Pillar-based photonic crystals for light extraction from 2D materials

We present results from pillar-based photonic crystal cavities that have been designed to enhance quantum light extraction from 2D materials. In this work, we calculate the confined field distribution within the cavity and propose exploiting the sagging of 2D materials within the cavity. This has the potential to efficiently couple quantum dots in 2D materials to the maximum intensity of the cavity’s mode. In addition, we propose the use of solid immersion lenses to enhance the vertical confinement of the cavity mode, therefore achieving higher Q-factor whilst remaining in the weak coupling regime. In recent years, 2D materials have created a plethora of new scientific and technological breakthroughs across many disciplines, one being their use in quantum information. Naturally occurring or artificially created defects in 2D materials, such as hexagonal Boron Nitride monolayers, have shown room temperature quantum light emission due to zero-dimensional exciton confinement [1]. This opens the door to a wide range of applications relating to quantum communication [2] and photonic quantum computing [3]. However, it remains difficult to efficiently couple light emitted from 2D materials into optoelectronic systems. In this work, we propose a novel design of a pillar-based photonic crystal cavity for this purpose, as illustrated in the figure 1 (left). 3D finite difference time domain simulations of the structure show that the cavity exhibits an air photonic mode, with an Ex and Ey (figure 1, middle and right¬¬¬ respectively)field confinement with Q-factors exceeding 6000. The 2D supercell contains dielectric pillars in a triangular lattice with a cross-sectional radius 0.185a, where a is the lattice constant. The pillars are surrounded by air in the x-y direction and a silicon wafer surface at the bottom. Above the cavity, we are also proposing the use of a solid immersion lens, to help increasing vertical confinement whilst enhancing light extraction in the vertical direction. The frequency of the confined mode was found to be approximately 0.877a. This method of efficiently coupling of quantum light from 2D materials represents the first step in the design of robust quantum optoelectronic components based on artificial defects in the emerging 2D material system [1] T. Tran et al., Nature Nanotechnology, 242, 37-41 (2015) [2] N Gisin et al., Reviews of Modern Physics, 74, 145 (2002) [3] E Knill et al., Nature, 409, 46-52 (2001)