Black phosphorus (BP) is a material made up of atomically thin layers of phosphorus atoms that has remarkable electrical and mechanical properties, much like graphene (an atomically thin sheet of carbon atoms). Since 2014, a series of studies has shown that samples of BP less than 10 atomic layers’ thick display exceptional optical characteristics. A new study by researchers at the Graphene and Nanomaterials Research Center of Mackenzie Presbyterian University (MackGrafe) and the National University of Singapore (NUS) has once again found that BP has the potential to manipulate light on a nanometric scale (Advanced Materials, October 18, 2016). Led by Christiano de Matos and Rafael de Oliveira, of MackGrafe, and José Viana Gomes, of the NUS, the research team fired ultrafast pulses of high-power infrared laser at samples of BP. “We observed that the material emitted a very bright green light,” says Matos. The researchers demonstrated that BP electrons can combine the energy from three light particles (photons) emitted by the infrared laser into a single green photon with three times the energy. According to Matos, the extremely efficient emission of this light, at triple the frequency and energy, suggests that BP may also be capable of producing similar effects when it comes to mixing photons. This property may prove useful in the development of nanophotonic circuits that are smaller and more efficient than current devices.