title: Modal decomposition without a priori scale information.
abstract: The modal decomposition of an arbitrary optical field may be done without regard to the spatial scale of the chosen basis functions, but this generally leads to a large number of modes in the expansion. While this may be considered as mathematically correct, it is not efficient and not physically representative of the underlying field. Here we demonstrate a modal decomposition approach that requires no a priori knowledge of the spatial scale of the modes, but nevertheless leads to an optimised modal expansion. We illustrate the power of the method by successfully decomposing beams from a diode-pumped solid state laser resonator into an optimised Laguerre-Gaussian mode set. Our experimental results, which are in agreement with theory, illustrate the versatility of the approach.
authors.affiliation: Institute of Applied Optics, Friedrich Schiller University Jena, Jena, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Schulze
authors.forename: Sandile
authors.initials: S
authors.lastname: Ngcobo
authors.forename: Michael
authors.initials: M
authors.lastname: Duparré
authors.forename: Andrew
authors.initials: A
authors.lastname: Forbes
mesh_terms: D004867:Equipment Design; D006696:Holography / Q000295:instrumentation / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D053844:Lasers, Solid-State; D008027:Light; D008962:Models, Theoretical