Diode-pumped broadband vertical-external-cavity surface-emitting semiconductor laser applied to high-sensitivity intracavity absorption spectroscopy

A diode-pumped broadband multiple-quantum-well vertical-external-cavity surface-emitting semiconductor laser has been developed for high-sensitivity intracavity laser-absorption spectroscopy. The semiconductor structure design has been optimized so as to provide maximum laser-emission bandwidth and wavelength tunability. The laser has a 100-mW threshold of continuous room-temperature operation, and it can be tuned within 25 nm around its design wavelength (980 nm). A detection limit lower than ${10}^{-10}$ per centimeter of absorption path has been achieved, given $\sim 3\times {10}^{-11}\hspace{0.5em}{\mathrm{cm}}^{-1} {\mathrm{Hz}}^{-1/2}.$ Its spectro-temporal dynamics has been studied in the time range from a few microseconds to ∼1 s. No evidence of nonlinear mode interactions, which in many cases limit the sensitivity, has been observed. We have also shown that with a cavity length reduced to 2.5 cm, the laser is very attractive as a tunable single-frequency source owing to its stable operation in a single ${\mathrm{TEM}}_{00}$ mode at a pump power of up to 1 W.