Researchers in the United States have built a lithium-niobate microresonator on a chip and shown that it can produce photon pairs more than 100 times more efficiently than other chip-based photon sources. By integrating it with other optical components, they reckon the tiny resonator could help enable the “pervasive adoption” of quantum devices.
The microresonator, made on a micron-thin layer of crystal, generates photon pairs via the nonlinear process of spontaneous parametric down-conversion (SPDC). An intense laser beam directed at the device leads photons to be confined within the structure, where some of them split into pairs of photons at lower energies.
Lithium niobate, an artificial salt, is one of the most widely used crystals for such research, as it exhibits significant optical nonlinearities; it’s also transparent across a range of frequencies and generates strong electro-optic effects. As a result, the material is already employed in numerous optical and electronic devices.