Engineering Short-range Correlation in Bi-disperse Self-Assembled Photonic Structures

Short-range correlations in disordered photonic structures composed of sub-micron scatterers can give rise to correlation-driven photonic gaps. However, methods to systematically tune such structural correlations remain limited. Here, we investigate that the scatterer size ratio (β) in self-assembled bi-disperse photonic structures provide a pathway to engineer short-range correlations and hence the photonic gaps. We identify a transition around β ≈ 0.83, which governs the correlation-induced reflectivity peaks with a simultaneous dip in both transport (lt) and scattering (ls) mean free paths. While further reduction in β value suppress short-range correlations and eliminates the photonic gaps. Pair correlation and structure factor analysis reveals that the observed transition from well resolved gaps to vanishing gaps is governed by the breakdown of short-range correlations. Experimentally extracted lt and ls further show that enhanced backscattering is associated with short-range correlations. Moreover, tuning β value not only shifts gap energy but also modulates its strength, which is supported by finite difference time domain simulations. Together, these results advance disorder-enabled design strategies for photonic materials, enabling precise control of scattering and bandgap characteristics.