Figure 5

PL spectra analysis and adjustable lasing action of a protein-based 3D WGM microlaser in aqueous environments.

(a) 3D-waterfall arranged PL spectra from a 60-μm-diameter (2.5-μm designed thickness of upper-part microdisks) protein-based 3D WGM microlaser in pure water (see inset optical microscopic image, scale bar, 10 μm) pumped with increasing intensities of 532-nm ps-laser light. (b) The spectrum of test number 7 in (a) pumped by ~3.84-μW/μm² 532-nm ps-laser light. (c) Peak values of PL spectra from the protein-based 3D WGM microlaser in (a) vs 532-nm pumping intensities. Insets: optical microscopic fluorescent images of the protein-based 3D WGM microlaser in (a) under different pumping intensities; 1, ~1.17 μW/μm²; 2, ~2.07 μW/μm²; 3, ~3.26 μW/μm²; scale bar, 10 μm. (d) 3D-waterfall arranged lasing spectra from a 60-μm-diameter (2.5-μm designed thickness of upper-part microdisks) protein-based 3D WGM microlaser in aqueous solutions with increasing Na₂SO₄ concentrations; pumping intensity of 532-nm ps-laser light, ~2.0 μW/μm². (e) 2D stacked lasing spectra in (d). (f) Wavelength blueshift of a particular peak in lasing spectra (near to central wavelength) of (a) and (b) along with Na₂SO₄-concentration increasing.