Normally, you think of things casting a shadow as being opaque. However, new research shows that under certain conditions, a laser beam can cast a shadow. This may sound like nothing more than a novelty, but it may have applications in using one laser beam to control another. If you want more details, you can read the actual paper online.

Typically, light passes through light without having an effect. But using a ruby crystal and specific laser wavelengths. In particular, a green laser has a non-linear response in the crystal that causes a shadow in  a blue laser passing through the same crystal.

The green laser increases the crystal’s ability to absorb the blue laser beam. which creates a matching region in the blue beam that appears as a shadow.

If you read the article, there’s more to measuring shadows than you might think. We aren’t sure what we would do with this information, but if you figure it out, let us know.

Ruby has a long history with lasers, of course. That green laser pointer you have? It might not be all green, after all.

You might think that visualizing music with lasers would be a complicated and difficult affair. In fact, it’s remarkably simple if you want it to be, and [byte_thrasher] shows us just how easy it can be.

At heart, what you’re trying to do is make a laser trace out waveforms of the music you’re listening to, right? So you just need a way to move the laser’s beam along with the sound waves from whatever you’re listening to. You might be thinking about putting a laser on the head of a servo-operated platform fed movement instructions from a digital music file, but you’d be way over-complicating things. You already have something that moves with the music you play — a speaker!

[byte_thrasher’s] concept is simple. Get a Bluetooth speaker, and stick it in a bowl. Cover the bowl with a flexible membrane, like plastic wrap. Stick a small piece of mirror on the plastic. When you play music with the speaker, the mirror will vibrate and move in turn. All you then have to do is aim a safe laser in a safe direction such that it bounces off the mirror and projects on to a surface. Then, the laser will dance with your tunes, and it’ll probably look pretty cool!

We’ve seen some beautiful laser visual effects before, too. Just be careful and keep your power levels safe and your beams pointing where they should be.

put a bluetooth speaker in a bowl, cover the bowl with plastic wrap pulled taut, glue a shard of mirror to the plastic wrap, point a laser beam at the mirror so that it bounces off towards the ceiling, play music, enjoy pic.twitter.com/Vs6lBJihCg

— avi (@byte_thrasher) November 9, 2024