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Epsilon-near-zero phase-matching for second-harmonic generation in semiconductor-based nanowire hyperbolic metamaterial
(2023-01-01)
Wicharn, Surawut
;
Buranasiri, Prathan
Hyperbolic metamaterials have been widely used for nonlinear optical applications. Their unique functionality for nonlinear optics enhancement due to the hyperbolic dispersion is induced by a strong shape anisotropy. In this work, we numerically investigated the second-harmonic generation (SHG) in two-dimensional periodic arrays of aluminium gallium arsenide (AlGaAs) nanowires embedded in ordered porous aluminum oxide (Al2O3) or the nanowire hyperbolic metamaterial (NHMM). Under local effective medium approximation, the homogenization of the NHMM was achieved due to deep sub-wavelength size of each nanowire radius. Then this medium was classified as an effective uniaxial medium with anisotropic electric permittivity. The NHMM provided the spectral position of second-harmonic (SH) wavelength, which is determined at the epsilon-near-zero (ENZ) by the optimal design of NHMM structural parameters such as AlGaAs radius or fill fraction. Consequently, a gigantic increment of SHG conversion efficiency was achieved because of dramatic phase-matching at ENZ point. This mechanism is attributed to electric field enhancement of SHG inside the metamaterial. According to numerical results, the NHMM can be applied as nonlinear frequency converters in integrated nanophotonic systems.
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Phase-matched second-harmonic generation in core-shell nanowire hyperbolic metamaterial
(2022-09-01)
Wicharn, Surawut
;
Banerjee, Partha P.
;
Buranasiri, Prathan
Second-harmonic generation is well-known nonlinear frequency conversion technique, which can be applied in nonlinear optical characterization of materials and all-optical signal processing. This phenomenon requires phase-matching to maximize the conversion efficiency of generated second-harmonic field. But the phase-matching condition is difficult to achieve because of dispersion of naturally existing materials. To overcome this limitation, we propose an innovative phase-matching technique, which is called hyperbolic phase-matching, that can be possibly achieved by managing dispersion of a hyperbolic metamaterial. Here, the hyperbolic metamaterial is made of two-dimensional periodic arrays of core-shell nanowires, which have aluminium gallium arsenide as a core and gold as a shell, immersed in anodic aluminium oxide matrix. We have demonstrated phase-matched conditions for two different non-collinear second-harmonic interacting configurations in the metamaterial, which can be created by tuning incident angle of pump field to optimal values. Finally, conversion efficiencies of transmitted and reflected second-harmonic pulses as a function of incident angle and input pulse intensity were examined. The maximum conversion efficiencies are obtained at optimal incident angle and largest pumping intensity.
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Recursive-formula for second-harmonic generation problem in photonic hypercrystal
(2022-09-01)
Buranasiri, Prathan
;
Plaipichit, Suwan
;
Puttharugsa, Chokchai
;
Wicharn, Surawut
In this work, we proposed a recursive-formula based on transfer-matrix method to solve problem of second-harmonic generation by obliquely incident fundamental-harmonic wave in a photonic hypercrystal, which is composed of one-dimensional periodically alternating arrangement of nonlinear hyperbolic metamaterial layer with anisotropic permittivities: ε<inf>axx</inf>, ε<inf>azz</inf> and layer thickness: a and linear dielectric layer with isotropic permittivity: ε<inf>a</inf> and layer thickness: b. This proposed formula was very simple and accurate for calculating conversion efficiency of second-harmonic generation at various incident angles of fundamental-harmonic wave and thicknesses of nonlinear hyperbolic metamaterial layer. The numerical results showed that the maximum conversion efficiency can be achieved by the strong local field confinement of fundamental-harmonic wave in the photonic hypercrystal and phase-matching due to optimal values of hypercrystal layer thickness and incident angle of fundamental-harmonic wave.
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A numerical investigation of enhanced backward second-harmonic generation in one-dimensional PIM/NIM structure
(2018-01-01)
Wicharn, Surawut
;
Buranasiri, Prathan
In this paper, we have demonstrated a numerical investigation of an enhanced backward second-harmonic generation (BSHG) effect in a one-dimensional positive-index material/negative-index material (1D-PIM/NIM) structure with nonlinear deep grating. The 1D-PIM/NIM structure composed of common linear PIM layers and NIM layers, whose electric permittivity and magnetic permeability are described by Drude model for allowing negative refractive index behavior, embedded in nonlinear χ<sup>(2)</sup> material in periodically arrangement. To model BSHG phenomenon, we have developed a completed set of nonlinear coupled-mode equations (NCMEs) by perturbing nonlinear wave equation by a small factor with appropriate scale following a way of multiple-scale approach (MSA). Then, we have numerically solved the NCMEs to achieve the second-harmonic frequency output and conversion efficiency of backward field. We have also discussed a backward phase-matching (BWPM) condition, which has been satisfied by tuning a fundamental frequency (FF) at ω in a negative refractive index region and second-harmonic (SH) frequency at 2ω in a positive refractive index region, and band-edge local field enhancement condition, which has been created by rearranging PIM and NIM layers in optimal periodic fashion. By using both conditions, a conversion efficiency of BSHG can be dramatically enhanced.

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