RESUMEN
We propose a new design for fabrication of a highly power-efficient double axicon to generate self-imaged three-dimensional intensity voids along the propagation of a beam. The conventional conical structure of an axicon is modified and shaped like an axiconlike structure with a double-gradient surface profile. The gradient conical surfaces generate Bessel beams with varying radial wave vectors that are superimposed and interfere to generate a sequence of three-dimensional intensity voids. The proposed element was fabricated using electron-beam lithography, and experimental verification of the design is reported.
RESUMEN
We propose using a solitary kinoform-type spiral phase plate structure to generate an array of vortices located in a single beam. Kinoform-type spiral surfaces allow each wavelength component of the phase modulation value to be wrapped back to its 2 pi equivalent for optical vortices of high charge. This allows the surface-relief profiles of high-charge vortices to be microfabricated with the same physical height as spiral phase plates of unity-charged optical vortices. The m-charged optical vortex obtained interacts with the inherent coherent background, which changes the propagation dynamics of the optical vortex and splits the initial m charge into /m/ unity-charged optical vortices within the same beam. Compared to a hologram, a multistart spiral phase plate is more efficient in the use of available spatial frequencies and beam energy and also is computationally less demanding. Furthermore, using microfabrication techniques will allow for greater achievable tolerances in terms of smaller feature sizes.