A team from the L.V. Kirensky Institute of Physics of the Siberian Branch of RAS and Siberian Federal University (SFU) suggested a new approach to developing a dynamically controlled diffraction grating in atomic media that eliminates all existing limitations in this area. Diffraction gratings are able to deflect light beams in different directions and are included into various devices due to this property. The results of the study were published in the Physical Review A journal.
Diffraction gratings are an important tool not only for scientific research but also for practical applications. They are used in acoustic and integral optics, holographics, optical data processing, and spectral analysis. Being an optical component with a periodic structure, a grating can deflect (diffract) a light beam from its initial path and break it into several beams scattered into different directions. The gratings with dynamically controlled properties are of great interest for science and technology.
Modern approaches to developing such grids are based on induced changing of their absorption properties using the effect of electromagnetically induced transparency. Under certain conditions an opaque medium may perming the light of a laser with a certain wavelength though in the presence of another (managing) laser radiation. If the managing radiation is a standing wave (the fluctuation amplitude has stable ups and downs), the medium becomes periodically spatially modulated, i.e. its properties change according to a certain periodic law. Such a medium can acts as a diffraction grid, but has considerable limitations.
"Periodic atomic structure based on electromagnetically-induced transparency is not efficient in cases of considerable deflection of the passing light, because the signal is not very intensive and difficult to control. In our work we presented a completely different approach that has no such challenge," explains Vasily Arkhipkin, head of the laboratory of coherent optics of the Kirensky Institute of Physics SB RAS, and Professor of the Institute for Engineering Physics and Radio Electronics, SFU.
The model of the Siberian scientists is based on the Raman-type interaction between the signal radiation and the standing pump wave (with increased fluctuation amplitude) that may increase the diffracted signal wave. In case a grating is based on electromagnetically-induced transparency, the light is controlled due to changes in the absorption in presence of varying external conditions. On the contrary, the new approach is based on spatial modulation of Raman amplification. As a result, under certain conditions, the diffracted fields may be considerably enhanced. According to calculations, this scheme allows for the control of strongly diffracted (deflected) beams and diffraction angles.
"We called our scheme a Raman-induced diffraction grating. The peculiarities of the outcoming signal and possibilities for adjustment make it a multi-beam optical beam splitter with amplification," concludes Sergey Myslivets, candidate of physical and mathematical sciences, senior research assistant at the Institute of Physics of SB RAS and the Institute for Engineering Physics and Radio Electronics, SFU.