Microcavity-based cascaded Raman microlaser in air and in buffer

Due to the non-linear effects in whispering gallery mode microresonators, low threshold microlaser development is possible. The lasing threshold is significantly lowered as high circulating optical intensities build up within the resonator, resulting from long photon lifetimes attributed to the ultra-high quality factor. With such characteristics in place, microresonators can operate as lasers even in complex media. We show cascaded Raman microlaser behavior in an undoped silica microsphere in air and HEPES buffer environments. The first emission peak is at around 800nm with a pump source of around 771nm. The lowest obtained threshold of the first emission line is 105 mu W in air and a higher threshold power of 760 mu W is required in buffer. Cascaded behavior of up to ten lasing peaks has been observed in air and up to two peaks were seen in buffer.