Resonant absorption in semiconductor nanowires and nanowire arrays: Relating leaky waveguide modes to Bloch photonic crystal modes

Abstract

We present a unified framework for resonant absorption in periodic arrays of high index semiconductor nanowires that combines a leaky waveguide theory perspective and that of photonic crystals supporting Bloch modes, as array density transitions from sparse to dense. Full dispersion relations are calculated for each mode at varying illumination angles using the eigenvalue equation for leaky waveguide modes of an infinite dielectric cylinder. The dispersion relations along with symmetry arguments explain the selectivity of mode excitation and spectral red-shifting of absorption for illumination parallel to the nanowire axis in comparison to perpendicular illumination. Analysis of photonic crystal band dispersion for varying array density illustrates that the modes responsible for resonant nanowire absorption emerge from the leaky waveguide modes.

Unraveling the Janus Role of Mie Resonances and Leaky/Guided Modes in Semiconductor Nanowire Absorption for Enhanced Light Harvesting

“…In fact, broad band and broad angle absorption is expected for the lowest m = 1 Mie resonances (HE 11 mode) shown therein, indeed occurring for both TM-and TE-polarized light (see Figure 6c,d), being stronger at normal incidence for TM polarization. 28 In addition, Figure 6d reveals that the TM 01 leaky mode band lies, as mentioned in the preceding section, close to the m = 0 TM Mie resonance at large oblique angles, which yields a large absorption area at ∼2.5 eV (500 nm) near θ ≃ 70°, as a result in turn of the overlap with the m = 1 Mie band. In the low energy region below 2.5 eV, this m = 0 TM Mie resonance continues, as mentioned above, as a weak absorption band for smaller angles of incidence.…”

Profiling Photoinduced Carrier Generation in Semiconductor Microwire Arrays via Photoelectrochemical Metal Deposition

“…4,[19][20][21][22][23][24][25][26] The macroscopic optoelectronic and electrochemical properties of such wire arrays have been experimentally characterized [27][28][29][30][31] , but nanoscale analyses that aim to provide a microscopic understanding of these properties have been mostly limited to theoretical and computational methodologies. [32][33][34][35] The optical excitation of photoactive semiconductor substrates immersed in a metal-ion solution can provide the driving force for deposition of a metal. 36 Photoelectrochemical metal deposition has been used to generate arbitrarily patterned metallic deposits on a semiconductor surface by use of a photomask or by use of scanning laser illumination.…”

Broadband light absorption of silicon nanowires embedded in Ag nano-hole arrays

“…For consistency, these material setup was also used for the electric field distribution calculations. 19 The band diagram of TE-polarized eigen-modes for SiNWs along Z direction is shown in Fig. 2(b).…”

“…Under band calculation, Bloch boundary conditions are applied to SiNWs along X, Y and Z direction. 19 Although the length of SiNWs along Z direction should be regarded as infinite, it is deliberately given a period of 1a to obtain the Bloch wave vector k z within the reduced Brilloiin zone, from 0 to 0.5 (2π/a). A wide band Gaussian wave with E x polarization was randomly positioned in the SiNWs to excite arbitrary eigen-modes.…”