Fig. 1. Dual-channel OPO^[53]. (a) Schematic; (b) experimental setup; (c) idler spectra output during dual-channel operation

Fig. 2. Simulated signal bandwidth (－20 dB) and maximum pump pulse energy versus intracavity GDD^[79]

Fig. 3. Measured signal spectra and bandwidths at different incident pump powers^[79]. (a)-(e) Measured signal spectra at different incident pump powers, where the dashed line in figure (e) shows calculated phase-matching curve of 3 mm long PPLN crystal; (f) measured signal bandwidth versus incident pump power

Fig. 4. Relationship between bandwidth of output signal bandwidth and nonlinear parameter deff2/n2 of nonlinear crystal by simulation^[80]

Fig. 5. Signal spectra at different pump powers^[80]. (a)-(d) Experimentally measured signal spectra at different pump powers, where the dashed line in figure (a) is phase matching curve of 3 mm long KTA; (e) simulated signal spectrum (solid line) and intracavity GDD (dashed line)

Fig. 6. Numerical simulation: output signal before and after pulse-compression^[88]. (a)-(b) Signal pulse and spectrum without pulse-compression; (c)-(d) signal pulse (dashed line is the fitted hyperbolic secant curve) and spectrum with pulse-compression (the pump power was 0.7 W)