Frequency stabilisation of a broad-band dye laser by light-induced drift

A new method for frequency locking of a broad-band laser based on light-induced drift is presented. The main advantages of the technique are: good stabilisation provided by sensitivity and good signal-to-noise ratio of the error signal; unnecessary dithering of the laser frequency; use of an atomic transition with low frequency drift. The method is well suited to broad-band applications because the light-induced drift effect can naturally integrate over a broad-band of frequencies (of the order of the Doppler width) to find the average. Tests carried out on Na immersed in a buffer gas of Ar, have allowed long-term frequency stabilisation of the central frequency of a 2.5 GHz-bandwidth dye laser.