Fig. 1. Hyperfine energy-level structure of D₂ line

Fig. 2. Absorption spectrum of sodium atom for D₂ lines

Fig. 3. Return light intensity versus guide star laser line width under different pumping pulsed laser energies

Fig. 4. Schematic of experimental system for synchronous detection of return light intensity of sodium guide star

Fig. 5. Typical single-frame retroreflective dot-matrix plane and sectional view of sodium guide stars. (a) Single-frame retroreflective dot-matrix plane of sodium guide stars; (b) sectional view of sodium guide stars

Fig. 6. Intensities of return light in polarizationpump experiment

Fig. 7. Return light intensities under different conditions

Fig. 8. Experimental data for spectral line broadening under double-line pumping condition

Fig. 9. Schematic of multi-longitudinal mode laser spectral broadening under double-line pumping mode. (a) Without broadening; (b) with broadening