Tuning and imaging random photonic modes

We demonstrate experimentally the ability to control the properties of an individual photonic mode in a two-dimensional disordered photonic GaAs slab. The random modes can be fine-tuned by local sub-micrometer-scale oxidation of the semiconductor slab and their frequency can be gradually shifted. In particular we demonstrate the tuning of a selected mode to spectral superposition with the frequency of other two modes, located a few micrometers apart and spatially overlapping with the tuned mode. For different pairs of modes we observe either frequency crossing or anti-crossing behaviours. This provides the experimental proof-of-principle that optically isolated regions can be connected, offering new possibilities in the control of light propagation in disordered media.