Spatially localized wavelength-selective absorption in morphology-modulated semiconductor nanowires

Abstract

In this study, we proposed morphology-modulated Si nanowires (NWs) with a hexagonal cross-section and numerically investigated their resonant optical absorption and scattering properties. The calculated absorption and scattering efficiency spectra of the NWs exhibited optical resonances that could be controlled by tuning the aspect ratio (AR) of the NW cross-sectional shapes. The spectra also revealed interesting spectral behaviors including resonant peak shifts in the absorption spectrum and asymmetric line shapes in the scattering spectrum. To achieve spatially confined and wavelength-selective light absorption, we periodically modulated the geometry of the diameter in a single NW by combining two different ARs; we call these "diameter-modulated NWs." We designed various diameter-modulated NWs with short and long pitch sizes, and we observed unique and interesting features in the optical resonance and corresponding light absorption spectra such as grating modes and three-dimensional cavity modes. The proposed diameter-modulated NWs can be promising building blocks for the nanoscale localized light absorption and detection in compact nanophotonic integrated circuits.

Improving Absorption in Single Silicon Nanowires by Symmetry-breaking Design from Square to Rectangular Cross-section

“…It has been shown that the light absorption could be increased by engineering the size, geometry, and orientation of the NWs [12][13][14][15][16][17][18]. We have also shown that the light absorption could be further enhanced by introducing a single shell [19,20] or graded dual shells [21].…”

Off-Resonant Absorption Enhancement in Single Nanowires via Graded Dual-Shell Design

“…Therefore, various strategies have been implemented to improve the light absorption in the whole solar spectrum range. It was shown that the light absorption could be readily tuned by controlling the size, geometry, and orientation of the NWs [18][19][20][21][22][23][24][25][26]. Moreover, our previous studies [27,28] showed that the light absorption could be further improved by introducing a non-absorbing dielectric shell as the antireflection coating, which was experimentally and numerically demonstrated in the recent studies [29][30][31][32][33].…”

Enhanced Light-Harvesting in Single Rectangular Silicon Nanowires

“…Therefore, a great variety of strategies have been employed to improve light-harvesting ability. It has been shown that the light absorption could be readily engineered by controlling the size, geometry and orientation of the NWs [18][19][20][21][22][23][24]. Our previous studies [25][26][27] showed that the light absorption could be further improved by introducing a non-absorbing dielectric shell (or graded dual shells) as the antireflection coating, which was experimentally and numerically demonstrated in the recent studies [28][29][30][31][32].…”