Modeling and Fabrication of an Antireflection Microstructure on an AgClBr Fiber by Single-pulse Femtosecond Laser Ablation

AgClBr polycrystalline fibers with refractive index above 2 are used to transmit radiation of the infrared range. To improve the efficiency of AgClBr fiber based devices, it is beneficial to increase the fiber end faces transmittance. The conventional method for increasing the surface transmittance is to use antireflection coatings (ARCs). However, in the case of AgClBr ARCs cannot be applied to a fiber end face due to its unevenness. The plasticity and softness of the material prevent chipping, cleavage, and polishing. Thus a slicing technique should be used to cut the fiber, but even with the most precise technique perfect flatness cannot be achieved. An alternative approach is to fabricate antireflection microstructures (ARMs) [1] on the surface of a fiber end face. In this work a single-pulse direct femtosecond laser ablation for ARM fabrication was used. This technique provides good quality of ARM [2] and has already been tested on A 2 B 6 group semiconductors [3] which are promising gain media matrices [4] , chalcogenide glasses used for optical fiber production [5] , and infrared nonlinear crystals [6] .