Photonic crystal band structure in luminescence response of samples with Ge/Si quantum dots grown on pit-patterned SOI substrates

In this paper, we study the emission spectrum of the photonic crystal slab (PCS) with embedded Ge/Si quantum dots using the original technique of a directional micro-photoluminescence (DPL). This technique is a powerful combination of two approaches to the experimental study of PCS. First, it allows to collect photoluminescence (PL) signal within small solid angles in the selected directions and thereby to study the dispersion dependence of PCS modes. Second, it gives the experimental opportunity to analyze the quality-factor change of observed PL peaks with an increase in the collection angle and allows us to find in the PL spectrum the high-quality modes, namely the bound states in the continuum. A comparison with theoretical dispersion dependencies of PCS modes calculated by the Fourier-modal method in the scattering matrix form demonstrates a clear correspondence between PCS dispersion curves and angular dependencies of observed PL peak positions. The obtained results indicate that the DPL technique can be successfully used both to visualize the photonic band structure and to determine the nature of the PCS modes.