Fig. 1. Variation of SPM-SHG spectrum with crystal rotating angle α for the (29°, 30°) and (45°, 30°) BBO samples pumped by an 800 nm laser source, where (a)–(f) correspond to the (29°, 30°) sample and (g), (h) correspond to the (45°, 30°) sample. Output spectra at α = (a) –4.7°, (b) –1.2°, (c) 0°, (d) 2.3°, (e) 7.0°, (f) 12.1°, (g) 9.8°, and (h) 31.4°.

Fig. 2. Variation of SPM-SHG spectrum with crystal rotating angle α for the (29°, 30°) and (45°, 30°) BBO samples pumped by a 1030 nm laser source, where (a)–(f) correspond to the (29°, 30°) sample and (g), (h) correspond to the (45°, 30°) sample. Output spectra at α = (a) –9.1°, (b) –4.5°, (c) 0°, (d) 6.9°, (e) 10.6°, (f) 18.2°, (g) 13.2°, and (h) 31.0°.

Fig. 3. For 800 nm pumped BBO crystal: (a) output power of λ_o versus pump power of λ_p; (b) optical conversion efficiencies of different λ_o at a fixed pump power of 600 mW. For 1030 nm pumped BBO crystal: (c) output power of λ_o versus pump power of λ_p; (d) optical conversion efficiencies of different λ_o at a fixed pump power of 1200 mW.

Fig. 4. Pulse width at λ_p = 800 nm: (a) τ = 38 fs at 800 nm, (b) τ = 360 fs at 440 nm, and (c) τ = 390 fs at 460 nm (where the discrete points show the experimental data and solid lines show sech² fitting curves).

Fig. 5. Calculated PM curves (solid lines) and measured PM angles (discrete points) for SPM-SHG of BBO crystal: (a) λ_p = 800 nm and (b) λ_p = 1030 nm.

Fig. 6. 193–207 nm tunable UV output by the cascading frequency conversions of three BBO crystals. (a) Experimental setup. (b) Tunable range of each BBO crystal. (c) DUV output spectrum of 207 nm from BBO3. (d) VUV output spectrum of 193 nm from BBO3.