Physicists have "sharpened" the laser for surgeons
Lasers have become an integral part of modern technology. And they can penetrate even deeper into our lives if we solve a few problems. One of them – the inhomogeneity of the pulses emanating from the laser, embedded in the very design of laser devices, was overcome by scientists of the Scientific and Technological Center of acousto-optics of NUST MISIS in cooperation with colleagues from the Institute of Applied Physics of the Russian Academy of Sciences (IPF RAS) in Nizhny Novgorod. The results of the study are published in the journal Photonics Research (Gacheva et al., Fiber laser with random-access pulse train profiling for a photoinjector driver).
Konstantin Yushkov, one of the creators
laser pulse monitoring systems
The essence of the problem follows from the very principle of laser operation, and is hidden in the mechanism of amplification of the laser pulse. The fact is that the laser beam itself is just light of a certain wavelength. And the initially generated laser pulses are quite weak in their power. For practical use, they need to be strengthened in most cases. But during the amplification, the energy characteristics of the pulses change differently. And if we have a beam of approximately the same pulses at the input to the amplifier, then a strong distortion is obtained at the output. In addition, sources of laser pulses emit them at a single frequency (say, a million per second), while for experiments or for surgery on the retina of the eye, sequences with a frequency of one hundred or, for example, ten thousand pulses per second are needed, and sometimes even single pulses of a given intensity are required.
This problem has been known to scientists for a long time, and they struggle with it in different ways. For example, to create identical pulses at the output, distortions of the flow of incoming pulses are created. However, until now it has been possible to regulate the pulses only at the level of the entire beam. Now a more precise approach has been applied: employees of the Center for Acousto-optics of NUST MISIS Efim Kazanov, Konstantin Yushkov, Alexander Chizhikov and Vladimir Molchanov, in collaboration with colleagues from the Institute of Applied Physics of the Russian Academy of Sciences (IPF RAS) in Nizhny Novgorod, in fact, created a digital system for correcting each pulse in a laser beam, bringing control over laser radiation to a new level.
The creation of new laser pulsed radiation sources with controlled intensity and frequency of pulses in beams is necessary for both fundamental and applied purposes.
Konstantin Yushkov, one of the authors of the development, a leading researcher at the Center for Acousto-Optics of NUST MISIS, tells: "Speaking of fundamental applications, we can use our technology to better control the energy of charged particles in accelerators, which will make it easier and more efficient to find new elementary particles and get to dark matter faster. Also, the technology of controlling the intensity and frequency of laser pulses can be used for more accurate heating of plasma in promising fusion reactors operating on the basis of synthesis reactions. There are also more practical applications – by controlling the intensity of each pulse, we can form a binary, or for example an octal code from our beam. Plus, it is possible to encode information by varying the time between two adjacent pulses by cutting out unnecessary ones. As a result, we get an incredible information transmitter from a conventional pulsed laser, even at one wavelength capable of transmitting several orders of magnitude more information. To give a very rough example, it used to be possible to transmit something no more complicated than Morse code, and now it's a video signal."
There have been talks about such information transfer technology since the early nineties. But the technological level did not allow this opportunity to be realized on an industrial scale. Now it has become quite real. Another application of the development can be found in medicine: due to the control of each pulse, this technology will allow to bring ophthalmic operations, lithotripsy (crushing of kidney stones) and other operations where jewelry laser intervention is required to a new level.
The laser pulse modulation system has already successfully passed experimental testing on an installation being developed at the IPF RAS.
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