Two wavelength band emission WGM lasers via photo-isomerization.

Wavelength switchable microcavity is indispensable component for various integrated photonic devices. However, achieving two wavelength band emission of the whispering gallery mode (WGM) laser is challenging. Here, we propose a strategy to realize two wavelength band emission WGM lasers activated by photo-isomerization based on excited-state intramolecular proton transfer (ESIPT) process in isolated/coupled polymer microfiber cavities. The WGM microcavity is built by highly polarized organic intramolecular charge-transfer (ICT) dye molecules. The two cooperative gain states of ICT dye molecules can be controlled by optimizing energy levels. Thereby, the lasing wavelength can be reversibly switched under photo-isomerization activated in the ESIPT energy-level progress. The photonic bar code can be generated by following the strategy of proposed design. This work provides a promising route to achieve switchable WGM laser in on-chip photonic integration.