The World's First Hydraulic Laser

August 29th, 2011

Here’s a video demonstrating how it works:

The basic concept arose from something I noticed many years ago. I finally got around to building one and it worked on the first attempt. This is not at all like a hydraulic ram or similar pump; it operates on exactly the same principles as a real optical laser. Here’s a diagram of its layout:

The drop of water falling from the second edge into the pool has kinetic energy, so it creates a small splash, which in turn makes a ripple – a wave – that travels forward to the edge. As it approaches the edge, the wave’s height increases, just like a wave at a beach. When the wave hits the edge, the water in the wave spills over the edge and into the next pool. The key idea is that MORE water splashes over the second edge than splashed over the first edge – and the reason why there’s more water is the kinetic energy of the falling drop of water. Since each step adds more water and therefore more kinetic energy to the wave, it grows larger and larger with each step.

There are many variables to consider in optimizing this process. I have drawn the steps as right triangles, but I suspect that this might not be optimal. The frequency of the laser pulses out the bottom of the laser depends upon the time it takes for a wave to bounce back and forth from the edge to the high wall and back. I considered replacing the wedge-shaped steps with thin dams set at an angle, and that might improve performance, but it also destroys the wave-heightening effect of the shallowing bottom of the pool. Another crucial factor is the tilt angle of the laser, but this also depends upon the water flow rate. If there’s too much water, then we’ll just get a turbulent flow down the staircase, rather like rapids in a river. I believe, and have roughly confirmed, that the most pronounced laser action appears with the lowest flow rates, but this gets difficult to measure because, as the peak-to-trough distance of the pulses rises, the peak height itself falls. In other words, with very low flow rates, the pulses are more pronounced, but they’re also tiny. 

What good is it?
If you asked this question, then you flunk Science 1A. Science is about learning about the universe, not building great machines. Often, of course, our discoveries lead to useful applications, and in fact, I can think of three useful applications of a hydraulic laser.

Educational: This device beautifully illustrates how an optical laser operates. It shows in plain mechanical terms what happens at the quantum level.

Entertainment: Perhaps a really strange water slide at a water park? Surely a videogame can be built using this technology.

Military: almost any new discovery in physics can be weaponized. Imagine a 500-foot high hydraulic laser fed with a fire hose, shooting out blasts of water that obliterate tanks trucks, buildings, etc.

I’m putting this idea into the public domain: anybody is free to use it in any manner they desire. I do ask that you credit me. Also, if you build one and come up with a design improvement, please notify me and send me details so that I can add your embellishments to this page. Let’s treat this as an “open source” laser.