Gamma waves are the most energetic electromagnetic waves in the EM spectrum. They have the smallest wavelength of 10^-11 meters though 10^-15 meters and highest frequency of all, ranging from 10^21 Hz to 10^24 Hz. They are produced by the most super-hot and energetic structures in the universe, like black holes, supernovas, and neutron stars, but are also found in nuclear material and lightning.
Uses for Gamma Radiation
Gamma radiation is very deadly to living cells, making it a first choice for cancer treatment, as they can kill the cancerous cells and prevent cellular regeneration. It can also be used to identify what kind of activity is happening inside something, like having an asthmatic breathe slightly radioactive material, a device can be used to scan how the patient's lungs are working. This is called "Tracing" and can be used for a number of different objects or body processes. Gamma rays can also kill microbes, making them very useful for sterilizing food or equipment. Harmfully concentrated gamma radiation is given off when either a nuclear reaction is set off or when matter is destroyed by an antimatter, this is the reason nuclear weapons are so destructive because gamma rays cause radioactive decay in large concentrations.
A nuclear explosion. In case you couldn't tell.
Gamma Ray Lens
Gamma ray-amplifying lenses, an idea created and brought to life by both the Ludwig Maximilian University of Munich in Germany and the Institute Laue-Langevin in France, was originally being developed because of the massive success of the x-ray refracting lens invented just beforehand. Gamma waves do not bend very easily, usually going almost straight through a transparent material, however, lenses made of a heavy material like gold can refract gamma waves much more potently, allowing for wearable lenses that allow the user to view gamma waves like they were visible light waves. Once the technology is perfected, anyone that looks through them will, in theory, be able to see gamma waves clearly, making them a perfect nuclear deterrent, as they would be able to detect a nuclear device or even to detect an issue in a nuclear powerplant. Possibilities also exist in the medical industry, allowing for easy tracking of depression by creating a 3D image of the subject's brain on a micrometer range. This technology was released to the official public in 2012.