Abstract

In the last years the interest in low-cost production techniques for integrated optics and diffractive optical elements (DOEs) has rapidly grown. Different methods like embossing, moulding and casting were reported [1,2,3,4]. This technologies are well established for the production of submicron grating structures, like moulded CDs and hot embossed holograms. However, all this methods are not suitable for materials like glasses (e.g. silica) or semiconductors (e.g. InP, GaAs). In order to overcome this problem, grayscale and halftone masks with different gray levels were proposed, were a serie of gray levels corresponds, after a optical lithography process, to different resist depths [5,6]. These structures were finally transferred by dry etching processes to the substrate material. In this paper we present a new 3D-structure replication technique for this wide range of optical and semiconductor materials and for high structure depths. Deep microrelief structures up to 10 μm or more and structures with very high lateral resolution (< 200 nm) can be replicated. Due to the 3D-amplitude/phase mask it is possible to suppress edge ringing by means of modulating the amplitude and the phase of the light. The fabrication process of the mask is based on repeated multi-steps of photolithographic and ion-beam-sputter-deposition techniques. An in situ monitoring system is used to control the optical thickness and the transmission of the mask structures.

© 1996 Optical Society of America