Figure 4

For femtosecond pump pulses with center wavelength λ p = 840 nm and average input power P av = 650 mW (peak power equals 78 kW), when the PCF length is changed from 30, to 33, to 36, and to 39 cm, respectively, (a) the observed output spectra of the SHs, and (b) the measured output power P SH and conversion efficiency η SH of the SHs as a function of the PCF length.