Comparative study of the spectroscopic properties of Rhodamine 6G dimers in ethanol solutions and in mesoscopic silica-Pluronic sol−gel films has been performed by means of steady state and transient absorption and fluorescence methods. The dimers act as fluorescence quenchers in solutions, while their fluorescence yield is about 36 times higher in the mesoscopic films where they dominate in the fluorescence spectra. The difference is caused by about 6 times slower nonradiative excited state decay and about 6 times stronger oscillator strength of the fluorescence transition of the dimers in the films in comparison with solutions. We demonstrate that the dimer fluorescence originates from the oblique sandwich-type dimers both in solutions and in mesoscopic films. We suggest that the higher fluorescence yield of the dimers in the mesoscopic films is mainly caused by the stronger deviation from the planar geometrical arrangement of the sandwich-type dimer, thus causing opening of the forbidden low energy excitonic transition.

We demonstrated a 100 W class hybrid laser system based on fiber seed laser and two free-space end-pumped Yb:YAG amplifiers capable of delivering record high pulse energy in a rod-type active medium setup operating at room temperature. The achieved output pulse energy was >10 mJ at 10 kHz pulse repetition rate. The output pulses of 1.09 ps duration were close to Fourier transform-limit. The output beam quality remained high (M 2 < 1.3) despite being affected by thermally induced stress in the gain medium.

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In this work we present a novel method for depolarization compensation based on spatially variable wave plate. Thermally induced depolarization losses were reduced from 14.3% to 1.3% and bifocusing eliminated in a double-pass Yb:YAG amplifier.