Yochay Danziger

Discontinuous phase elements for transverse mode selection in laser resonators

Discontinuous phase elements can be inserted into laser resonators so that the lasers will operate with only one desired high order transverse mode. These elements introduce sharp discontinuous phase changes so as to result in minimal losses for a desired transverse mode but high losses to others. The basic principles, along with experimental results with Nd:yttrium–aluminum–garnet and CO2 lasers, illustrating improved output powers with a high beam quality of low divergence, are presented.

Laser mode discrimination with intra-cavity spiral phase elements

A novel method for discriminating and selecting a specific high order mode is presented. It is based on introducing spiral phase elements into a laser resonator, so as to improve the output beam quality over that when the laser operates with multi-modes, and yet maintain a relatively high output power. The theoretical analysis, along with experimental results with CO and Nd:YAG lasers are presented. The results reveal that a 50% increase of laser output power over that operating with 2

Multilevel diffractive elements for generalized wavefront shaping

A new approach to designing computer-generated multilevel diffractive elements, in which the phase and the amplitude of the output wavefront can be controlled independently, is presented. In this ap- proach the diffraction efficiency of the elements can be arbitrarily con- trolled to reach 100% efficiency over the entire element. The approach is based on varying the local diffraction efficiency by changing the width and the number of levels in every period. To reduce complexity, an al- gorithm for designing the element with the least number of levels and masks is developed. This design algorithm determines the needed mask parameters in which compensation for distortions introduced by the litho- graphic recording of the element are taken into account. Calculated and experimental investigations that confirm the new design approach are presented.

Diffractive optics: Design, realization, and applications

This paper presents methods for designing and recording optimal computer-generated diffractive optical elements. The design method is based on an analytic ray-tracing procedure for minimizing aberrations. The recording involves computer-generated masks and multiple lithographic processes in order to form reflective and transmissive multilevel, surface relief-phase, diffractive elements. As a result, the elements can have high diffraction efficiencies over a broad range of incidence angles. Even generalized diffractive elements that operate with highly uniform diffraction efficiency and polychromatic radiation can be designed and recorded by optimizing the shape and height of the relief gratings. To illustrate the effectiveness of the diffractive optical elements, they have been incorporated into a number of applications, involving visible as well as infra-red radiation. Some that deal with coordinate transformation, beam shaping, and polarization control are briefly reviewed.