Frequency stabilized diode laser with variable linewidth at a wavelength of 4047 nm

We report on a frequency stabilized laser system with a variable linewidth at a wavelength of 404.7 nm used as an incoherent repump on the 6P30↔7S31 transition in mercury. By directly modulating the laser diode current with Gaussian white noise, the laser linewidth can be broadened up to 68 MHz. A Doppler-free dichroic atomic vapor laser lock spectroscopy provides an error signal suitable for frequency stabilization even for the broadened laser. Without the need of an acousto-optic modulator for the linewidth tuning or lock-in technique for frequency stabilization, this laser system provides an inexpensive approach for an incoherent and highly efficient repumper in atomic experiments.