Highly birefringent phase-shifted fiber Bragg gratings inscribed with femtosecond laser.
We demonstrate a highly birefringent phase-shifted fiber Bragg grating (PS-FBG) inscribed in H2-free fiber with a near-infrared femtosecond Gaussian laser beam and uniform phase mask. The PS-FBG was fabricated from an ordinary fiber Bragg grating (FBG) in a case in which overexposure was applied. The spectral evolution from FBG to FS-FBG was observed experimentally with a decrease in transmission loss at dip wavelength, blueshift of the dip wavelength, decrease in the cladding mode loss, and an increase in the insertion loss. A high birefringence was demonstrated experimentally with the existence of PS-FBG only in TM polarization. The formation of the PS-FBG may be due to a negative index change induced by the higher intensity in the center of the Gaussian laser beam.
Jun
J
He
Yiping
Y
Wang
Changrui
C
Liao
Qiaoni
Q
Wang
Kaiming
K
Yang
Bing
B
Sun
Guolu
G
Yin
Shen
S
Liu
Jiangtao
J
Zhou
Jing
J
Zhao