This device can generate deep-UV light with a very narrow wavelength range that is safe for humans but lethal for germs. This device can generate deep-UV light with a very narrow wavelength range that is safe for humans but lethal for germs. The researchers have overcome these challenges by using a process called ‘second harmonic generation,’ which relies on the fact that the frequency of a photon, or particle of light, is proportional to its energy. By using a specially designed waveguide that can control the orientation of the aluminum-nitride crystal, the resear...