| Infrared laser light, known as the pump, is beamed into a ring-shaped microresonator and converted through an optical parametric oscillation into two new wavelengths of light, known as the signal and the idler (top). The signal has a wavelength that lies in the visible range while the idler has an infrared wavelength that is longer than that of the pump laser. Since energy is conserved, the energy carried by two pump photons must equal the sum of the energy carried by a single photon from each of the two output wavelengths (bottom right). Credit: S. Kelley/NIST. |
