An improvement to the saturated absorption technique of long term stabiliza
tion of lasers is reported. This new method enables stabilization to the ce
ntre of saturated absorption features regardless of whether the peaks are s
ymmetric or asymmetric. Another feature of the locking system is its abilit
y to stabilize the laser at precisely known small detunings from the centre
of the absorption line. The locking system has been applied to both dye la
ser and titanium sapphire laser systems. The long term drift for each was m
easured to be smaller than the laser jitter bandwidth of about 1 MHz for pe
riods of hours, and no mode hops were recorded over several weeks of operat
ion.