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 tunable delays of up to 20 ps, using a slow light photonic crystal waveguide only 300  μm 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.

H.J. Bakker (Huib)
Phys. Rev. Lett.

Beggs, D. M., Rey, I. H., Kampfrath, T., Rotenberg, N., Kuipers, K., & Krauss, T. F. (2012). Ultrafast tunable optical delay line based on indirect photonic transitions. Phys.Rev.Lett., 108(Article number: 213901), 1–4. doi:10.1103/PhysRevLett.108.213901