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Slit Beam Shaping for Femtosecond Laser Point-by- Point Inscription of High-Quality Fiber Bragg Gratings.
- Source :
- Journal of Lightwave Technology; 8/1/2021, Vol. 39 Issue 15, p5142-5148, 7p
- Publication Year :
- 2021
-
Abstract
- Fiber Bragg gratings (FBGs) inscribed by using femtosecond laser point-by-point (PbP) technology typically have high birefringence due to the elliptical cross-sectional pattern of refractive index modulations (RIMs) created in the fiber core. Additionally, a highly reflective type II PbP FBG, which has a large coupling coefficient, also exhibits large insertion loss due to the limited RIM area induced by a single femtosecond laser pulse. Here we demonstrate a slit beam shaping method for femtosecond laser PbP inscription of high-quality FBGs, featuring by high reflectivity, low insertion loss, and low birefringence. The slit beam shaping method could reduce the ellipticity in the cross-sectional pattern of RIMs without reducing the cross-sectional area, leading to low birefringence and low insertion loss. The experimental results agree well with numerical calculations. Hence, a high-quality type II PbP FBG, which has high reflectivity of 99.12% (i.e., Bragg resonance attenuation of 20.52 dB), low insertion loss of 0.30 dB, and low birefringence of 1.86 × 10−6, was successfully created by use of a slit width of 0.8 mm. Moreover, an enlarged cross-sectional area was created by use of a slit width of 0.2 mm, resulting in a high ratio of 172.46 of the coupling strength coefficient to the scattering loss coefficient in the fabricated PbP FBG, which exhibits very high reflectivity of 99.99% (i.e., a strong Bragg resonance attenuation of 46.65 dB) and low insertion loss of 0.27 dB. Such high-quality FBGs will be promising in many applications, such as optical fiber communications, sensors, and lasers. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 07338724
- Volume :
- 39
- Issue :
- 15
- Database :
- Complementary Index
- Journal :
- Journal of Lightwave Technology
- Publication Type :
- Academic Journal
- Accession number :
- 153880433
- Full Text :
- https://doi.org/10.1109/JLT.2021.3082566