Theoretical and experimental studies of the photon and stimulated photon echo generated at the transition 0-1 of Yb-174 atoms are reviewed. Analogues of the phenomena induced by collisions of Yb-174 atoms with buffer gas atoms are also considered. The nature of collisions is analyzed.

The kinetics of the reflection signals of the nanostructures consisting of the same number of quantum wells with identical compositions InxGa1-xAs (x = 0, 32) with barriers of GaAs consisting of 2, 4, 6, and 8 monolayers grown on a semiconductor reflector under identical conditions has been studied by the pump-probe method. A trend of reduction of the recovery time for thinner barriers has been revealed. The prospects of further investigation and practical application of quantum wells coupled by tunneling of charge carriers have been discussed.

The influence of the structure of quantum wells and the features of their manufacturing technology on the performance and maximum modulation depth of optical gates based on quantum wells A(3)B(5), designed for mode locking of near-IR lasers, is analyzed.

Experimental data have been obtained for the relaxation rates of population, orientation, and alignment of the 174 Yb(6 s 6 p ) 3 P 1 level due to collisions of 174 Yb atoms with atoms of noble gases.

В докладе сообщается о корреляции между строением квантовых ям (их состав, толщина барьеров, концентрация дефектов, степень согласованности по параметрам решетки материалов квантовых ям и барьеров и даже особенности технологии переноса слоев квантовых ям на диэлектрический широкополосный отражатель) и основными параметрами оптических затворов (механическая прочность, уровень ненасыщаемых потерь, максимальная глубина насыщения и быстродействие).

The article presents a review of the design and manufacturing technology, methods and results of research on optical spectra and reflection kinetics of coupled quantum wells A(3)B(5), as well as the results of using optical gates developed on their basis for femtosecond laser mode locking Yb3+:KY(WO4)(2) with a high pulse repetition rate (about 1 GHz).

Проанализировано влияние строения квантовых ям и особенностей технологии их изготовления на быстродействие и максимальную глубину модуляции оптических затворов на основе квантовых ям A3B5, предназначенных для синхронизации мод лазеров ближнего ИК-диапазона.

For the first time, a complete set of decay parameters, due to collisions of 174Yb atoms with noble gas atoms and with ytterbium atoms, was experimentally found for the 174Yb (6s6p) 3P1 level. The method of stimulated photon echo with special angles between the polarization vectors of light pulses forming an echo at the 174Yb (6s2) 1S0—(6s6p) 3P1 transition (type 0↔1 ) is used. For each buffer gas of He, Ne, Ar, Kr, Xe, and Yb, the decay rate constants of population, orientation and alignment for the collision destruction of the 3P1 level of 174Yb atoms are determined. All the decay rates demonstrated their linear increase with a buffer gas pressure, and the corresponding relaxation constants are determined. Each of the indicated relaxation constants, as well as the difference between the alignment and orientation relaxation constants, increases with the increasing buffer gas mass.

A stable passive mode-locking regime for a Yb:KYW laser using two types of optical shutter was obtained. The first type was a SESAM and the second type was based on the same type saturable absorber with a dielectric reflector DSAM. The typical parameters of the mode-locking regime were as follows: a pulse duration of about 200 fs for both types of shutter, an average power of 2.54 W for SESAM and 0.92 W for the DSAM. The efficiency relative to the incident pump power was 57% for the SESAM and 19% for the DSAM. The mirror damage threshold estimate for the SESAM was at least 8.9 mJ cm -2 .

A stable passive mode-locking regime for a Yb3+ :KY(WO4)(2) laser with optical pumping by a continuous diode laser was obtained using two types of optical shutter with a saturable absorber based on coupled GaAs/In0.25Ga0.75As/GaAs quantum wells. The shutters differed in their reflecting part: the first type was a semiconductor mirror and the second type was a dielectric one. The typical parameters of the mode-locking regime were as follows: a pulse duration of about 200 fs for both types of shutter, an average power of 2.54 W for the allsemiconductor shutter (SESAM) and 0.92 W for the dielectric mirror with a saturable absorber (DSAM). The efficiency relative to the incident pump power was 57% for the SESAM and 19% for the DSAM. The maximum pulse repetition rate was 982 MHz. The measured recovery time was about 2 ps for both saturable absorbers. The mirror damage threshold estimate for the SESAM was at least 8.87 mJ cm(-2).

12W-picosecond SESAM mode-locked Yb:LuAP laser was developed. 2ps-laser pulses were obtained at the central wavelength around 999nm and optical-to-optical efficiency of 38% at 70MHz PRF. 4.8W of second harmonic radiation was obtained using 20mm LBO crystal with critical angular phase matching. Tunability from 668nm to 783nm was obtained in preliminary experimental study of LBO based synchronously pumped OPO.

A series of high-voltage (20–50 kV) DC power sources (1–10 kW) was developed based on the circuit of high-frequency conversion with wide-range regulation of the output voltage via conversion frequency tuning. A sinusoidal current shape provides switching of power transistors at the zero current and the short-circuit protection in a load. The source provides an output voltage with small ripples and, when powered from a three-phase network, it does not require a smoothing mains filter.

The reflection of probe infrared femtosecond radiation pulses from a gallium arsenide substrate of the (001) orientation in the presence of more powerful pump pulses of the same radiation with a peak power of up to 1 GW/cm2 was investigated. A Yb3+:KY(WO4)2 laser with a central wavelength of 1 035 nm, a repetition rate of 70 MHz, a pulse duration of 130 fs, and an average power of not more than 0.9 W worked in the GaAs transparency region. The experimental dependence of the recorded signal on the pump radiation intensity is in qualitative agreement with the model dependence for two-photon absorption. The results are important for the correct interpretation of reflectivity kinetics of quantum wells.

We report on growth, spectroscopy and continuous-wave, mode-locking lasing and chirped pulse regenerative amplification of Yb:YAl3(BO3)(4) (Yb:YAB) crystal. Efficient CW laser operation with 9.2 W output power, 46% optical-to-optical and 74% slope efficiencies was demonstrated. Efficient SESAM mode-locked Yb:YAB bulk laser was demonstrated for sigma-polarization with 4 W average output power at 70 MHz pulse repetition frequency (PRF) and 195-fs pulse duration resulting in the pulse energy of 57 nJ and pulse peak power of 0.3 MW. Optical-to-optical efficiency of 27% in mode-locked regime is demonstrated. Chirped pulse regenerative amplifier based on Yb:YAB crystal demonstrated with maximum output power of 4.6 W (6 W of chirped pulses and optical-to-optical efficiency of 25%) and 695 fs pulse duration at 100 kHz PRF for the first time to the best of our knowledge.

Two types of mirror structures with saturable absorption are under consideration: monolithic mirrors grown from semiconductor materials and mirrors with a dielectric reflector, with quantum well containing semiconductor structures transferred to the dielectric. Both types of mirrors manifest high reflectivity in the NIR range of the spectrum: the table width is about 100 nm for semiconductor reflectors and more than 200 nm for dielectric reflectors. It is shown that a maximum depth of absorption modulation from 1 to 40% is possible. The recovery time of the saturable absorber (2 ps) makes these mirrors significantly fit for using in lasers with a pulse repetition rate of 1 GHz.

The nonmonotonic kinetics of a collision-induced photon echo has been investigated for a number of buffer atoms. The collision-induced photon echo was generated at the 174 Yb (6 s 2 ) 1 S 0 ↔ (6 s 6 p ) 3 P 1 (0 ↔ 1) transition by a pair of linearly and mutually orthogonally polarized resonant radiation pulses in ytterbium vapor and its mixtures with He, Ne, Ar, Kr, and Xe. The kinetics of the conventional photon echo generated by pulses with identical linear polarizations was recorded in the same mixtures. The derived decay rate constants for both types of echo are equal to within the measurement errors. For the collisions of 174 Yb atoms between themselves and with other ytterbium isotopes in a natural mixture of isotopes, an upper limit for the anisotropy parameter has been estimated, 0.22 ± 0.07 of the photon echo signal decay rate.