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Chae, Sanghoon

Publications and source records attributed to Chae, Sanghoon.

Electro-refractive modulation in photonic structures

Methods, systems, and devices are described for electro-optic tuning. An example device may comprise a first layer comprising a transition metal di-chalcogenide material, a second layer comprising a conductive material, and a third layer comprising a dielectric material. The third layer may be disposed at least partially between the first layer and the second layer. An electrical potential difference applied between the first layer and the second layer may cause a tunable refractive index change in the first layer.

Lipson, Michal↗

Femtosecond exciton dynamics in WSe 2 optical waveguides

Van-der Waals (vdW) atomically layered crystals can act as optical waveguides over a broad range of the electromagnetic spectrum ranging from Terahertz to visible. Unlike common Si-based waveguides, vdW semiconductors host strong excitonic resonances that may be controlled using non-thermal stimuli including electrostatic gating and photoexcitation. Here, we utilize waveguide modes to examine photo-induced changes of excitons in the prototypical vdW semiconductor, WSe 2 , prompted by femtosecond light pulses. Using time-resolved scanning near-field optical microscopy we visualize the electric field profiles of waveguide modes in real space and time and extract the temporal evolution of the optical constants following femtosecond photoexcitation. By monitoring the phase velocity of the waveguide modes, we detect incoherent A-exciton bleaching along with a coherent optical Stark shift in WSe 2 .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗