EXPERIMENTAL STUDY OF OPTICAL POWER EFFECT ON THE STRUCTURE OF FIBER-OPTICAL DIFFUSER OBTAINED BY FIBER CORE MELTING

Subject of Research. The paper presents experimental findings of a fiber-optic diffuser structure formed by optical fiber melting. Method. An optical scheme of ytterbium fiber laser is demonstrated consisting of such main components as: a laser pump diode (980 nm, with power up to 30 W), an active GTWave fiber (24 m), and two fiber Bragg gratings with reflection coefficients of 100 % and 30 %. The presented ytterbium radiation source is used to form a periodic structure of microcavities inside the fiber core using the melting effect of the material. The described technology application provides the creation of scattering structures with a given period without removing the protective acrylate fiber coating. Thus, there is no need for the optical fiber re-coating with a polymer composition, and its strength characteristics are maintained. Main Results. The experimental setup developed during the study gives the possibility to record the scattering structure in the core of the optical fiber by destroying the material using laser radiation. In order to determine the dependence of the properties of the created structures on the input radiation power, a number of samples was obtained recorded for various radiation characteristics. It was established experimentally that with an increase of laser radiation power, the period of localization of microcavities decreases. At the same time, their sizes are reduced, and the uniformity of the structure increases. The optimal radiation power value for the scattering structure formation is established to be about 2 W. Practical Relevance. The studied scattering structures can be used in medical research, laser photodynamic therapy, laser pacemakers, fluorescence diagnostics, and also as a backlight for minimally invasive operations. The fiber optic diffuser can be applicable as a sensor of physical quantities, in particular, for measuring high temperatures, since the upper limit of the diffuser working temperature is comparable to the melting temperature of the optical fiber quartz part