by Scott Mattison (@Fools Pizza)
Last time, we determined a theoretically useful wavelength (500 nm) for arming sharks with a laser beam. This wavelength was useful as it would provide a decent transmission range through salt water. There are still three more major challenges facing the successful completion of our design (and several other smaller ones).
Laser is actually an acronym for light amplification through stimulated emission of radiation. Stimulated emission is the release of a photon of light as an electron relaxes from an excited energy state back to a ground state after absorbing energy. This means that when one photon goes in, two photons come out, generating additional light. Stimulated emission was predicted in Einstein’s quantum theory of radiation, and the first laser was built in 1960 by Theodore Maiman.
The big take away of stimulated emission is that to build a laser, we typically need electrons to be in an excited state. There are several different materials that can give light amplification through this method including glasses infused with rare earth elements, semi-conductor materials, dyes, and even various gases like carbon dioxide and Helium Neon.
There are important considerations for selecting the type of laser for a specific application. In our case, we are going to be operating a laser in the ocean, without an easy method for retrieval. Fortunately, as we are subcontracting for an evil organization, money is not a major consideration. However, the movements of the shark and harsh conditions of the ocean would require a stable laser source, and we need this source to be fairly small, as we do not want the laser to interfere with the shark’s ability to swim. Most importantly, we want to be able to cook a fish from a distance. From the American National Safety Institute standard Z136.1, we can determine the maximum safe exposure for skin to a laser beam. We will assume that we want the fish to cook in under 0.1 seconds as both the shark and fish will likely be moving. This means that we will require a laser intensity of over 6 W/cm2 just to pass the safety threshold of laser exposure. Likely, a high powered diode pumped solid state laser could provide the power and stability we need at our target wavelength; however, there are still a few more issues to consider.
The second major challenge is building a laser that can actually cook a fish underwater. Lasers are excellent at providing targeted heating. That is what makes lasers great tools for precision cutting, which is why we have laser cutters and use lasers for targeted treatment of cancers. Unfortunately, despite what movies and television shows tend to depict (looking at you Big Bang Theory), this means lasers are not good at doing more than targeted heating. With a laser, the shark isn’t going to get a warm meal, instead it will simply sear meat in one location. In fact, if we increase the laser power to increase heating, we are more likely to cut the fish in half than actually cook it (think laser cutter). We could work around this using beam steering components, but even if we could steer the beam to hit the shark’s meal, our laser wouldn’t penetrate deeply enough into the fish without burning away the outer layers (this would also probably smell terrible).
If this wasn’t enough of a problem, our final challenge is powering this laser, underwater. A laser diode runs typically with no better than 20% efficiency. This means to output 1 watt of optical power, the laser requires 5 watts of electrical power. Obviously, to save energy (and increase competitive advantage), the laser would not be operating constantly and instead would use some form of motion tracking to switch on and off. Even under these conditions, the laser would require a very powerful battery in order to operate effectively. Currently, finding a lightweight and durable power source that the shark can carry around and provide a long enough operational lifetime to make the efforts worthwhile is a tough challenge. This might be the final deal breaker in our arming sharks with laser beams scenario.
So far we have really only discussed the large number of technical challenges to arming sharks with laser beams to provide a warm meal. We have completely ignored the ethical dilemmas (short answer: it’s bad) and whether the laser would even provide a competitive advantage to the shark (it won’t). Additionally, we haven’t even discussed how to actually arm the sharks with lasers. Based on this low level of analysis, we can conclude that following the ideas of a person who calls himself Dr. Evil might be a bad idea.