EXPERIMENTAL INVESTIGATION OF THE EFFECT OF BUFFER LAYER THICKNESS ON THE SHAPE OF LENSED OPTICAL FIBERS

10.25712/ASTU.1811-1416.2024.03.014

Abstract

The effect of the thickness of a xylene buffer layer on the shape of conical surface at the end of a single-mode optical fiber during the formation of axicons by chemical etching in a hydrofluoric acid solution was studied experimentally. Photographs of lensed fiber ends with different signs of surface curvature were obtained and analyzed. These quartz lensed fibers are intended for inputting optical radiation into various elements of photonic integrated circuits. The dependence of the cone shape on the thickness of the buffer layer was determined for given parameters of the technological process. It was found that when optical fibers are etched, a thinning of the cladding is formed in an air environment due to the formation of droplets of a hydrofluoric acid solution from the vapor above the xylene-air interface. To reduce the influence of this effect, it is necessary to increase the thickness of the buffer layer, which should prevent the diffusion of hydrofluoric acid molecules into the air space of the reactor. On the other hand, reducing the buffer layer can be used to form waists with adjustable thickness of the etched area on sections of the fiber away from the lensed end. Such constrictions can be used to design optical sensors, the operation of which is based on the contact of the fiber core with the medium under study.