一种对双包层大芯径光纤光栅反射率和纤芯折射率调制估算的方法

A methode of estimating the reflectivity and refractive-index modulation of double-cladding large core fiber Bragg grating

报道了一种简单而又实用对双包层大芯径光纤光栅反射率和纤芯折射率调制的估算方法.通过监测和记录光栅刻写过程中光纤激光器输出功率随时间的变化,将实验数据和掺铥光纤激光器的速率方程理论相结合,对刻写光栅反射率和纤芯折射率变化进行估算.光纤光栅的最大反射率大约为96.4%,纤芯折射率调制达到1.2×103.利用显微镜对光栅进行观测,纤芯的折射率调制变化均匀,且周期与模板周期一致.将光纤光栅应用在全光纤化掺铥光纤激光器中,在抽运功率为51.6W时,获得15.5W的1950.6nm激光输出,斜率效率为37.9%,并在输出功率为15W时,利用刀口法测得光束质量M2≈1.4.

A simple and practical method of estimating reflectivity and refractive-index modulation is reported when writing fiber Bragg grating （FBG） into silica fiber core based on 800 nm femtosecond laser pulses and a phase mask. By monitoring and recording the variation of the fiber laser output power, the reflectivity and refractive-index modulation are estimated theoretically and experimentally. The reflectivity of FBG is approximate 96.4%, and the refractive-index modulation is about 1.2 ×10^-3. When the FBG is used as a linear cavity mirror, 15.5 W of output power is obtained under an incident pump power of 51.6 W, corresponding to a slop efficiency of 37.9%. A beam factor of M2 = 1.4 at an output power of 15 W is measured by using the knife-edge method.