Frequency doubling of cw 1560nm laser with single-pass, double-pass and cascaded MgO:PPLN crystals and frequency locking to Rb D2line

Abstract

We implemented and compared three different quasi-phase-matching (QPM) frequency-doubling configurations for 1560nm laser of single pass, double pass and cascade by using of MgO:PPLN bulk crystals. Also a fiber-pigtailed MgO:PPLN waveguide is utilized in single-pass frequency doubling configuration in the case of low-power 1560nm fundamental wave (FW) laser. Employing the second-harmonic wave (SHW) output at 780nm and a rubidium (Rb) vapor cell, we also performed the modulation transfer spectroscopy (MTS). MTS is insensitive to the fluctuation of laser intensity and the temperature drift of atomic vapor cell, so it is a good choice for laser frequency stabilization against atomic hyperfine transition line. The laser frequency stability is significantly improved after being locked via MTS scheme compared with the free-running case.