非旋波近似下的激光线宽

LASER LINEWIDTH WITHOUT ROTATING WAVE APPROXIMATION

研究非旋波近似下的激光线宽，精确到原子自然线宽与辐射频率的比值的平方．结果表明，线宽虽然仍然遵从著名的 Ｓｃｈａｗｌｏｗ Ｔｏｗｎｅｓ 公式，但是，由于非旋波项对稳态平均光子数的抑制作用，非旋波项引起激光线宽变宽．加宽的程度不仅依赖于原子自然线宽与辐射频率的比值的平方，而且与旋波近似下的稳态平均光子数有关．非旋波项对光子数起伏的影响较小，与之相比，非旋波项对激光线宽的影响要大得多．

In this paper the laser linewidth without rotating wave approximation is studied by keeping the ratio of the atomic natural decay rate to the radiation frequency to two orders.It is shown that while the linewidth is confined to the Schawlow\|Townes formula,the non\|rotating wave terms would cause the linewidth to increase since the non\|rotating wave terms decrease the average photon number.The degree of increasing in linewidth depends not only on the square of the ratio of the atomic natural decay rate to radiation frequency,but also on the average photon number in rotating wave approximation.The influence of the non\|rotating wave terms on the laser linewidth is much larger than on the photon number fluctuations. PACC: 4250; 4265; 0365