Physicists create new slow-light technique
Physicists create new slow-light technique
A physical phenomenon that is widely used to slow and store pulses of light in clouds of atoms has been seen for the first time in a system of nuclear-energy levels. The breakthrough has been made by a team of physicists in Germany that has seen evidence for the phenomenon, known as electromagnetically induced transparency (EIT), as X-rays pass through nanometre-scale layers of iron. The researchers think their method, which is also the first to achieve EIT using just two energy levels rather than the usual three, could lead to the development of devices for controlling X-rays, which is currently very tricky to do.
EIT occurs in special media that do not usually transmit light at a certain wavelength but can be made transparent by applying a second "control" beam of light at a slightly different wavelength. If this control beam is switched on and off at just the right time, EIT can been used to slow down a pulse of light.
EIT requires that atoms within the medium to have a specific configuration of three energy levels in which transitions between one specific pair of levels are forbidden. While such three-level configurations can be found in many atomic systems, they are not readily available in nuclear systems. To get round this problem, Ralf Röhlsberger and colleagues at the DESY lab in Hamburg have devised a way to make a two-level nuclear system behave like a three-level system suitable for EIT. The researchers also hope that similar techniques could be applied to other two-level systems such as quantum dots.
