Fig. 2: Pump-induced frequency translation at a fixed delay time.
From: Broadband frequency translation through time refraction in an epsilon-near-zero material
a–b The frequency of a 1235 nm probe beam redshifts at the delay time td = −60 fs in a and blueshifts at the delay time td = 60 fs in b. The insets show the relative position of the pump and the probe. The top-most (bottom-most) spectra in both panels correspond to the largest (zero) pump intensity and, consequently, the largest (zero) change in the refractive index.
