Distributed feedback lasers based on perylenediimide dyes for label-free refractive index sensing.

The refractive index sensing capabilitity of distributed feedback (DFB) lasers based on highly photostable (under ambient conditions) perylenediimide-based active films, are reported. The sensor bulk sensitivity is determined from changes in the laser emission wavelength upon exposure to different liquids. The role of the active film thickness ( h f ) on the sensor sensitivity and on the laser parameters is studied. Sensors based on very thin films ( h f = 160 nm) show the highest sensitivities, but their laser thresholds are relatively high and their operational durabilities moderate. The use of thicker films ( h f = 850 nm) allows reducing the laser threshold and increasing the durability by two orders of magnitude. In this case, a higher sensitivity is achieved when the sensor operates at the wavelength corresponding to the first-order TE 1 mode, instead of at the TE 0 one. Finally, it is also shown that the inclusion of a high refractive index TiO 2 layer on top of the sensor structure improves the sensitivity by around two times. [ABSTRACT FROM AUTHOR]