Diffractive multifocal lenses by computer-generated holograms

Abstract

Diffractive lenses are optical elements commonly used in many applications owing to their simple and compact design. A multifocal diffractive lens enables the simultaneous focusing of an incident laser beam on several positions along the optical axis. The distances between the focal points and the energy densities in the foci can be changed by varying grating parameters, i.e., the modulation depth and the grating period. This requires grating structures that have to be fabricated for each targeted optical arrangement. Even though some methods for designing diffractive lenses with variable focal positions are available, they do not provide real-time control over the energy distribution and focal locations of the foci. We aimed to develop coaxial or multiaxial multifocus diffractive lenses with computer-generated holograms. The focal distances and energy densities in the foci can be dynamically controlled by programmable holographic codes. The generated holographic lenses can be used for imaging with dynamic repositioning of created images fast and easily. Such a holographic diffractive lens can withstand a highly intense laser radiation, so it can be used in nonlinear optics experiments and can be employed for high harmonic generation, pump-probe experiments, optical tweezers, filamentation, and other applications.