phase change temperature of VO2. Besides radiative cooling, a passive temperature control application based on this huge cooling power switching ability is theoretically demonstrated. We believe the proposed device can be applied for small radiative cooling and temperature control applications.

Mid-infrared metasurface made of composite right/left-handed transmission-line

We report on the realization of a mid-infrared metasurface based on the concept of composite right/left-handed transmission-line. The metasurface consists of a three-layer metal-insulator-metal structure patterned into transmission-lines by electron-beam lithography. Angle-variable reflection spectroscopy measurements reveal resonant absorption features corresponding to both right- and left-handed propagations in the leaky-wave guided mode region. Material loss is shown to dominate the quality factor of the left-handed modes, while the radiative loss dominates the right-handed ones. The experimental results are in good agreement with full-wave numerical simulations and are explained with an equivalent circuit model.

Highly efficient mid-infrared metasurface based on metallic rods and plate

Metasurface is a new kind of 2D metamaterial that is able to manage a variety of light beam modulations through steering the phase of the scattering waves. In this work, we utilize the metasurface to manipulate the light beam in the mid-infrared regime. By using the metallic rod and the plate structure, the metasurface presents a high polarization conversion efficiency and a wide working bandwidth. With specially rotated metallic rods, the metasurface can realize various light beam manipulations, such as negative reflection, beam collimation, and focusing. All of these results show that such a metasurface will have potential applications in future mid-infrared optics.