Meet ADAM: A Laser System that Protects Our Troops from Bad Guy Missiles


I can’t get over how crazy the development of military laser technology has been lately.  There’s been a real push to create a competitor for projectile weapons.  For example, earlier this week I talked about the new German Phalanx-style laser weapon that kills drones and little metal balls from the sky.  At one time before it was abandoned, the US Air Force was working on something called the YAL-1, which was a 747 mounted with a chemical laser that was designed to kill nuclear ICBMs from a long, long distance.  I thought it was actually pretty cool, but I can understand why it was scrapped; my assumption is that they’re holding out for a more multi-burst solid state laser instead of a single-shot, highly dangerous chemical laser.


I have to say that at one point in my life I was pretty frustrated that more money goes into military laser tech than goes into scientific research and development, or even medical laser development.  However, what I realized was that as this technology becomes more readily available via all of this defense money solving big problems up front, less than death uses and systems will “come out in the wash,” as an old colleague usually says.  Just like anything else that we steal from military technology (cable bundling, for example), at some point laser technology from military development will make its way to the civilian and private sector development.

One such system is something that Lockheed Martin calls ADAMArea Defense Anti-Munitions.  This system is designed to be towed into a hostile area where the US has set up a Forward Operating Base, or FOB, in enemy territory.  While our guys sleep and stand guard and all of those things, ADAM is watching over the area, blanketing it with radar that’s watching out for munitions coming into the area from enemy forces — mortar shells, shoulder-fired missiles, etcetera — and destroys the incoming round with a laser.  Check this out, this is a prototype test of a rocket being fired at the ADAM:

Ok, that is insane.  So right now, a system exists that can detect incoming enemy rockets and shells to a base.  Can you imagine what would happen if you were to deploy a handful of these systems across a battlefield?  That sounds like it would be a pretty awesome sight.  From a press release at Lockheed Martin’s website, they’ve also tested the ADAM against drones (UAVs, or Unmanned Aerial Vehicles) and small caliber shells:

Since August, the ADAM system has successfully engaged an unmanned aerial system target in flight at a range of approximately 1.5 kilometers (0.9 miles) and has destroyed four small-caliber rocket targets in simulated flight at a range of approximately 2 kilometers (1.2 miles).

“Lockheed Martin has invested in the development of the ADAM system because of the enormous potential effectiveness of high-energy lasers,” said Doug Graham, Lockheed Martin’s vice president of advanced programs for Strategic and Missile Defense Systems. “We are committed to supporting the transition of directed energy’s revolutionary capability to the war fighter.”

Designed for short-range defense of high-value areas including forward operating bases, the ADAM system’s 10-kilowatt fiber laser is engineered to destroy targets up to 2 kilometers (1.2 miles) away. The system precisely tracks targets in cluttered optical environments and has a tracking range of more than 5 kilometers (3.1 miles). The system has been designed to be flexible enough to operate against rockets as a standalone system and to engage unmanned aerial systems with an external radar cue. The ADAM system’s modular architecture combines commercial hardware components with the company’s proprietary software in an integrated and easy-to-operate system.

Here’s a video of the test they’re talking about, where ADAM shoots down a drone:

I for one am pretty excited to see what happens next.  This could lead to some amazing advancements in light.


Thanks Business Insider, Army Recognition!

In Germany, It’s the Drones that Get Struck – BY A LASER

When I was a kid, I was always so fascinated with my father’s work.  My Dad was in the Navy, a Senior Chief Machinist’s Mate (MMCS), and he always has great stories about his days aboard a ship at sea bound for war.  When you’re a kid, the strangest things fascinate you.  I was always so very fascinated by Dad’s stories of the different systems at work on a Navy ship.  My Dad was the guy who ran the Engine Rooms.  I grew up reading about super-hot steam, hydraulic pressure that would squeeze an elephant into a thin film, and obviously Navy weapons.  If you don’t think about what military weapons systems are really made for, they’re really unbelievably cool.


One of those technologies was a weapons system called the Phalanx CIWS, or Close-In Weapons System.  The Phalanx was made by General Dynamics back in the late 1970’s, with contractor Raytheon taking a contract to improve the weapons system a few years ago.  Apparently this system has come a long way — I asked my father to describe what his experience was with the weapon since he was on a few shops that had it in its infancy back in the 1970’s:

“The gun sounded like a large weed eater/lawn mower; extremely loud, running past its governor, with lotsa fire and smoke.  Also, when locked on a target it was deadly.”  I asked Dad to clarify what “running past its governor” meant, and he said that the gun would overspeed to the point where you thought it might come apart.  Sounds like it’s come a long way!

What these are used for is generally for protecting the ship of anything that gets past the outer defensive systems on a ship — typically high speed flying missiles.  So, just in case you need a little more explanation, the Phalanx is used to shoot missiles out of the sky that have been fired at the ship.  What makes all of this relevant is what exactly this thing is made of, and a new upgrade that the Germans have developed.  First and foremost, check this out — it’s a video of the Phalanx CIWS firing at a target.  Keep in mind that we’re talking about a weapon that fires 4,500 rounds per minute at a target, tracking it with unbelievable speed and accuracy.  It’s a Gatling Gun that fires 20mm depleted Uranium bullets.  Watch this:

This particular Phalanx system is mounted on the ground:

This one, however, is mounted on a ship:

Now you know all of this hullaballoo that we’ve been hearing on Drones and Drone Strikes lately?  I mean, it has been all over every freaking television and news channel from here to Al Jazeera.  Imagine one of those Phalanx CIWS systems now with a 50kW laser attached to it instead of the 4,500 bullets per minute that it fires.  How do you think that would be in the movies?  Pretty cool?

No need to wait to see it in the movies.  That sh*t is already here, and guess who invented it?  Germany.  Check this video out of a laser-mounted Phalanx-type system shooting down a drone from over 2km:

The German company who made this amazing thing, called Rheinmetall Defence, has created quite the science fiction scenario – a laser that can shoot drones out of the sky from over 3km away.  If that isn’t impressive enough, the German-made system went for broke on their big impressive grand finale, shooting and destroying an 80mm steel ball traveling at 50 meters per second.  That’s quite smaller than a drone and about 50 times as fast.  But, no match for this German death ray machine!


You might notice two ports on the front of that mammoth thing — it’s a 50kW laser that is run into a combiner that takes a 20kW beam and a 30kW beam and combines them to a 50kW beam!  It’s mounted on a platform similar to that of the Phalanx, and it’s got radar that rivals that of the Phalanx – in short, it is one bad mothertrucker.  The Germans also have plans in the works to produce a 60kW and a 100kW model of the mega-laser that includes a 35mm Gatling cannon as well as the big drone-killing laser.  Overkill?  Who knows.  When it comes to keeping our American sailors safe, I’m sure that most families will say that both is the best way to go.  Even now on some ships the Phalanx is tied to a missile system called a RAM missile, or Rolling Airframe Missile.  The RAM missile is a comglomeration between a Sidewinder and a Stinger missile — you’ve probably heard of these in the movies, right?

From a post at Singularity Hub:

The system isn’t actually a single laser but two laser modules mounted onto Revolver Gun air defense turrets made by Oerlikon and attached to additional power modules. The laser modules are 30 kW and 20 kW, but a Beam Superimposing Technology (BST) combines two lasers to focus in a “superimposed, cumulative manner” that wreaks havoc on its targets.

First, the system sliced through a 15mm- (~0.6 inches) thick steel girder from a kilometer away. Then, from a distance of two kilometers, it shot down a handful of drones as they nose-dived toward the surface at 50 meters per second. The laser’s radar, a widely used system called Skyguard, was capable of tracking the drones through their descent up to three kilometers away.

After successfully testing their 50kW laser system, Rheinmetall Defense has its sights on a truck-mounted mobile system with 100kW of metal-slicing power.

For its finale, the laser’s ability to track a very small ballistic target was demonstrated. It honed in on and destroyed a steel ball 82mm in diameter traveling at 50 meters per second. The small ball was meant to simulate an incoming mortar round. Rheinmetall says their laser will reduce the time required for C-RAM – Counter Rocket, Artillery, and Mortar measures – to a matter of seconds, even in adverse weather conditions. In fact, weather at the Ochsenboden Proving Ground in Switzerland where the demonstration was carried out included ice, rain, snow, and extremely bright sunlight – far from ideal.


Thanks to Singularity Hub, Motherboard, and DailyTech!


When you see Eric Standley’s work, there are some things you must remember:

  1. Yes, these things really exist;
  2. It took Eric Standley a long, long time to make them;
  3. they are multiple layer, multi-dimensional laser cut pieces.

Now that we’re over that, check this out:


Eric Standley apparently has lots of Islamic, Gothic, and almost Buddhist inspiration in these pieces, or at least that’s what the artist wants us to think:






Laser cutting, supreme style.  I think that’s like Animal Style, but with more awesome.  Check out other of Eric Standley’s works at his website, there are lots of wonderful pieces there!

Thanks, 50 Watt!

Laser Tattoo Removal?! It’s Like A SKIN ERASER!

First — no, I’m never getting my tattoos removed, and yes, I plan on getting both sleeves!  A friend sent me a link, and boom — there was a dude getting his tattoos removed.  Take a moment and check this out, it is actually quite amazing:


This process of laser tattoo removal is called laser ablation, or even better — selective photothermolysis.  That’s certainly a five dollar word, isn’t it?  If you break it down it’s pretty simple:  photo means light, thermo means heat, and lysis means destruction.  So destruction using light and heat.  Can you dig it?  To put this into perspective of, say, the entertainment industry, laser ablation is used to make glass and/or metal gobos, and can be done with ridiculous precision.  Ridiculous.  Laser Ablation is something that typically uses a pulsed laser because of its high power; when something is laser ablated, the power and temperature is usually at such a magnitude that the material being removed is often plasma-fied or just vaporized altogether.

Wanna get really nerdy with me?  I also checked out a paper called Optimizing Outcomes of Laser Tattoo Removal, talking about different wavelengths and laser types.  Yes, it’s interesting!

Hey, did I mention that video above has a guy basically getting his tattoos erased?!

Thanks, LikeCool

LIDAR Helps Scientists Add Mass to Dinosaurs

…and all of it without having to use the strawberry milkshake protein powder that I got from Walmart.  That stuff was horrible!!!

One of my favorite laser publications,, posted this awesome article — dinosaur skeletons, LIDAR, and imagining the mass of dinosaurs when they were alive.  The article is pretty cool, check it out here.

From the article:

A team at the University of Manchester has developed a new method for doing so that shows promise, by applying a lidar scanning technique to one of the largest mounted dinosaur skeletons in the world. The findings are published in Biology Letters.

Starting from the principle that the best estimates of dinosaur mass come from a volumetric approach, whereby a model of the animal is created and its mass then calculated via its density, the team scanned a complete skeleton using a lidar scanner supplied by Z+F, specialists in laser scanning and data capture.

I had to know more about this LIDAR business — LIDAR means Light Detection and Ranging.  From the wikipedia:

In general there are two kinds of lidar detection schema: “incoherent” or direct energy detection (which is principally an amplitude measurement) and Coherent detection (which is best for doppler, or phase sensitive measurements). Coherent systems generally use Optical heterodyne detection which being more sensitive than direct detection allows them to operate a much lower power but at the expense of more complex transceiver requirements.

In both coherent and incoherent LIDAR, there are two types of pulse models: micropulse lidar systems and high energy systems. Micropulse systems have developed as a result of the ever increasing amount of computer power available combined with advances in laser technology. They use considerably less energy in the laser, typically on the order of one microjoule, and are often “eye-safe,” meaning they can be used without safety precautions. High-power systems are common in atmospheric research, where they are widely used for measuring many atmospheric parameters: the height, layering and densities of clouds, cloud particle properties (extinction coefficient, backscatter coefficient, depolarization), temperature, pressure, wind, humidity, trace gas concentration (ozone, methane, nitrous oxide, etc.).[1]

There are several major components to a LIDAR system:

  1. Laser — 600–1000 nm lasers are most common for non-scientific applications. They are inexpensive, but since they can be focused and easily absorbed by the eye, the maximum power is limited by the need to make them eye-safe. Eye-safety is often a requirement for most applications. A common alternative, 1550 nm lasers, are eye-safe at much higher power levels since this wavelength is not focused by the eye, but the detector technology is less advanced and so these wavelengths are generally used at longer ranges and lower accuracies. They are also used for military applications as 1550 nm is not visible in night vision goggles, unlike the shorter 1000 nm infrared laser. Airborne topographic mapping lidars generally use 1064 nm diode pumped YAG lasers, while bathymetric systems generally use 532 nm frequency doubled diode pumped YAG lasers because 532 nm penetrates water with much less attenuation than does 1064 nm. Laser settings include the laser repetition rate (which controls the data collection speed). Pulse length is generally an attribute of the laser cavity length, the number of passes required through the gain material (YAG, YLF, etc.), and Q-switch speed. Better target resolution is achieved with shorter pulses, provided the LIDAR receiver detectors and electronics have sufficient bandwidth.[1]
  2. Scanner and optics — How fast images can be developed is also affected by the speed at which they are scanned. There are several options to scan the azimuth and elevation, including dual oscillating plane mirrors, a combination with a polygon mirror, a dual axis scanner (see Laser scanning). Optic choices affect the angular resolution and range that can be detected. A hole mirror or a beam splitter are options to collect a return signal.
  3. Photodetector and receiver electronics — Two main photodetector technologies are used in lidars: solid state photodetectors, such as silicon avalanche photodiodes, or photomultipliers. The sensitivity of the receiver is another parameter that has to be balanced in a LIDAR design.
  4. Position and navigation systems — LIDAR sensors that are mounted on mobile platforms such as airplanes or satellites require instrumentation to determine the absolute position and orientation of the sensor. Such devices generally include a Global Positioning System receiver and an Inertial Measurement Unit (IMU).

This scanning technology is actually pretty widely used all over the place — along with terrestrial map data from suppliers, the GPS companies’ travel vans are mostly fitted with LIDAR scanners.  These scanners are actually pretty cool – the company listed in the article, Z+F UK, has some particularly interesting looking devices!  Also, Radiohead apparently used lots of LIDAR capture to film their House of Cards video.  Here’s a bit of them doing some scanning work:

Crazy.  Also, if you’re one of those nerds like me who likes to comb through the images and content on places like NOAA and see the output from satellites at the various observation stations, check out the LIDAR stuff at the USGS (US Geological Survey) website.

Cars With Fricken Laser Beams

Ok, so maybe not quite.

However, this is still neat: The BMW Group has been developing laser headlights for vehicles. With intensity a thousand times, a fuel consumption at less than half even their current LEDs, and a size one hundred times smaller, the desire to develop this technology is quite self-explanatory.

This opens up all sorts of new possibilities when integrating the light source into the vehicle. The BMW engineers have no plans to radically reduce the size of the headlights however, although that would be theoretically possible. Instead, the thinking is that the headlights would retain their conventional surface area dimensions and so continue to play an important role in the styling of a BMW, while the size advantages could be used to reduce the depth of the headlight unit, and so open up new possibilities for headlight positioning and body styling.

The laser diodes used originally emit blue, but through interacting with a fluorescent phosphor is converted to a “pure white light.” BMW highlights the safety of the lasers for all road users profusely in their press release. The laser headlight technology would be compatible with BMW’s LED “Dynamic Light Spot” which is an intelligent, targeted illumination of obstacles.

Further knowledge: For design geeks, the film Objectified is a fantastic documentary, in which Chris Bangle of the BMW group speaks on industrial design. As if that’s not enough, Apple’s stud muffin Sir Jonathan Ive talks about robust aluminium.


Laser Powered Broadband? In Space? Wait. What?

Ok, there is something very interesting taking place with NASA this month.  On September 23, NASA decided to approve three projects that are being called “Technology Demonstration Projects.”  A space-based optical communication system (which is what I find the most exhilarating), a deep space atomic clock, and a big ol’ space sail.  From the NASA Office of the Chief Technologist‘s office:

NASA has selected three proposals as Technology Demonstration Missions that will transform its space communications, deep space navigation and in-space propulsion capabilities. The three Space Technology projects will develop and fly a space solar sail, a deep space atomic clock, and a space-based optical communications system. These crosscutting flight demonstrations were selected because of their potential to provide tangible, near-term products and infuse high-impact capabilities into NASA’s future space exploration and science missions. By investing in high payoff, disruptive technologies that industry does not have in-hand today, NASA matures the technologies required for its future missions while proving the capabilities and lowering the cost for other government agency and commercial space activities. 

Ok.  Personal commentary?  What a weird three projects to say “Hey, don’t take our money away, you crazy Congress people and President Obama, we’re NASA.”  I can see the space based laser communication system, that’s pretty cool.  Now granted no one asked me (and I know better that’s probably the main cause we don’t have a space-based laser that can scratch your back), but I’m sure there is reasoning behind these other two projects.  Right?


Check this out – again,. from the press release at NASA – it’s about this big space laser data communication thingie, called the  Laser Communications Relay Demonstration Mission:

Led by the NASA Goddard Space Flight Center in Greenbelt, MD, the Laser Communications Relay Demonstration (LCRD) will demonstrate and validate a reliable, capable, and cost effective optical communications technology for infusion into operational near earth and deep space systems. The Space Communications and Navigation (SCaN) office in the Human Exploration and Operations Mission Directorate is collaborating with the NASA Office of the Chief Technologist in sponsoring this technology demonstration. 

Optical communications (also known as laser communication – lasercom) is a transformative technology that will enable NASA, other government agencies and the commercial space industry to undertake future, complex space missions requiring increased data rates, or decreased mass, size, and power burdens for communications. For approximately the same mass, power, and volume, an optical communications system provides significantly higher data rates than a comparable radio frequency (RF) system. 

High-rate communications will revolutionize space science and exploration. Data rates 10-100 times more capable than current RF systems will allow greatly improved connectivity and enable a new generation of remote scientific investigations as well as provide the satellite communication’s industry with disruptive technology not available today. Space laser communications will enable missions to use bandwidth-hungry instruments, such as hyperspectral imagers, synthetic aperture radar (SAR), and other instruments with high definition in spectral, spatial, or temporal modes. Laser communication will also make it possible to establish a “virtual presence” at a remote planet or other solar system body, enabling the high-rate communications required by future explorers. 

As an example, at the current limit of 6 Mbps for the Mars Reconnaissance Orbiter (MRO), it takes approximately 90 minutes to transmit a single HiRISE high resolution image back to earth. In some instances, this bottleneck can limit science return. An equivalent MRO mission outfitted with an optical communications transmitter would have a capacity to transmit data back to earth at 100 Mbps or more, reducing the single image transmission time to on order of 5 minutes. 

The LCRD mission will:

  • Enable reliable, capable, and cost effective optical communications technologies for near earth applications and provide the next steps required toward optical communications for deep space missions
  • Demonstrate high data rate optical communications technology necessary for:
    • Near-Earth spacecraft (bi-directional links supporting hundreds of Mbps to Gbps)
    • Deep Space missions (tens to hundreds of Mbps from distances such as Mars and Jupiter)
  • Develop, validate and characterize operational models for practical optical communications
  • Identify and develop requirements and standards for future operational optical communication systems
  • Establish a strong partnership with multiple government agencies to facilitate crosscutting infusion of optical communications technologies
  • Develop the industrial base and transfer technology for future space optical communications systems

Ok, now that does sound pretty cool.

How do you feel about these projects?  Worth the money?  NOT worth the money?  Leave a comment below!

Crazy Friday Science: Mini-Interview with Sonja Franke-Arnold on Rotary Photon Drag

I wrote an article about a paper I read in the journal Science a few weeks ago – the article was about Rotary Photon Drag Enhanced by A Slow Light Medium.  I got two handfuls of emails about the article, so I got in contact with one of the original paper’s editors, Sonja Franke-Arnold.  When you have questions, it’s best to go to the source!  Hi Sonja, welcome to! I’m very interested in your research, and we’ve gotten a lot of interesting response to the post I wrote on your paper, “Rotary Photon Drag Enhanced by a Slow-Light Medium.”  Can you take a moment and give us a bare-bones layperson’s look at what you and your team has discovered? What exactly has happened here in your experiment?

Sonja Franke-Arnold:  We were wondering how the world looks like through a spinning window!  About 200 years ago Augustin-Jean Fresnel predicted that light can be dragged if it travels through a moving medium. If you were to spin a window faster and faster, the image would actually be slightly rotated as the light is dragged along with the window. However, this effect is normally only some millionth of a degree and imperceptible to the eye.

We managed to increase the image rotation by a factor of about a million to an easily noticeable rotation of up to 5 degrees. This happened by slowing the light down to roughly the speed of sound during its passage through the “window” (in fact a ruby crystal). The light therefore spent a longer time in the ruby rod and could be dragged far enough to result in an observable image rotation.  Can you explain the significance of the wavelength of light you used? Why was 532nm (green) used for the experiment?

Sonja Franke-Arnold:  This wavelength excites a transition within the ruby crystal (the same that is also used in ruby lasers). Light at 532nm is absorbed and excites an atomic level with a very long (20 millisecond) lifetime. This allows to “store” the energy of the photon as an internal excitation of the rotating ruby crystal – generating slow light.  Tell me about the significance of the shape of the coherent beam in the experiment – was the shaped beam simply to observe a change in the image, or was a different purpose considered?

Sonja Franke-Arnold:  We used an elliptical light beam for two reasons, one of these is to define the image rotation angle as you suggested. The elliptical beam travelling through the spinning ruby rod however also plays an important part in making the slow light itself: At any particular position of the ruby, the elliptical light – spinning with respect to the ruby – looks like an intensity modulation. The varying intensity produces a large refractive index of about one million which slows the light down from the speed of light to roughly the speed of sound – a method pioneered by our co-worker Robert Boyd.  Could you give a few examples of uses for this discovery? How can the general populous relate to what this discovery really means for light and photonics?

Sonja Franke-Arnold:  For me, the main highlight was that we managed to observe a 200 year old puzzle – that images are indeed dragged along with rotating windows. We are now working on possible applications in quantum information processing: our image rotation preserves not only the intensity but also the phase of the light and could therefore be used to store and rotate quantum images. Access to the angle of an image could allow a new form of image coding protocol.

Thanks so much, Sonja!  Very cool paper for those of us nerds out here!

Laser Goofing, JimOnLight Style

I was a fairly big laser nerd before I met Rick Hutton, but after becoming friends with THAT mega-nerd, I have begun to really get into lasers and the whole use of coherent light.  I think one of the highlights of 2011 so far was hitting Photonics West with Ocean Optics and SeaChanger and walking the laser show floor with Rick.  You see, I see the term mega-nerd as about the best compliment you could give a person.

I have been goofing a bit with my 1W blue (445nm), my 10mW HeNe (632.8nm), and a Coherent Radius 405 (violet, 405nm) I picked up pretty cheap on eBay.  I also have a ton of amazing optics and bench components that I was given by the great folks at InLight Gobos and Laser Surplus Sales.  I want to make some fun art with the stuff that I have, and as I acquire more, and one of these days I’ll save up and get a 5W Argon laser (oh HELL yes) and I’ll build some crazy system of galvos and any other crackadelic thing I can come up with to occupy my non-working, non-sleeping time.

I can’t afford the several thousand dollars for a decent laser breadboard for my hobby, so I pulled a DIY and built my own out of two chunks of fine-grade pine that I glued together and fastened with a few large gauge fasteners.  It cost me about 40 bucks total, which is a lot less than $1977.74, let me tell you.  I have about a 16th of an inch deflection over the course of the surface of the table, a grid of holes drilled on one inch centers over a 24″ x 60″.

Just a few teaser shots – I’m oretty bummed at the loss of my DSLR, my little 12MP Elph just ain’t cutting it with this specific wavelength photography:


Holy sh*t I love lasers. Wear your laser safety glasses, kids!

Rotary Photon Drag Enhanced by a Slow-Light Medium. Right? Right.

Remember that scene in the Jody Foster movie called Contact when they got all of those drawings of “the machine?”  There was a part of the movie where Ellie realized that the images were encoded somehow, and the key to encoding them was by looking at them in three dimensions.  Remember that minute little detail?

I read an article on this just the other day, and after I read the entire article in the journal Science, I really want to share the gist of this thing with you all.  It totally reminds me of this for some reason.  I was explaining this all to a friend on Skype, and I got tired of typing, and then the researcher slice of my brain started going ape-sh**.  Pardon me.

First, read the abstract of the article written by Sonja Franke-Arnold (School of Physics and Astronomy (SUPA), University of Glasgow, Scotland), Graham Gibson and Robert W. Boyd (Department of Physics, University of Ottawa, Ottawa, Canada), and Miles J. Padgett (The Institute of Optics and Department of Physics and Astronomy, University of Rochester, Rochester, NY):

Transmission through a spinning window slightly rotates the polarization of the light, typically by a microradian. It has been predicted that the same mechanism should also rotate an image. Because this rotary photon drag has a contribution that is inversely proportional to the group velocity, the image rotation is expected to increase in a slow-light medium. Using a ruby window under conditions for coherent population oscillations, we induced an effective group index of about 1 million. The resulting rotation angle was large enough to be observed by the eye. This result shows that rotary photon drag applies to images as well as polarization. The possibility of switching between different rotation states may offer new opportunities for controlled image coding.

Ok, got it?  Yeah, read it a few times, but generally the concept of the experiment is pretty simple, and the results are very interesting!  What these folks were doing was shining a shaped, collimated beam of light through a spinning ruby disk rotating at a given speed – in this case a maximum of 30 cycles per second.  The ruby disk causes a bit of “drag” on the photons travelling through it, causing the light to refract and exhibit some interesting behavior.  Check out this little video, from the paper and from the journal Science:

to view the .MOV file, click here

Ruby has a heavy Index of Refraction, which means the light is slowed down (refracted) at a rate of X when it leaves the air and enters the ruby itself.  If you imagine the 1.0 value of the Index of Refraction as how light travels through regular ol’ air (and not taking into account humidity, pollution, or any of that schtuff), anything greater than 1.0 is refracting.  Diamond has an Index of Refraction of about 2.42, and Ruby’s Index of Refraction is about 1.77.  Ruby refracts less than diamond.  Make sense if you didn’t already get it?

Here’s the weird thing – Ruby is not what we consider isotropic – meaning that no matter what the incidence angle is and no matter what the orientation of the crystal is, the light travels through the crystalline matrix equally as it travels through the medium.  Glass, sodium chloride crystals, and a lot of polymers exhibit this kind of “perfect” structure.  Sodium chloride is basically a cubic structure, relatively perfectly bonded in a cube matrix.  Ruby, on the other hand, is an anisotropic crystalline structure, meaning that there are more than one axes that are different within the structure of the crystal matrix.

Here’s a good image of the difference between an isotropic and anisotropic crystal structure, optically, from Olympus America’s Microscopy Resource Center.  Figure A is a sodium chloride crystal, which is isotropic.  Figure B is a calcite crystal, which has calcium ions and carbonate ions in it.  Calcite is anisotropic.  Check it:

Ok – now if you think of a crystal structure with light shining through its matrix, and the light is going to pass through two different planes of refraction, essentially – what do you expect to happen to one beam of light as it enters the anisotropic crystal structure and slows down?

Who said it’s going to split into two beams?  (DJ Lemma, pout your hand down, I know you already know the answer!)  You’d be correct – the incident beam splits into two beams, each sort-of along that individual crystal plane.  Take a look at this image of a calcium carbonate crystal, and how it is creating a double image:

This phenomenon is called birefringence.  Deep breath – bi-re-frin-gence.  Ruby, the gem used in the experiment, is also an anisotropic crystal, and it exhibits traits of birefringence.

So, imagine taking that birefringent crystal disk, spinning it at a relatively high rate (30 Hz), and shining a very specific wavelength of light (ie, a laser), that is in a certain shape through the ruby disk as it spins.  A bunch of stuff was discovered with this experiment, all related to the image.  The generalities of the experiment, as I paraphrase, is that the group shone a very bright laser with a square-ish shape through the ruby disk, noted the position that the laser had ont he other side of the ruby disk after it was on the other side of the disk.  When you shine a shaped laser beam at 532 nanometers (green) through a spinning ruby disk (which is a very slow-light medium, slowing the light down to just a few tens of meters per second) spinning at a rate between not spinning and 30 rotations per second, the image refracts from about a third of a degree to about ten degrees as the ruby disk increases from slow revolutions per second to thirty revs per second.

What a crazy experiment, huh?  I needed a good dose of photonics and optics in my Thursday!

The ramifications of this experiment have to do with encoding images with extra data – if you can imagine an image that has more information in it depending on which way the image is spinning, that is some trippy Minority Report shizzyhizzle.  “Oh, you’ve stolen my image!  But since you don’t know which wavelength to use and at which speed to spin the image, you’ll never decode my super secret plans of world domination!!!

Yeah, I have a vivid imagination.

HUGE number of thanks:
the journal Science
the Index of Refraction of Ruby and Sapphire (actually a very cool fact doc, check it out!)