Building An Optically Pumped Laser Pointer

As a society, we’ve largely come together to agree that laser pointers are mostly useless. They’re now the preserve of university lecturers and those destined to wind up in a jail cell for harassing helicopter pilots. Most pointers are of the diode-pumped solid state variety. However, [Zenodilodon] treads a different path.

The laser cavity glows in operation, though it’s probably inadvisable to look directly at it.

Instead of the usual DPSS build, this pointer packs an optically pumped semiconductor laser, or OPSL. These lasers have the benefit of a wider selection of output wavelengths, and can be built to offer less variance in beam parameters such as divergence.

The build is an attractive one, with the pointer chassis being manufactured out of brass, with several components plated in yellow and rose gold. There’s even a sliding window to observe the laser cavity, which glows brightly in operation. [Zenodilodon] goes into great detail during the machining process, showing all the steps required to produce a visually appealing device.

It’s certainly one of the prettiest laser builds we’ve seen, and it’s always nice to see makers exploring different technologies. Similarly to our recently featured 1.4 W laser pointer, it’s largely a packaging operation, but if you’re building your own laser diodes at home – you know where to send ’em. Video after the break.

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Building A 1.4W Laser Pointer In A Tiny Housing

Laser pointers were cool for about 30 seconds when they first came out, before becoming immediately passé and doing absolutely nothing to improve the boss’s quarterly reports presentation. However, just as with boom boxes and sports cars, more power can always make things better. [Styropyro] was unimpressed with the weak and unreliable laser pointers he’d sourced from eBay, so gutted one and began a fresh build.

After fiddling with some basic 1mW eBay green lasers, [styropyro] had some fun turning up the wick by fiddling with the internal trimpots. This led to the quick and untimely death of the cheap laser diodes, leaving a compact laser pointer shell ripe for the hacking.

To replace the underwhelming stock components, [styropyro] chose a Nichia NDG7475 high-powered laser diode, fitting it into a small heatsink for thermal management. Current draw was far too high to use the original switch, so the stock housing’s button is instead used to switch a MOSFET which delivers the full current to the laser driver. To reach the higher output power of 1.4W, the laser diode is being run over specification at 2.3 amps. All this current draw would quickly overwhelm standard AAA batteries, so a pair of lithium polymer 10440 batteries are substituted in to do the job.

The build shows that with clever parts selection and some easy hand soldering, you too can build an incredibly dangerous laser pointer at home, that fits neatly in your shirt pocket. Alternatively, you might prefer something on the larger scale. Video after the break.

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Text Projector With — You Know — Lasers

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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Creating Coherent Sound Beams, Easily

Lasers work by emitting light that is “coherent” in that it doesn’t spread out in a disorganized way like light from most sources does. This makes extremely focused beams possible that can do things like measure the distance from the Earth to the Moon. This behavior isn’t just limited to electromagnetic waves, though. [Gigs] via [CodeParade] was able to build a device that produces a tightly focused sound wave, essentially building an audio laser.

Curiously enough, the device does not emit sound in the frequency range of human hearing. It uses a set of ultrasound speakers which emit a “carrier wave” in the ultrasound frequency. However, with a relatively simple circuit a second signal in the audible frequency range is modulated on top of it, much the same way that an AM radio broadcast has a carrier wave with an amplitude modulated signal on top of it. With this device, though, the air itself acts in a nonlinear way and demodulates the signal, producing the modulated signal as audible sounds.

There are some interesting effects of using this device. First, it is extremely directional, so in order to hear sound from the device you would need to be standing directly in front of it. However, once the ultrasound beam hits a solid object, the wave is instantly demodulated and reflected from the object, making it sound like that object is making the sounds and not the device. It’s obvious that this effect is hard to experience via video, but it’s interesting enough that we’d like to have one of our own to try out. It’s not the only time that sound waves and electromagnetic waves have paired up in interesting ways, either.

Thanks to [Setvir] for the tip! Continue reading “Creating Coherent Sound Beams, Easily”

Those Voices in Your Head Might be Lasers

What if I told you that you can get rid of your headphones and still listen to music privately, just by shooting lasers at your ears?

The trick here is something called the photoacoustic effect. When certain materials absorb light — or any electromagnetic radiation — that is either pulsed or modulated in intensity, the material will give off a sound. Sometimes not much of a sound, but a sound. This effect is useful for spectroscopy, biomedical imaging, and the study of photosynthesis. MIT researchers are using this effect to beam sound directly into people’s ears. It could lead to devices that deliver an audio message to specific people with no hardware on the receiving end. But for now, ditching those AirPods for LaserPods remains science fiction.

There are a few mechanisms that explain the photoacoustic effect, but the simple explanation is the energy causes localized heating and cooling, the material microscopically expands and contracts, and that causes pressure changes in the sample and the surrounding air. Saying pressure waves in air is just a fancy way of explaining sound.

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K40 Gets A Leg Up With Open Source Z Table

If you’ve done even the most cursory research into buying a laser cutter, you’ve certainly heard of the K40. Usually selling for around $400 USD online, the K40 is not so much a single machine as a class of very similar 40 watt CO2 lasers from various Chinese manufacturers. As you might expect, it takes considerable corner cutting to drive the cost down that low, but the K40 is still arguably the most cost-effective way to get a “real” laser cutter into your shop. If you’re willing to do some modifications on the thing, even better.

One of the shortcomings of the K40 is that it lacks a Z axis, and with thick material that needs multiple cuts at increasingly deeper depths, this can be a hassle. [Aaron Peterson] decided to take it upon himself to design and build an adjustable Z table for the K40 at his local makerspace (River City Labs), and being the swell guy that he is, has made it available under an open source license so the rest of the K40-owning world can benefit from his work.

[Aaron] started the design with a number of goals which really helped elevate the project from a one-off hack to a sustainable community project. For one, he only wanted to use easily available commodity hardware to keep the cost down. The most complex components should all be 3D printable so the design would be easy to replicate by others, and finally, he wanted the user to have the ability to scale it in all dimensions. The end result is a electronically controlled lifting platform that anyone can build, for any laser cutter. It doesn’t even have to be limited to laser cutters; if you have a need for precisely raising or lowering something, this design might be exactly what you’re looking for.

The table is primarily constructed out of 15×15 aluminum extrusion, and uses standard hardware store expanded wire mesh as a top surface. Height is adjusted by rotating the four 95 mm T8 leadscrews with a GT2 belt and pulleys, which prevents any corner from getting out of sync with the others. Connected to a standard NEMA 17 stepper motor, this arrangement should easily be capable of sub-millimeter accuracy. It looks as though [Aaron] has left controlling the stepper motor as an exercise for the reader, but an Arduino with a CNC shield would likely be the easiest route.

We’ve seen a lot of hacking around the K40 over the last couple of years, from spring loaded beds to complete rebuilds which are hardly recognizable. If you’re looking for a cheap laser with a huge catalog of possible hacks and modifications, you could do a lot worse than starting with this inexpensive Chinese machine.

A Foggy Lightsaber Build

Lightsabers have enchanted audiences since their appearance in the very first Star Wars film in 1977. Unfortunately, George Lucas hasn’t shared the technology in the years since then with the broader public, so we’re left to subsist on pale imitations. This is just such a build.

The closest human analog to Jedi technology is the laser, and this build uses 8 of them in combination with two LEDs. They’re aimed to coincide at a fixed distance above the hilt. A CO2 bicycle inflater is then used to blow through an e-cigarette to create a fog. This makes the red lasers readily visible to the human eye.

This ersatz lightsaber does have its limitations – fast motion tends to scatter the fog, making it once again invisible, and it’s really at its best held in a vertical orientation. There’s also some divergence beyond the focused point. With that said, it does look somewhat impressive when held still, smouldering away.

Until we gain a better mastery of plasma physics, perhaps you can make do with this fire-based build? Video after the break.

[Thanks to qrp-gaijin for the tip!]

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