<title>Excimer laser ablation used for the fabrication of micro-optic phase and diffraction elements</title>

Abstract

Micro Optics frequently require the fabrication of complex 3D structures with surface qualities and metrological tolerances that challenge many manufacturing techniques. In this paper we describe two excimer laser abalation techniques for creating spiral phase modulation structures and a technique for fabricating a diffractive optical structure. The spiral phase structures are intended to be used to convert a 780nm TEM<SUB>00</SUB> laser beam into the doughnut mose TEM*<SUB>01</SUB> field and the diffractive structure is used to create the double-D TEM<SUB>01</SUB> mode in the transmitted first order diffraction. Each of the techniques involve the use of mask projection excimer laser abalation. One of the techniques used to create the smoothly varying ramp of the spiral phase structure involes the use of a single mask that rotates about one of its vertices while the matching laser is pulsed. The second process uses a set of 15 separate patterns that are prepared on a chrome-on-quartz mask. The fabrication of the diffractive optical element is performed in a similar way. We have used 248nm radiation from a KrF laser source to demonstrate the fabrication in polycarbonate of the spiral phase modulation structure and have been able to produce the diffractive optical element in both polycarbonate and glass microscope slides.