Equilateral pentagon polarization maintaining photonic crystal fibre with low nonlinearity

A new pentagon polarization maintaining photonic crystal fibre with low nonlinearity is introduced. The full vector finite element method was used to investigate the distribution and the effective area of modal field, the nonlinear properties, the effective indices of two orthogonal polarization modes and the birefringence of the new PM-PCF effectively. It is found that the birefringence of the new polarization maintaining photonic crystal fibre can easily achieve the order of 10-4, and it can obtain higher birefringence, larger effectively mode-field area and lower nonlinearity than traditional hexagonal polarization maintaining photonic crystal fibre with the same hole pitch, same hole diameter, and same ring number. It is important for sensing and communication applications, especially has potential application for fibre optical gyroscope.

雷竹新造林地不同套种模式初步研究

为了充分利用雷竹新造林地空间,扩大种植效益,对雷竹/花生、雷竹/芝麻、雷竹/红薯3种套种模式和雷竹纯林林地的土壤物理化学性质、雷竹造林成活率和出笋个数进行比较研究。结果表明:雷竹新造林地套种花生能够显著降低土壤容重和速效P含量,增加土壤孔隙度、碱解N、速效K、有机质含量,促进雷竹造林后第二年出笋个数的提高,同时不影响雷竹造林成活率,能够充分利用雷竹新造林地空间,填补雷竹新造林地的经济效益空白,达到以耕代抚,以短养长的目的。