Generation of optofluidic laser in stable fiber Fabry-Perot microcavities

In the study, we investigate the generation of optofluidic laser in stable planar-concave Fabry-Perot (FP) microcavities. The concave mirror is created on the end-facet of a fiber using the method of CO2 laser ablation and subsequent coating with dielectric layers. Coumarin 6 in ethanol is used as the gain solution to test the FP microcavities. For comparison, we first test the laser generation in a stable FP microcavity formed by a concave mirror on a fiber and a planar mirror on the substrate of a fused silica without cavity assembly. In this configuration, we can obtain the laser emission with an ultralow pumping energy of 25.5 mu J/ mm(2) at the gain concentration of 10 mu M and a detection limit of gain solution as low as 2 mu M. Then, the generation of optofluidic laser is explored in a polymeric optofluidic chip integrated with a stable fiber FP microcavity in the format of planar-concave mirrors and a microfluidic channel. Laser results in this configuration show a laser threshold of 36.9 mu J/mm(2) at the gain concentration of 10 mu M and a deduced Q-factor of 7.8x10(5) of the FP microcavity.