Fast Holographic Wavefront Sensor

ABSTRACT In this talk we will present a new zonal wavefront sensor. The de vice is able to take a single incident beam and diffract it into multiple beams with diff erent focal locations, according to the presence and strength of particular aberrations. The Zernike terms in the beam are simply r ead out according to the location of the fo ci on the image plane CCD. We have created a hologram design such that the locations of the beams can be quickly and easily determined, providing all necessary information to correct for these aberrations, so that the wavefront information is derived without the need for any computations. It is a very compact and practical device that could potentially have applications for the USAF airborne laser or atmospheri c distortion characterization. Keywords: Wavefront sensor, holography, optical processing 1. INTRODUCTION Phase aberrations can have a signifi cant detrimental effect on the ability to focus and propagate a beam 1 . The purpose of a wavefront sensor is to take an input light beam and quanti tatively determine the phase at different locations on a cross section. Wavefront sensors thus have several different appl ications. They can be used to test the quality of optical components by deriving the phase errors introduced on a predetermined wavefront. They can also be used for laser diagnostics in characterizing er rors present in the laser cavity itself such as thermal lensing and transverse modes. Wavefront sensors are more significantly used in adaptive optics for correction of light waves aberrated by propagation through the atmosphere or by optical systems. The technique involves sensing the wavefront phase error then applying the inverse error to the wavefront using a deformable or addressable phase device. The wavefront sensing such cases may be quite slow as in the case of ophthalmic applications, or quite rapid for transmission of optical beams through regions of extreme turbulence. Typical wavefront sensors such as interferometric, curvature or Shack-Hartmann have been shown to work very well