Applications of the orbital angular momentum of light for imaging

A thesis accepted by Tallinn University of Technology for the Degree of Master of Science

Author:
Liis Rebane

Tallinn University of Technology, Estonia

Promoters:
Pearu Peterson, PhD

Institute of Cybernetics at Tallinn Technical University, Estonia

Joan P. Torres, DSc., Assoc. Prof.

The Institute of Photonic Sciences, Universitat Politecnica de Catalunya, Spain

Opponents:
Jaan Kalda, PhD.

Institute of Cybernetics at Tallinn Technical University, Estonia

Abstract:

In this thesis the imaging applications of orbital angular momentum of light are studied. The orbital angular momentum of a light beam, encoded to its spiral spectrum, is directly related to topological properties of the wave-front (intensity and phase distribution) and can thus provide information that is inaccessible by other methods. Two different imaging techniques have been discussed.

Digital spiral imaging is based on analyzing the image carrying wave with the information encoded into its spiral spectrum. We present an experimental study of the spiral spectrum of the light wave and show how the step-height of a phase jump can be estimated by analyzing the weights of different spiral modes.

Spiral phase contrast imaging is related to holographic Fourier plane filtering, using a spiral phase element as a filter. We have demonstrated experimentally how spatial filtering of the object field with a spiral phase element in a Fourier plane of the optical path results in a strong and isotropic edge enhancement at the output image. Numerical simulations predict that phase jumps as small as 1 per cent of the optical wavelength could be detected.

Place/venue:

The presentation of the thesis took place on June, 2006, at Tallinn University of Technology, Tallinn, Estonia.

Softcopy:

http://cens.ioc.ee/~pearu/theses/liis_msc_2006.pdf (1.5MB).