Indirect transitions of a signal interacting with a moving refractive index front
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The dynamic manipulation of light can be achieved by the interaction of a signal pulse propagating through or reflected from a refractive index front. Both the frequency and the wave vector of the signal are changed in this case, which is generally referred to as an indirect transition. We have developed a theory to describe such transitions in integrated photonic crystal waveguides. Through indirect transitions, the following effects can be envisaged: large frequency shifts and light stopping and order of magnitude pulse compression and broadening without center frequency shift. All effects can be potentially realized with a refractive index modulation as small as 0.001. For the experimental realization, we have used slow light photonic crystal waveguides in silicon. The refractive index front was obtained by free carriers generation with a switching pulse co-propagating with the signal in the same slow light waveguide. The group velocities of the signal and the front could be varied arbitrarily by choosing the right frequencies of the signal and switching pulses. The indirect transition was unambiguously demonstrated by considering two situations: a) the front overtaking the signal and b) the signal overtaking the front. In both cases, a blue shift of the signal frequency was observed. This blue shift can only be explained by the occurrence of the expected indirect transition and not by a direct transition without wave vector variation.
Munoz , M C , Petrov , A Y , O'Faolain , L , Li , J , Krauss , T F & Eich , M 2014 , Indirect transitions of a signal interacting with a moving refractive index front . in G S Subramania & S Foteinopoulou (eds) , Active Photonic Materials VI . vol. 9162 , Proceedings of SPIE , vol. 9162 , SPIE , Bellingham , Conference on Active Photonic Materials VI , San Diego , United States , 17-21 August . DOI: 10.1117/12.2063078conference
Active Photonic Materials VI
Munoz, M. C., Petrov, A. Y., O'Faolain, L., Li, J., Krauss, T. F., & Eich, M., "Indirect transitions of a signal interacting with a moving refractive index front," In Subramania, G. S., & Foteinopoulou, S. (Eds.), Active Photonic Materials VI. (Proceedings of SPIE), 9162 (2014). Copyright 2014 Society of Photo Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.
This research was supported by the German Research Foundation DFG (EI 391/12-2).
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