外加气体对碘的简并四波混频的影响

Effects of Foreign Gases on the Degenerate Four-Wave-Mixing in I_2

研究了入射激光能量密度,外加气体(N_2,CO_2,NO_2)对碘的简并四波混频(DFWM)光谱和信号强度的影响,测定了I_2的DFWM信号的饱和强度与外加气体压强之间的关系.结果表明外加气体对I_2的DFWM光谱结构的影响不大,但对信号强度的影响较大,而且与激光能量密度有关.I_2的DFWM信号的饱和强度(I_(sat))与N_2压强(p)之间的关系为I_(sat)∝p^(0.7).当激光能量密度足够大时,外加气体对信号的增强作用是热光栅所产生的.

The effects of laser fluence and foreign gas (N2, CO2, NO2) pressure on the degenerate four - wave - mixing (DFWM) spectrum and signal intensity of 12 have been studied. The dependence of DFWM saturation intensity on foreign gas pressure is measured and found to be Isat∝ p0.7 . Results show that the foreign gas has little effect on the DFWM spectrum structure but has great effect on the signal intensity, which depends on the laser fluence. At high laser fluence, the addition of foreign gas can enhance the DFWM signal, and thermal grating contribution dominates. Using the relationship of Isat∝ p0.7 and the two - level model, the dependence of I2 DFWM intensity on foreign gas pressure can be well fitted.