Self-induced optical pulling in complex photonic band structure

Abstract

The photonic band gap effect has been proposed to achieve a gradient-induced long-range optical pulling force, but how the properties of the photonic band gap affect the optical pulling force remains to be revealed. In this work, based on the theory of complex photonic band and Einstein–Laub formulation of force density, a concise formula is developed to investigate such unusual optical pulling force. It indicates that the optical pulling force is mainly decided by the imaginary part of the wave vector of evanescent mode in the photonic band gap and the refractive index of the object. A larger imaginary part of the wave vector and a higher refractive index of the object typically result in a larger optical pulling force, which is verified by the numerical simulation. In addition, a critical length is defined to predict the occurrence of optical pulling force. Our work gives an insight into such an optical pulling force based on the complex photonic band and offers guidance for achieving a larger optical pulling force, which is very beneficial to optical sorting and optical conveying.