Dept. Elect. Eng.Technion – Israel Institute of Technology

Rotating Beams

Yoav Y. Schechner

1

Joint studies with J. Shamir, R. Piestun, A. Greengard

Yoav Schechner

Waves having a Phase Dislocation

propagation direction

a helical wavefront

Yoav Schechner

propagation direction

helical wavefront surface

local k-vectors (normals to the wavefront surface) have azimuthal

component

local k-vectors

orbital angular

momentum in the

wave

k vector : momentu

m

Waves having a Phase Dislocation

Schechner & Shamir

propagation direction

Isotropic dislocation: helical

wavefront

propagation directionAnisotropic dislocation

Parameterizations

Morphological:• Stretch angle

• Eccentricity

• Dark fringe: a limit of eccentricity

Physical:

• Superposition of

isotropic waves • Dark fringe:

annihilation of isotropic dislocations

• Angular momentum

Anisotropic Dislocations

Rotating PSF

Schechner

Schechner et. al, Physical Review E 1996

Computer-Generated Hologram

(Diffractive Optical Element)

Utopian Geometric PSF

Width changes linearly with z

z

Yoav Schechner

Standard PSF

Width changes with z

…by just a 2nd order

z

Rotating PSF

Standard PSF

Greengard, Schechner, Piestun

Greengard, Schechner, Piestun: Depth from diffracted rotation