Fig. 1. TDLAS measurement principle

Fig. 2. Second harmonic method measurement principle

Fig. 3. Schematic diagram of system composition

Fig. 4. Experimental system diagram. (a) Cesium vapor pool heating device; (b) Cesium vapor pool;(c) Optical path collimation; (d) Cs atomic concentration detection system

Fig. 5. (a) Spectra of laser at 25 ^oC and 40 ^oC; (b) Corresponding relationship between the output power of laser and the driving current

Fig. 6. Laser absorption and second harmonic signal

Fig. 7. Trend diagram of theoretical calculation results of Cs atomic concentration

Fig. 8. Actual trend diagram of Cs atomic concentration