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Updated: Feb 11, 2026

High-Throughput Total Internal Reflection Fluorescence and Direct Stochastic Optical Reconstruction Microscopy Using a Photonic Chip
Published on: November 16, 2019
Reflection from a free carrier front via an intraband indirect photonic transition
Mahmoud A Gaafar1,2, Dirk Jalas3, Liam O'Faolain4,5,6
1Institute of Optical and Electronic Materials, Hamburg University of Technology, Hamburg, 21073, Germany. mahmoud.gaafar@tuhh.de.
Abstract:
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.
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