An atomic-beam set-up for 0.5 MHz absolute frequency stabilisation of a single-mode CW dye laser

The construction and performance of a simple atomic-beam apparatus, used only for the absolute frequency stabilisation of the dye laser, is described. The laser frequency is stabilised on the maximum of the near-Doppler-free fluorescence signal of a Ne* atomic beam crossing the laser beam. Different detection techniques to optimise the signal-to-background ratio have been investigated. Optical fibres are used to transport the laser beam to the atomic-beam apparatus, which is advantageous in comparison with direct transport by mirrors. Using a computer-controlled stabilisation loop a flexible stabilisation scheme is obtained which gives the possibility of performing measurements at slightly shifted frequencies and to interrupt the computer-controlled main experiment after detection of a mode hop.