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A diode-pumped Nd:YAG oscillator with an endpumped zigzag slab architecture and polymer coating of total internal reflection (TIR) surfaces is developed. An output power of 105 W with a slope efficiency of 34% and an optical conversion efficiency of 25% is achieved from the plane-plane resonator, which emits the maximum power at 400-W pump power. The influence of evanescent wave losses on the lasing efficiency is demonstrated. Output power, W 120 100 80 60 40 20 0 0 50 100 150 200 250 300 350 400 Input power, W 10 bounces 12 bounces 14 bounces Input/output data for slab laser at different number of bounces of TIR surfaces c

The nonlinear optical responses of perovskite films CsPbI2Br, MAPbI3 + 1% PVC, MA0.15FA0.75Cs0.1PbI2.85Br0.15, and MA0.15FA0.75Cs0.1PbI3, irradiated by femtosecond laser pulses with wavelengths of 1064 and 532 nm, are investigated using z-scan measurements. Nonlinear absorption is found to occur in perovskite films irradiated at a wavelength of 1064 nm; the nonlinear absorption coefficient in thin films (45 – 65 nm) greatly exceeds that in thick ones (120 – 350 nm): 524 – 928 and 38 – 50 cm GW−1, respectively. It is shown that the nonlinear absorption saturation intensity for perovskite films depends on the pump pulse duration and increases with pulse shortening. It is also established that the nonlinear absorption coefficient of organometallic perovskite films exceeds that of a film of inorganic perovskite CsPbI2Br. Bleaching of film samples during z-scanning at a wavelength of 532 nm is related to the irreversible photochemical degradation of films exposed to intense light. The kinetics of photochemical bleaching of the films is detected at a wavelength of 532 nm.

Efficient operation of diode-pumped solid-state lasers with both high average power and good beam quality is generally limited by thermal effects in the laser gain medium. The effects of these distortions can be mitigated by application different pumping and extraction architecture. Zigzag slab lasers (see, for example, [1,2]) have demonstrated near-diffraction-limited output power at above 1 kW, because zigzag propagation by means of total internal reflections (TlR) eliminates thermally induced optical path differences over the entire beam area [3]. All the best slab architecture could demonstrate only at homogeneous pump distribution over active volume. We investigate experimentally the degree of absorbed pumping inhomogeneity which could influence the beam quality.In experiment we have used the composite active slab made of three parts by a method of diffusion bonding.The central 40-mm length of the slab is 0.6 % Nd:Y AG, with I I-mm-long diffusion-bonded undoped Y AG end caps that reduce end effects. End faces of the slab have been cut under 45°, for use of a longitudinal pumping. Special polymer has been put on TIR planes to reduce losses at total internal reflection of a laser beam. The pumping was symmetrically organized from both faces with two set of laser diode modules.We used laser beam of Nd:YV04 laser as a probe beam at 1.064 !lm. The expanded beam went on a mask in which 4 apertures have been made. The mask settled down in immediate proximity from the slab. Thus, on an end face of an active slab four parallel beams fell. The probe beam goes through 12 bounces in the slab in the same manner as the laser output beam. After the pumping with the controlled quantity of inhomogeneity was switched on the probe beams have been deviated from its directions (Fig. 1 ). It is clear seen that focusing is existed in both directions and even in zigzag direction too. The optical power of the thermal lens is different over the cross-section of the slab and strongly depends on the pumping Inhomogeneity.Temperature distribution along the optical axis of the slab was studied by the interferometric technique. The steady state interference pattern allows to observe temperature distribution along the slab corresponding to the some pumping rate. While using the interferometric investigation it is possible to calculate the real temperatures along the slab ( fig.2). This temperature profile does not effect the lasing efficiency and beam quality in the case of homogeneous pumping distribution in a slab cross-section. In the case of inhomogeneous pumping in the slab the 3-D thermal lens is arrived. Its appearance and influence is clearly seen when using the pulsed pumping instead of CW ( fig.3). When the pumping pulsewidth is short in comparison with the thermal time constant 71 � 0.2 s there are no thermal lens influence on output characteristics, but as the pumping pulsewidth becomes comparable with the 71 value the 3-D thermal lens immediately makes a strong impact on lasing.The computer modeling was also done for beam qual...

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