Generation of high-order optical vortices with nanostructured phase masks

•Design and development of a new graded index phase mask made of lead–bismuth-gallium glasses dedicated to the generation of high-order vortex beams.•Experimental verification of the formation of optical vortex beams with topological charge up to 5 using the fabricated components in free space set-up.•Experimental demonstration of the performance of the component integrated into the standard fiber tip for generation optical vortex beams with topological charge up to 4.•The technology for the development of the nanostructured flat-surface gradient index microoptical components was successfully verified for Gaussian beam conversion into high-order vortex beams.