Metasurface Design Methods Can Make LED Light Act More Like Lasers

June 18, 2020 by 33 Comments

Light-emitting diodes (LEDs) are not exactly new technology, but their use over time has evolved from rather dim replacements of incandescent signal lights in control panels to today’s home lighting. Although LEDs have the reputation of being power-efficient, there is still a lot of efficiency to be gained.

UC Santa Barbara researchers [Jonathan Schuller] and his team found that a large number of the photons that are generated never make it out of the LED. This means that the power that was used to generate these photons was essentially wasted. Ideally one would be able to have every single photon successfully make it out of the LED to contribute to the task of illuminating things.

In their paper titled ‘Unidirectional luminescence from InGaN/GaN quantum-well metasurfaces‘  (pre-publication Arxiv version) they describe the problem of photon emission in LEDs. Photons are normally radiated in all directions, causing a ‘spray’ of photons that can be guided somewhat by the LED’s packaging and other parameters. The challenge was thus to start at the beginning, having the LED emit as many photons in one direction as possible.

Their solution was the use of a metasurface-based design, consisting out of gallium nitride (GaN) nanorods on a sapphire substrate. These were embedded with indium gallium nitride (InGaN) quantum wells which emit the actual photons. According to one of the researchers, the idea is based on subwavelength antenna arrays already used with coherent light sources like lasers.

With experiments showing the simulated improvements, it seems that this research may lead to even brighter, more efficient LEDs before long if these findings translate to mass production.

(Thanks, Qes)

Burning Things With Big Lasers In The Name Of Security

January 29, 2020 by 4 Comments

Several fields of quantum research have made their transition from research labs into commercial products, accompanied by grandiose claims. Are they as good as they say? We need people like Dr. Sarah Kaiser to independently test those claims, looking for flaws in implementation. At the 2019 Hackaday Superconference she shared her research on attacking commercially available quantum key distribution (QKD) hardware.

Don’t be scared away when you see the term “quantum” in the title. Her talk is very easy to follow along, requiring almost no prior knowledge of quantum research terminology. In fact, that’s the point. Dr. Kaiser’s personal ambition is to make quantum computing an inviting and accessible topic for everyone, not just elite cliques of researchers in ivory towers. You should hear her out in the video below, and by following along with the presentation slide deck (.PPTX).

Quantum Key Distribution

So why is QKD is so enticing? Unlike existing methods, the theoretical foundation is secure against any attacker constrained by the speed of light and the laws of physics.

Generally speaking, if your attacker is not bound by those things, we have a much bigger problem.

But as we know well, there’s always a difference between the theoretical foundation and the actual implementation of cryptography. That difference is where exploits like side-channel attacks thrive, so she started investigating components of a laser QKD system.

As a self-professed “Crazy Laser Lady”, part of this investigation examined how components held up to big lasers delivering power far outside normal operating range. This turned up exciting effects like a fiber fuse (~17:30 in the video) which is actually a plasma fire propagating through the fiber optic. It looks cool, but it’s destructive and useless for covert attacks. More productive results came when lasers were used to carefully degrade select components to make the system vulnerable.

If you want to learn more from Dr. Kaiser about quantum key distribution, she has a book chapter on the topic. (Free online access available, but with limitations.) This is not the first attempt to hack quantum key distribution, and we doubt it would be the last. Every generation of products will improve tolerance to attacks, and we’ll need researchers like our Crazy Laser Lady to find the reality behind advertised claims.

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Use Blueprint Process To Print On Fabric With Lasers

December 18, 2019 by 11 Comments

[Shih Wei Chieh] has built a laser cyanotype printer for fabrics. You know, for art!

How do you get an inkjet head on a shoe or a couch? Most printing processes require a flat surface to print. But hearkening back to the days when a blueprint was a blueprint, a mixture of an iron salt and an acid are mixed and applied to a surface an interesting reaction occurs when the surface is exposed to UV light. The chemicals react to form, of all things, prussian blue. After the reaction occurs simply washing away the remaining chemicals leaves a stable print behind.

[Shih Wei Chieh] uses two galvanometers and a laser to cure the fabric. He uses a slightly newer process which reduces the exposure time required. This lets him print very large pictures, but also on uneven surfaces. As you can see in the video, viewable after the break, the effect is very pretty. There’s a new way to have the coolest pen plotter on the block.

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Making Models With Lasers

November 16, 2019 by 4 Comments

Good design starts with a good idea, and being able to flesh that idea out with a model. In the electronics world, we would build a model on a breadboard before soldering everything together. In much the same way that the industrial designer [Eric Strebel] makes models of his creations before creating the final version. In his latest video, he demonstrates the use of a CO2 laser for model making.

While this video could be considered a primer for using a laser cutter, watching some of the fine detail work that [Eric] employs is interesting in the way that watching any master craftsman is. He builds several cubes out of various materials, demonstrating the operation of the laser cutter and showing how best to assemble the “models”. [Eric] starts with acrylic before moving to wood, cardboard, and finally his preferred material: foam core. The final model has beveled edges and an interior cylinder, demonstrating many “tricks of the trade” of model building.

Of course, you may wish to build models of more complex objects than cubes. If you have never had the opportunity to use a laser cutter, you will quickly realize how much simpler the design process is with high-quality tools like this one. It doesn’t hurt to have [Eric]’s experience and mastery of industrial design to help out, either.

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Giant LEDs, Ruby Lasers, Hologram Displays, And Other Cool Stuff Seen At Maker Faire Rome

October 25, 2019 by 16 Comments

Hackers from all over Europe descended upon Rome last weekend for the Maker Faire that calls itself the “European Edition”. This three-day event is one of the largest Maker Faires in the world — they had 27,000 school students from all over Italy and Europe attend on Friday alone.

This was held at Fiera Roma, a gigantic conference complex two train stops south of the Rome airport — kind of in the middle of nowhere. I was told anecdotally that this is the largest event the complex hosts but have no data to back up that claim. One thing’s for certain, three days just wasn’t enough for me to enjoy everything at the show. There was a huge concentration of really talented hardware hackers on hand, many who you’ll recognize as creators of awesome projects regularly seen around Hackaday.

Here’s a whirlwind tour of some of my favorites. On that list are a POV holographic display, giant cast-resin LEDs, an optical-pump ruby laser built out of parts from AliExpress, blinky goodness in cube-form, and the Italian audience’s appreciation for science lectures (in this case space-related). Let’s take a look.

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Tracking Ants And Zapping Them With Lasers

October 5, 2019 by 28 Comments

Thanks to the wonders of neural networks and machine learning algorithms, it’s now possible to do things that were once thought to be inordinately difficult to achieve with computers. It’s a combination of the right techniques and piles of computing power that make such feats doable, and [Robert Bond’s] ant zapping project is a great example.

The project is based around an NVIDIA Jetson TK1, a system that brings the processing power of a modern GPU to an embedded platform. It’s fitted with a USB camera, that is used to scan its field of view for ants. Once detected, thanks to a little OpenCV magic, the coordinates of the insect are passed to the laser system. Twin stepper motors are used to spin mirrors that direct the light from a 5 mW red laser, which is shined on the target. If you’re thinking of working on something like this we highly recommend using galvos to direct the laser.

Such a system could readily vaporize ants if fitted with a more powerful laser, but [Robert] decided to avoid this for safety reasons. Plus, the smell wouldn’t be great, and nobody wants charred insect residue all over the kitchen floor anyway. We’ve seen AIs do similar work, too – like detecting naughty cats for security reasons.

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Text Projector With — You Know — Lasers

February 14, 2019 by 9 Comments

We missed [iliasam’s] laser text projector when it first appeared, perhaps because the original article was in Russian. However, he recently reposted in English and it really caught our eye. You can see a short video of it in operation, below.

The projector uses raster scanning where the beam goes over each spot in a grid pattern. The design uses one laser from a cheap laser pointer and a salvaged mirror module from an old laser printer. The laser pointer diode turned out to be a bit weak, so a DVD laser was eventually put into service. A DVD motor also provides the vertical scan which is just a slight wobble of a mirror. A Blue Pill CPU provides all the smarts. You can find the code on GitHub.

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