Fluid-controlled stable single longitudinal mode microcavity laser based on an antiresonant hollow-core fiber

A stable single longitudinal mode optofluidic microcavity laser based on an antiresonant hollow-core fiber (AR-HCF) is proposed and experimentally demonstrated. A hexagonal silica ring inside the AR-HCF is used as the resonator of the optofluidic laser. Experimental results show that the laser can operate in a stable single longitudinal mode without optical mode-selection device and only by introducing a micro-fluid control device. With 5 mmol l⁻¹ Rhodamine B as gain medium, the threshold of the single longitudinal mode microcavity laser is 554 nJ mm⁻² and the lasing wavelength is 594.3 nm. When the micro-fluid control speed is 1.5 µl min⁻¹, the output power fluctuation of the laser is less than 4% within 35 min. By changing the concentration and type of gain medium, the stability of the single longitudinal mode lasing output can be maintained and the lasing wavelength can be regulated. It holds great promising applications in the multiplexing of optofluidic lasers in the spectral domain, integrated optics and biomedical analysis with high sensitivity. (letter)