Abstract
Efficient and high-speed photodetection in the NIR is essential in several applications such as LiDAR and imaging. Silicon is an established choice as the base material for absorbing and converting photons to charge carriers. However, its high absorption length in the NIR imposes a trade-off between the absorption efficiency and detection bandwidth. Here, the rigorous coupled-wave analysis method together with the particle swarm optimization algorithm has been employed to optimize photonic crystal slab architectures with hexagonal symmetry to achieve efficient coupling of incoming pulses of light to the guided modes of the silicon photodetector. Our optimal design yields an ultra-efficient compact photodetector with more than 80% average absorption in the wavelength range 700 – 900 nm. Furthermore, considering scatterers of arbitrarily shaped polygonal cross-section, augments significantly the landscape in the optimization parameter space and results in further enhancement of the absorption efficiency. Our results show that introducing different length scales in the texturing leads to efficient broadband absorption in the compact device.