Protein-based Y-junction optical micro-splitters with environment-stimulus-actuated adjustments

Herein, by using maskless and noncontact femtosecond laser direct writing (FsLDW) form protein aqueous ink, protein-based Y-junction optical micro/nano-splitters (PYOMs) have been readily customized with environmental-stimulus-actuated light-splitting adjustments for the first time to our knowledge. Bio/eco-compatible protein-based biopolymer successfully acted as the ideal alternative of artificial polymers for optical waveguide devices. Based on flexibly programmable “one-step” FsLDW, applicable shape-symmetric PYOMs were facilely fabricated with tailorable light-power-splitting ratios (from ∼1:1 to ∼3:1 in air). Significantly, via environmental responses and sensitivity of protein hydrogels, another type of “heterogeneous” PYOMs exhibited “smart” dynamic adjustments of light-power-splitting ratios by simply tuning surrounding chemical stimuli for example of pH value (∼1:1 in air, ∼1.35:1 in pure water, and 1.48:1-1.85:1 under pH 2.0-6.0), showing their application promise for optical sensing and environment-signal-actuated tunable micro/nano-optics.