Telecommunications will be pushed to a new level through the development of scientists from Moscow State University and Russian Skolkovo quantum center made jointly and foreign counterparts: they have managed to make a breakthrough in the creation of compact, stable working optical devices for generating stable ultrashort laser pulses.
Development electronics and communications equipment base requires increasing accuracy, ergonomics and throughput. So, for communications satellites and GPS-navigation is very important reduction of the mass of useful equipment and noise reduction, as well as ensuring the stability of the signal.
Silent combs GPS
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Last year MSU scientists together with Swiss colleagues conducted a work that could serve this purpose. Then the researchers were able to show that the reason why the optical “comb” (a wide range of a large number of equidistant narrow lines) arise noise lies in the nonlinear processes of generation and not in thermodynamic noise. For the first time it was found that the interference is not due to some fundamental limitations, and they can fight. The corresponding work was published in Nature Photonics, «Times” told about it .
Night December 23 Moscow time in the journal Nature Photonics published a new article on how scientists are developing and extending its success.
According to one of the authors, Professor of the Faculty of Physics, Moscow State University and Russian officer quantum center in Skolkovo Michael Gorodetsky, the study actually received three important results: scientists developed a method for the generation of stable femtosecond (about 10 – 15 seconds) of the pulses, optical “comb” and microwave frequencies.
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Scientists using microcavity (in this case – mm disc of crystal magnesium fluoride, which can be excited looped, ie moving along a closed path electromagnetic waves) managed to turn a continuous laser radiation in periodic ultrashort pulses. Known devices operating in this mode are the femtosecond laser, which is generated at a rapid short duration comparable with 10-15 seconds of high power pulses.
Without them embedded in modern spectroscopic methods substance research and telecommunications, and even modern ophthalmology in which femtolazery used for eye surgery.
«In a mode-locked lasers to generate pulses uses sophisticated optical devices, media and special mirrors. We were able to get such stable pulses in a simple passive resonator using only the intrinsic nonlinearity of the crystal “, – says Gorodetsky. This allows to dramatically reduce the amount of perspective of the device.
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generated in microcavity short pulses are so-called optical solitons (soliton – is a stable particle-like wave propagating in a nonlinear medium, an example of a soliton in nature – the tsunami ). “We can generate stable single soliton, which runs inside the microcavity in a circle. In this case, the output fiber obtained pulses following each other through one revolution, “- says Gorodetsky.
duration of such pulses 100-200 femtoseconds, but the authors believe that actually achieve significantly shorter solitons.
They believe that their innovation is the creation of compact, stable and cheap generators of short optical pulses in regimes unattainable by other methods. Such pulses in spectral terms are so-called optical “comb”, which revolutionized metrology and spectroscopy, and were awarded the Nobel Prize in 2005 (it received the American John Hall and Theodor Hänsch German “for his contribution to the development of laser precision spectroscopy, including the optical technique chaser »).
Existing generators combs have much larger dimensions.
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same time, as shown by the researchers, the electrical signal from a comb is a very clean microwave signal with low noise. Ultra low-noise compact microwave generators play a huge role in modern technology and are used in metrology, radar, telecommunications equipment, including satellites.
The authors note that their results are critical for the development of areas such as broadband spectroscopy, telecommunications, radar and astronomy.
Material prepared by the department of science “Gazety.Ru” and MSU in cooperation with the “Festival of Science» .
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