Semi-immersive photonic hook and optical trapping along an air-liquid interface

In this paper, we demonstrate a novel semi-immersive photonic hook, which is a bent light focus by a dielectric micro-cylinder partially immersed at the edge of a thin liquid film. It only propagates along the air-liquid interface (ALI) and possesses a formation mechanism without material processing for micro-particle and modulation of light irradiation. The existence of ALI at the shadow end of the micro-cylinder and contrasts of refractive indexes over there cause this phenomenon at the specific depths of liquid films. Compared to the previously discovered photonic hooks, its unique setup can generate an optical force field in the ALI region to realise optical trapping for applications in microfluidics, micro/nano-engineering, and biomedical research. The morphology of this photonic hook and its optical trapping forces to micro-object varying locations were analysed to study the formation and feasibility of optical trapping along ALI in this approach.