Li Feng, Li Qian, Yuan Jinhui, Wai P K A
Opt Express. 2014 Nov 3;22(22):27339-54. doi: 10.1364/OE.22.027339.
The low coherence of the supercontinuum (SC) generated using picosecond pump pulses is a major drawback of such SC generation scheme. In this paper, we propose to first self-similarly compress a high power picosecond pump pulse by injecting it into a nonlinearity increasing fiber. The compressed pulse is then injected into a non-zero dispersion-shifted fiber (NZ-DSF) for SC generation. The nonlinearity increasing fiber can be obtained by tapering a large mode area photonic crystal fiber. The fiber nonlinearity is varied by varying the pitch sizes of the air holes. By using the generalized nonlinear Schrödinger equation, we show that a 1 ps pump pulse with random noise can be compressed self-similarly down to a pulse width of 53.6 fs with negligible pedestal. The noise level of the compressed pulse is reduced at the same time. The 53.6 fs pulse can then be used to generate highly coherent SC in an NZ-DSF. By using the proposed scheme, the tolerance of noise level for highly coherent SC generation with picosecond pump pulses can be improved by 5 order of magnitude.
使用皮秒泵浦脉冲产生的超连续谱（SC）的低相干性是这种超连续谱产生方案的一个主要缺点。在本文中，我们建议首先将高功率皮秒泵浦脉冲注入到非线性增加光纤中进行自相似压缩。然后将压缩后的脉冲注入到非零色散位移光纤（NZ-DSF）中以产生超连续谱。非线性增加光纤可以通过对大模面积光子晶体光纤进行锥化来获得。通过改变气孔的间距尺寸来改变光纤的非线性。利用广义非线性薛定谔方程，我们表明一个带有随机噪声的1皮秒泵浦脉冲可以自相似压缩到脉宽为53.6飞秒，且基座可忽略不计。同时，压缩脉冲的噪声水平降低。然后，这个53.6飞秒的脉冲可用于在NZ-DSF中产生高相干超连续谱。通过使用所提出的方案，皮秒泵浦脉冲产生高相干超连续谱时的噪声水平容限可以提高5个数量级。
