Way back in the 1960s, the newly invented laser was described as “a funny but useless experimental demonstration in physics”, and a “solution looking for a problem”. Today though, lasers are an integral part of everything from DVD burners to semiconductor manufacturing to eye surgery. Could you imagine a world where cats have no red dots to chase?
I didn’t think so.
What astonished me though, is that nobody ever thought to shine one through a drop of water. If, by chance someone has, then it’s quite odd that nobody took the time to document its effects. That is, until now. Upon witnessing the image of a mosquito magnified in a laser beam outside, I decided to investigate the phenomenon further.
The experiment was started by first, locating some dirty water. Ponds lacking it seemed that the next best option was a sample of water from a potted spider plant.
A plastic syringe was filled and hung above a laser so that a drop of water, almost ready to fall, was in the beam path. Below is a diagram of the incredibly complex apparatus involving a book, sticky-tac, a 250mW DPSS green laser and a plastic syringe. Glass ones didn’t seem to work too well as there was not enough cohesion to prevent the drop from falling.
While I originally hypothesized that nothing special would come from the experiment, the results were quite surprising.
For the most part the projection was a bunch of blobs swimming around, but their irregular motions suggest that these blobs are in fact, living bugs.
Interference greatly reduces the detail of the projected image, and from the looks of it this is due to the fact that my laser had a high mode beam. Since the transverse mode is not TEM00, the ‘beamlets’ wreak optical havoc on the projected image…
Retrying the experiment with a 445nm laser diode proved to be fruitless, as the beam emitted from such a diode laser is of much worse quality than the one emitted from even this cheap DPSS laser. Sadly, I have no images to show for that later experiment. A red diode provided an even worse projection, though that could be due to its longer wavelength.
As of right now, my research in this ends here. Until high-powered single mode laser diodes become available, there is not much left that I can do! ∎