The mathematical phenomenon of super-oscillation, in which a spectrally bound function oscillates locally at a rate faster than its fastest Fourier component, has found use in both theoretical and applied areas of optical research. We show the existence of a complementary phenomenon we term sub-oscillation, in which a spectrally lower bound limited function oscillates locally at an arbitrarily low frequency beyond the lower band limit. We construct a spatially sub-oscillatory optical beam to experimentally demonstrate optical super defocusing i.e. a very fast, exceptional, expansion of a partially blocked light beam. The relevance of super-oscillations to varied fields such as quantum measurement, optical beam shaping and super-resolution, particle manipulation, electron beam shaping and radio frequency antenna design, suggest that sub-oscillations could find interesting uses in varied fields as well. Our demonstration of super defocusing by itself might be relevant for optical dark-field microscopy. [1] Y. Eliezer and A. Bahbad, Optica 4, 440 (2017)

Date Published: 24 May 2018
PDF
Proc. SPIE 10677, Unconventional Optical Imaging, 106770Z (24 May 2018); doi: 10.1117/12.2302785

Published in SPIE Proceedings Vol. 10677:
Unconventional Optical Imaging
Corinne Fournier; Marc P. Georges; Gabriel Popescu, Editor(s)