Mowing The Lawn With Lasers, For Science

September 3, 2024 by Maya Posch 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.

Continue reading “Mowing The Lawn With Lasers, For Science” →

The Strangest Way To Stick PLA To Glass? With A Laser And A Bit Of Foil

September 2, 2024 by Donald Papp 7 Comments

Ever needed a strong yet adhesive-free way to really stick PLA to glass? Neither have we, but nevertheless there’s a way to use aluminum foil and an IR fiber laser to get a solid bond with a little laser welding between the dissimilar materials.

A piece of sacrificial aluminum foil bonds the PLA to glass with a form of laser welding, with precise control and very little heat to dissipate.

It turns out that aluminum can be joined to glass by using a pulsed laser process, and PLA can be joined to aluminum with a continuous wave laser process. Researchers put them together, and managed to reliably do both at once with a single industrial laser.

By putting a sacrificial sheet of thin aluminum foil between 3D printed PLA and glass, then sending the laser through the glass into the aluminum, researchers were able to bond it all together in an adhesive-free manner with precise control, and very little heat to dissipate. No surface treatment of any kind required. The bond is at least as strong as any adhesive-based solution, so there’s no compromising on strength.

When it comes to fabrication, having to apply and manage adhesives is one of the least-preferable options for sticking two things together, so there’s value in the idea of something like this.

Still, it’s certainly a niche application and we’ll likely stick to good old superglue, but we honestly didn’t know laser welding could bond aluminum to glass or to PLA, let along both at once like this.

Laser Art Inspired By The Ford Motor Company

August 17, 2024 by Al Williams 7 Comments

Have you ever heard of Fordite? It was a man-made agate-like stone that originated from the Ford auto factories in the 1920s. Multiple layers of paint would build up as cars were painted different colors, and when it was thick enough, workers would cut it, polish it, and use it in jewelry. [SheltonMaker] uses a similar technique to create artwork using a laser engraver and shares how it works by showing off a replica of [Van Gogh’s] “Starry Night.”

The technique does have some random variation, so the result isn’t a perfect copy but, hey, it is art, after all. While true Fordite has random color layers, this technique uses specific colors layered from the lightest to the darkest. Each layer of paint is applied to a canvas. Only after all the layers are in place does the canvas go under the laser.

The first few layers of paint are white and serve as a backer. Each subsequent layer is darker until the final black layer. The idea is that the laser will cut at different depths depending on the desired lightness. A program called ImagR prepared the image as a negative image. Adjustments to the brightness, contrast, and gamma will impact the final result.

Of course, getting the exact power settings is tricky. The best result was to start at a relatively low power and then make more passes at an even lower power until things looked right. In between, compressed air cleared the print, although you have to be careful not to move the piece, of course.

There are pictures of each pass, and the final product looks great. If art’s not your thing, you can also do chip logos. While the laser used in this project is a 40-watt unit, we’ve noted before that wattage isn’t everything. You could do this—probably slower—with a lower-powered engraver.

Fordite image By [Rhonda] CC BY-SA 2.0.

Getting A Laser Eye Injury And How To Avoid It

August 2, 2024 by Maya Posch 27 Comments

Most people love lasers, because they can make cats chase, read music from a shiny disc, etch and cut materials, and be very shiny in Hollywood blockbusters, even when their presence makes zero sense. That said, lasers are also extremely dangerous, as their highly focused nature and wide range of power levels can leave a person dazzled, blinded or dead from direct and indirect exposure. A lapse in laser safety was how [Phil Broughton] ended up with part of his retina forever marked, as he describes his adventures with an overly enthusiastic laser company sales person.

Quanta Ray PRO350 with frequency doubling, emitting a 532nm beam – Sales brochure image from Quanta Ray, unknown date — Quanta Ray PRO350 with frequency doubling, emitting a 532 nm beam – Sales brochure image from Quanta Ray, unknown date

It didn’t take much, just this sales person who made a really poor decision while trying to please some customers and nearly ended with multiple adults, a local school, pilots at a nearby airfield getting their retinas blasted out due to an absolutely harebrained idea to use a fairly high-powered Quanta-Ray Nd:YAG laser on reflective surfaces in the open.

This was in 1999, and fortunately [Phil] only suffered some fairly minor damage to his retina from the laser beam reflection. What happened to the customers (who wore argon laser safety glasses) or the sales critter (who left soon after) is not described, but both may have received some bad news when they had their eyes checked shortly after at the ophthalmologist.

These kind of stories are a stark reminder that laser safety is not optional. Lasers producing a visible (400 – 700 nm) wavelength above Class 2 should only be operated in a fully secured environment, with safety glasses for the appropriate laser wavelength. Class 2 lasers producing a non-visible wavelength can cause permanent damage because the blink reflex of the eye does not offer any protection here.

As even some dodgy laser pointers are being (illegally) sold online are actually Class 2, this should make it clear that laser eye injury can happen to anyone, and it only takes a second to change someone’s life forever.

George Washington Gets Cleaned Up With A Laser

July 27, 2024 by Tom Nardi 5 Comments

Now, we wouldn’t necessarily call ourselves connoisseurs of fine art here at Hackaday. But we do enjoy watching [Julian Baumgartner]’s YouTube channel, where he documents the projects that he takes on as a professional conservator. Folks send in their dirty or damaged paintings, [Julian] works his magic, and the end result often looks like a completely different piece. Spoilers: if you’ve ever looked at an old painting and wondered why the artist made it so dark and dreary — it probably just needs to be cleaned.

Anyway, in his most recent video, [Julian] pulled out a piece of gear that we didn’t expect to see unleashed against a painting of one of America’s Founding Fathers: a Er:YAG laser. Even better, instead of some fancy-pants fine art restoration laser, he apparently picked up second hand unit designed for cosmetic applications. The model appears to be a Laserscope Venus from the early 2000s, which goes for about $5K these days.

Now, to explain why he raided an esthetician’s closet to fix up this particular painting, we’ve got to rewind a bit. As we’ve learned from [Julian]’s previous videos, the problem with an old dirty painting is rarely the paining itself, it’s the varnish that has been applied to it. These varnishes, especially older ones, have a tendency to yellow and crack with age. Now stack a few decades worth of smoke and dirt on top of it, and you’ve all but completely obscured the original painting underneath. But there’s good news — if you know what you’re doing, you can remove the varnish without damaging the painting itself.

In most cases, this can be done with various solvents that [Julian] mixes up after testing them out on some inconspicuous corner of the painting. But in this particular case, the varnish wasn’t reacting well to anything in his inventory. Even his weakest solvents were going right through it and damaging the paint underneath.

Because of this, [Julian] had to break out the big guns. After experimenting with the power level and pulse duration of the 2940 nm laser, he found the settings necessary to break down the varnish while stopping short of cooking the paint it was covering. After hitting it with a few pulses, he could then come in with a cotton swab and wipe the residue away. It was still slow going, but it turns out most things are in the art conservation world.

This isn’t the first time we’ve covered [Julian]’s resourceful conservation methods. Back in 2019, we took at look the surprisingly in-depth video he created about the design and construction of his custom heat table for flattening out large canvases.

Continue reading “George Washington Gets Cleaned Up With A Laser” →

Sketch of the UED setup at EPFL, 1) Electron gun, 2) High-Voltage connector, 3) Photo-cathode, 4) Anode, 5) Collimating solenoid, 6) Steering plates, 7) Focusing solenoid, 8) RF cavity, 9) Sample holder, 10) Cryostat, 11) Electron detector, 12) Turbo pump, 13) Ion gauge. Credit: Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2316438121

Using Femtosecond Laser Pulses To Induce Metastable Hidden States In Magnetite

July 20, 2024 by Maya Posch No comments

Hidden states are a fascinating aspect of matter, as these can not normally be reached via natural processes (i.e. non-ergodic), but we can establish them using laser photoexcitation. Although these hidden states are generally very unstable and will often decay within a nanosecond, there is evidence for more persistent states in e.g. vanadates. As for practical uses of these states, electronics and related fields are often mentioned. This is also the focus in the press release by the Ecole Polytechnique Federale de Lausanne (EPFL) when reporting on establishing hidden states in magnetite (Fe₃O₄), with the study published in PNAS (Arxiv preprint link).

[B. Truc] and colleagues used two laser frequencies to either make the magnetite more conductive (800 nm) or a better insulator (400 nm). The transition takes on the order of 50 picoseconds, allowing for fairly rapid switching between these metastable states. Naturally, turning this into practical applications will require a lot more work, especially considering the need for femtosecond pulsed lasers to control the process, which makes it significantly more cumbersome than semiconductor technology. Its main use at this point in time will remain a fascinating demonstration of these hidden states of matter.

Lasers Al Fresco: Fun With Open-Cavity Lasers

July 3, 2024 by Dan Maloney 11 Comments

Helium-neon lasers may be little more than glorified neon signs, but there’s just something about that glowing glass tube that makes the whole process of stimulated emission easier to understand. But to make things even clearer, you might want to take a step inside the laser with something like [Les Wright]’s open-cavity He-Ne laser.

In most gas lasers, the stimulated emission action takes place within a closed optical cavity, typically formed by a glass tube whose ends are sealed with mirrors, one of which is partially silvered. The gas in the tube is stimulated, by an electrical discharge in the case of a helium-neon laser, and the stimulated photons bounce back and forth between the mirrors until some finally blast out through the partial mirror to form a coherent, monochromatic laser beam. By contrast, an open-cavity laser has a gas-discharge tube sealed with the fully silvered mirror on one end and a Brewster window on the other, which is a very flat piece of glass set at a steep angle to the long axis of the tube and transparent to p-polarized light. A second mirror is positioned opposite the Brewster window and aligned to create a resonant optical cavity external to the tube.

To switch mirrors easily, [Les] crafted a rotating turret mount for six different mirrors. The turret fits in a standard optical bench mirror mount, which lets him precisely align the mirror in two dimensions. He also built a quick alignment jig, as well as a safety enclosure to protect the delicate laser tube. The tube is connected to a high-voltage supply and after a little tweaking the open cavity starts to lase. [Les] could extend the cavity to almost half a meter, although even a waft of smoke was enough obstruction to kill the lasing at that length.

If this open-cavity laser arrangement seems familiar, it might be because [Les] previously looked at an old-school particle counter with such a laser at its heart. Continue reading “Lasers Al Fresco: Fun With Open-Cavity Lasers” →