Tailoring the Local Density of Optical States and Directionality of Light Emission by Symmetry Breaking

We present a method to simultaneously engineer the energy-momentum dispersion and the local density of optical states (LDOS). Using vertical symmetry breaking in high-contrast gratings, we enable the mixing of modes with different parities, thus producing hybridized modes with controlled dispersion. By tuning geometric parameters, we control the coupling between Bloch modes, leading to flatband, M- and W-shaped dispersion as well as Dirac dispersion. This dispersion-engineering leads to tailored LDOS and we experimentally demonstrate a two order of magnitude enhancement of photoluminescence from weak emitters—defects in silicon—via optical modes with adjustable angle of emission. This vertical symmetry-breaking method could readily be used in various photonic crystals and metasurfaces devices and opens up a new way to strongly boost light emission on-chip and to steer it to arbitrary directions.