Bragg Fiber Taper for Subwavelength Beam Generation

We demonstrated light confinement in a subwavelength-diameter silica core by addincxg a Bragg multilayer cladding. The output beam properties of Bragg fiber taper were studied using a beam propagation method (BPM), and the result showed a 34% stronger light confinement than that of air-clad silica taper. We optimized the shape of silica core and the Bragg multilayer structure. An HE
₁₁
mode-shaped beam with a wavelength of 0.85 ¿m and a full-width at half-maximum (FWHM) of 0.75 ¿m was successfully generated by 1.1-¿m-core Bragg fiber tapers. Our devices may have applications in nanophotonics and nonlinear optics.