Optofluidic Fabry–Perot Laser With Plasmon-Enhanced Tunable Emission

Optofluidic lasers that integrate microcavities with liquid gain media offer the potential for miniaturized and tunable lasers. Although capillaries are excellent microcavities, their implementation in optofluidic lasers have been hampered by notable limitations: whispering gallery mode lasers typically require complex system configurations and exhibit nondirectional emission, while random lasers suffer from both nondirectional and spectrally instable emission. These limitations complicate integration and reduce coupling efficiency with subsequent components. Here, an optofluidic Fabry-Perot laser with a simple system configuration of filling capillaries with dye solutions is presented. Radial pumping enables the capillary wall to function as a Fabry-Perot etalon, providing interference feedback for directional and spectrally stable emission. It exhibits a tuning range of 41 nm using Rhodamine 590, 610, and 640 dye solutions, with corresponding lasing thresholds of 4.5, 5.0, and 6.7 mJ/cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> per pulse, respectively. Furthermore, by incorporating gold nanoparticles into the dye solutions, the Fabry-Perot lasing thresholds are further reduced to 1.53, 1.46, and 2.15 mJ/cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> per pulse, respectively. The reduced threshold is attributed to the collaboration of plasmon-enhanced fluorescence and interference feedback. This work facilitates the development of optofluidic lasers for future applications.