Efficient long-term laser excitation of a collimated beam of potassium atoms on the K(D2) line

With the aim to provide a reliable scheme for efficient laser excitation of the potassium D2 line over long periods of time, we have developed a robust stabilization of a single mode laser of frequency f(0) = (f(12) + f(23))/2 onto a crossover peak in the saturation spectrum of the K-39( D2) line (4s S-2(1/2), F --> 4p P-2(3/2), F'). The two hyperfine transitions F = 1 --> F' = 2 ( frequency f(12)) and F = 2 --> F' = 3 ( frequency f23) are simultaneously excited by the first order sidebands f(+/-) = f(0) +/- f(EOM) of the laser beam (f(0)), generated by its electro-optical modulation at the frequency f(EOM) = ( f(12) - f(23))/2. In this way stable excitation of the two transitions on their proper frequencies is achieved and hyperfine pumping compensated.