This demonstration of optical vortices was put together by the UQ Physics Museum. It represents a strand of optical research carried on at the UQ Physics Labs which started in the 1990's and still continues today.
It consists of a small base onto which a diode laser, holographic plate, mirrors, and a magnifying lens are affixed. The laser beam is shone onto one mirror and then shone through the holographic plate. The resulting light pattern is then reflected off two further mirrors. This extends the path length, and allows the beam to expand. At the end of the path, the light passes through a lens in order to further magnify the final beam.
Much like how water going down a plug hole will spiral and leave a gap in the centre where there is no water, an optical vortex is where a beam of light creates a helical pattern with a point of darkness in its centre. When the laser beam passes through the computer-generated holographic plate, it is encoded with a helical structure. This causes the light beam to interfere with itself and cancel out at the centre, creating a point of zero intensity. This gives the optical vortex its distinct pattern of a dark spot surrounded by a ring of light. In fact, the light does in a sense swirl around the centre point, carrying an angular momentum. A tiny particle absorbing this light can be set into rotation.
Recent work at UQ has concentrated on using light with angular momentum in “optical tweezers” with the aim of trapping microscopic particles and moving and rotating them in three dimensions.
This item is part of the UQ Physics Museum ‘2015, International Year of Light’ Tour
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This item is part of the UQ Physics Museum ‘100 Years of Physics at UQ’ Tour
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JDB, SN
Hologram pattern
cardboard model of wavefront in optical vortex
Optical vortex demonstration
DPSS laser
Laser beam striking hologram
Row of optical vortices
Row of optical vortices
Row of optical vortices
