Ever wish you could do a little target shooting in a galaxy far, far away? Well then you’re in luck, as the Star Wars inspired GlowBlaster designed by [Louis Abbott] can help you realize those dreams with a real-life laser pistol — albeit a much weaker one than you’d want to carry into a Mos Eisley cantina.

Inside the 3D printed frame of the GlowBlaster is a 5 mW 405 nm module, an Arduino Nano, a speaker, a vibration motor, and a 9 V battery. When you pull the trigger, it pushes down on a 12 mm tactile button which causes the Arduino to fire the laser and sprinkle in a bit of theatrics by way of the speaker and vibration motor. There’s also a second button on the side of the blaster that lets you pick between firing modes.

The idea behind this project is that even a momentary blast from a 405 nm laser will excite a phosphorescent material enough that it will show a hit. So all you’ve got to do is draw a target on a glow-in-the-dark sheet, and you’ll be able to see where your shots land from clear across the doom. Admittedly it will have to be a dimly lit room, but still.

Technically that 5 mW figure puts the GlowBlaster’s output on par with a laser pointer, but in the documentation, [Louis] cautions that laser modules sourced online are often more powerful than their labels claim. So you, and anyone else around, would be wise to wear eye protection while the laser is being fired.

This is a far simpler solution than previous laser marksmanship projects we’ve covered, as the target side is totally passive. Although we have to admit, seeing the target actually get knocked down is a lot of fun.

You can get a red laser diode pretty cheap these days—as cheap as £1 in fact. [Beamer] had purchased one himself, but quickly grew bored with just pointing it at the walls. He decided to figure out if he could use it for some kind of communication, and whipped up a circuit to test it out.

To do the job, he designed a modulator circuit that could drive the laser without damaging it. The build is based around the common 7805 regulator and the venerable 555 timer IC. The 555 is set to pulse at a given rate with the usual array of capacitors and resistors. Its output directly drives the input of a 7805 regulator. It’s set up as a constant current source in order to deliver the correct amount of current to run the laser. The receiver is based around a photodiode, which should prove fairly straightforward.

[Beamer]’s still working on the full setup, but plans to use the laser’s pulses to drive a varying analog meter or something similar. Not every communications method has to send digital data, and it’s good to remember that! Video after the break.

Lasers are pretty much magic — it’s all done with mirrors. Not every laser, of course, but in the 1980s, the most common lasers in commercial applications were probably the helium-neon laser, which used a couple of mirrors on the end of a chamber filled with gas and a high-voltage discharge to produce a wonderful red-orange beam.

The trouble is, most of the optical power gets left in the tube, with only about 1% breaking free. Luckily, there are ways around this, as [Les Wright] demonstrates with this external passive cavity laser. The guts of the demo below come from [Les]’ earlier teardown of an 80s-era laser particle counter, a well-made instrument powered by a He-Ne laser that was still in fine fettle if a bit anemic in terms of optical power.

[Les] dives into the physics of the problem as well as the original patents from the particle counter manufacturer, which describe a “stabilized external passive cavity.” That’s a pretty fancy name for something remarkably simple: a third mirror mounted to a loudspeaker and placed in the output path of the He-Ne laser. When the speaker is driven by an audio frequency signal, the mirror moves in and out along the axis of the beam, creating a Doppler shift in the beam reflected back into the He-Ne laser and preventing it from interfering with the lasing in the active cavity. This forms a passive cavity that greatly increases the energy density of the beam compared to the bare He-Ne’s output.

The effect of the passive cavity is plain to see in the video. With the oscillator on, the beam in the passive cavity visibly brightens, and can be easily undone with just the slightest change to the optical path. We’d never have guessed something so simple could make such a difference, but there it is.

If sharks with lasers on their heads weren’t bad enough, now China is working on submarines with lasers on their butts. At least, that’s what this report in the South China Morning Post claims, anyway.

According to the report, two-megawatt lasers are directed through fiber-optic cables on the surface of the submarine, vaporizing seawater and creating super-cavitation bubbles, which reduce drag on the submarine. The report describes it as an “underwater fiber laser-induced plasma detonation wave propulsion” system and claims that the system could generate up to 70,000 newtons of thrust, more than one of the turbofan engines on a 747.

The report (this proxy can get around the paywall) claims that the key to the system are the tiny metal spheres that direct the force of the cavitation implosion to propel the submarine. Similar to a magnetohydrodynamic drive (MHD), there’s no moving parts to make noise. Such a technology has the potential to make China’s submarines far harder to detect.

Looking for more details, we traced the report back to the original paper written by several people at Harbin Engineering University, entitled “Study on nanosecond pulse laser propulsion microspheres based on a tapered optical fiber in water environment“, but it’s still a pre-print. If you can get access to the full paper, feel free to chime in — we’d love to know if this seems like a real prospect or just exaggerated reporting by the local propaganda media.

[Image via Wikimedia Commons]

No matter how small you make a pair of tweezers, there will always be things that tweezers aren’t great at handling. Among those are various fluids, and especially aerosolized droplets, which can’t be easily picked apart and examined by a blunt tool like tweezers. For that you’ll want to reach for a specialized tool like this laser-based tool which can illuminate and manipulate tiny droplets and other particles.

[Janis]’s optical tweezers use both a 170 milliwatt laser from a DVD burner and a second, more powerful half-watt blue laser. Using these lasers a mist of fine particles, in this case glycerol, can be investigated for particle size among other physical characteristics. First, he looks for a location in a test tube where movement of the particles from convective heating the chimney effect is minimized. Once a favorable location is found, a specific particle can be trapped by the laser and will exhibit diffraction rings, or a scattering of the laser light in a specific way which can provide more information about the trapped particle.

Admittedly this is a niche tool that might not get a lot of attention outside of certain interests but for those working with proteins, individual molecules, measuring and studying cells, or, like this project, investigating colloidal particles it can be indispensable. It’s also interesting how one can be built largely from used optical drives, like this laser engraver that uses more than just the laser, or even this scanning laser microscope.