部分相干螺旋自加速贝塞尔光束

Partially Coherent Spiral Self-Accelerating Bessel Beam

理论分析了螺旋贝塞尔光束的产生机理。根据高斯-谢尔模型的交叉谱密度公式及交叉谱密度传播理论,推导得出了部分相干螺旋贝塞尔光束的表达式。研究了部分相干螺旋贝塞尔光束的传输特性,同时分析了相干度对其传输特性的影响。结果表明,随着传输距离的增加,光束截面光强分布对比度逐渐下降,光场分布由贝塞尔型分布逐渐向高斯型分布转变,但是光束仍具备螺旋自加速特性;高阶光束出现了暗核消退现象,并且暗核消退距离随阶数的增加而增加。随着相干长度的下降,贝塞尔光场分布区间逐渐减小,光束的无衍射距离缩短。同时,探讨了光场调控对光束的影响,其中包括了全息片的参数设定以及光场相干度的调节。

The principle of generating the spiral Bessel beam is theoretically analyzed. Based on the cross-spectral density function of Gaussian-Shell model and the theory of cross-spectral density propagation, the expression of partially coherent spiral Bessel beam is derived. The propagation characteristics of partially coherent spiral Bessel beam are studied and the influence of coherence on its transmission characteristics is analyzed. The results show that with the increase of transmission distance, the contrast of beam intensity distribution of beam cross section decreases, and the distribution of light field changes from the Bessel type to the Gaussian type. However, the beam still maintains the self-acceleration property. For the high-order beam, a phenomenon of dark core fadi.ng can he found easily and the fading distance of the dark core increases with the increasing of the beam order. With the decreasing of the coherent length, the distribution of Bessel light field decreases gradually, and the non-diffraction distance of the beam is shortened. Moreover, the influence of light field regulation on the beam is also discussed, which includes the parameter setting of the hologram and the adjustment of the coherence of the light field.