Lasers

A laser is a device that emits monochromatic light amplificated by stimulated emission of electromagnetic radiation, hence the name (“Light Amplification by Stimulated Emission of Radiation”).

The first laser was built in 1960 by Theodore H. Maiman, based on theoretical work by Charles Hard Townes and Arthur Leonard Schawlow. What makes a laser different from other light sources is the fact that it emits its light coherently. This means that the stream of light will stay narrow over a long distance and can also be focused in a tight spot, like for example for laser cutting or a laser pointer.

A laser consists mainly of five parts: the gain medium, the laser pumping energy, the high reflector, an output coupler and a laser beam. The gain medium is a material which allows light to amplify. This is usually located in an optical cavity. What this means is that there is a mirror on either side of the medium, in order to make the light bounce back and forth. This amplifies the light, as it passes through the gain medium each time. One of the mirrors is usually not 100% reflective, since there will a small output (the laser beam). For anything to happen within the optical cavity we need a power source that allows the gain medium to amplify the light. This energy is supplied through a process called pumping and is usually either light or an electrical current.

When the laser was invented in 1960, it was initially described as "a solution without a problem"(citation?), as it wasn't immediately obvious what it would be useful for. In retrospect we know that this is one of the most valuable inventions in the last 100 years as lasers are used for a wide variety of things; surgery, measurements, information reading and processing, industrial purposes and weapons. They also have a central role in a lot of popular culture and is loved by nerds all over the world.

Enter the bio-laser

In 2011, a paper was published in Nature Photonics[*] on using a single mammalian cell as the gain medium for a bio-laser, describing the coherence and amplification seen in non-biological lasers. There have been several other cases of work on bio-lasers afterwards, including the very successful 2016 TU Delft iGEM project. All of these projects have mentioned the potential of using the amplification effect of a bio-laser to improve sensitivity of existing measurement methods, as the amplification effect of a laser could make for very sensitive changes in the concentration of fluorescent material. This is a potential we wanted to investigate. One of the great limitations of science is the sensitivity of the methods of measurement, and being able to improve this would surely be a boon to cell biology in the future.

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