Coherent 420 nm laser beam generated by four-wave mixing in Rb vapor with a single continuous-wave laser

Liu Hao^{1, 2}, Yuan Jin-Peng^{1, 2, †}, Wang Li-Rong^{1, 2, ‡}, Xiao Lian-Tuan^{1, 2}, Jia Suo-Tang^{1, 2}

(a) The energy levels involved in the parametric FWM process of rubidium atoms. (b) Experimental setup. L: lens, F: 420 nm bandpass interference filter; M: high reflection mirror, PMT: photomultiplier tube, DM: dichroic mirror, HWP: half-wave plate, QWP: quarter-wave plate, PBS: polarization beam splitter, PD: photodiode, TC: temperature controller, WM: wavelength meter, GS: narrow range grating spectrometer, CCD: charge coupled device.