聚焦径向调制Bessel-Gaussian光束实现亚波长尺寸纵向偏振光束

Longitudinally polarized subwavelength beam generated by focusing radially modulated Bessel-Gaussian beam

亚波长尺寸纵向偏振光束在粒子加速,单个分子偶极矩测量,二次谐波成像和纵向偏振共焦显微镜等方面有非常广泛的应用.本文提出径向调制的Bessel-Gaussian光束模型,经高数值孔径显微物镜聚焦可以获得高纯度的纵向偏振光束.利用矢量衍射理论数值模拟了焦点附近光强分布、磁场分布和能流密度空间分布.结果表明光斑半高全宽度可以达到0.4λ.该方法无需环形孔径或环形相位滤波器,光能利用率高,分辨率好,达到改进各种应用的效果.

Longitudinally polarized subwavelength beams have found many applications such as particle acceleration,single molecule dipole detection,second harmonic generation imaging,longitudinally polarization confocal microscopy.We present a radially modulated Bessel-Gaussian beam model which produces longitudinally polarized beams with high purity after being focused by high numerical aperture objective.Based on the vector diffraction theory,the electric field intensity distribution,magnetic field intensity distribution and energy flux density near the focal plane are numerically simulated.The result shows that the full-width at half-maximum is as small as 0.4λ.The method does not require a physical annulus or annular phase filter and it features high energy efficiency,high resolution,thus improving application performances.