engleski

Optical frequency comb on potassium D1 resonance line

We present direct observation of the velocity-selective optical pumping of the potassium (39K) ground state hyperfine levels induced by 5s2S1/2  5p2P1/2 (D1 transition) femtosecond pulse-train excitation. Experiment has been performed with a modified direct frequency comb spectroscopy. Spectra physics Tsunami mode locked Ti:sapphire laser with duration of the pulse of about 100 fs and a repetition rate of about 80 MHz has been used as a pump laser and it was centered on D1 transition. Weak Toptica ECDL had been used as a probe laser. It was also centered on the same transition and had a linewidth less than 1 MHz. We observed how the optical frequency comb was inprinted on the Doppler profile of the resonance line. Theoretical calculation has also been performed and it is in very good agreement with experiment. In addition we show the interaction of the frequency comb and potassium atoms in external magnetic field from 0 to 75 Gauss. In that range we found oscillations in the intensity of modulations (amplitude of the comb fringes).

frequency comb; femtosecond laser; potassium; spectroscopy

nije evidentirano