Reflectivity of three-dimensional GaAs photonic band-gap crystals of finite thickness

Abstract

We study the optical reflectivity of real three-dimensional (3D) photonic band-gap crystals with increasing thickness. The crystals consist of GaAs plates with nanorod arrays that are assembled by an advanced stacking method into high-quality 3D woodpile structures. We observe intense and broad reflectivity peaks with stop bands that correspond to a broad gap in the photonic band structures. The maximum reflectivity quickly reaches high values, even for a few crystal layers. Remarkably, the bandwidth of the stop bands hardly decreases with increasing crystal thickness, in good agreement with finite-difference time domain (FDTD) simulations. This behavior differs remarkably from the large changes observed earlier in weakly interacting 3D photonic crystals. The nearly constant bandwidth and high reflectivity are rationalized by multiple Bragg interference that occurs in strongly interacting photonic band-gap crystals, whereby the incident light scatters from multiple reciprocal lattice vectors simultaneously, in particular, from oblique ones that are parallel to a longer crystal dimension and thus experience hardly any finite-size effects. Our insights have favorable consequences for the application of 3D photonic band-gap crystals, notably since even thin structures reveal the full band-gap functionality, including devices that shield quantum bits from vacuum fluctuations.

Enhanced Absorption in thin and ultrathin silicon films by 3D photonic band gap back reflectors

“…Cubic inverse woodpile photonic crystals have a broad maximum band gap width ∆ω/ω c = 25.3% relative to the central band gap frequency ω c for pores with a relative radius r a = 0.245 [50,51]. Our prior results reveal that a reflectivity in excess of R > 99% -hence transmission T < 1% -occurs even for a thin inverse woodpile photonic crystal with a thickness of a few unit cells (L 3DP C ≥ 3c) [39,43]. Therefore, we choose here a cubic inverse-woodpile crystal with an optimal pore radius r a = 0.245 and with a thickness L 3DP C = 4c = 1200 nm as a back reflector for the calculation of the absorption of light by the solar cell.…”

“…To enhance the weak absorption of silicon above the electronic band gap at wavelengths in the range 600 nm < λ < 1100 nm, we tailor the lattice parameters of the inverse woodpile photonic crystal to a = 425 nm and c = 300 nm such that the band gap is in the visible range. The chosen lattice parameters are 37% smaller than the ones usually taken for photonic band gap physics in the telecom range [39][40][41][42][43][44][57][58][59]. The required dimensions are well within the feasible range of nanofabrication parameters [60][61][62].…”

“…In this paper, we explicitly focus on photonic crystal back reflectors with a complete 3D photonic band gap [38,39], a frequency range for which the propagation of light is rigorously forbidden for all incident angles and all polarizations simultaneously, as recently demonstrated in experiments and calculations [40][41][42][43][44]. To illustrate the concept, Fig.…”

Surface States on Photonic Crystals As Hybrid Dielectric Metasurface Bound States of the Termination Layer

“…Photonic crystals are periodic media that affect the electromagnetic wave propagation by defining allowed and forbidden frequency bands . Light localization in dielectric photonic crystals is extensively investigated, and their landscape has been exploited in numerous ways for trapping and manipulating dark states, from truncated volumes, − defect cavities with high quality factors, − and photonic crystal waveguides, − to lattice deformations. , At the same time, due to their controllable properties, photonic crystals have been used in a plethora of applications such as switches, lasers, optical fibers, solar cells, and many more. − …”

Controlled light propagation in random, periodic, and superperiodic silicon nanophotonic materials

“…The modes are called evanescent modes, and the wave amplitudes decay exponentially as Introduction with a complex wave vector k+iκ. Within the gap, no light modes are allowed in the crystal due to multiple Bragg interference [58][59][60][61], hence the density of states (DOS) strictly vanishes. Within the band gap, light only enters to a limited depth called the Bragg length L B , given by the length scale (L B = 1/κ) of the exponent in equation (1.8).…”