Fabry-Perot Resonator Research Articles

Ultrahigh-Sensitivity and Low-Thickness THz Refractive Index Sensor Based on Excitation of Tamm Plasmon Polaritons and Exploiting Fabry–Perot Resonances

Ultrahigh-Sensitivity and Low-Thickness THz Refractive Index Sensor Based on Excitation of Tamm Plasmon Polaritons and Exploiting Fabry–Perot Resonances

Influencing factors of self-aligned imaging in near-field lithography for the Fabry–Perot cavity effect

In near-field lithography, the Fabry–Perot (F-P) cavity enhancement effect can significantly improve image quality and resolution. This paper considers changes in the refractive index and air distance in self-aligned imaging. Simulation results demonstrate that the Fabry–Perot resonator effect achieves effective self-alignment in 3D imaging. The proposed structure builds on traditional near-field imaging structures and F-P resonator research, suggesting a Cu/SiO2 structure as the front layer. Rigorous coupled wave analysis (RCWA), finite element method (FEM), and finite-difference time-domain (FDTD) methods were employed to verify the self-alignment effect on single gratings and rectangular hole arrays. The results indicate that the self-alignment lithography method based on the F-P effect not only enhances lithography contrast and normalized image log-slope (NILS) but also shows robust performance against variations in air distance and complex refractive index. Notably, for the rectangular aperture array structure, with changes in air distance and complex refractive index within a certain range, the NILS remains stable above 2.8, and the contrast stays near 0.70. These simulation results confirm that the F-P resonator-based scheme is viable for plasma imaging lithography with small critical dimensions.

Total resonant terahertz absorption enabled by a large-scale adjustable admittance inverse matching in a metal groove with graphene

Abstract We propose a tunable terahertz (THz) perfect absorber based on a metal groove with graphene-loaded dielectric resonator and theoretically study its basic properties. The proposed absorber allows switching between the regimes of perfect absorption at the Fabry-Perot resonance excited near the cut-off frequency of the metal groove and almost total reflection away from the resonance by changing the Fermi energy in graphene. For this purpose, we propose a “bottom up” approach which is based on tuning the admittance of input line (the metal groove in our case) instead of the structure admittance in order to reach the perfect admittance matching condition. We demonstrate that this effect can be realized at arbitrary selected frequency in the entire THz range due to the dispersion of incoming wave in metal groove, which ensures a large-scale tunability of its characteristic admittance. As a result, the total absorption can be realized in the Fabry-Perot resonance even in a simple graphene-loaded dielectric cavity for any admittance of graphene layer, which is advantageous as compared to majority of existing THz absorbers with more complicated design.

Interplay of surface plasmon and Fabry-Perot resonances in metallic hole arrays on dielectric layers

Interplay of surface plasmon and Fabry-Perot resonances in metallic hole arrays on dielectric layers

Numerical Verification of a Polarization-Insensitive Electrically Tunable Far Infrared Band-Stop Meta-Surface Filter

Tunable filters have many potential applications in diverse fields, including high-capacity communications, dynamic beam shaping and spectral imaging. Although providing a high-performance solution for actively tunable devices, metasurface combined with tunable materials faces the great challenges of limited tuning range and modulation depth. Here, we propose a far-infrared tunable band-stop filter based on Fabry-Perot (FP) resonators and graphene surface plasmons. By switching the wavelength of the critical coupling condition of the filter via the gate voltage applied on graphene, achieving the dynamically tunable band-stop filtering at the central wavelengths from 12.4 μm to 14.1 μm with a modulation depth of more than 99%. Due to the symmetry of the proposed meta-atoms, the filter is insensitive to the polarization direction of the incident light. And it can realize more than 85% filtering efficiency within 60° angle of incidence around the vertical direction. By adjusting the geometry of the meta-atoms structure, it is feasible to move the operational range from the near-infrared to terahertz bands.

High-sensitivity multi-gas detection using dual-ridge metasurface emitters with polarization-distinguishable emission spectra

The metasurface thermal emitter offers an energy-efficient, compact, and sensitive solution as a radiation source for non-contact gas detection, enabling the “molecular fingerprint” technique to be widely applied, from medical diagnostics to environmental monitoring. However, most narrowband emitters are designed for a single target gas, hindering the miniaturization of multi-gas detection systems. In this work, a one-dimensional dual-ridge grating emitter is employed, achieving dual-band and tri-band polarization-distinguishable emission spectra through the excitation of Fabry-Perot (FP) resonances and quasi-bound states in the continuum (qBICs). These emission spectra can be readily matched to multiple non-overlapping absorption peaks of gases such as CH4, CO2, CO, NO, and NH3 within the 3–6 µm range, thereby reducing the impact of mixed gases on measurements. Compared to conventional metal-dielectric-metal structures, the use of a single metal layer results in lower material losses, enabling higher Q-factors and more pronounced directional radiation intensity variations. Furthermore, adjusting the asymmetry to modulate the qBIC-excited absorption peaks does not affect the Q-factor of the FP resonance absorption, thus achieving high-sensitivity multi-band gas detection. This work provides a promising approach for the miniaturization and integration of multi-gas channel detection, facilitating more accurate and sensitive sensing strategies.

Suppression of the Effect of Parametric Instability in the LIGO Voyager Gravitational Wave Detector

The number of unstable combinations of elastic and Stokes optical modes of the LIGO Voyager gravitational wave detector, frequencies and spatial distributions of displacement vectors of elastic modes of mirrors were calculated. The values of overlap factors for unstable modes up to ninth-order optical modes are calculated, taking into account the azimuthal condition of parametric instability. An analysis of the influence of the temperature dependence of the Young’s modulus of the mirror material on the number of unstable modes in the Fabry-Perot resonator was performed.

High-sensitive Fabry-Perot cavity-enhanced optical resonator for photoacoustic sensing with wide frequency range

High-sensitive Fabry-Perot cavity-enhanced optical resonator for photoacoustic sensing with wide frequency range

Sound absorption metamaterials designed by machine learning and their applications

Acoustic metamaterials are artificial materials composed of acoustic functional elements along the spatial order, which have extraordinary acoustic properties that are not possessed by homogeneous materials. Since the conception of phononic crystal in the 1990s, acoustic metamaterials have gradually matured, which prospects industrial application. In our report, we present an acoustic metamaterial design method based on deep learning for sound absorption. The design method is firstly set up with the array of Fabry-Perot resonators, then adapted for the array of Helmholtz resonators. The method uses a tandem inverse design model based on the convolution neural network(CNN), which is capable of on-demand design. It can generate acoustic metamaterial design of high absorption in targeted frequency range. Three designs of acoustic metamaterials for different purposes are presented. Firstly, sound absorption metamaterials with selective bandwidth absorption, are used to control tonal noise from electric transformers. Secondly, metamaterials with broadband absorption are used in vehicle cabin noise control. Lastly, full-band near-perfect absorption materials are created to construct acoustic anechoic chambers.

Nanoscale grating-based perovskite solar cell with improved efficiency

MAPbI3 perovskite-based solar cell (PSC) has attracted much attention due to its high absorption rate. The top flat electrode degrades the behavior of PSC due to limiting the light reached to the absorber layer, which reduces the efficiency. In this study, the influence of texturing the top FTO electrode surface with a triangular saw-tooth grating on both the optical and electrical performance is reported. The interference effects are also considered in this work by modeling the PSC structure as a Fabry–Perot resonator. In this regard, the finite difference time domain method is utilized to precisely simulate the optical characteristics of the nano-structural design. Also, the optical behavior of PSC is studied at different triangular grating (TG) structures and dimensions at which the light absorption is maximized. Furthermore, the effect of absorber thickness and defect density on the optoelectronic performance is investigated. We configured the conversion efficiency (η) of the proposed PSC structure by using the bulk and Langevin recombination mechanisms. The proposed grating structure enhances the light coupling, and hence the light absorption and the generated current density are increased. For absorber thickness of 350 nm, we reported a maximum conversion efficiency (η) of 19.5% for the proposed triangular grating (TG) structure with an enhancement of 19.6% compared to the structure with a flat FTO layer. As the defect density is increased from 1012 cm−3 to 1018 cm−3, the efficiency of the optimum TG PSC is reduced from 19.5% to 10.1%, respectively. The simulation results, therefore, contribute to the understanding of the PSC-based MAPbI3 design and can be used to improve its physical behavior.

Gain improvement of conformal circularly polarized Fabry-Perot resonator antenna based on metasurface

Conformal antenna can keep consistent with the shape of the carrier perfectly, which greatly saves the space of the carrier, so it is widely used in military, aerospace and other fields. In this paper, a cylindrical conformal circular polarization Fabry-Perot resonator antenna is designed, and the adverse effect of conformal on antenna gain is overcome by transmission phase compensation. Firstly, a linear to circular polarization conversion metasurface with adjustable transmission phase is designed. The main reason for choosing the metasurface here is to take advantage of its excellent electromagnetic control ability. The metal structures of the metasurface are printed on the ultra-thin dielectric plates, and then attached to the support structure machined by 3D printing, so as to achieve the conformal design of the metasurface. Secondly, the proposed metasurface is used as the superstructure and is combined with a conformal feed to form a cylindrical conformal circularly polarized Fabry Perot resonator antenna. The conformal feed is a patch antenna which is conformal designed in the same way as the metasurface. The conformal feeder is placed under the conformal metasurface to ensure that the electromagnetic wave radiated by the feeder can enter the resonant cavity composed of the feeder and the metasurface. The curvature of the cylindrical conformal of feed and metasurface is the same, which can ensure the high unity of the different positions in the resonator. Next, by adjusting the transmission phase of the unit on the metaurface, the phase compensation of the transmitted electromagnetic wave is realized, so that the electromagnetic wave radiated by the conformal antenna still presents the characteristic of plane wave. Finally, the conformal Fabry-Perot resonator antenna obtains the same high-gain radiation characteristics as the planar resonator antenna. The designed antenna achieves a maximum gain of 13.1dBic at 10 GHz. The size of the antenna is 2.9λ × 2.9λ, so the aperture efficiency is about 19.9 %. The antenna proposed in this paper overcomes the influence of conformal design on the gain of the antenna, so that it can be conformal on the surface of a cylindrical object and obtain better gain characteristics.

Maximizing light absorption and photocurrent in organic solar cells by aligning intrinsic absorption peaks with Fabry-Perot resonances

We provide a physical interpretation of the mechanism by which maximum light absorption is achieved in organic solar cells (OSCs) through the tailoring of Fabry-Perot (FP) resonances. Overlapping the intrinsic absorption peaks of the active layer with the FP resonances in a planar OSC structure maximizes light absorption, leading to the highest short-circuit current density (JSC). The OSC with a 119 nm-thick active layer of PTB7-Th:IEICO-4F, where intrinsic absorption peaks occur at wavelengths of 715 nm and 885 nm, exhibits fundamental FP resonant modes at wavelengths of 500, 715, 750, and 850 nm. The strong electric field intensity generated by the FP resonance coincides with the intrinsic absorption peaks of the active layer at 715 nm and 885 nm, leading to an experimentally observed JSC of 26.50 mA/cm2. Optical admittance analyses are conducted to investigate the reduced reflection associated with enhanced light absorption. These results provide a deeper understanding of the fundamental mechanism for designing multilayer photonic and optoelectronic devices. This design principle is general and can be applied to various optoelectronic devices, such as photovoltaics, sensors, and photodetectors across a wide range of wavelengths.

Enhanced Antireflection and Absorption in Thin Film GaAs Solar Cells Using Dielectric Composite Nanostructures

This study investigates the application of dielectric composite nanostructures (DCNs) to enhance both antireflection and absorption properties in thin film GaAs solar cells, which are crucial for reducing production costs and improving energy conversion efficiency in photovoltaic devices. Building upon previous experimental validations, this work systematically explores the underlying theoretical mechanisms using the finite difference time domain (FDTD) method to analyze the light interaction with the proposed DCNs. The results show that the combination of Mie resonance, Fabry–Perot resonance, and guided resonance, induced by the surface structuring of the DCNs, significantly enhances light absorption in the active layer, particularly at longer wavelengths. For solar cells featuring a 500-nm-thick absorber layer, SARL-decorated solar cells demonstrated an average reflectivity of 12.18%, whereas those incorporating DCNs exhibited a significantly reduced average reflectivity of 4.52%. These findings indicate that DCNs structures are highly effective in enhancing the performance of thin and ultra-thin GaAs solar cells by minimizing surface reflection and increasing photon utilization, offering a promising solution for high efficiency, cost effective photovoltaic devices.

Dual-dielectric Fabry-Perot film for visible-infrared compatible stealth and radiative heat dissipation

Multiband camouflage of space satellite to against advanced detection has attracted rising attention. However, the combination of compatible camouflage and radiative heat dissipation for space satellite still remains challenging, which requires low visibility and selective thermal emission in a dark and deep cold background. In this work, a dual dielectric Ge/SiO2 layer embedded Fabry-Perot multilayer film (W/Ge/SiO2/W/SiO2) is proposed for space stealth and heat dissipation. Ge and SiO2 films with appropriate thickness are designed to realize high visible absorption and spectra selective IR emission, simultaneously. The optimized multilayer film achieves a high absorbance (α = 0.983) in visible light (0.38–0.80 μm) for visible stealth, low emissivity (ε3–5 μm = 0.038; ε8–14 μm = 0.200) in atmospheric windows for infrared stealth, and relative high emissivity outside the atmospheric windows (ε5–8 μm = 0.487) for radiative heat dissipation. The simulation results indicate that the coupling of tunneling effect in ultrathin metallic W film and Fabry-Perot resonant is the main contribution to the excellent absorptivity and emissivity tunability. The proposed dual spacers embedded Fabry-Perot multilayer film paves a new way for multispectral camouflage of space satellite and other applications such as solar-thermal conversion, thermal management, energy saving, and detective technologies.

Ultra-wideband solar absorber via vertically structured GDPT metamaterials

We explore a new solar absorber via vertically structured metamaterials integrating 2D graphene, dielectric layers of silica (SiO2), aluminum oxide (Al2O3), and phase-transition vanadium dioxide (VO2) graphene, dielectric, phase transition (GDPT), achieving broadband absorption and polarization independence. Applying the finite-difference time-domain (FDTD) method, the optical performance of the absorber is analyzed under the normal incidence of a plane wave spanning wavelengths from 250 to 4000 nm. Particularly, our investigation reveals a broad bandwidth exceeding 90 % absorption, spanning 3559 nm from 250 to 3809 nm, with an impressive average absorption efficiency of over 95.9 %. Significantly, the absorber demonstrates polarization independence and insensitivity to large angles of incidence, enhancing its practical capability. We illuminate the important role of Fabry-Perot resonance in absorption by precisely tuning layer thicknesses to induce interference effects. The integration of graphene, dielectric layers, and VO2, augmented by Fabry-Perot resonance, provides a vital foundation for high-performance solar energy conversion technology. This technology has important applications in efficient and broadband solar absorbers, and these absorbers can maintain high performance under different conditions. Our goal is to solve current technological challenges and contribute to the development of next-generation solar energy conversion for various photon technologies, such as energy harvesting, electromagnetic wave capture, and photovoltaic devices.

The sensitivity of refractive index sensors based on defected 1D photonic crystals: an analytical approach

In this paper, an analytical formula for the sensitivity of optical sensors based on one-dimensional photonic crystals (PCs) with a defect was derived for the first time. Based on this formula, a comparative analysis of the sensitivity of defected PCs with and without mirror symmetry was carried out. In addition, the exact values of sensitivity in the limit of an infinite PC with a quarter-wave unit cell were obtained. It was shown that the sensitivity of a defective PC with an infinitely thick defect layer is equal to that of a perfectly reflecting Fabry–Perot resonator and does not depend on the specific structure of the PC. The results of this work provide a significant simplification of the analysis and optimization of optical sensors based on defective PCs, as well as a better understanding of the numerous numerical results obtained previously.

Ultra-low-thickness, highly sensitive, and perfect-absorption THz refractive index and temperature sensors based on Tamm plasmon polaritons and Fabry-Perot resonators

In this paper, an ultra-low thickness with high sensitivity and perfect absorption based on the excitation of Tamm plasmon polaritons and Fabry-Perot resonance for sensing applications is presented. The sensor comprises a graphene sheet, a spacer layer, an analyte region, and a one-dimensional periodic stack of the dielectric and metal layers. The sensor’s performance is evaluated using the transfer matrix method under different conditions, including the presence of the graphene sheet and metallic layers of the periodic stack, a change in the chemical potential of the graphene sheet, the thickness of the layers, as well as the incident polarization and angle. The simulation results show that the presence of the graphene sheet causes stimulation of Tamm plasmon polaritons, and the presence of metal layers simultaneously increases the absorption and decreases the thickness of the sensor. The sensitivity of the sensor is 0.9667 THz/RIU (equivalent to 305 μm/RIU) with an absorption peak of 99.99 %. The use of silicon as the analyte allows the proposed structure to perform as a temperature sensor in the range of 1 THz, which results in a temperature sensitivity of 0.055 THz/°C (equivalent to 16.45 nm/°C). The proposed sensor has the advantages of extremely thin thickness, perfect absorption, high sensitivity, tunability, and fabrication-friendly structure. The proposed sensor has high potential for use in various sensing applications.

Single-cell laser emitting cytometry for label-free nucleolus fingerprinting

The nucleolus, a recognized biomolecular condensate, serves as the hub for ribosome biogenesis within the cell nucleus. Its quantity and morphology are discernible indicators of cellular functional states. However, precise identification and quantification of nucleoli remain challenging without specific labeling, particularly for suspended cells, tissue-level analysis and high-throughput applications. Here we introduce a single-cell laser emitting cytometry (SLEC) for label-free nucleolus differentiation through light-matter interactions within a Fabry–Perot resonator. The separated gain medium enhances the threshold difference by 36-fold between nucleolus and its surroundings, enabling selective laser emissions at nucleolar area while maintaining lower-order mode. The laser emission image provides insights into structural inhomogeneity, temporal fluid-like dynamics, and pathological application. Lasing spectral fingerprint depicts the quantity and size of nucleoli within a single cell, showcasing the label-free flow cytometry for nucleolus. This approach holds promise for nucleolus-guided cell screening and drug evaluation, advancing the study of diseases such as cancer and neurodegenerative disorders.

Perovskite manganese oxide-based superposed multilayer film with high emittance tunability for smart radiation devices

Smart radiation devices (SRDs) with the ability to switch emittance according to the radiator surface’s temperature are significant for spacecraft thermal control on exploration missions with drastic changes in thermal environments. However, it is quite urgent to improve the performance of the intelligent thermal control films in SRDs due to the limitations such as low emittance tunability and inappropriate phase transition temperature. Consequently, a film with self-adaptive infrared emittance based on anti-reflective design is proposed in this paper. The main structure is a superposed multilayer film based on a doped perovskite manganese oxide La0.825Sr0.175MnO3 (LSMO) and BaF2 stacks. The emittances of the designed multilayer film are 0.18 and 0.83 at the temperatures of 100 K and 295 K, and therefore the emittance tunability achieves 0.65. Compared with single-layer LSMO, the emittance tunability has increased 25 % approximately. The enhancement in emittance tunability can be explained by the fact that multilayer films with staggered low and high refractive index dielectric layers may cause destructive interference and suppress the Fresnel reflections at high temperatures. In addition, the thickness of dielectric part is carefully designed to avoid the formation of high emissivity Fabry-Perot (FP) resonance when LSMO switches to metallic state at low temperatures. This perovskite manganese oxide-based multilayer film exhibits remarkable intelligent thermal control properties. It provides a significant opportunity to improve the performance of SRDs and a promising potential for maintaining the optimal operating temperature of the spacecraft.

VO2-Based Spacecraft Smart Radiator with High Emissivity Tunability and Protective Layer.

In the extreme space environment, spacecraft endure dramatic temperature variations that can impair their functionality. A VO2-based smart radiator device (SRD) offers an effective solution by adaptively adjusting its radiative properties. However, current research on VO2-based thermochromic films mainly focuses on optimizing the emissivity tunability (Δε) of single-cycle sandwich structures. Although multi-cycle structures have shown increased Δε compared to single-cycle sandwich structures, there have been few systematic studies to find the optimal cycle structure. This paper theoretically discusses the influence of material properties and cyclic structure on SRD performance using Finite-Difference Time-Domain (FDTD) software, which is a rigorous and powerful tool for modeling nano-scale optical devices. An optimal structural model with maximum emissivity tunability is proposed. The BaF2 obtained through optimization is used as the dielectric material to further optimize the cyclic resonator. The results indicate that the tunability of emissivity can reach as high as 0.7917 when the BaF2/VO2 structure is arranged in three periods. Furthermore, to ensure a longer lifespan for SRD under harsh space conditions, the effects of HfO2 and TiO2 protective layers on the optical performance of composite films are investigated. The results show that when TiO2 is used as the protective layer with a thickness of 0.1 µm, the maximum emissivity tunability reaches 0.7932. Finally, electric field analysis is conducted to prove that the physical mechanism of the smart radiator device is the combination of stacked Fabry-Perot resonance and multiple solar reflections. This work not only validates the effectiveness of the proposed structure in enhancing spacecraft thermal control performance but also provides theoretical guidance for the design and optimization of SRDs for space applications.