Point-by-Point Femtosecond-Laser Inscription of 2-<italic>&#x03BC;</italic>m-Wavelength-Band FBG Through Fiber Coating

• Main Authors: Wei He, Lianqing Zhu, Wen Zhang, Feng Liu, Mingli Dong
• Format: Article
• Language: English
• Published: IEEE 2019-01-01
• Series: IEEE Photonics Journal
• Subjects: Femtosecond pulsed laser; erbium-doped fiber laser; fiber Bragg grating; 2-μm-wavelength-band
• Online Access: https://ieeexplore.ieee.org/document/8539990/

We propose a point-by-point inscription method for fiber Bragg grating (FBG) fabrication using a femtosecond pulsed laser focused through a fiber polyimide coating, realizing a 2-&#x03BC;m-wavelength-band FBG. A femtosecond laser acts as the inscription laser, focused by a 63&#x00D7; oil lens. A first-order FBG was fabricated with a grating interval of 700 nm. The 15-&#x03BC;W pulsed laser was focused directly on the fiber core through the polyimide coating and cladding. A first-order FBG for 2004.8-nm light with more than 56% reflectances was fabricated. High wavelength sensitivity and linearity of the FBG were demonstrated by temperature and strain-sensing testing. The first-order FBG of 2004.8 and 2000.2 nm resonant wavelengths could be realized simultaneously through parallel inscription method in 3000 &#x03BC;m long grating area.