Structural color modulation by laser post-processing on metal-coated colloidal crystals.

A method to use a pulsed solid-state laser to create structural color modulation on metal-coated colloidal crystal surfaces by changing the scanning speed has been proposed. Vivid colors as cyan, orange, yellow, and magenta are obtained with different predefined stringent geometrical and structural parameters. The effect of laser scanning speeds and polystyrene (PS) particle sizes on the optical properties is studied, and the angle-dependent property of the samples is also discussed. As a result, the reflectance peak is progressively red shifted along with increasing the scanning speed from 4 mm/s to 200 mm/s with 300 nm PS microspheres. Moreover, the influence of the microsphere particle sizes and incident angle are also experimentally investigated. For 420 and 600 nm PS colloidal crystals, along with a gradual decrease in the scanning speed of the laser pulse from 100 mm/s to 10 mm/s and an increase in the incident angle from 15° to 45°, there was a blue shift for two reflection peak positions. This research is a key, low-cost step toward applications in green printing, anti-counterfeiting, and other related fields.