Fig. 1. Convergent beam FHG optical path. (a)FHG scheme of a convergent beam; (b) cutting schematic diagram of DKDP crystal; (c) schematic diagram of convergent 2ω beam's direction

Fig. 2. Experimental results. (a) 4ω near-field distributions at different F numbers at T=T_NCPM; (b) 4ω near-field distribution at F=5 and T≤T_NCPM

Fig. 3. Experimental results. (a) Dependence of convergent-beam FHG efficiency on temperature; (b) dependence of T_PM on 2ω beam intensity at different F numbers

Fig. 4. Dependence of FHG efficiency of convergent beam on 2ω beam intensity at T=T_PM

Fig. 5. Dependence of FHG efficiency on wavelength of fundamental laser at T=T_PM

Fig. 6. Experimental results. (a) Cross section of 2 sub-beam segmentation; (b) FHG scheme of 2 convergent sub-beams

Fig. 7. Comparison of 4ω near-field distribution of non-segmentation beam and segmentation beam at F=5 and T=T_PM

Fig. 8. Experimental results. (a) Dependence of phase-matching temperature on Z position at D=D_NCPM; (b) dependence of phase-matching deuterium content on Z position at T=T_NCPM

Fig. 9. 4ω near-field distribution at F=5 and T=T_PM(Z) or x=x_PM(Z)