Narrow-band, tunable, semiconductor-laser-based source for deep-UV absorption spectroscopy

Tunable, narrow-bandwidth $\left(<200-\mathrm{MHz}\right)$, $\sim 215-\mathrm{nm}$ radiation was produced by frequency quadrupling the $\sim 860-\mathrm{nm}$ output of a high-power, pulsed GaAlAs tapered amplifier seeded by an external-cavity diode laser. Pulsing the amplifier increased the $860 \mathrm{nm}\to 215 \mathrm{nm}$ conversion efficiency by 2 orders of magnitude with respect to cw operation. Detection of nitric oxide and sulfur dioxide by high-resolution absorption spectroscopy was demonstrated.