Hyperbolic metamaterials (HMMs) are artificial extreme anisotropic media, which are characterized by indefinite or hyperbolic dispersion relation where the out-ofplane dielectric constant has an opposite sign to the in-plane dielectric constants. [1] These effective bulk metastructures are usually composed of metallic and dielectric elements, and display extraordinary optical properties over a wide frequency band from visible to terahertz. The HMMs showing hyperbolic dispersion can be classified based on the sign of their dielectric components, such as type I (−ε ⊥ and ε ll ) and type II (ε ⊥ and − ε ll ). The type I HMM is usually realized using metallic nanowires immersed in a dielectric matrix, [2] while the type II HMM assumes stacked metal/dielectric multilayers. [3] In particular, the type II is the most studied HMM because of its straightforward fabrication using conventional thin film physical vapor deposition (PVD) techniques. Various metal-dielectric multilayer stacks have been proposed to realize hyperbolic dispersion over the frequency band from visible to terahertz. [1][2][3][4][5][6][7] In recent years, the type II multilayered HMMs have received much attention and used as the technological core in many potential applications including ultrasensitive biosensors, [8][9][10] absorbers, [11,12] single photon sources, [13] super-resolution imaging, [14] and Cherenkov radiation. [15] In addition, thermal flux engineering has been achieved using HMMs, [16] which is considered to be the near-field analog of a blackbody. Also, the occurrence of super-Planckian thermal energy transfer has been predicted in HMMs. [17] The overall optical response of HMM can be qualitatively predicted in the framework of the so-called effective medium theory (EMT) since both the layers of HMMs are deeply subwavelength. [18] In particular, HMM is a 1D subwavelength photonic crystal when stacking multiple periodic bilayers of metal/dielectric is formed. The optical response of HMM can be homogenized if the number of bilayers in the stack is large enough and their thickness is deeply subwavelength. Therefore, the overall uniaxial optical response can be described using an effective dielectric permittivity, whose components (parallel and perpendicular to the surface of HMM) can be calculated by applying boundary conditions. [19] HMM supports both radiative and nonradiative guided modes. Bulk plasmon polariton (BPP) [20] or high-k optical Hyperbolic metamaterials (HMMs) are used to demonstrate extreme sensitivity biosensing by exciting their high-k modes. However, momentum couplers, such as subwavelength diffraction grating or bulky high-index prism, are required to excite these nonradiative modes, which is not cost-effective and thus not suitable for point-of-care applications. Here, a cost-effective and scalable HMM-based sensor platform is proposed and experimentally demonstrated, by exciting the Brewster mode of HMM from free-space. The excitation of Brewster modes is shown in a multilayered HMM comprising of alternating thin l...
Achieving the broadband response of metamaterial absorbers has been quite challenging due to the inherent bandwidth limitations. Herein, the investigation was made of a unique kind of visible light metamaterial absorber comprising elliptical rings-shaped fractal metasurface using tungsten metal. It was found that the proposed absorber exhibits average absorption of over 90% in the visible wavelength span of 400-750 nm. The features of perfect absorption could be observed because of the localized surface plasmon resonance that causes impedance matching. Moreover, in the context of optoelectronic applications, the absorber yields absorbance up to ~ 70% even with the incidence obliquity in the range of 0°-60° for transverse electric polarization. The theory of multiple reflections was employed to further verify the performance of the absorber. the obtained theoretical results were found to be in close agreement with the simulation results. in order to optimize the results, the performance was analyzed in terms of the figure of merit and operating bandwidth. Significant amount of absorption in the entire visible span, wide-angle stability, and utilization of low-cost metal make the proposed absorber suitable in varieties of photonics applications, in particular photovoltaics, thermal emitters and sensors. In recent years, optical metamaterials have gained considerable attention in both the engineering and scientific lexicons owing to the exotic electromagnetic (EM) response, that led to varieties of technological applications 1-6. As has been in reports, these artificially engineered materials allow the versatile utility to manipulate the amplitude, phase, and polarization of the incidence radiation at a deep subwavelength scale 7. Metamaterials are generally comprised of nano-resonators, scatterers and meta-molecules of different size, shape, geometry, orientation, and arrangement. Within the context, the negative refractive index (RI)-based metasurfaces enable intriguing applications in super lensing 8 , planar filters 3 , optical cloaking 9,10 , wavefront manipulation 11,12 , optical chirality 13 , medical imaging 14 , and perfect absorption 15-17. These are also tremendously exploited in various other EM applications, namely asymmetric transmission, plasmon-induced transparency, holography, and bio-sensing 6,17-19. Extensive studies have been reported on metamaterial absorbers operating in different frequency regimes 20-22 owing to the prevalent applications in bolometer, holograms, stealth technology, solar energy harvesting, wireless communications, and sensors 15-17,23-27. From the perspective of absorption bandwidth, the narrowband metamaterial absorbers covering the visible and infrared (IR) regimes find applications, such as thermal emission manipulation, nano-antennas, sensors, and resonators 28,29. On the other hand, wideband absorbers have potentials in solar energy converters, artificial colors, thermal emitters, and many other optoelectronic applications 30,31. Within the context, photovoltaics have im...
Abstract:The paper demonstrates the utilization of a tunable band-pass filter in producing tunable multi-wavelength Brillouinerbium fiber lasers within a Fabry-Perot cavity. The optimization of the Brillouin pump wavelength position within the bandwidth of the self-lasing cavity modes is important to achieve the maximum stable output channels. The same number of 14 output channels with constant channel spacing of 10.5 GHz were able to be generated within 32 nm range. Besides the tunability, this design also has the advantage of consistent power requirement of both the 980 nm laser diode and the Brillouin pump in generating the 14 channels through the broad tuning range.Amplitude, dBm
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