Abstract

Long-period fiber gratings (LPFGs) have been found wide applications in optical communications and smart sensing. Among various techniques for fabrication of LPFGs, infrared femtosecond laser writing is one of the most attractive methods in terms of its flexibility, being applicable to either photo sensitive or insensitive fibers, and possessing no needs for any pre-designed masks. Because the radius of focused femtosecond laser beam is typically few micrometers or less, both the dimension and location of modified refractive index region can be thus conveniently altered according to specific requirement. This leads to the attractive advantage of writing LPFGs with near infrared femtosecond laser over with CO₂ laser in the aspect of generating more versatile grating profiles.

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