Low phase noise beams for Raman transitions with a phase modulator and a highly birefringent crystal

We present a technique to excite Raman transitions with minimum phase noise. A phase modulator generates the Raman beams and a long calcite crystal rotates the polarization of the sidebands by 90° with respect to the carrier. That polarization converts the destructive interference of the Raman pairs into constructive interference, opening the possibility to drive both co-propagating and counter-propagating transitions at high detuning with the same setup. The technique has low phase noise and a low sensitivity to vibrations or temperature fluctuations. We apply it to drive velocity insensitive Raman transitions. The crystal can be also configured to filter out one of the sidebands.