All-fiber nanostructured gradient optics vortex beam converter

We study optical performance of a vortex beam converter comprising a nanostructured gradient index vortex mask, a compact gradient index microlens and an optical fiber. The converter generates high quality focused optical vortex from the input Gaussian beam without support of any additional external optical elements. Integration of a nanostructured lens allows control of the size and the position of focus of vortex beams, while at the same time maintaining their quality. This confirms that nanostructured gradient index micro-optical components can be used sequentially to form complex optical systems and maintain full compatibility with fiber optics. Our experimental results are supported by numerical simulations.