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

TL;DR

This paper demonstrates an all-optical method to delay broadband ultrafast pulses using off-resonant Raman absorption in a KTP waveguide, achieving significant delay with potential for quantum photonics.

Contribution

It introduces a novel Raman-based scheme for ultrafast optical delay lines applicable to broadband signals at room temperature.

Findings

Achieved up to 140 fs delay for 650 fs pulses

Demonstrated delay-bandwidth product of approximately 1

Applicable to single-photon signals and tunable wavelengths

Abstract

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, signal pulse; the available delay-bandwidth product is $\approx1$. Our approach is applicable to single photon signals, offers wavelength tunability, and is a step toward processing ultrafast photons.