Fast focus field calculations
We present a fast calculation of the electromagnetic field near the focus of an objective with a high numerical aperture (NA). Instead of direct integration, the vectorial Debye diffraction integral is evaluated with the fast Fourier transform for calculating the electromagnetic field in the entire focal region. We generalize this concept with the chirp z transform for obtaining a flexible sampling grid and an additional gain in computation speed. Under the conditions for the validity of the Debye integral representation, our method yields the amplitude, phase and polarization of the focus field for an arbitrary paraxial input field on the objective. We present two case studies by calculating the focus fields of a 40×1.20 NA water immersion objective for different amplitude distributions of the input field, and a 100×1.45 NA oil immersion objective containing evanescent field contributions for both linearly and radially polarized input fields.
Keywords: (070.2580) Fourier optics and signal processing ; Paraxial wave optics ; (180.0180) Microscopy ; Microscopy ; (220.2560) Optical design and fabrication ; Propagating methods ; (260.1960) Physical optics ; Diffraction theory
Record created on 2008-02-25, modified on 2016-08-08