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Color Switching with Enhanced Optical Contrast in Ultrathin Phase-Change Materials and Semiconductors Induced by Femtosecond Laser Pulses

Ultrathin semiconductors on metals constitute color filters, which selectively absorb wavelength ranges of incident light. This paper demonstrates that these coatings are attractive for tunable color devices by reversibly switching ultrathin phase-change materials on gold between two colors with femtosecond laser pulses. The optical contrast is enhanced compared to conventional thick phase-change materials, and its spectral maximum is tunable via the thickness of the phase-change material. Color switching is even feasible if the phase-change material is replaced by a conventional group IV semiconductor, whose amorphous and crystalline phases are optically less distinct. These structures hold significant promise for optical data storage and for display applications.