A Multi-Color Switchable Dye Laser Based on CAET in Side-Hole Microstructured Optical Fibers

We demonstrate a novel multi-color switchable dye laser based on cavity-assisted energy transfer induced by microfluidic droplets flowing in side-hole microstructured optical fibers that provide dual channels for, respectively, loading donor and acceptor and offer the high-
$Q$
microring resonator for effective optical feedback. The droplet generator produces periodical acceptor droplets flowing by the focus point to activate color switching thanks to the cavity-assisted energy transfer effect. The lasing thresholds of rhodamine B at 1 mM and LDS730 at 1.5 mM are, respectively, 233 and 369 nJ when the flow rates of the LDS730 solution and the carrier fluid are kept at 5
$\mu \text{L}$
/min. The influence of flow rate on switching time of dual-color lasing emission is also investigated. And moreover, experimental results indicate that by varying the acceptor concentration the proposed dye laser could operate in uni-color or dual-color laser switching mode. The compact multi-color switchable dye laser provides a promising candidate to serve as miniaturized laser for biochemical and color display applications.