Fig. 1. Schematic layout of the conversion experiment. The laser beam is coming from the laser system via the laser beam distribution system (LAS+LBDS). Single components of the setup are denoted as follows: a quarter waveplate (QWP), a half waveplate (HWP), conversion crystals (LBO), a partially reflecting sampling wedge (SW) and a beam dump (BD). Diagnostics consists of a dichroic beamsplitter (DBS), mirrors (M), lenses (L), beamsplitters (BS), an energy meter (EM), a near-field camera (C1) and a far-field camera (C2 – not present during the experiment). The layout of diagnostic lines is the same for all three wavelengths and is shown only once.

Fig. 2. Temporal evolution of the energy meter’s calibration coefficients: while the calibration coefficient for input energy (1030 nm) and unconverted fundamental 1ω (1030 nm) stabilized of the order of tens of seconds, the second-harmonic 2ω (515 nm) took hundreds of seconds and the third-harmonic 3ω (343 nm) did not stabilize at all.

Fig. 3. The s- and p-component profiles of the laser beam after passage through the de-magnifying telescope with optimized polarization at the input and output of the laser system. Images were taken after the polarizer was transmitting vertical polarization with 4% of total energy (a) or horizonal polarization with 96% of total energy (b). Beam profiles at the complementary polarizations were taken under the same conditions and were normalized to the sum of both intensities. The white lines in the pictures correspond to cross-sections through the center of the beam.

Fig. 4. Temporal evolution of the energy of the third-harmonic frequency 3ω together with input energy (1030 nm) and unconverted residual energy at the fundamental 1ω (1030 nm) and second-harmonic 2ω (515 nm) frequencies. Points where the crystal phase-matching angle was optimized are marked with arrows.

Fig. 5. Temporal evolution of the energy of the third-harmonic frequency 3ω (343 nm) together with input energy (1030 nm) and unconverted residual energy at the fundamental 1ω (1030 nm) and second-harmonic 2ω (515 nm) frequencies after SHG oven temperature stabilization.

Fig. 6. Temporal evolution of the energy of the third-harmonic frequency 3ω (343 nm) together with input energy (1030 nm) and unconverted residual energy at the fundamental 1ω (1030 nm) and second-harmonic 2ω (515 nm) frequencies after SHG oven temperature stabilization and fine tuning of the SHG LBO phase-matching angle. Conversion efficiency E_3ω/E_input is shown in pink and is related to the scale on the right.

Fig. 7. Beam profile at the third-harmonic frequency (343 nm) with energy of more than 50 J at the repetition rate of 10 Hz in the beginning of the experiment (a) and after oven temperature stabilization for 90 minutes (b). The color bar was adjusted to better show the intensity variation in the beam in the presence of hot spots that affected the normalization.