Generation of low-threshold optofluidic lasers in a stable Fabry-Pérot microcavity

We present the generation of optofluidic lasers in a Fabry-Pérot (FP) microcavity with low pumping threshold. The FP microcavity is constructed with one micro-concave mirror and another planar mirror facing each other to form a stable cavity. The two mirrors are coated with dielectric layers with reflectivity ≥99.9%. Laser behaviors are tested with gain medium, Rhodamine 6 G (R6G), dissolved in ethanol and ion water, respectively; a lowest pumping threshold as small as 0.13 μJ/mm2 is achieved in the ethanol solution, corresponding to a theoretically calculated quality value Q0 about 4×105. Meanwhile experimental results demonstrates that the lowest concentration of dye medium that can emit laser signal in the FP microcavity is 3 μM.