Laser pulses turn water into ice – optics.org

On the face of it this doesn’t sound like much but the researchers hope to be able to use the results for optimize crystal growth.

Firing laser pulses into supercooled water creates ice crystals at specific locations in the liquid.

Using laser pulses to crystallise supercooled water into ice may seem counter-intuitive, but that’s exactly what researchers in Germany and the UK have achieved. Because the pulses can be focused to a specific point in the liquid, the researchers believe that their technique will be valuable for future material and crystal growth studies. (Physical Review Letters 99 045701)

Laser pulses turn water into ice – optics.org

Using Lasers to Peer Inside Cells

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Researchers at MIT’s George R. Harrison Spectroscopy Laboratory have developed a new use for laser interferometry that allows 3D images of the internal structure of cells to be created in just 0.1 seconds. Michael Feld and his team use the change in refractive index of a laser beam passing through the cell to create a series of 2D maps.

The researchers made their measurements using a technique known as interferometry, in which a light wave passing through a cell is compared with a reference wave that doesn’t pass through it. A 2D image containing information about refractive index is thus obtained.

To create a 3D image, the researchers combined 100 two-dimensional images taken from different angles. The resulting images are essentially 3D maps of the refractive index of the cell’s organelles. The entire process took about 10 seconds, but the researchers recently reduced this time to 0.1 seconds.

One major result of this research is we can now see the internal structure of cells without modifying the cells themselves through fixing or adding dyes.

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"When you fix the cells, you can’t look at their movements, and when you add external contrast agents you can never be sure that you haven’t somehow interfered with normal cellular function," said Badizadegan.

The current resolution of the new technique is about 500 nanometers, or billionths of a meter, but the team is working on improving the resolution. "We are confident that we can attain 150 nanometers, and perhaps higher resolution is possible," Feld said. "We expect this new technique to serve as a complement to electron microscopy, which has a resolution of approximately 10 nanometers."

Thanks to ScottY for the link.

Using holograms to diagnose astigmatism

image This is pretty cool and something that even hobbyist holographers could make.

Laser Focus World is reporting that researchers at New South Wales University have developed a holographic astigmatism test that’s faster to use than the lens-flipping "how does the chart look now?" test we’ve all endured when having our eyes checked.

The current method of looking at a distant object through a number of lenses to prescribe corrective glasses is at best cumbersome. In an alternate approach, the researchers recorded the wavefront emanating from various sunburst patterns located at different distances from the eye in a hologram. When a subject views through this hologram (illuminated by a plane wave), he or she will see the images of various sunburst patterns located at different distances from the eye.

Unfortunately there’s no additional information at the university site.  Perhaps they’ll put something up soon.

Optics.org has a bit more information and a few extra photos available.

My own flying death machine

I don’t have one of these babies yet but you can bet they’ll be on my Christmas list.

Laser tag is sweet. R/C helicopters are sweet. When you combine the two only good things can happen. That’s why I’m pretty amped about the news that a Chinese toy maker has armed its new R/C chopper with an IR transmitter and sensor, allowing for two to have laser dogfights in midair. If one gets hit, its power gets cut, sending it crashing to the ground. Cold blooded!

UK military targets civilians

Oops.

IT was not quite a Star Wars death ray, but air force Top Guns accidentally focused high-powered lasers on to a civilian car in May this year – potentially endangering the eyesight of peaceful earthlings.
RAAF F/A-18 fighters from the Williamtown base north of Newcastle were conducting exercises near the NSW mid-north coast town of Forster when the incident happened.

The pilots thought their laser targeting system was turned off for the training flight.

Unfortunately it wasn’t and the powerful light beams, known as class four lasers, were shone twice on to a road intersection for a total of 43 seconds.

Guys, remember to put your equipment into O.F.F mode first.

Graffiti by laser

I’d seen mention of this group before but never a description of how their laser tagging actually works.  Until I read the article in the NYT that is.

As Mr. Powderly neared the museum’s entrance, he jumped off the cycle and pointed it toward a bare stretch on a garage door across the street. Mr. Roth pulled a laser pointer from his pocket, and as he moved the laser’s green dot across the wall, a line of what looked like thick, drippy paint lit up its surface, roughly following the motion of his hand.

This actually sounds pretty darn cool.

Joining the crowd of cyclists, Mr. Powderly followed them as they moved through the honking streets of Brooklyn. In search of a spot to project their graffiti, they settled on the handball courts of McCarren Park in Greenpoint.

Mr. Powderly positioned the cycle to face the court’s gray concrete wall. Within a few minutes, someone had drawn a detailed sketch of a bicycle, and another person had traced an outline of an American flag.

Dance for me, little atom!

Do they wear dancing costumes?

Reuters reports that NIST has developed what may someday become a building block for quantum computing.

Suspended in laser light, thousands of atoms pair up and dance, each moving in perfect counterpoint to its partner. Porto’s team isolated pairs of atoms in a lattice of light formed by six laser beams all fixed on one point, suspending the atoms in a uniform pattern. "There is no container. It is levitated by the laser beams."

Continue reading “Dance for me, little atom!”

More Teleportation?

It won’t be coming any sooner than the last time I mentioned researchers teleporting atoms but researchers in Australia have proposed a way to teleport atoms from one location to another.

The full paper is available here as well as an animated description here.

What differentiates our scheme from what is usually termed quantum teleportation is that our scheme does not require the sender and receiver to share entangled states, as there is no measurement step involved in sending the information.

In this scheme the sender and receiver require a reservoir of extremely cold atoms, known as a Bose-Einstein condensate (BEC).

BEC is a state of matter that occurs when atoms become very cold, (about 100 billionths of a degree about absolute zero).

Due to a phenomenon known as Bose-Enhancement, all the atoms like to act the same way. This causes the atoms to act as one macroscopic matterwave, rather than a collection of individual atoms.

Laser fusion

image The proposed European High Power Laser Energy Research (Hiper) facility — a device intended to demonstrate the feasibility of laser-driven fusion as an energy source — is entering the preparation phase after completion of a two-year study by an international team of scientists.

As reported by Photonics.com

Fusion energy is an attractive, environmentally clean power source using sea water as its principal source of fuel. No greenhouse gases and long-lived radioactive waste are produced. Demonstration of the scientific proof of principle is expected between 2010 and 2012 as part of an ongoing international program. What is now needed is to move from the scientific proof of principle stage to a commercial reactor. HiPER provides the critical next step along this route.

New laser star

image An artificial, laser-fed star now shines regularly over the sky of Paranal, home of ESO’s Very Large Telescope, one of the world’s most advanced large ground-based telescopes. This system provides assistance for the adaptive optics instruments on the VLT and so allows astronomers to obtain images free from the blurring effect of the atmosphere, regardless of the brightness and the location on the sky of the observed target. Now that it is routinely offered by the observatory, the skies seem much sharper to astronomers.