PROCEEDINGS ARTICLE | November 27, 2000
Proc. SPIE. 4316, International Conference on Lasers for Measurements and Information Transfer
KEYWORDS: Beam splitters, Diffractive optical elements, Modulation, Manufacturing, Transmission electron microscopy, CCD cameras, Telecommunications, Chemical elements, Modes of laser operation, Optical interconnects
Novel Diffractive Optical Elements of MODAN-type open up new promising potentialities of solving the tasks of generation, transformation, superposition and subsequent separation again of different transversal laser modes with high efficiency. In we presented for the first time a MODAN capable of transforming a Gaussian TEM00 input beam into a unimodal Gauss-Hermite (GH) (1,0) complex amplitude distribution. Now we present new results achieved by combining several MODANs in one optical set-up: The aim of these investigations is to transform a single TEM00 input laser beam into several partial beams, each of them described by a different unimodal GH (n,m) mode structure. After separately modulating these partial beams in time, and subsequent superposing them to again one beam by means of a conventional beamsplitter, this unified multimode beam is permitted to propagate in space. Following that, an 'analyzing' MODAN is applied to this transversal multimode beam -- a diffractive element which is capable of realizing a spatial modal decomposition of an illuminating beam. For the investigations to be presented here, we restricted ourselves to two unimodal beams and selected as transforming MODANs one element of TEM00-to-GH (1,0) type described and one of TEM00-to-GH (0,1) type. The analyzing MODAN was calculated as a phase-only element using the crossed-gratings method and manufactured with the same technology like the two other elements. Theoretical as well as first experimental results demonstrate promising perspectives for the selected concept.
