Tunable soft-matter optofluidic waveguides assembled by light

Abstract: Development of artificial materials exhibiting unusual optical properties is one of the major strands of current photonics research. Of particular interest are soft-matter systems reconfigurable by external stimuli that play an important role in research fields ranging from physics to chemistry and life sciences. Here, we prepare and study unconventional self-assembled colloidal optical waveguides (CWs) created from wavelength-size dielectric particles held together by long-range optical forces. We demonstrate robust non-linear optical properties of these CWs that lead to optical transformation characteristics remarkably similar to those of gradient refractive index materials and enable reversible all-optical tuning of light propagation through the CW. Moreover, we characterize strong optomechanical interactions responsible for the CW self-assembly; in particular, we report self-sustained oscillations of the whole CW structure tuned so that the wavelength of the laser beams forming the CW is not allowed to propagate through. The observed significant coupling between the mechanical motion of the CW and the intensity of light transmitted through the CW can form a base for designing novel mesoscopic-scale photonic devices that are reconfigurable by light.