Laser Hacks

683 Articles

Yellow YAG Produces Powerful Pulses In Les’ Leftover Laser

August 4, 2026 by 7 Comments

[Les] likes lasing lasers, and who doesn’t? [Les] likes larger lasers than lots of folks, with his current project being an Nd:YAG (that’s Neodymium:Yttrium Aluminum Garnet) flash pumped laser intended for tattoo removal. Like most of its ilk, the YAG crystal at the heart of that device is a rosy purple color, so when [Les] spotted a Yellow YAG with different doping promising powerful pulses, he purchased it promptly.

Specifically, the retailer was claiming a 30-50% efficiency increase for this yellow rod, thanks to cerium doping. It’s still considered an Nd:YAG, though you can label it as an Nd:Ce:YAG for clarity. The efficiency gain comes from the cerium atom taking unused energy from the flashbulb pulse — which is much broader-wavelength than the thin absorption line of the Nd ions in the rod — and giving that energy to the Nd atoms that do the lasing via fluorescence. He doesn’t try it, but reports on a paper showing these crystals can actually lase with reasonable efficiency from sunlight alone, which we’d love to see. Send us a tip if you try.

His original Nd:YAG rod produced 72.8 mJ pulses, while in the same setup with the yellow laser is peaking at 153 mJ, more than double the original output. That’s even better than the 30-50% [Les] expected, but he reckons it is because the old YAG is, well, old. The coatings break down over time, and UV light from the flashbulbs degrades the crystals too. That’s another benefit of tossing cerium in there, as apparently it acts as sunscreen for your laser rod. It lasts longer and works better, making it a no-brainer of an upgrade.

We’ve seen [Les]’s laser-based hacking before, like this  diode-laser PSU and we’re always glad to take a look with our remaining eye. We also featured his tattoo removal laser back when he started working on it, along with less-lasery projects like his crystal-growing rig.

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Congratulations To The Frikkin Laser Winners!

August 3, 2026 by 5 Comments

Apparently you all love lasers just as much as we do. We put out a challenge to use, build, or otherwise abuse our favorite coherent light sources, and you responded. Some of the projects had been in the works for quite a while and were ridiculously polished, some were whipped together on the fly just for the contest, and we truly enjoyed both.

We only have three $150 DigiKey gift certificates to give out, though, so without further ado, we present to you…

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A plastic device sits on a desk, with a computer display and an oscilloscope behind it. A fiber-optic cable runs from the device to a laser diode source.

2026 Frikkin Lasers Challenge: Measuring Nanometer-Scale Displacements With An Optical Cavity

July 26, 2026 by 4 Comments

Optical cavities – two mirrors arranged to reflect light multiple times between them – form the basis of lasers and certain optical filters. Since any angle between the two mirrors results in light being scattered away, parallel alignment is essential, yet difficult to maintain. Nevertheless, [Timothy Giles] managed to 3D-print and align such an optical cavity, and used it to detect minute shifts in space and wavelength.

The cavity has two semi-transparent mirrors facing towards each other. One mirror is held in a 3D-printed mount, and the other is attached to the diaphragm of a speaker with a hole drilled through the center. The hole avoids the speaker coil, and allows light exiting the optical cavity through the semi-transparent mirror to appear on a paper target, which is monitored by a webcam. On the other side of the optical cavity, a laser diode coupled to a single-mode fiber shines in through the other mirror. Alignment is challenging, but the webcam makes it easier; as the mirrors tilt relative to each other, the pattern seen on the paper target changes, providing feedback for more precise adjustment.

Light reflected within the cavity can interfere constructively or destructively with incoming light, changing the brightness of the emitted beam. [Tim] used the speaker as a linear actuator to vary the cavity’s length, which, by counting the peaks in brightness, allowed him to measure the diaphragm’s displacement. This also demonstrated a laser diode’s wavelength instability: when the cavity was set to a constant length and the laser started up, the output brightness would cycle a few times. As the diode was warming up, its output wavelength was shifting, creating the same changing interference pattern.

To get a Gaussian beam distribution, [Tim] used a fiber-coupled laser; if you’d like to build one, we’ve seen a coupling mechanism built before. Most lasers are built around an internal optical cavity, but some instead use an external cavity.

2026 Hackaday Freaking Lasers Contest
A scanning-electron micrograph is shown of a cricket's body, focusing on the head, which has been sliced off just above the eyes.

Cross-Sectioning Crickets With A Femtosecond Laser

July 18, 2026 by 14 Comments

Unlike most cutting lasers, femtosecond lasers don’t vaporize materials; rather, they produce such short, intense bursts of light that the affected region is ablated without having the chance to heat its surroundings. This makes them good at cutting away material without damaging the surroundings, something [Ben Krasnow] exploited to cut cross-sections of samples while still in a scanning-electron microscope.

In this case, the samples were crickets, and before imaging they had to be prepared. First, the bodies were soaked in glutaraldehyde to cross-link the proteins and stabilize the structure. Next, a series of solvent exchanges replaced the water in the bodies with a low-surface-tension solvent; this meant that during the next step, drying, surface tension wouldn’t distort the crickets’ internal structure. Finally, the insect bodies were charred under argon, which made the bodies conductive and more absorptive to laser light.

The laser itself and the scanning galvo are mounted outside the microscope, and shine in through a transparent window. To protect the detector and electron optics from a spray of ablated carbon, a servo motor swings an aluminium shutter between these and the sample while the laser is active. This caused some mysterious problems during testing: after the first ablation run, the electron microscope’s image would contain so much noise as to be unusable, but it would improve over time. As it turned out, the shutter was painted, and the other side of the paint was getting coated with charged carbon particles. This created a small capacitor which disrupted the electron optics as it discharged. Eventually, after solving this and a few other strange problems, [Ben] was able to take several time-lapse videos of the laser gradually ablating a cricket, 30 microns at a time, revealing its inner structure.

Although scanning-electron microscopes are unfortunately shard to come by, it’s still possible to restore a secondhand microscope or, as [Ben] did, build your own. Femtosecond lasers are yet more inaccessible, though they can be used to replicate themselves.

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2026 Frikkin Lasers Challenge: Laser Bandsaw

July 14, 2026 by 31 Comments

Can you call it a bandsaw if it has neither band nor saw? [WeldingRod1] does, with his entry in the laser contest — a manually-controlled laser cutter that he’s dubbed a Laser Bandsaw. Some might quibble that it’s not actually sawing with the beam, and others will inevitably find the safety implications rather frightening. We think it’s a fun project and that [WeldingRod1] can call it what he wants, as long as he follows his own advice and keeps his laser goggles firmly on his precious vision orbs.

He has actually put some thought into what started as the physical manifestation of a joke in a podcast. The blue diode laser — a NUBM44 diode rated at 7 W — got a custom-made copper heatsink. It’s also got a hefty beam dump in the form of a stack of box knife blades. That’s very necessary to keep the beam from reflecting where it shouldn’t, especially when you consider this operates like a regular band saw: you turn it on, and it’s ready to cut. With only 7 W of laser power it can’t cut that much, mind you, but apparently it’s great on balsa wood and blasts black paint off like nobody’s business.

Now if this was our shop we’d probably want to put the laser diode onto some kind of CNC platform, be it Cartesian or SCARA. But we’ve seen that done many, many times and if you’ve got the motor skills this might be just the tool for you. There’s a pinout and STLs for the 3D printed frame on the project page if you’re interested. If not, why are you still here? The article is finished. Go make something lase and send it in. The deadline for the 2026 Frikkin Laser Contest is fast approaching!

2026 Hackaday Freaking Lasers Contest

A series of simulations of a shape are shown, with that shape traced out in a petri dish with a laser below. The shape is roughly like a 90-degree corner bisected by a third arm.

Printing Fungal Art With Laser Control

July 12, 2026 by No comments

Preservationists usually take great care to prevent fungi from appearing the world of art, but in the case of [Kexin Wang]’s Funguy project, the fungus itself is the art. It uses a laser diode to repeatedly trace an outline onto a dish of agar gel in which fungus is growing, and the photophobic fungus grows only up to the edge of the laser-traced figure, potentially creating complex designs.

This project evolved out of a research project in which they developed a computer model for fungal growth, then used its predictions and a laser to control a fungus’s growth pattern. The model has two parts: a temporal convolutional neural network which learns fungi growth patterns from a series of images, and a cellular automaton to simulate these growth patterns under different starting conditions. The cellular automaton’s rules aren’t fixed; each cell runs a small neural network which learns the rules under supervision from the convolutional network. By training these networks on images of the growth stages of three different fungi, it was able to realistically predict the different growth patterns of the different species.

To actually control the growth pattern, the researchers tried a series of different wavelengths and laser powers; shorter wavelengths tended to work better, with a 405 nm laser working best. The growth model complemented the laser setup by predicting in which areas the growth medium had run out of nutrients. Since fungus would no longer spread in these regions, the laser no longer needed to trace these sections. The Funguy kit’s laser system itself is similar to a laser engraver, with an XY-kinematic system seemingly built from a DVD drive frame. It uses fungi from the Mucor genus, though it can print with other photophobic microorganisms, such as slime molds.

This project seems aimed at artistic and educational uses, but considering the various electronic parts that have been made of fungi, more functional applications should be possible.

A black plastic cube is shown in front of another, larger rectangular black plastic box. The plastic cube has a silver microscope objective protruding from one side, with green light being emitted from it into a small plastic tube held on a positioning stage.

2026 Frikkin Lasers Challenge: A 3D-Printed Raman Spectrometer

July 5, 2026 by 19 Comments

When light reflects off a surface, not all of it reflects off at the same wavelength; some photons impart a portion of their energy to raising the vibrational energy of the surface’s molecules, and are thus scattered away at a lower energy and longer wavelength. This is called Raman scattering, and the precise wavelength shifts are characteristic of the particular molecule being illuminated. It can therefore be used in Raman spectroscopy to identify molecules; these spectrometers are normally elaborate, expensive instruments, but [Allegedly Science] was able to build a simple system with surprising sensitivity.

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