+1/-1相位掩模板和532nm激光下低损耗As_2S_3硫系光纤布喇格光栅的制备

采用改进型Sagnac干涉光栅写入系统,利用532nm准带隙光曝光源和带+1/-1衍射级的相位掩模板,在两种不同直径的低损耗As_2S_3硫系玻璃光纤上刻写布喇格光栅,并研究曝光期间光栅的动态特性.实验表明,As_2S_3光纤布喇格光栅透射峰值随光纤直径的减小而增强;在曝光过程中,布喇格波长先是较快地向短波长方向移动,随着曝光时间的延长,布喇格波长缓慢地向长波长方向回复.曝光时间为800~1 000s时,在包层直径为140μm的As_2S_3光纤上获得质量良好的布喇格光栅光谱,其透射峰值可达-2.6dB,带宽为0.37nm.对As_2S_3硫系光纤纤芯的光敏性分析结果表明,折射率调制幅度和平均折射率变化随曝光时间分别可达到10-4和10-3数量级.

Fabrication of Bragg Gratings in Low-loss As2S3 Chalcogenide Fibers Using +1/-1 Phase Mask and 532 nm Laser

Adopting modified Sagnac interference grating writing system,the fiber Bragg gratings were written in two kinds of As2S3 chalcogenide fibers with different cladding diameter by use of a near bandgap light at 532 nm and-4-1/-1 diffracted orders phase mask,and the gratings dynamic characteristics during the exposure were studied.It is found that the depth of grating transmission peak in low-loss As2S3 chalcogenide fiber increases with a decrease of the cladding diameter.During exposure,the Bragg wavelength shifts fast towards short wavelength at first,and then with increasing exposure time restores slowly towards long wavelength.At exposure time from 800 s to 1000 s,the good quality Bragg grating with about-2.6 dB bandgap and about 0.37 nm bandwidth in transmission spectra was fabricated in As2S3 chalcogenide fiber with about 140 μm cladding diameter.In addition,an analysis of photosensitivity in the As2S3 chalcogenide fiber core shows that the refractive index modulation amplitude and the change of average refractive index with the exposure time can achieve to be on the order of 10-4and 10-3,respectively.