Laser physics and nonlinear optics

Works in the field of laser physics and nonlinear optics at IAP RAS are carried out primarily by researchers at the Division of Nonlinear Dynamics and Optics (ND&O). Two scientific schools in optics were established at the division. One of these schools, founded by V. I. Bespalov and G. I. Freidman, is concerned with development of high-power laser systems. The other, named after I. L. Berstein and Ya. I. Khanin, deals with problems of quantum radiophysics, laser dynamics, precision optical measurements, and femtosecond optics. A great role in the development of this research area in Nizhny Novgorod belongs to academician V. I. Talanov and the corresponding member of RAS A. M. Sergeev who headed the ND&O Division for ten years.

The brightest results obtained at the division in the recent years were in the field of femtosecond optics, intense laser fields, and high average power laser sources.

IAP RAS possesses one of the largest Russia's parks of femtosecond laser facilities, including a petawatt laser complex based on parametric amplification in large-aperture nonlinear DKDP crystals, a terawatt Ti:sapphire system, subterawatt Ti-sapphire systems with high pulse repetition rate (1 kHz), and compact fiber-optic frequency-tuned femtosecond lasers. Each of these systems is intended for a specific research program.

The major research program of the ND&O Division in the recent decade was creation of a petawatt radiation source – the femtosecond laser complex PEARL (PEtawatt pARametric Laser). The project was implemented at the department headed by the corresponding member of RAS E. A. Khazanov in collaboration with colleagues from the Russian Federal Nuclear Center (RFNC-VNIIEF, Sarov). PEARL is an experimental base for developing in our country of a new research and technology trend – creation of secondary sources of X-ray and gamma radiation and accelerated particles with unique characteristics based on the interaction of petawatt optical pulses with laser targets.

Creation of PEARL opened up opportunities for constructing at IAP RAS another laser system – PEARL-10 with record multipetawatt power and a feasibility to attain a giant intensity of 1023 W/сm2. Still more ambitious goals are set in the XCELS (Exawatt Center for Extreme Light Studies) project that was included by the RF Government in the list of 6 megascience projects to be implemented in our country in the current decade. The XCELS laser facility will have a radiation peak power of 0.2 EW (200 PW). This power level surpasses the present day world record by more than two orders of magnitude. Achievement of the petawatt power level does not reduce the interest in the problems studied in less powerful femtosecond facilities at IAP RAS.

Many important laser applications concern not only high peak power but also high average power of radiation. These lasers are used in many areas, such as medicine, precision material processing, ecological monitoring, production process control, and military applications. The basic problems in the development of such lasers are related to destruction of their active elements due to high heat load and laser damage, as well as to deterioration of output beam qua lity caused by thermally induced phase distortions and depolarization. Special laser architecture with the use of methods of adaptive and nonlinear optics is developed for solution of these problems at IAP RAS. One of the most promising ways of creating high average and high peak power lasers is coherent combining of beams from multichannel laser systems.

The researchers at the ND&O Division implement projects aimed at creating high average power laser facilities in different frequency ranges and with different pulse durations – from nanoseconds to femtoseconds. Developed are nano- and picosecond lasers with cryogenically cooled disk active elements at the wavelengths of about 1 µm, including ytterbium-doped laser ceramics elements; lasers generating picosecond pulses in the eye-safe wavelength range of 1.5 µm; as well as two-micron lasers based on thulium ions in various matrices, including ceramic ones.

The research carried out at IAP RAS for a few decades enabled creating a unique technology of producing large-aperture nonlinear optical elements of water soluble KDP crystals, including high-rate growth of profiled large-aperture crystals and their precision finishing by the method of diamond micromilling. Development of new technologies of growing large-size nonlinear optical crystals was stimulated, first of all, by the demands of the systems for controlled laser fusion available or constructed both abroad (in the USA, France, Japan) and in Russia (UFL-2М at RFNC-VNIIEF, Sarov). Each such system demands several hundred crystal elements with the aperture up to 40×40 сm that are used in electrooptic shutters and frequency multipliers of laser radiation. Large-aperture DKDP crystals are also key amplifying elements of parametric systems for producing petawatt optical pulses, under the megascience XCELS project inclusive.

IAP RAS achievements in laser physics and nonlinear optics have won worldwide recognition. The researchers of the ND&O Division participate in the major international laser projects: LIGO, VIRGO, ELI, HiPER. The optical devices and laser facilities created here operate in well-known research centers, such CERN, Sandia, KEK, and others.