 Researches & Developments
2009:
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The development was completed of a computer-controlled widely
wavelength-tuneable laser aimed at research and technological problems in the
domain of nano-physics and biology. The full working spectral range of this
laser extends from 275 to 1100 nm, while delivering the output line width of
0.5–1 GHz. Automatic tuning of the laser to a specified wavelength is done
with the help of a built-in high-precision wavelength meter and a proprietary
efficient algorithm of control over the selective elements of the laser.
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An all-fibre super-continuum generator has been developed that delivers
record-high output pulse energies reaching 40 uJ. This generator was created
on the basis of a unique ultra-long ytterbium master oscillator with output
pulse energy 4 uJ and a subsequent amplification stage, the output from which
was further guided into a 30-m long micro-structured fibre. With the pulse
duration 10 ns and their repetition rate 37 kHz, high-energy super-continuum
was generated within the spectral range of 500–1750 nm.
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An investigation was carried out of an unusual generation mode
observed for the first time in Yb lasers that features trains of picosecond
pulses with stochastic femtosecond ‘filling’. It was demonstrated that the
observed mode may impede the single-pulse generation in long mode-locked
fibre lasers. The newly obtained generation mode is characterised by a
peculiar double auto-correlation function of the output pulses having a narrow
femtosecond peak on a picosecond pedestal.
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2008:
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Mode-locked fiber laser was developed with a few record-breaking
parameters for this type of lasers: record-setting optical length of the
resonant cavity amounting to 3.8 km, ultra-low pulse repetition rate (77 kHz)
and energy per pulse reaching 3.9 uJ without Q-switching, cavity
dumping techniques, or additional optical amplifiers.
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Original fiber-based Q-switched master-oscillator &
power-amplifier system was developed by using Yb fiber with side pumping by
single source. The passive Q-switched system provides for pulse energy up to
110 uJ at CW 12 W single pump. Duration and repetition rate of generated
pulses at 1080 nm can be varied from 280 ns to 1,8 microsecond, and in the
range of 45-140 kHz depending on pump power at 980 nm.
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Different methods for dynamic control of parameters of
super-continuum generated in fibers both under pulse and CW pumping were
developed and researched. We show experimentally and numerically a sensitivity
of supercontinuum spectral power density to wavelength and repetition rate of
pump pulses. A novel method for control of SC generation under CW pumping is
proposed. We discuss the method for control of repetition rate and duration of
pulses generated with the help of dual-wavelength pumping by means of
adjusting input power and frequency difference. Developed super-continuum
generators with enhanced set of controlled parameters are essential for
cytometry, tomography, spectroscopy, communications and for other applications.
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2007:
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For the first time we experimentally demonstrate an efficient
method for the reduction of long-term radiation line drift in single-frequency
cw Ti:Sapphire and Dye lasers that relies on a fast and precise
wavelengthmeter together with a digital–analog feedback system.
The essence of this approach is in the use of high-precision radiation
wavelength meter as a spectral reference. Generation line drift of
lasers was reduced approximately by an order of magnitude down to 40 MHz/hour,
which corresponds to the residual drift in readings of the wavelength meter
itself. The implemented automatic frequency control system allows to locks
the laser generation frequency to a specified absolute value. This approach
may be used in single-frequency lasers of different types (solid-state, fiber,
diode, dye lasers, etc.)
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We research hybrid sub-picosecond systems based on a solid-state
Yb:KYW laser and a side-pumped fibre ytterbium amplifier manufactured using
GTWave technology. When the system was pumped with 12 W of CW radiation at
980 nm 0.9-ps output pulses with energy 40 nJ were generated at the repetition
frequency of 100 MHz and the average radiation power 4 W. The centre wavelength
of the system could be detuned within 1035–1055 nm (pulsed mode) and 1030–1070
nm (CW mode).
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Supercontinuum generation in optical fibers under pulsed and CW excitation is
studied. It was shown that different applications impose different and,
sometimes, opposite requirements on supercontinuum radiation. The optimal
generation regimes are analyzed with regard to various
applications of the effect.
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