Generation of a large orbital angular momentum beam via an optical fiber winding around a curved path and its application

Many papers have been published on the study of orbital angular momentum(OAM)of the laser modes based on the Laguerre-Gaussian(LG)beam and helical phase plate or rotating cylindrical lens,and the principal ray of the LG beam remains straight line.These ways are difficult to get a large OAM modes.In this paper,we propose a novel method to prepare a large OAM modes when the light propagates through a optical fiber winding around a curved path,and establish a theoretical framework based on the principal ray path changing.Firstly,we investigate three kinds of winding structure.Secondly,based on the analytical solutions and numerical calculations,we can find that the spiral body can achieve a large OAM temporal pulse.At the same time,based on the zero OAM diffraction diagram,we can obtain an improvement of resolving power beyond Rayleigh’s criterion.Finally,applying a large OAM diffraction pattern to realize 12-bitencodes,we can obtain a high-security optical information transfer system.

Tripartite continuous-variable entanglement of NOPA system

We investigate the fundamental limits to the achievable tripartite continuous-variable （CV） entanglement criterion of a generalized Vl criterion. Our numerical simulation results show that the non-degenerate eigenvalues do effect the performances of the estimated minimum variances. From below the threshold to above the threshold, with the increase of the pump parameter, the tripartite CV entanglement gradually disappears. The different off-diagonal elements seriously distort the weights for entanglement. We can obtain a good tripartite CV entanglement by appropriately controlling the values of off-diagonal elements eij.