β -BaB ₂ O ₄ with special cut-angle applied to single crystal cascaded third-harmonic generation

Abstract

High-efficiency single crystal cascaded third-harmonic generation (THG) was realized in β -BaB 2 O 4 (BBO) material with special cut-angle. By analyzing effective nonlinear optical coefficient (d eff ) of the cascaded THG process, which was composed by type-II frequency doubling and type-I sum-frequency, the optimum phase matching (PM) direction in BBO crystal was determined to be (θ = 32.1 • , φ = 11 • ). With an optimized 9-mm long sample which was processed along this direction, the highest cascaded THG conversion efficiency reached 42.3%, which is much superior to the similar components reported previously, including ADP, KDP, and Gd x Y 1−x COB crystals.

High Efficiency Third-Harmonic Generation in a Medium with Quadratic Susceptibility Due to Cubic-like Nonlinearity Caused by Cascaded Second-Harmonic Generation

“…The GVM between SH and FW pulses only influences the pulse shapes without strong changing of the THG efficiency (Figures 17-19). In contrast, the GVM between TH and FW remarkably influences the frequency conversion process (Figures [20][21][22][23][24]. To compensate for this negative influence, we proposed and discussed some physical schemes for three-wave interaction (Section 6.3).…”

“…A beam with a sufficiently big diameter was used in this experiment to avoid the influence of its diffraction. This approach was also implemented for Gd x Y 1−x COB [22], ammonium-dihydrogen-phosphate (ADP) [23], and β-barium borate (BBO) [24] crystals with similar results.…”

“…Figure24. Pulse shapes and their spectra in the section z = 50 (a,d), z = 200 (b,c,e,f), as well as incident pulse distribution and spectra (dash-dotted line), and the frequency conversion efficiency along z-coordinate (g,h,i) for the incident pulse duration τ P = 100 fs (a,d,g), 1 ps (b,e,h) and 10 ps (c,f,i).…”