Novosibirsk State University

R&D Researches & Developments


atomic clock

Miniaturised atomic clock with reduced energy consumption

Studied are the prospects of reduced energy consumption of a quantum frequency standard on the basis of coherent population trapping effect. It is established that energy consumption may be reduced by a factor of 1.5 without significant worsening of the clock stability compared to the standard implementation through optically pumping of 87Rb vapour with multi-frequency laser radiation formed by sidebands of a single frequency diode laser when its injection current is modulated at a fractional (1/3) frequency of the hyperfine splitting of the ground state.

wavelenth tuning

Femtosecond erbium fibre laser with record-wide output wavelength tuning

Developed and studied is a mode-locked erbium fibre laser featuring uniquely broad tuning of the central wavelength of its femtosecond pulses from 1524 to 1602 nm. The proposed novel drop-shaped cavity topology of this fibre laser allowed creation of a compact broadly tuneable fs fibre laser of a new generation with only one discrete volumetric element—a diffraction grating used for spectral tuning of the laser’s output.



Raman femtosecond pulse clusters with record-high energy

A new approach has been developed to a single-stage Raman conversion of laser pulses from the 1.1-um spectral range into that of 1.3 um. The conversion is performed with the aid of femtosecond pulse clusters, synchronous pumping of an external phosphosilicate fibre resonator, and locking of the pump pulse repetition rate to the inter-mode frequency of the external cavity. This resulted in generation of femtosecond pulse clusters with record-high energy of 63 nJ at 1270 nm. The cluster envelope had duration of 88–180 ps, while individual sub-pulses were 200-fs long.

wavelenth tuning

Ultrashort-pulsed fiber laser with electronic control over generation regimes

For the first time, we demonstrate that broadly different generation regimes can be sustained in an mode-locked ytterbium fibre laser. Electronic control allowed establishment of stable pulse generation regimes with varying degree of coherence and adjustment of their parameters within comparatively broad limits: duration, by more than a factor of 2 (30–65 ps for coherent pulses and 77–160 ps for incoherent ones); energy, by more than a factor of 8 for coherent pulses (1.9–16.2 nJ) and by over an order of magnitude for incoherent ones (2.2–24.8 nJ). The proposed laser features a relatively high maximal average output power (340–520 mW, depending on the generation regime) achieved without any additional amplification stages.



Laboratory prototype of compact atomic clock

A laboratory prototype of atomic reference clock has been developed and built on the basis of a coherent population trapping resonance in 87Rb vapour contained in a miniature spherical optical cell with anti-reflection coating. The reference frequency stability is demonstrated at 7x10–13 over a 1000-s period. Frequency stability achieved in the developed system approaches the theoretical limit for a similarly sized cell.

Pulse compression

Fibre-based linear compressor of ultra-short pulses

A linear compressor of phase-modulated ultra-short pulses has been developed on the basis of optical fibre with anomalous dispersion and relatively large core diameter (25 um) close to the critical size for single-mode light propagation. The developed device compresses input pulses down to Fourier limit at peak power of up to 9.4 kW or the average radiation power of 120 mW. At radiation power exceeding these values, compression is possible down to a certain shortest duration, which is longer than the theoretical Fourier minimum and is determined by a minimal achievable value of the time-bandwidth product of the input pulses over an optimal length of the fibre-optical compressor.



Powerful Yb-fibre ultrashort-pulse master oscillator

We developed and manufactured an Yb-fibre master oscillator mode-locked by a non-linear amplifying loop mirror and featuring record-high average output power exceeding 1 W. Generated femtosecond clusters at repetition rate of 25 MHz had envelope duration within 23 ps and typical duration of internal sub-pulses below 200 fs.

Pulse compression

Frequency-doubled CW fibre laser

A CW fibre laser has been developed and built that features frequency doubling in a high-finesse cavity partially coupled with the laser resonator. This frequency-doubling configuration of a CW fibre laser in a partially coupled external cavity has been proposed for the first time and resulted in substantially higher frequency doubling efficiency at relatively low fundamental pump power, at the same time allowing efficient spectral tuning of the second harmonic radiation line within the 521–545 nm range.



Autoscanning laser: high-precision computer-controlled wavelength tuning in ultra-wide spectral range

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.

High-energy pulse fibre supercontinuum source

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.

Generation of double-scale femto/pico-second optical lumps in mode-locked fiber lasers

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.



Unique pulsed fiber laser was developed with record-breaking parameters

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.

A novel Q-switched fiber system was developed

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.

Methods of dynamically control the parameters of fiber supercontinuum generators were developed and researched

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.



New approach to long-term stabilisation of radiation frequency generated by single-frequency lasers has been experimentally demonstrated

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.)

Unique hybrid fiber/bulk laser system was designed

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).

Fiber supercontinuum generators are investigated at pulsed and CW pump

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.