Subwavelength focusing of terahertz waves in silicon hyperbolic metamaterials

Kannegulla, Akash; Cheng, Li-Jing

doi:10.1364/ol.41.003539

Cited by 35 publications

(17 citation statements)

References 19 publications

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“…To illustrate this, each metal slit generate high K modes due to the effect of diffraction generated at the two slit edges. At certain angle, these high k modes could interfere perfectly at an angle with respect to the normal (perpendicular to HMM surface) 7 , 32 . The direction of propagation is dependent on the choice of the permittivity tensor components at specific wave length that causes the focusing effect.…”

Section: Numerical Simulation and Discussionmentioning

confidence: 99%

Tunable Mid IR focusing in InAs based semiconductor Hyperbolic Metamaterial

Desouky

Mahmoud

Swillam

2017

Sci Rep

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Noble Metals such as Gold and Silver demonstrated for mid IR metamaterials have suffered many obstacles such as: high losses and lack of tunability. The application of doped semiconductors has allowed overcoming the tunability restriction, besides, possessing lower losses as compared to metals. In addition, doped semiconductors have small magnitude of negative real permittivity which is required to realize mid IR Hyperbolic Metamaterials (HMMs). We theoretically demonstrate super focusing based on an all Semiconductor planar HMM using InAs heterostructure. By applying a single slit integrated with doped InAs/InAs HMM, incident light can be coupled to high propagation wave vectors of the HMM modes leading to sub diffraction focusing within the mid IR wave length range. Our proposed structure shows a wide controllable/ tunable operation by changing the doping concentration of InAs. As a consequence, focusing resolution can be tuned over the mid IR ranging from 4.64 μm to 19.57 μm with the maximum achieved resolution is up to 0.045λ at an operating wavelength of 19.57 μm. In addition, we show the effect of substrate refractive index on tuning and enhancing the focusing resolution. Our proposed HMM is an all single based material in which it will not suffer lattice mismatch restrictions during fabrication.

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Section: Numerical Simulation and Discussionmentioning

confidence: 99%

Tunable Mid IR focusing in InAs based semiconductor Hyperbolic Metamaterial

Desouky

Mahmoud

Swillam

2017

Sci Rep

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“… where ɛ ∞ = 15.5, ω p is the plasma frequency and Γ is the scattering rate. The values of ω p and Γ are extracted from previous literatures 27 , 35 . The dispersion relation of the structure comprising InAs of doping concentration N d 7.5 × 10 19 cm −3 is presented in Fig.…”

Section: Theoretical Designmentioning

confidence: 99%

“…However, the difficulty of fabricating the curved hyperlens restricts its practical application. Despite of the demonstration of numerous studies concerning sub-diffraction focusing inside the HMM medium [22][23][24][25][26] , lensing in the near field www.nature.com/scientificreports www.nature.com/scientificreports/ of HMMs is rarely introduced in real structures except for few attempts -such as Si pillars arrays in the THz range 27 -providing minor focusing resolution. The challenge of near field focusing outside the HMM is imposed by the rapid decay of the evanescent waves in free space.…”

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confidence: 99%

Free space super focusing using all dielectric hyperbolic metamaterial

Salama¹,

Desouky²,

Obayya³

et al. 2020

Sci Rep

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Despite that Hyperbolic Metamaterial (HMM) has demonstrated sub-wavelength focusing inside of it, sub-wavelength imaging in free space of HMM is rarely introduced. The decay of hyperbolic momentum space outside the hyperbolic medium has hindered the realization of sub-wavelengh focusing in the near field of HMM. Furthermore, manipulating the negatively refracted waves exiting the HMM have addressed another major obstacle to realize free space sub-wavelength focusing. In this work, we report extended sub-wavelength focusing in free space based on negative refraction of light exiting the HMM. The proposed structure is composed of multilayers of doped InAs/intrinsic InAs integrated with metallic slit. We theoretically simulate the doped InAs/intrinsic InAs HMM and investigate the negative refraction behavior outside the HMM. We optimized the structure for achieving high resolution down to 0.2λ, extended to a distance of 3.2 µm in free space. Also, sub-wavelength focusing in free space has been studied at different doping concentrations showing that the small doping concentrations exhibit enhancement in resolution at short distances up to 600 nm away from the HMM. Extending the focusing distance is achieved up to distance 3.5 µm from the hyperbolic structure by manipulating the doping concentration. This proposed lens configuration is expected to find potential usage in mid IR thermal imaging and photolithography application.

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“…Chernomyrdin et al 81 have achieved promising resolution enhancement by utilizing solid immersion imaging and wide-aperture spherical lens. 82 In another trend, for the enhancement of the imaging systems, subwavelength focusing using hyperbolic meta materials is proposed by Kannegulla et al [83][84][85] However, as it will be discussed in this paper, GaN-based devices can fundamentally address the resolution by enabling THz imaging systems with frequencies higher than 5 THz and enhancing the photon intensity. For instance, GaN-based quantum-cascade lasers (QCL) can operate in 5 to 12 THz, 86 whereas the operation of conventional naturally cooled GaAs-based QCLs in the upper THz frequency band is limited by longitudinal-optical (LO) phonon of 36 meV.…”

Section: Introductionmentioning

confidence: 98%

Review of GaN-based devices for terahertz operation

Ahi

2017

Opt. Eng

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Abstract. GaN provides the highest electron saturation velocity, breakdown voltage, operation temperature, and thus the highest combined frequency-power performance among commonly used semiconductors. The industrial need for compact, economical, high-resolution, and high-power terahertz (THz) imaging and spectroscopy systems are promoting the utilization of GaN for implementing the next generation of THz systems. As it is reviewed, the mentioned characteristics of GaN together with its capabilities of providing high two-dimensional election densities and large longitudinal optical phonon of ∼90 meV make it one of the most promising semiconductor materials for the future of the THz emitters, detectors, mixers, and frequency multiplicators. GaNbased devices have shown capabilities of operation in the upper THz frequency band of 5 to 12 THz with relatively high photon densities in room temperature. As a result, THz imaging and spectroscopy systems with high resolution and deep depth of penetration can be realized through utilizing GaN-based devices. A comprehensive review of the history and the state of the art of GaN-based electronic devices, including plasma heterostructure field-effect transistors, negative differential resistances, hetero-dimensional Schottky diodes, impact avalanche transit times, quantum-cascade lasers, high electron mobility transistors, Gunn diodes, and tera field-effect transistors together with their impact on the future of THz imaging and spectroscopy systems is provided.

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Subwavelength focusing of terahertz waves in silicon hyperbolic metamaterials

Cited by 35 publications

References 19 publications

Tunable Mid IR focusing in InAs based semiconductor Hyperbolic Metamaterial

Tunable Mid IR focusing in InAs based semiconductor Hyperbolic Metamaterial

Free space super focusing using all dielectric hyperbolic metamaterial

Review of GaN-based devices for terahertz operation

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