Reverse propagation properties of light wave in tapered micro-nano fiber for cell endoscopy

There have been many reports on tapered micro-nano optical fiber used in cell monitoring, so it is necessary to discuss the reverse propagation properties in tapered fiber. In this paper, we use Finite Difference Time Domain (FDTD) algorithm to simulate the propagation of light wave propagating back and forward in fiber taper, respectively. The results indicate that most of the light is remain in core in the back way. But little light propagates at a relatively far distance from core in cladding and most of light energy will back to core at the end part of fiber taper, which is different from forward propagation. In the subsequent experiment, the conclusion is further proved. Based on this feature, the light signal in living cell can be easily guided out and the true sense of "endoscopic" for cell detection would be realized.