”This is it—the paradigm shift,” archaeologist Chris Fisher told Ars. “Just like the advent of radiocarbon dating, LiDAR will have the same impact.”

LiDAR, or “light detection and ranging,” acts as a sort of radar with light, painting the target area with lasers and recording the time it takes to reflect back to the instruments.

An archaeologist specializing in Western Mexico, Fisher studies the way environments affect and change cultures. LiDAR has helped him repaint the picture of ancient Mexico, bringing the little-known Purepecha empire a lot more historical prominence.

(via Indiana Jones goes geek: Laser-mapping LiDAR revolutionizes archaeology) 

I don’t know about you, but when I think of lasers, I think of boxes on heavy, stabilized tables. Inside the boxes, the optical elements are mounted on stabilized mounts and everything is generally held as solidly in place as possible. The one thing that you generally don’t do is give a laser a good shaking. Unless it has already stopped working, in which case, have at it… preferably with a hammer.

Finding a paper that demonstrated a laser with better performance when it was being shaken compared to when it was held came as a bit of a shock.

The reason why the idea of shaking a laser is so shocking to me is that the lasers I am used to working with have optical elements that need to maintain a precise alignment with respect to one another. Temperature changes, vibrations, shaking, and “thumping the box to fix it” are all really bad ideas. But of course not all lasers are like this.

The laser in your laser pointer, CD, DVD, and Blu-Ray players are all monolithic devices. That is, they are made from a single piece of material, or materials, that are deposited on one another. You can obviously shake a laser pointer (much to the delight of cats), but this capability doesn’t scale. If you were to shake a laser pointer with acoustic waves that had a wavelength about the same size as the device (in the GHz range), then I would expect that things would probably go wrong rather quickly.

In most cases, at least. A group of researchers from Germany and Russia have now made a laser that works better when it is shaken. The reason why this occurs lies in the peculiar nature of the laser used by the researchers.

The laser that the researchers worked with was made from quantum dots (see side bar) embedded in a semiconductor material that had mirrors deposited on either side of it. This means that the distance between the two mirrors was extremely short. The researchers don’t state how big the distance was, but from the figures, I estimate that it wasn’t much longer than eight micrometers. For comparison, the wavelength emitted by the quantum dots was around 900nm.

(via A laser that works better shaken, not stirred)

Cloaking devices are one of the inventions of science fiction that have made a few tentative steps towards the real world in recent years. Now, researchers have moved the concept into the fourth dimension, creating a setup that hides a specific point in time from being perceived by observers. But if you want to make an event disappear, you have to act fast: right now, we can only hide a few picoseconds worth of time.

The cloaking devices we’ve made all work based on a similar principle: light that enters the device is bent in such a way that when it exits, its location and direction make it appear that the device itself, and anything within it, were not present. In other words, while within the device, light travels as if it were present. It’s just that, once it exits the other side, there’s no evidence that anything unusual has taken place. The same general idea governs the action of a temporal cloaking device.

The basic idea is that, when it’s not in operation, a light beam can pass through the cloaking device unhindered. When it’s switched on, a short temporal gap is opened up in the beam, then sealed back up on its way out of the hardware. One way to think of this is to view the light beam as a bit of old-fashioned magnetic tape. You can cut the tape so that a single instant of a recording can be physically separated. While separated, you can pass anything you want through the gap, but when you glue the tape back together, the recording is seamless. There’s only a before and after while the tape is cut and separated.

It’s easy to do that with tape, but a bit harder to do it with a beam of light. The key to the process is what’s being termed a split time lens, which is matched with a dispersive medium. When activated, the lens takes the light that comes before the point of cloaking and shifts it to bluer wavelengths, which travel faster through the dispersive medium than the base speed of the light in the same medium. At the cloak point, the lens switches, shifting the light beam to longer, redder wavelengths. These travel through the dispersive medium more slowly.

(via Optical setup helps researchers hide an event from time)

World’s first microlaser emitting in 3-D

If this is true, this is huge.

Versatile electronic gadgets should employ a number of important criteria: small in size, quick in operation, inexpensive to fabricate, and deliver high precision output. A new microlaser, developed at the Jožef Stefan Institute in Ljubljana, Slovenia embodies all these qualities. It is small, tunable, cheap, and is essentially the world’s first practical three-dimensional laser

As described in Optics Express, an open-access journal published by the Optical Society (OSA), Slovenian scientists Matjaž Humar and Igor Muševič have developed a microdroplet 3-D laser system in which laser light shines forth in all directions from dye molecules lodged within spherical drops of helical molecules dispersed in a liquid solution.

This is the first practical 3-D laser ever produced,” says Muševič, who expects that the microdroplet lasers, which can be made by the millions in seconds, will be used in making arrays of coherent light emitters. These will be handy for a variety of imaging purposes, for example “internal-source holography.” Here a 3-D laser would be embedded inside the object which is to be imaged; light coming directly from the source interferes with the light scattered by the surroundings. A three-dimensional image of the object can then be reconstructed from the interference pattern.

(Source: opticsinfobase.org)

German physicists create a ‘super-photon’

Physicists from the University of Bonn have developed a completely new source of light, a so-called Bose-Einstein condensate consisting of photons. Until recently, expert had thought this impossible. This method may potentially be suitable for designing novel light sources resembling lasers that work in the X-ray range. Among other applications, they might allow building more powerful computer chips. The scientists are reporting on their discovery in the upcoming issue of the journal Nature.

By cooling Rubidium atoms deeply and concentrating a sufficient number of them in a compact space, they suddenly become indistinguishable. They behave like a single huge “super particle.” Physicists call this a Bose-Einstein condensate.

For “light particles,” or photons, this should also work. Unfortunately, this idea faces a fundamental problem. When photons are “cooled down,” they disappear. Until a few months ago, it seemed impossible to cool light while concentrating it at the same time. The Bonn physicists Jan Klärs, Julian Schmitt, Dr. Frank Vewinger, and Professor Dr. Martin Weitz have, however, succeeded in doing this – a minor sensation.

How warm is light?

When the tungsten filament of a light bulb is heated, it starts glowing – first red, then yellow, and finally bluish. Thus, each color of the light can be assigned a “formation temperature.” Blue light is warmer than red light, but tungsten glows differently than iron, for example. This is why physicists calibrate color temperature based on a theoretical model object, a so-called black body. If this body were heated to a temperature of 5,500 centigrade, it would have about the same color as sunlight at noon. In other words: noon light has a temperature of 5,500 degrees Celsius or not quite 5,800 Kelvin (the Kelvin scale does not know any negative values; instead, it starts at absolute zero or -273 centigrade; consequently, Kelvin values are always 273 degrees higher than the corresponding Celsius values).

When a black body is cooled down, it will at some point radiate no longer in the visible range; instead, it will only give off invisible infrared photons. At the same time, its radiation intensity will decrease. The number of photons becomes smaller as the temperature falls. This is what makes it so difficult to get the quantity of cool photons that is required for Bose-Einstein condensation to occur.

And yet, the Bonn researchers succeeded by using two highly reflective mirrors between which they kept bouncing a light beam back and forth. Between the reflective surfaces there were dissolved pigment molecules with which the photons collided periodically. In these collisions, the molecules ‘swallowed’ the photons and then ‘spit’ them out again. “During this process, the photons assumed the temperature of the fluid,” explained Professor Weitz. “They cooled each other off to room temperature this way, and they did it without getting lost in the process.” 

A condensate made of light

The Bonn physicists then increased the quantity of photons between the mirrors by exciting the pigment solution using a laser. This allowed them to concentrate the cooled-off light particles so strongly that they condensed into a “super-photon.”

This photonic Bose-Einstein condensate is a completely new source of light that has characteristics resembling lasers. But compared to lasers, they have a decisive advantage, “We are currently not capable of producing lasers that generate very short-wave light – i.e. in the UV or X-ray range,” explained Jan Klärs. “With a photonic Bose-Einstein condensate this should, however, be possible.”

This prospect should primarily please chip designers. They use laser light for etching logic circuits into their semiconductor materials. How fine these structures can be is limited by the wavelength of the light, among other factors. Long-wavelength lasers are less well suited to precision work than short-wavelength ones – it is as if you tried to sign a letter with a paintbrush.

X-ray radiation has a much shorter wavelength than visible light. In principle, X-ray lasers should thus allow applying much more complex circuits on the same silicon surface. This would allow creating a new generation of high-performance chips - and consequently, more powerful computers for end users. The process could also be useful in other applications such as spectroscopy or photovoltaics.

Provided by University of Bonn (news : web)