Capillary-condensation-based optical switch is bistable

Researchers at the European Laboratory for Nonlinear Spectroscopy and INFM-BC (Florence, Italy) and the University of Trento (Trento, Italy) have developed a novel form of optical switch that relies on the interaction of light with capillary condensation of organic vapors in photonic structures.

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Researchers at the European Laboratory for Nonlinear Spectroscopy and INFM-BC (Florence, Italy) and the University of Trento (Trento, Italy) have developed a novel form of optical switch that relies on the interaction of light with capillary condensation of organic vapors in photonic structures. The approach leads to optical bistability (which makes for a switch that more reliably remains in its on or off state).

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An optical superlattice fabricated from porous silicon has pore sizes that fall in the tens-of-nanometers range, which is on the order of the diameter for vapor condensation at room temperature. The superlattice has a periodic modulation in refractive index overlaid on a linear index gradient, creating a photonic structure for which the photonic-band central frequency depends on position. As the organic vapor condenses, it partially fills the pores, changing the refractive-index gradient. Evaporation induced by a 973-nm-emitting laser restores resonance. The bistability resulted from different thresholds for evaporation (Pth1) and condensation (Pth2). The 10 ms switching time could be reduced to the microsecond range by reducing device volume, say the researchers. Contact Pierre Barthelemy at [email protected].

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