
26 ◾ Mitsuo Takeda
SF10 glass block. e signal transmitted through this block was used as
the strongly chirped pulse for upconversion. e group delay dispersion
of the block (10
4
fs
2
) together with the delay of 300 fs resulted in a spec-
tral shear of 4.8 THz. is chirp was adequate to ensure that each pulse
replica was upconverted with a quasi-cw (continuous wave) eld, and the
spectral shear was small enough to satisfy the sampling theorem. e
two delayed pulses were mixed noncollinearly with the stretched pulse in
a 30-μm thick type II BBO (β-barium borate) crystal. e upconverted
pulses were detected in a 0.3-m imaging spectrograph equipped ...