Thermally induced whispering gallery mode laser in MEH-PPV solutions

• Silica optical fiber is coated with the MEH-PPV solution by capillary driven action.
• Heating of the solution coating changes the RI and allows WGM laser.
• WGM laser is switched on by optically induced thermal effects.
• Demonstration of WGM laser switch on/off by externally modulated RI change.

We report on thermally activated whispering gallery laser modes of a solution of MEH-PPV conjugated polymer supported by a silica optical fiber. The viscosity of the polymer solution gives place to a thin shell of the gain solution around the fiber driven by capillary action. Whispering gallery modes (WGMs) are thermally induced by a decrease in the refractive index of the polymer solution under intense optical pumping. The laser emission is produced because the evanescent waves of the WGMs couple the surrounding gain medium. These results support the use of conjugated polymers in optofluidic laser systems and highlight the importance of physicochemical properties, such as viscosity and optically induced heating, on the performance of the devices.

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