Ultrafast tuneable optical delay line based on indirect photonic transitions

TL;DR

This paper presents a novel ultrafast optical delay line using indirect photonic transitions in a photonic crystal waveguide, enabling tunable delays up to 20 ps with pulse-by-pulse control and high efficiency.

Contribution

It introduces the concept of indirect photonic transitions for dynamic, tunable optical delays, demonstrating ultrafast control and pulse-specific manipulation in a compact device.

Findings

Achieved up to 20 ps tunable delay in a 300 μm waveguide.

Controlled individual pulses separated by 30 ps.

Demonstrated 30% conversion efficiency for the indirect transition.

Abstract

We introduce the concept of an indirect photonic transition and demonstrate its use in a dynamic delay line to alter the group velocity of an optical pulse. Operating on an ultrafast time scale, we show continuously tuneable delays of up to 20 ps, using a slow light photonic crystal waveguide only 300 $\mu$m in length. Our approach is flexible, in that individual pulses in a pulse stream can be controlled independently, which we demonstrate by operating on pulses separated by just 30 ps. The two-step indirect transition is demonstrated here with a 30% conversion efficiency.