摘要
基于功率密度的二阶矩方法,数值模拟研究了非傍轴余弦平方-高斯光束的束宽、远场发散角和M^2因子。计算结果表明:1)束腰宽度W_0(0)随ω_0/λ的增大而增大。当ω_0/λ较大(ω_0/λ≥0.5)时,束腰宽度随着偏心参数的增大而减小。2)当ω_0/λ→0时,远场发散角趋于渐近值θ_(0max)=63.435°,与偏心参数α无关。3)在非傍轴范畴,余弦平方-高斯光束的M^2因子不仅与偏心参数α有关,而且还与初始束腰宽度和波长之比ω_0/λ有关。当ω_0/λ足够小时,M^2因子可小于1。对给定的偏心参数α,M^2因子随ω_0/λ的变化并非总是单调的。M^2因子随ω_0/λ的增大而增大,当达到最大值后又逐渐减小,最后渐近趋于一稳定值。
On the basis of the second-order moment of the power density, beam width, far-field divergence angle and M2 factor nonparaxial cosine-squared Gaussian beams were illustrated and analyzed with nu-merical simulation. The conclusions are as following. 1） The waist width W0/λ increases with increasing wo/λ parameter. W0/λ decreases with increasing decentred parameter a when wo/λ is relatively large （wo/λ 〉 0.5）. 2） As the parameter wo/λ→0, the far-field divergence angle approaches an asymptotic value of θmax=63.435°, which is independent of the decentred parameter （x. 3） In the nonparaxial regime, the M2 factor of cosine-squared Gaussian beams depends not only on the decentred parameter a, but also on the initial waist-width to wavelength ratio W0/λ the M2 factor may be less than 1 as W0/λ becomes small enough. The M2 factor does not always vary monotonically with W0/λ for different decentred parameter a, and it increases with increasing W0/λ and reaches the maximum value, then gradually decreases, and finally tends to be a saturated value.
出处
《量子电子学报》
CAS
CSCD
北大核心
2013年第3期284-287,共4页
Chinese Journal of Quantum Electronics
基金
教育部科学技术研究重点项目(208110)
海南省自然科学基金项目(10801)
琼州学院2010年度科研项目(QY515-201002)
