Self-induced transparency in waveguides

В. В. Козлов, Evald E. Fradkin

Mariam Mariam, Mohammad, Nasser +4 more

Andreas Pusch

This thesis explores the existence and properties of self-induced transparency (SIT) solitons in nanophotonic waveguides. SIT solitons are shape-preserving solutions of the semi-classical Maxwell-Bloch equations, a system of nonlinearly coupled differential equations. In a first investigation, collisions of counterpropagating simultons (SIT solitons in absorbing three-level systems) are studied numerically in the plane-wave approximation and a polarisation- and group-velocity dependent soliton birth is uncovered. Apart from their fundamental interest, such light-light interaction effects may be of use for optical computing applications if they can be transferred to tightly confined light pulses. Confining light is usually achieved by using dielectric waveguides that exhibit group velocity dispersion leading to chirped pulses, which experience absorption when entering an absorbing medium. If the chirp is strong enough and the pulse intense enough, they can even completely invert an absorber. When investigating chirped pulse propagation through a dense ensemble of two-level system it is found that the chirped pulses dynamically reshape into unchirped pulses experiencing transparency. Furthermore, the conditions on the waveguide geometry to enable SIT are analysed, identifying a nanophotonic slot waveguide with a low-index gap, exhibiting high electric field enhancement and a homogeneous field profile, as the ideal candidate system for guided SIT solitons. This analysis is supported by two-dimensional numerical calculations that show the solitary character is maintained during propagation if the absorber density is high enough to ensure a slow-down of the pulse and to thus counteract the waveguide dispersion. Finally, the soliton birth due to simulton collisions and optical memory schemes proposed for plane-wave SIT are investigated in the two-dimensional slot waveguide and found to also be possible in this geometry.

Naohiro Tanno

Masataka Nakazawa, Yasuo N. Kimura, Kazunori Suzuki +2 more

The recent development of the EDFA (erbium-doped fiber amplifier) offers the possibility for uses of the fibers to experiments on coherent pulse propagation such as self-induced transparency (SIT). The guiding of the radiation by the fiber structure eliminates diffraction effects and makes possible the interaction of the radiation with the fiber medium which has resonance effects over long distances. To date, however, experiments on SIT solitons have suffered from diffraction effects that were further complicated by nonlinear interactions. In the present paper, we report for the first time the observation of SIT soliton propagation in an erbium- doped resonant fiber waveguide.

Masataka Nakazawa, Yasuo N. Kimura, Kenji Kurokawa +1 more

Self-induced transparency (SIT) has been observed in an erbium-doped resonant fiber waveguide. The waveguide had an erbium ion concentration of 8900 ppm, and was cooled to 4.2 K. The pulse source was a 1.53-\ensuremath{\mu}m mode-locked Er-doped glass laser with a pulse width of 500 ps. Stable 2\ensuremath{\pi}, 4\ensuremath{\pi}, and multiple soliton pulses that broke up were clearly observed.