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According to TFA, the stimulated emission of light actually takes place in an indium phosphide (InP) laser diode. The laser diode is bonded to a silicon waveguide, which acts like a miniature optical fiber to guide the laser light around the chip. The "evanescence" is because the laser light is evanescently coupled from the laser diode into the waveguide. A proper description of evanescent coupling requires a pretty sophisticated understanding of electromagnetism, but the short version is that if you shine a laser beam parallel and adjacent (within a few microns) of a waveguide or optical fiber, some of the laser light will hop over and start propagating down the waveguide or fiber. In particular, by placing the actual laser parallel to and near a carefully-designed waveguide, you can have almost all of the laser light emitted into the waveguide, even though the constituent atoms of the waveguide are not emitting any light at all! For this reason, I think the name "silicon evanescent laser" is misleading since the silicon isn't emitting any light, and Roland Piquepaille's description of evanescent lasers is just flat out wrong. Getting silicon to emit light remains an extremely difficult task, and as far I know, no one has succeeded yet in getting silicon to convert electricity directly into laser light.

If anyone wants to read the Optics Express paper referenced in TFA, it's available online at http://www.opticsexpress.org/abstract.cfm?id=14097 3. However, that paper doesn't really define the term "evanescent laser" anywhere, so I had to go back to one of the research group's earlier papers to find a decent description of an evanescent laser and understand the physics of the device.

According to TFA, the stimulated emission of light actually takes place in an indium phosphide (InP) laser diode. The laser diode is bonded to a silicon waveguide, which acts like a miniature optical fiber to guide the laser light around the chip. The "evanescence" is because the laser light is evanescently coupled from the laser diode into the waveguide. A proper description of evanescent coupling requires a pretty sophisticated understanding of electromagnetism, but the short version is that if you shine a laser beam parallel and adjacent (within a few microns) of a waveguide or optical fiber, some of the laser light will hop over and start propagating down the waveguide or fiber. In particular, by placing the actual laser parallel to and near a carefully-designed waveguide, you can have almost all of the laser light emitted into the waveguide, even though the constituent atoms of the waveguide are not emitting any light at all! For this reason, I think the name "silicon evanescent laser" is misleading since the silicon isn't emitting any light, and Roland Piquepaille's description of evanescent lasers is just flat out wrong. Getting silicon to emit light remains an extremely difficult task, and as far I know, no one has succeeded yet in getting silicon to convert electricity directly into laser light.

If anyone wants to read the Optics Express paper referenced in TFA, it's available online at http://www.opticsexpress.org/abstract.cfm?id=14097 3. However, that paper doesn't really define the term "evanescent laser" anywhere, so I had to go back to one of the research group's earlier papers to find a decent description of an evanescent laser and understand the physics of the device.

In case anyone is wondering what a negative index of refraction would look like, this is a very good start:

http://www.opticsexpress.org/abstract.cfm?id=88325

Examples (including avi's) rendered in Povray, the free raytracer. One of the authors is Chris Hormann, one of Povray's main code contributors.

Of course they're looking for more grant funding. Everyone is, always. :)

At least at my school (and apparently at Georgia Tech as well), there's a separate "news office" that does the reports like this -- an internal "journalist" (or half reporter, half PR person) comes to the lab and interviews the professor when they get wind of something impressive/marketable. They write the article, based on background and specifics given by the professor. They distribute it, via the university's website and alumni magazine and possibly the student newspaper (if it's big enough).

That's why the "article" is credited to "Institute Communications & Public Affairs" rather than the individual lab, and why the "article" describes it as a "wavelength demultiplier". If the academics had prepared it, or even had approval on the final copy, they surely would've caught the mistake. (The question of why such "reputable" science bloggers as Roland Piquepaille didn't catch it is easily answered -- paraphrasing the PR is easier than condensing the actual article.)

I as well was wondering this. They reference this "film" repeatedly, and no film is shown on there, nor a link to it. FINALLY somebody that notices these things too. I'm usually the only one to see such greivous errors as mentioning a film yet not having one.

Lucky for you, I'm bored at work and have access to google's translation tools. It found a part of the university that did this, and it linked to a place that DOES have films:

Film: http://www.opticsexpress.org/abstract.cfm?URI=OPEX -11-25-3498

Just for reference, it was linked form here:
http://www.uni-bonn.de/Aktuelles/Presseinformation en/2003/455.html

> a screen would have to show different images depending on the angle

In theory you might be able to do that, using the same sort of principle as lenticular animations, with a holographic lens. For some applications you could get away with only doing it in two dimensions, so you show up clearly to anyone lying on the ground looking up at you silouetted against the sky, or anyone looking down at you from a staircase, but not to anyone with eyes at normal head level. Slightly more plausibly, you can be hidden from one particular person whose movements you track (using your magic nano-cameras) and show the image needed for their viewpoint only.

http://www.cl.cam.ac.uk/~nad/pubs/IBC99-Dodgson.pd f
http://kagakukan.toshiba.co.jp/en/02visual/newtech 101.html
http://www.opticsexpress.org/ViewMedia.cfm?id=8665 4&seq=0

If we want real scientific information to be available to the masses, we should get the scientific journals to publish their material online for free.

Good luck. Someone has to pay. If you want to do that you will need an author pays model, such as in Optics Express. Alternatively you could go to the arXiv, of course there, you won't get the "benefit" of peer review.

Then, not being scientificly trained in the appropriate field, how do you make any sense of what you are reading?

It's not such an easy problem to solve.

I'm not sure if anyone already posted the actual paper. ScienceBlog only links to itself and references a future printed publication. Well, here it is:

http://www.opticsexpress.org/abstract.cfm?URI=OPEX -13-1-82

Here is the link to the technical paper: http://www.opticsexpress.org/abstract.cfm?URI=OPEX -13-12-4560 Enjoy!

For those interested, here is the link to the published Optics Express article. Best of all, the full article is free to read.

here

I've seen something similar to this being done before by sending out very short but wide-angle pulses from a laser. By capturing an image with a high speed camera, only a thin slice (in the z-axis) of your scene will be illuminated at any time. By adjusting the timing between the pulse and the shutter, you will be able to control how far away the laser blink gets, and thus you will be able to create a continuous depth-map of the scene.

- jeps

Go to Optics Express and you will see an example of a reputable online scientific journal in action. Optics Express is becoming one of the most cited journals in the Optical Science community. It is peer reviewed and completely free to read. It is supported by publication page charges - i.e. the authors pay to have their work published in the journal.

The paper can be found at Optics Express. One can also find video of the tweezers in action.

Aaahhh! and it runs Linux. Mod me up.

("We are currently using a Linux operating system with custom drivers for the boards.")

Near-infrared neural imaging is already a very useful technique.

This is a new application whether or not you approve.
-j

Abouraddy,A., Saleh,B., Sergienko,A., and Teich,M. Quantum holography (PDF, 169KB, 8pages), Optics Express, 9, 498-505 (2001).

Read the damn thing (if you can :-)), then discuss.