Schematic of quantum measurement basis on whiteboard

Shedding Light On Quantum Measurement With Calcite

January 26, 2025 by Heidi Ulrich 19 Comments

Have you ever struggled with the concept of quantum measurement, feeling it’s unnecessarily abstract? You’re not alone. Enter this guide by [Mithuna] from Looking Glass Universe, where she circles back on the concept of measurement basis in quantum mechanics using a rather simple piece of calcite crystal. We wrote about similar endeavours in reflection on Shanni Prutchi’s talk at the Hackaday SuperConference in 2015. If that memory got a bit dusty in your mind, here’s a quick course to make things click again.

In essence, calcite splits a beam of light into two dots based on polarization. By aligning filters and rotating angles, you can observe how light behaves when forced into ‘choices’. The dots you see are a direct representation of the light’s polarization states. Now this isn’t just a neat trick for photons; it’s a practical window into the probability-driven nature of quantum systems.

Even with just one photon passing through per second, the calcite setup demonstrates how light ‘chooses’ a path, revealing the probabilistic essence of quantum mechanics. Using common materials (laser pointers, polarizing filters, and calcite), anyone can reproduce this experiment at home.

If this sparks curiosity, explore Hackaday’s archives for quantum mechanics. Or just find yourself a good slice of calcite online, steal the laser pointer from your cat’s toy bin, and get going!

Continue reading “Shedding Light On Quantum Measurement With Calcite” →

Perfecting 20 Minute PCBs With Laser

January 5, 2025 by Al Williams 41 Comments

Normally, you have a choice with PCB prototypes: fast or cheap. [Stephen Hawes] has been trying fiber lasers to create PCBs. He’s learned a lot which he shares in the video below. Very good-looking singled-sided boards take just a few minutes. Fiber lasers are not cheap but they are within range for well-off hackers and certainly possible for a well-funded hackerspace.

One thing that’s important is to use FR1 phenolic substrate instead of the more common FR4. FR4 uses epoxy which will probably produce some toxic fumes under the laser.

Continue reading “Perfecting 20 Minute PCBs With Laser” →

2024 Brought Even More Customization To Boxes.py

January 1, 2025 by Tom Nardi 20 Comments

If you have access to a laser cutter, we sincerely hope you’re aware of boxes.py. As the name implies, it started life as a Python tool for generating parametric boxes that could be assembled from laser-cut material, but has since become an invaluable online resource for all sorts of laser projects. Plus, you can still use it for making boxes.

But even if you’ve been using boxes.py for awhile, you might not know it was actually an entry in the Hackaday Prize back in 2017. Creator [Florian Festi] has kept up with the project’s Hackaday.io page all this time, using it as a sort of development blog, and his recent retrospective on 2024 is a fascinating read for anyone with an eye towards hot photonic action.

Continue reading “2024 Brought Even More Customization To Boxes.py” →

Taking “Movies” Of Light In Flight

December 25, 2024 by Elliot Williams 10 Comments

This one isn’t clickbait, but it is cheating. [Brian Haidet], the guy behind Alpha Phoenix, has managed to assemble movie footage of a laser beam crossing his garage, using a rig he put together for just a few hundred dollars. How, you ask? Well, for the long version, you’re going to want to watch the video, also embedded below. But we’ll give you the short version here.

Light travels about a foot in a nanosecond. What have you got that measures signals on a nanosecond scale pretty reliably? Of course, it’s your oscilloscope. The rest of [Brian]’s setup includes a laser that can pull off nanosecond pulses, a sensor with a nanosecond-ish rise time, and optics that collect the light over a very small field of view.

He then scans the effective “pinhole” across his garage, emitting a laser pulse and recording the brightness over time on the oscilloscope for each position. Repeating this many thousands of times and putting them all together relative to the beginning of each laser pulse results in a composite movie with the brightness at each location resolved accurately enough to watch the light beam fly. Or to watch different time-slices of thousands of beams fly, but as long as they’re all the same, there’s no real difference.

Of course, this isn’t simple. The laser driver needs to push many amps to get a fast enough rise time, and the only sensor that’s fast enough to not smear the signal is a photomultiplier tube. But persistence pays off, and the results are pretty incredible for something that you could actually do in your garage.

Photomultiplier tubes are pretty damn cool, and can not only detect very short light events, but also very weak ones, down to a single photon. Indeed, they’re cool enough that if you get yourself a few hundred thousand of them and put them in a dark place, you’re on your way to a neutrino detector. Continue reading “Taking “Movies” Of Light In Flight” →

Automated Rig Grows Big, Beautiful Crystals Fast

December 12, 2024 by Dan Maloney 8 Comments

We haven’t seen [Les Wright] in a while, and with the release of his new video, we know why — he’s been busy growing crystals.

Now, that might seem confusing to anyone who has done the classic “Crystal Garden” trick with table salt and laundry bluing, or tried to get a bit of rock candy out of a supersaturated sugar solution. Sure, growing crystals takes time, but it’s not exactly hard work. But [Les] isn’t in the market for any old crystals. Rather, he needs super-sized, optically clear crystals of potassium dihydrogen phosphate, or KDP, which are useful as frequency doublers for lasers. [Les] has detailed his need for KDP crystals before and even grown some nice ones, but he wanted to step up his game and grow some real whoppers.

And boy, did he ever. Fair warning; the video below is long and has a lot of detail on crystal-growing theory, but it’s well worth it for anyone taking the plunge. [Les] ended up building an automated crystal lab, housing it in an old server enclosure for temperature and dust control. The crystals are grown on a custom-built armature that slowly rotates in a supersaturated solution of KDP which is carefully transitioned through a specific temperature profile under Arduino control. As a bonus, he programmed the rig to take photographs of the growing crystals at intervals; the resulting time-lapse sequences are as gorgeous as the crystals, one of which grew to 40 grams in only a week.

We’re keen to see how [Les] puts these crystals to work, and to learn exactly what a “Pockels Cell” is and why you’d want one. In the meantime, if you’re interested in how the crystals that make the whole world work are made, check out our deep dive into silicon.

Continue reading “Automated Rig Grows Big, Beautiful Crystals Fast” →

Holograms: The Art Of Recording Wavefronts

December 3, 2024 by Maya Posch 22 Comments

The difference between holography and photography can be summarized perhaps most succinctly as the difference between recording the effect photons have on a surface, versus recording the wavefront which is responsible for allowing photographs to be created in the first place. Since the whole idea of ‘visible light’ pertains to a small fragment of the electromagnetic (EM) spectrum, and thus what we are perceiving with our eyes is simply the result of this EM radiation interacting with objects in the scene and interfering with each other, it logically follows that if we can freeze this EM pattern (i.e. the wavefront) in time, we can then repeat this particular pattern ad infinitum.

Close-up of the wavefront pattern recorded on the holographic film (Credit: 3Blue1Brown, YouTube)

In a recent video by [3Blue1Brown], this process of recording the wavefront with holography is examined in detail, accompanied by the usual delightful visualizations that accompany the videos on [3Blue1Brown]’s channel. The type of hologram that is created in the video is the simplest type, called a transmission hologram, as it requires a laser light to illuminate the holographic film from behind to recreate the scene. This contrasts with a white light reflection hologram, which can be observed with regular daylight illumination from the front, and which is the type that people are probably most familiar with.

The main challenge is, perhaps unsurprisingly, how to record the wavefront. This is where the laser used with recording comes into play, as it forms the reference wave with which the waves originating from the scene interact, which allows for the holographic film to record the latter. The full recording setup also has to compensate for polarization issues, and the exposure time is measured in minutes, so it is very sensitive to any changes. This is very much like early photography, where monochromatic film took minutes to expose. The physics here are significant more complex, of course, which the video tries to gently guide the viewer through.

Also demonstrated in the video is how each part of the exposed holographic film contains enough of the wavefront that cutting out a section of it still shows the entire scene, which when you think of how wavefronts work is quite intuitive. Although we’re still not quite in the ‘portable color holocamera’ phase of holography today, it’s quite possible that holography and hologram-based displays will become the standard in the future.

Continue reading “Holograms: The Art Of Recording Wavefronts” →

Getting Started In Laser Cutting

November 27, 2024 by Jenny List 20 Comments

If you were to walk into most of the world’s hackerspaces, it’s likely that the most frequent big-ticket tool you’ll find after a 3D printer is a laser cutter. A few years ago that would inevitably been one of the ubiquitous blue Chinese-made K40 machines, but here in 2024 it’s become common to see something far more sophisticated. For all that, many of us are still laser cutter noobs, and for us [Dominic Morrow] gave a talk at last summer’s EMF Camp in the UK entitled “Getting Started In Laser Cutting“. [Dominic] is a long-term laser cutting specialist who now works for Lightburn, so he’s ideally placed to deliver this subject.

It’s fair to say that this is an overview in the time available for a hacker camp talk rather than an in-depth piece, so he takes the approach of addressing people’s misconceptions and concerns about cutters. Perhaps the most important one he addresses is the exhaust, something we’ve seen a few in our community neglect in favor of excessive attention to laser cooling or other factors. An interesting one for us though was his talking about the cheaper diode lasers, having some insight into this end of the market is valuable when you have no idea which way to go.

We’re sorry to have missed this one in the real world, perhaps because of the allure of junk.

Continue reading “Getting Started In Laser Cutting” →