An ultrathin-film microring laser was fabricated using inkjet printing and a simple lift-off technique. Whispering-gallery-mode lasing was observed under optically pumped conditions in the film. The freestanding laser can be transferred to arbitrary surfaces for multifunctional applications, such as acoustic and relative humidity sensing. Using the first eigenmode of a membrane vibration, an acoustic sensor with a 0.15 Pa limit of detection was demonstrated via laser bandwidth broadening. A relative humidity sensor with a 1.1% limit of detection via wavelength shifts was demonstrated by placing the device on an optical fiber facet. These cost-effective, transferrable, multifunctional laser sensors will have many additional applications.
Keywords: acoustic sensing; humidity sensing; microring laser; transferrable; ultrathin.