New Kind Of Optical Tweeters Based On Digital Optical Phase Conjugation

Optical Tweezers use gradient field to manipulate or trap microscopic objects as small as a single atom like dielectric spheres, viruses, bacteria, living cells, organelles, small metal particles, and even strands of DNA, and are widely used in the area of biology, medicine, physics, chemistry and materials. Traditional optical tweezers are constituted by high-precision microscope and three dimensional motion platform, which are complicated, cannot conduct complex controls as well as realize multiple optical tweezers at this time.This paper develops a new type of optical tweezers system based on digital optical phase conjugation (DOPC). The core idea of the system is to use a tapered waveguide structure formed by a bunch of single-mode fiber to decompose and reconstruct the complex optical wave front. In the thin end of the tapered optical waveguide, the single-mode fibers draw near to each other to mutually couple. Meanwhile, in the thick end of the tapered optical waveguide, the single-mode fibers accelerate away from each other and get isolated. When a complex optical wave front incidents to the thin end of the tapered optical waveguide, it is guided to the thick side, and decomposed with the Eigen mode in single mode fiber. Using spatial light modulator, and with the aid of micro lens to focus coupling, the single-mode optical fiber phase conjugate light wave can be produced in thick end. Because the reciprocity of path, the phase conjugate light propagate back, it will follow the original path, and restore the original complex optical wave front. This paper firstly introduces the mode matching method, then using it to analytically describe the theory of DOPC. An effective optical tweezers system based on DOPC by using mocro lens is simulated by OptiFDTD computing the electromagnetic filed with FDTD. The simulation shows that optical tweezers system based on DOPC can achieve diffraction limited resolution, also it can realize two and more optical tweezers at the same time with high precision.Optical tweezers system based on DOPC has no optical lens aberration which is presented at traditional optical tweezers. Also, Optical tweezers system based on DOPC can produce multiple optical tweezers simultaneously through spatial light modulator, and manage the control of each optical tweezers in real-time and high precision. It does not need sophisticated motors, so the structure can be more simple, more powerful. It can conduct the complex control like DNA surgery, group assembly that are difficult for traditional optical tweezers. The system has a wide application prospect.