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511 Articles

Laser Painting Explained

October 17, 2024 by 7 Comments

If you get an inexpensive diode laser cutter, you might have been disappointed to find it won’t work well with transparent acrylic. The material just passes most of the light at that wavelength, so there’s not much you can do with it. So how did [Rich] make a good-looking sign using a cheap laser? He used a simple paint and mask technique that will work with nearly any clear material, and it produces great-looking results, as you can see in the video below.

[Rich] starts with a piece of Acrylic covered with paper and removes the paper to form a mask. Of course, even a relatively anemic laser can slice through the paper covering with no trouble at all. He also cuts an outline, which requires a laser to cut the acrylic. However, you could easily apply this to a rectangular hand-cut blank. Also, most diode lasers can cut thin acrylic, but it doesn’t always come out as cleanly as you’d like.

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Photochromic Dye Makes Up This Novel Optical Memristor

October 10, 2024 by 20 Comments

Despite being much in the zeitgeist lately, we have to confess to still being a bit foggy about exactly what memristors are. The “mem” part of their name seems to be the important bit, implying a memory function, but the rest of the definition seems somewhat negotiable — enough so that you can make a memristor from a bit of photochromic dye.

Now, we’ll leave the discussion of whether [Markus Bindhammer]’s rather complex optical memory cell officially counts as a memristor to the comments below, and just go through the technical details here. The heart of this experimental device is a photochromic dye known as cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethene, mercifully shortened to CMTE, which has the useful property of having two stable states. Transitioning from the open state to the closed state occurs when UV light shines upon it, while switching back to the closed state is accomplished with a pulse of green light. Absent the proper wavelength of light, both states are stable, making non-volatile information storage possible.

To accomplish this trick, [Markus] filled a quartz cuvette with a little CMTE-doped epoxy resin. Inside a light-tight enclosure, two lasers — one at 405 nm wavelength, the other at 532 nm — are trained on the cuvette through a dichroic mirror. On the other side of the CMTE resin, he placed a VEML7700 high-accuracy ambient light sensor. An Arduino Nano reads the light sensor and controls the lasers. Writing and erasing are accomplished by turning on the proper laser for a short amount of time; reading the state of the cell involves a carefully timed pulse from the 405 nm laser followed by a 532 nm pulse and watching the output of the sensor.

Is a one-bit memory device that uses a dye that goes for €300 per gram and a pair of laser diodes practical? Of course not, but it’s still pretty cool, and we appreciate all the effort and expense [Markus] went to with this one. Now, if you want some fuel for the “It’s not a memristor” fire, memristors might not even be a thing.

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First Benchies In Stainless Steel, With Lasers

October 7, 2024 by 19 Comments

DIY 3D printing in metal is a lot more complicated than we thought. And this video from [Metal Matters] shows two approaches, many many false starts, and finally, a glorious 78.9% success! (And it’s embedded below for your enjoyment.)

The first half of the video is dedicated to the work on a laser welding system that doesn’t pan out in the end at all. But the missteps are worth watching as well, and they hammer home the difficulties of melting metal reliably with nothing more than coherent light. Things like reflection, the difficulty of getting good process control cameras, and finally the whole thing slumping as multiple layers stack up on each other make this approach to 3D construction look nearly impossible.

Indeed, around halfway through the video, the focus shifts toward a metal-powder sintering machine, and this one is a success! Metal dust is deposited layer by layer, and fused with a totally different laser. The tricky bits here range from esoteric problems like making the laser fuse the metal dust without blasting it, to simple things like the geometry of the scraper that ensures even layer heights. And once you’ve got all that down, getting a good pattern down for 2D infill in metal is non-trivial.

A sweet half-scale metal Benchy emerges at the end, so why does [Metal Matters] call this a 78.9% success? Because that’s the density of the final print, and he is shooting for 100%. But we wouldn’t be so harsh. We’ve seen how far he’s come since the first machines, and this is a huge advance. We’re looking forward to the next video update in a year or two!

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Most Powerful Laser Diodes, Now More Powerful

September 24, 2024 by 31 Comments

Many hobbies seem to have a subset of participants who just can’t leave well enough alone. Think about hot rodders, who squeeze every bit of power out of engines they can, or PC overclockers, who often go to ridiculous ends to milk the maximum performance from a CPU. And so it goes in the world of lasers, where this avalanche driver module turns Nichia laser diodes into fire-breathing beasts.

OK, that last bit might be a little overstated, but there’s no denying the coolness of what laser jock [Les Wright] has accomplished here. In his endless quest for more optical power, [Les] happened upon a paper describing a simple driver circuit that can dump massive amounts of current into a laser diode to produce far more optical power than they’re designed for. [Les] ran with what few details the paper had and came up with a modified avalanche driver circuit, with a few niceties for easier testing, like accommodation for different avalanche transistors and a way to test laser diodes in addition to the Nichia. He also included an onboard current sensing network, making it easy to hook up a high-speed oscilloscope to monitor the performance of the driver.

For testing, [Les] used a high-voltage supply homebrewed from a Nixie inverter module along with a function generator to provide the pulses. The driver was able to push 80 amps into a Nichia NUBM47 diode for just a few nanoseconds, and when all the numbers were plugged in, the setup produced about 67 watts of optical power. Not one to let such power go to waste, [Les] followed up with some cool experiments in laser range finding and dye laser pumping, which you can check out in the video below. And check out our back catalog of [Les]’ many laser projects, from a sketchy tattoo-removal laser teardown to his acousto-optical filter experiments. Continue reading “Most Powerful Laser Diodes, Now More Powerful” →

Laser Fault Injection, Now With Optional Decapping

September 20, 2024 by 3 Comments

Whether the goal is reverse engineering, black hat exploitation, or just simple curiosity, getting inside the packages that protect integrated circuits has long been the Holy Grail of hacking. It isn’t easy, though; those inscrutable black epoxy blobs don’t give up their secrets easily, with most decapping methods being some combination of toxic and dangerous. Isn’t there something better than acid baths and spinning bits of tungsten carbide?

[Janne] over at Fraktal thinks so, and the answer he came up with is laser decapping. Specifically, this is an extension of the laser fault injection setup we recently covered, which uses a galvanometer-scanned IR laser to induce glitches in decapped microcontrollers to get past whatever security may be baked into the silicon. The current article continues that work and begins with a long and thorough review of various IC packaging technologies, including the important anatomical differences. There’s also a great review of the pros and cons of many decapping methods, covering everything from the chemical decomposition of epoxy resins to thermal methods. That’s followed by specific instructions on using the LFI rig to gradually ablate the epoxy and expose the die, which is then ready to reveal its secrets.

The benefit of leveraging the LFI rig for decapping is obvious — it’s an all-in-one tool for gaining access and executing fault injection. The usual caveats apply, of course, especially concerning safety; you’ll obviously want to avoid breathing the vaporized epoxy and remember that lasers and retinas don’t mix. But with due diligence, having a single low-cost tool to explore the innards of chips seems like a big win to us.

Upgraded Raster Laser Projector Goes RGB

September 18, 2024 by 10 Comments

We’ve covered a scanning laser project by Ben Make’s Everything last year, and now he’s back with a significant update. [Ben]’s latest project now offers a higher resolution and RGB lasers. A couple of previous versions of the device used the same concept of a rotating segmented mirror synchronised to a pulsed laser diode to create scanlines. When projected onto a suitable surface, the distorted, pixelated characters looked quite funky, but there was clearly room for improvement.

More scanlines and a faster horizontal pixel rate

The previous device used slightly inclined mirrors to deflect the beam into scanlines, with one mirror per scanline limiting the vertical resolution. To improve resolution, the mirrors were replaced with identically aligned mirrors of the type used in laser printers for horizontal scanning. An off-the-shelf laser galvo was used for vertical scanning, allowing faster scanning due to its small deflection angle. This setup is quicker than then usual vector galvo application, as the smaller movements require less time to complete. Once the resolution improvement was in hand, the controller upgrade to a Teensy 4 gave more processing bandwidth than the previous Arduino and a consequent massive improvement in image clarity.

Finally, monochrome displays don’t look anywhere near as good as an RGB setup. [Ben] utilised a dedicated RGB laser setup since he had trouble sourcing the appropriate dichroic mirrors to match available lasers. This used four lasers (with two red ones) and the correct dichroic mirrors to combine each laser source into a single beam path, which was then sent to the galvo. [Ben] tried to find a DAC solution fast enough to drive the lasers for a proper colour-mixing input but ended up shelving that idea for now and sticking with direct on-off control. This resulted in a palette of just seven colours, but that’s still a lot better than monochrome.

The project’s execution is excellent, and care was taken to make it operate outdoors with a battery. Even with appropriate safety measures, you don’t really want to play with high-intensity lasers around the house!

Here’s the previous version we covered, a neat DIY laser galvo using steppers, and a much older but very cool RGB vector projector.

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Mowing The Lawn With Lasers, For Science

September 3, 2024 by 34 Comments
Cutting grass with lasers works great in a test setup. (Credit: Allen Pan, YouTube)

Wouldn’t it be cool if you could cut the grass with lasers? Everyone knows that lasers are basically magic, and if you strap a diode laser or two to a lawn mower, it should slice through those pesky blades of grass with zero effort. Cue [Allen Pan]’s video on doing exactly this, demonstrating in the process that we do in fact live in a physics-based universe, and lasers are not magical light sabers that will just slice and dice without effort.

The first attempt to attach two diode lasers in a spinning configuration like the cutting blades on a traditional lawn mower led to the obvious focusing issues (fixed by removing the focusing lenses) and short contact time. Effectively, while these diode lasers can cut blades of grass, you need to give them some time to do the work. Naturally, this meant adding more lasers in a stationary grid, like creating a Resident Evil-style cutting grid, only for grass instead of intruders.

Does this work? Sort of. Especially thick grass has a lot of moisture in it, which the lasers have to boil off before they can do the cutting. As [Allen] and co-conspirator found out, this also risks igniting a lawn fire in especially thick grass. The best attempt to cut the lawn with lasers appears to have been made two years ago by [rctestflight], who used a stationary, 40 watt diode laser sweeping across an area. When placed on a (slowly) moving platform this could cut the lawn in a matter of days, whereas low-tech rapidly spinning blades would need at least a couple of minutes.

Obviously the answer is to toss out those weak diode lasers and get started with kW-level chemical lasers. We’re definitely looking forward to seeing those attempts, and the safety methods required to not turn it into a laser safety PSA.

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