Air and silica core Bragg fibers for radiation delivery in the wavelength range 0.6–1.5 μμm

• The laboratory-designed Bragg fibers with silica and air cores of different diameters have been prepared.
• We demonstrated the efficient laser radiation delivery in the wavelength range from 600 to 1500 nm.
• All fibers have approximately 6 times higher damage threshold intensity (approximately 30 GWcm−2 for the 9-ns-laser pulses at the wavelength of 1064 nm) in comparison with gradient-index fibers.
• The lowest attenuation coefficient of 70 dB/km was determined for the 73-μm-air-core fiber at the wavelength of 1064 nm.
• All tested fibers exhibited negligible bending losses down to the bend diameter of about 5 cm.

This paper presents fundamental characteristics of laboratory designed and fabricated Bragg fibers with air and silica cores at wavelengths of 632, 975, 1064 and 1550 nm. Fibers with the 26-μμm-silica core and 5- or 73-μμm-air cores in diameters and claddings of 3 pairs of Bragg layers were prepared from one preform. The overall transmittance, attenuation coefficients, coupling losses, bending losses, and damage-intensity thresholds were determined using four continuous-wave laser sources with the maximum output power of 300 mW and a pulsed 9 ns laser with the maximum output energy up to 1 mJ. The lowest attenuation coefficient of about 70 dB/km was determined at 1064 nm with the 73-μμm-air-core Bragg fiber. All fibers have been found to exhibit negligible bending losses down to the bending diameters of 5 cm. In comparison with the conventional gradient optical fiber, all the prepared Bragg fibers have approximately six times higher damage intensity threshold of about 30 GWcm−2 and therefore they are very suitable for high power laser radiation delivery.