Laser frequency offset locking by marrying modulation sideband with the two-color polarization spectroscopy in a ladder-type atomic system

We present an investigation of two-color polarization spectroscopy (TCPS) based on cesium 6S1/2-6P3/2-7S1/2 (852 nm+1470 nm) ladder-type system in a room-temperature vapor cell. The 1470 nm laser can be offset locked by TCPS combining with frequency modulation sideband. This locking scheme offers a method of modulation-free and conveniently tunable the lock point of laser frequency relative to an excited state transition, and may have many applications such as in two-color magneto-optical trap, diamond-level structure four-wave mixing experiments.