Raman-induced slow-light delay of THz-bandwidth pulses

We propose and experimentally demonstrate a scheme to generate optically controlled delays based on off-resonant Raman absorption. Dispersion in a transparency window between two neighboring, optically activated Raman absorption lines is used to reduce the group velocity of broadband 765 nm pulses. We implement this approach in a potassium titanyl phosphate (KTP) waveguide at room temperature, and demonstrate Raman-induced delays of up to 140 fs for a 650-fs duration, 1.8-THz bandwidth, pulse. Our approach should be applicable to single-photon signals, offers wavelength tunability, and is a step toward processing ultrafast photons.