Laser Beam Shaping

Abstract

We consider the promising properties of very simple Diffractive Optical Elements (DOE) for reshaping the intensity profile of a laser beam. The first type of DOE that we have considered is a phase aperture which consists in a transparent plate with a circular relief introducing a π phase shift in the central region of the incident beam. The phase aperture is able to convert a Gaussian beam into a super‐Gaussian, a ring‐shaped or a doughnut profile. The second DOE that has been considered is an adjustable axicon able to transform a Gaussian laser beam into a dark hollow beam or a Bessel‐Gauss beam. The desired conical geometry is obtained from a deformable mirror formed by a 2 inches, 0.25mm thick silicon wafer supported by a standard 2 inches optical mount. To achieve the adequate deformation a small metallic ball pushes the back of the mirror wafer. The realized shape is monitored with a Shack‐Hartmann wave‐front sensor and it is shown that conical shape cannot be achieved. Nevertheless, recorded wave fronts exhibit important third order spherical aberration able to achieve beam profile transformation as conical lenses.