Reflection from a free carrier front via an intraband indirect photonic transition

Mahmoud A. Gaafar, Dirk Jalas, Liam O’Faolain, Juntao Li, Thomas F. Krauss, Alexander Yu. Petrov, Manfred Eich

Research output: Contribution to journalArticlepeer-review

29 Citations (Scopus)


The reflection of light from moving boundaries is of interest both fundamentally and for applications in frequency conversion, but typically requires high pump power. By using a dispersion-engineered silicon photonic crystal waveguide, we are able to achieve a propagating free carrier front with only a moderate on-chip peak power of 6 W in a 6 ps-long pump pulse. We employ an intraband indirect photonic transition of a co-propagating probe, whereby the probe practically escapes from the front in the forward direction. This forward reflection has up to 35% efficiency and it is accompanied by a strong frequency upshift, which significantly exceeds that expected from the refractive index change and which is a function of group velocity, waveguide dispersion and pump power. Pump, probe and shifted probe all are around 1.5 µm wavelength which opens new possibilities for “on-chip” frequency manipulation and all-optical switching in optical telecommunications.
Original languageEnglish
Article number1447
Number of pages10
JournalNature Communications
Publication statusPublished - 13 Apr 2018


Dive into the research topics of 'Reflection from a free carrier front via an intraband indirect photonic transition'. Together they form a unique fingerprint.

Cite this