Sum Frequency Mixing of two Tunable Nd:YAG Lasers for Sodium Fluorescence Lidar Measurements*

Abstract

An interesting coincidence of nature is that by sum frequency mixing the output of two appropriately tuned Nd:YAG lasers, the sum radiation may be made resonant with the sodium D2 transition wavelength. By exploiting this coincidence we have generated high power pulsed sodium resonance radiation. We plan to use this new source of sodium resonance radiation for characterizing the sodium layer in the earth's atmosphere. Figure 1 shows the cw wavelength tuning curves of the two Nd:YAG laser transitions. The 1.064 pm laser has a tuning range of about 6Å while the 1.319 μm laser has a tuning range of about 4Å. By operating the lasers at the wavelengths indicated by the arrows in Fig. 1 it is possible to generate sodium resonance radiation. In addition, it is possible to easily tune the sum radiation over the complete sodium Doppler absorption profile.