  An evaluation of the absolute frequency and tunability of collimated blue
light (CBL) generated in warm Rb vapour excited by low-power cw laser radiation
at 780 nm and 776 nm, has been performed using a Fabry-Perot interferometer and
a blue diode laser. For the conditions of our experiments the CBL tuning range
is more than 100 MHz around the resonant frequency of the 85Rb 5S1/2 (F=3) to
6P3/2 (F'=4) transition. A simple technique for stabilizing the power and
frequency of the CBL to within a few percent and 10 MHz, respectively, is
suggested and demonstrated.
