Low threshold Fabry-Perot optofluidic resonator fabricated by femtosecond laser micromachining.

We report the realization and characterization of an optofluidic microlaser based on a Fabry-Perot resonator fabricated by exploiting two direct writing fabrication techniques: the femtosecond laser micromachining and the inkjet printing technology. In this way a standard Fabry-Perot cavity has been integrated into an optofluidic chip. When using rhodamine 6G dissolved in ethanol at concentration of 5∙10^-3 mol/l, laser emission was detected at a threshold energy density of 1.8 μJ/mm² at least one order of magnitude lower than state-of-the-art optofluidic lasers. Linewidth below ~0.6 nm was measured under these conditions with a quality factor Q~10³. These performances and robustness of the device makes it an excellent candidate for biosensing, security and environment monitoring applications.