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从对激光光束质量研究进展开始,讨论了在傍轴和非傍轴范畴内激光光束质量的一些问题,主要是非傍轴光束的光束质量评价。光束传输的非傍轴矢量二阶矩理论可用于计算多种非傍轴光束的M2因子,但对M2因子的物理解释却有困难。例如,在非傍轴范畴,M2因子依赖于束腰宽度与波长之比,并可小于1。但远场发散角之值可趋于90,°这将导致很大的M2因子值。另一方面,若将公式中的光强用时间平均坡印廷矢量z分量代替,桶中功率(PIB),或等价地,!参数可推广用于评价非傍轴光束的远场光束质量。PIB表征了光束功率的可聚焦能力,是一种简明、直观评价不同激光光束的方法。然而,在!参数的公式中的束宽是按功率含量百分比定义的,因此双曲线传输规律不再严格成立。
Starting from the research progress of laser beam quality, some problems of laser beam quality in paraxial and non-paraxial domains are discussed, mainly the beam quality evaluation of non-paraxial beams. The non-paraxial vector second moment theory of beam transmission can be used to calculate the M2 factor of a variety of non-paraxial beams, but it is difficult to physically interpret the M2 factor. For example, in the non-paraxial domain, the M2 factor depends on the ratio of the waist width to wavelength and may be less than one. However, the far-field divergence angle can approach 90, which leads to a large M2 factor value. On the other hand, if the light intensity in the equation is replaced by the time-average Poynting vector z-component, the bucket power (PIB), or equivalently, the! Parameter can be generalized to evaluate the far-field beam quality of non-paraxial beams . PIB characterizes the focusing power of the beam power and is a simple and intuitive way to evaluate different laser beams. However, the beam width in the formula for the parameter is defined as a percentage of the power content, so the hyperbola transfer rule is no longer strictly established.