Polarization enhanced tunable Doppler-free dichroic lock technique for laser frequency locking

We present a technique, called the polarization enhanced tunable Doppler-free dichroic lock (PET-DFDL) technique, for frequency stabilization of a laser system. This technique is based on the magnetically induced circular dichroism for a pair of circularly polarized probe beams overlapped by oppositely circularly polarized counterpropagating pump beams. The amplitude and slope of the signal generated in the PET-DFDL technique at cooling transition F=2→F′=3 in 87Rb atom are nearly 4 times higher than those of signal generated from conventional Doppler-free dichroic lock (DFDL). The proposed PET-DFDL technique can also provide tunable lock-position. The frequency stability of a laser system locked with the PET-DFDL technique has been improved by factor of 2 as compared to frequency stability obtained by the DFDL technique. The dependence of PET-DFDL signal on pump beam power and magnetic field for the cooling transition of 87Rb atom is also investigated.