Silicon brings more colour to holograms

Silicon holograms harness the full visible spectrum to bring holographic projections one step closer

We can’t yet send holographic videos to Obi-Wan Kenobi on our droid, but A*STAR researchers have got us a little bit closer by creating holograms from an array of silicon structures that work throughout the visible spectrum1.

Many recent advances in hologram technology use reflected light to form an image; however the hologram made by Dong Zhaogang and Joel Yang from the A*STAR Institute of Materials Research and Engineering uses transmitted light. This means the image is not muddled up with the light source.

The team demonstrated the hologram of three flat images at wavelengths ranging from blue (480 nanometers) to red (680 nanometers). The images appeared in planes 50 microns apart for red and higher spacings for shorter wavelengths.

“In principle, it can be tuned to any wavelength,” says Yang.

Holograms can record three-dimensional images, which mean they can store large amounts of information in increasingly thin layers.

Recently, holograms that are mere hundredths of the thickness of a human hair have been made from metal deposited onto materials such as silicon. The holograms are created by nanoscale patterns of metal that generate electromagnetic waves that travel at the metal–silicon interface; a field called plasmonics.

Silicon holograms are slightly thicker than the metal-based ones, but have the advantage of being broadband. Plasmonic holograms only operate in the red wavelengths because they undergo strong absorption at blue wavelengths.

A disadvantage of the silicon holograms is their poor efficiency at only three per cent; however Dong estimates this could easily be tripled.

“The losses can be lowered by optimizing the growth method to grow polycrystalline silicon instead of amorphous silicon,” he says.

The hologram is an array of tiny silicon skyscrapers, 370 nanometers tall with footprints 190 nanometers by 100 nanometers. Unlike a city grid, however, the tiny towers are not laid out in neat squares but at varying angles.

The hologram operates with circularly polarized light, and the information is encoded on to the light beam by the varied angles of the skyscrapers. These alter the phase of the transmitted light through the ‘Pancharatnam–Berry effect’.

“What’s interesting about this hologram is that it controls only the phase of the light by varying the orientation of the silicon nanostructures. The amplitude is the same everywhere; in principle you can get a lot of light transmitted,” says Yang.

The A*STAR researchers focused on nanofabrication and measurements and collaborated with Cheng-Wei Qiu from National University of Singapore, whose team specializes in hologram design.

The A*STAR-affiliated researchers contributing to this research are from the Institute of Materials Research and Engineering and the Data Storage Institute

Reference

  1. Huang, K., Dong, Z., Mei, S., Zhang, L., Liu, Y. et al. Silicon multi-meta-holograms for the broadband visible light. Laser & Photonics Reviews 10, 500–509 (2016)| Article

 

Original on A*STAR journal website, published by Nature Group.

Shooting Star collides with star

I wrote this as a writing test in a job interview for CSIRO. Thought it was OK – but i didn’t get the job….

—–compact_binary_systems

Have you ever wondered what would happen if a shooting star collided with a star? Well, scientists at CSIRO think they have discovered just that! Unfortunately the collision is too far away to see, but the scientists have discovered that Star PSR J0738-4042 is bombarded – regularly!

Shooting stars are actually pieces of spacerock that burn up as they fall into our atmosphere. Spacerocks are falling into PSR J0738-4042 as a result of it exploding in the past, flinging out debris that is now falling back in on itself.

In the explosion the star became a pulsar that shoots out radio waves as it spins, at nearly three turns per second. The falling debris gets zapped by the radio waves, turning it into plasma, which then affects the star’s regular pulses. By measuring changes in the pulses the scientists calculated the mass of one of the rocks at around a billion tonnes!

 

Duck sex is so wrong

For Patricia Brennan, duck penis researcher from University of Massachusetts..

Give thanks for the birth of Duck minor
Mother duck has a corkscrew vagina
But daddy’s erection
curls in the other direction
Proof God’s no intelligent designer

Duck love making’s no simple deed
what’s more god has deceed
that the knob of this stud
will drop off in the mud
as soon as he’s planted his seed

If you think this seems a sad song
the drake will regrow his dong
this new percy I’ve heard
measures a third of the bird
a behemoth that’s 8 inches long!

Things then get wronger and wronger
Sir Drake scares his mates with his donger
If he thinks he’s the king
it shows up in his thing
which grows to be 20 % longer

So you think your love life’s out of luck
Be thankful you are not a duck.
your bits stay attached
and your organs are matched
when you’re both in the mood for a ….. cuddle.

How twisting a belt explains the Universe

Quantum physics is all about the simplest things in the universe. Matter – electrons and quarks (which make up neutrons and protons), and interactions – photons, forces etc.

The difference between the two is a simple rotation. It’s secret quantum mechanics knowledge, says head of ANU Dept of Quantum Physics, Professor Craig Savage.

Here he is proving it:

Filmed at Physics in the Pub ACT, 2016, August 17 at Smiths Alternative Bookshop