We demonstrate a chip-scale tunable optofluidic dye laser with Au-coated fibers as microcavity. The chip is fabricated by soft lithography. When the active region is pumped, a relatively low threshold of 6.7 μJ/mm2 is realized with multimode emission due to good confinement of the cavity mirrors, long active region, as well as total reflectivity. It is easy to tune the lasing emission wavelength by changing the solvent of laser dye. In addition, the various intensity ratios of multicolor lasing can be achieved by controlling flow rates of two fluid streams carried with different dye molecules. Furthermore, the convenience in fabrication and directional lasing emission outcoupled by the fiber make the tunable optofluidic dye laser a promising underlying coherent light source in the integrated optofluidic systems.
The whispering gallery mode (WGM) lasing in a polydimethylsiloxane (PDMS)-based microresonator is demonstrated with a convenient and crafty approach. Fabricated by directly brushing dye-doped PDMS solution on an optical fiber, the microresonator is self-formed due to the high surface tension. The size of the resonator can be widely tuned by using different droplet volumes and brushing speeds across the optical fiber. Lasing with a threshold as low as 2.5 μJ/mm2 is observed in this kind of fiber-stand PDMS microresonator. We also investigate the dependence of the lasing threshold on the different polarizations of the pump laser and size of the microresonator. This kind of WGM microresonator will find applications in optical sensors and on-chip integrated systems.