铌酸锂包层硫系中红外少模光纤的电光效应

Electro-Optical Effects of Chalcogenide Mid-Infrared Few-Mode Fibers with Lithium Niobate Cladding

提出了一种采用LiNbO3晶体为包层、光轴方向沿光纤轴线方向的中红外硫系少模光纤,采用全矢量有限元法研究了外加电场对LiNbO3晶体的主轴折射率比和光模式的传输特性的影响。结果表明,在2.25~3.85μm波长范围内,模式有效折射率与功率限制因子均随着波长增大逐渐降低,而差分模时延呈现上升趋势。外加轴向电场不但会减小各光模式的有效折射率与差分模时延,而且会增强对各模式能量的限制,并随着模式阶数升高,电场的限制就愈发明显。无外加电场时HE11模色散随波长增大而呈现上升趋势,而HE_(21),TE_(01)和TM_(01)模色散呈现抛物线型分布,且存在2个零色散波长。当电场增大时,光模式的色散均会增大并会导致色散零点蓝移。电场为4×10^(9)V/m时,HE_(11),HE_(21),TE_(01)和TM_(01)模短波长处的零色散波长比无电场时分别蓝移0.5695μm,0.3915μm,0.3862μm和0.5594μm。

A mid-infrared chalcogenide few-mode fiber with cladding made by LiNbO3 crystals in which the optical axis is running along the axis of optical fiber is proposed.Besides,the effect of the adding electric field on the rate of the extraordinary to the ordinary ray refractive index of LiNbO3 crystals and the transmission characteristics of optical modes are studied by using the full-vector finite element method.The results show that the effective refractive index and power confinement factor both decrease with increasing wavelength,but the differential mode delay shows an increasing trend at the wavelength of 2.25~3.85μm.Besides,the external axial electric field not only reduces the effective refractive index and differential mode delay of each optical mode,but also increases energy confinement for each mode.And the higher the mode orders is,the stronger energy confinement becomes.The dispersion of the HE11 mode rises with wavelength drop without an external electric field,whilst the HE_(21),TE_(01),and TM_(01) modes exhibit parabolic distribution with the wavelength increasing,and there exist two zero dispersion wavelengths.The dispersions of optical modes increase as the electrical field increases,which contributes to a blue shift of the dispersion zero point.In comparison with and without an electric field of 4×10^(9)V/m,the zero dispersion wavelengths at the short wavelengths of HE_(11),HE_(21),TE_(01)and TM_(01)modes are blue-shifted by 0.5695μm,0.3915μm,0.3862μm and 0.5594μm,respectively.