N. N. Rubtsova

High-power, efficient, semiconductor saturable absorber mode-locked Yb:KGW bulk laser.

A high-power, diode-pumped, semiconductor saturable absorber mode-locked Yb(5%):KGW bulk laser was demonstrated with high optical-to-optical efficiency. Average output power as high as 8.8 W with optical-to-optical efficiency of 37.5% was obtained for Nm-polarized laser output with 162 fs pulse duration and 142 nJ pulse energy at a pulse repetition frequency of 62 MHz. For Np polarization, 143 fs pulses with pulse energy of 139 nJ and average output power of up to 8.6 W with optical-to-optical efficiency of 31% were generated.

Velocity effects in atomic and molecular collisions: Study by coherent transients

The effect of translational velocity of active atoms and molecules on the properties of photon echo is investigated using the technique of coherent transient processes. A variation in the photon-echo decay with a frequency detuning of the excitation radiation relative to the center of the vibrational-rotational transition 0 ↔ 1 ν3R(4, 3) is observed in a mixture of 13CH3F with atomic buffers. The results are interpreted using the dependence of the echo decay rate on the magnitude of the translational velocity of active particles. The dependence of the relaxation matrix on the direction of the velocity of active atoms results in a new phenomenon of the collision-induced echo, which is investigated at the transition 0 ↔ 1 174Yb in mixtures with atomic buffers.

Semiconductor nanostructures modified by the UV laser radiation

The shortening of the absorption recovery time by a factor of more than 50 is observed for the semiconductor nanostructure consisting of ten GaAs/InxGa1-xAs/GaAs quantum wells irradiated with the nanosecond pulses of the XeCl laser.A possible reason for such a significant variation in the optical properties lies in the generation of point defects,which are responsible for recombination of charge carriers.The result can be employed in the UV photomodification of optical properties of semiconductor nanostructures.

Conventional and collision photon echo in ytterbium vapor

The polarization properties of the photon echo generated by two linearly polarized pulses of resonant radiation at the (6s6p)3P1 ↔ (6s2)1S0 transition of 174Yb are investigated. A complicated polarization behavior of the photon echo versus an angle between the polarization vectors of the excitation pulses is revealed in a mixture of ytterbium vapor with inert gas. For the angles ranging from 0° to 75°, a conventional echo with its linear polarization coinciding with the second excitation pulse dominates and the echo amplitude decreases with an increasing angle. For the angles ranging from 75° to 89°, the photon echo is elliptically polarized. Finally, for an angle of 90°, the conventional echo disappears and the collision echo becomes linearly polarized along the first excitation pulse.

Photon echo in gases: From the non-Faraday rotation to unpolarized echo

A retrospective review of both theoretical and experimental works on photon echo in gases in the presence of longitudinal magnetic fields is presented from the viewpoint of new possibilities opened by this research for polarization echo spectroscopy of gases. The main attention is given to the physical scenario of the magnetic field’s effect on the properties of the photon echo. New results on the photon echo and stimulated photon echo in ytterbium vapor at the 1 ↔ 0 transition in the presence of the longitudinal magnetic field whose strength ranges from weak to strong are presented. Possible applications of the magnetic field effects for optical data storage and processing are analyzed.

Effect of magnetic field on the stimulated photon echo in ytterbium vapors

Polarization of the stimulated photon echo (SPE) at the 0 ↔ 1 transition in ytterbium vapors in the presence of a longitudinal magnetic field of 0–40 G is experimentally and theoretically studied. The SPE is generated using three light pulses with identical linear polarizations, so that the SPE polarization is the same at zero magnetic field. In the presence of a weak magnetic field, the SPE polarization vector rotates around the magnetic field vector and the depolarization of the SPE signal takes place. Each of the SPE polarization components exhibits biharmonic oscillations depending on the magnetic field. In the presence of a strong magnetic field, these oscillations vanish and the SPE becomes depolarized. The experimental data are in qualitative agreement with the results of the numerical calculations performed with the method of the evolution operator for the finite-duration excitation pulses. The application of the results for the processing of optical data is discussed.

Collision-induced photon echo in ytterbium vapour at the transition 0–1: magnetic field effect

Collision-induced photon echo generated in ytterbium vapour at the transition (6s2) 1S0 ↔(6s6p) 3P1 (transition of the type 0 ↔ 1) was investigated in the presence of the longitudinal magnetic field strength between zero and 5.6 G. For the weak magnetic fields, not over 0.27 G, the collision-induced echo signal decreases with magnetic field increase. Further increase of the magnetic field strength reveals oscillatory behavior of the echo signal. Experimental results are in qualitative agreement with theoretical predictions.

Self-mode-locking of the Nd3+:KGd(WO4)2 laser using a multifunctional semiconductor mirror

A multifunctional semiconductor mirror that contains a saturable absorber based on quantum wells, a broadband reflector, and a Gires-Tournois interferometer that serves as a GVD compensator is designed and created. The mirror is fully characterized using the pump-probe technique with a subpicosecond resolution and the transmission and photoluminescence spectroscopy. The mirror that simultaneously executes the three functions and that is created in a single technological cycle provides stable mode-locking in the Nd3+:KGd(WO4)2 laser.

Depolarizing collisions in ytterbium vapor: Isotropic and anisotropic relaxation

Isotropic depolarizing collisions are studied using a stimulated photon echo with a specific polarization of the excitation radiation pulses in a mixture of ytterbium with krypton for the J = 1 ⇄ J = 0 transition of 174Yb. The difference between the relaxation rates of orientation and alignment γb(2) − γb(1) of the 3P1(6s6p) 174Yb level is measured as a function of the krypton pressure. The collision photon echo at the J = 1 ⇄ J = 0 transition induced by the anisotropic relaxation is studied for the Yb + Xe mixture. The power of the collision echo increases from zero with the addition of a buffer gas to ytterbium, reaches an optimal level, and decreases with an increase in the buffer gas pressure. The polarization of this collision-induced echo differs from the polarization of the conventional echo. The experimental results are in qualitative agreement with theoretical predictions.

A new technique to measure the phase characteristics of laser mirrors based on semiconductor heterostructures

A reflection interferometer based on a thin metal film is proposed to measure the phase of the reflection spectrum of laser mirrors. The device is applied to the study of the phase characteristics of the all-semiconductor mirror which combines the functions of the saturable absorber and the dispersion compensator (all-in-one) in the Nd3+:KGd(WO4)2 laser operating in the ultrashort-pulse regime. The method provides improvement of spectral resolutions and an increase in the accuracy in the measurement of the phase characteristics.