Design and performance of a few-kilohertz-linewidth dye laserstabilized by reflection in an optical resonator

Ultrahigh-resolution spectroscopy is limited by the spectral quality of lasers. We describe a servo system that stabilizes a dye laser by reflection in an optical resonator, which provides an error signal. We analyze the error signal to determine the spectral performance of the dye laser, which is shown to have a Gaussian-shaped spectrum with a width of less than 4 kHz.