The Study Of Light Intensity And Energy Transmission Of Nonparaxial Beam

The movement law of light wave, electromagnetic wave, is described by the Maxwell equations, so light field is the vector field in nature. Along with the development of near-field optics and the gradually increased using of small-scale but large divergence angle light, the scalar approximation of diffraction theory is no longer validity and vector diffraction theory must be applied. This research has studied the validity of vector diffraction field series solution and nonparaxial approximate solution. The results showed that the validity is closely related with the diameter of diffraction hole and the propagation distance.Light intensity has many definitions and it is defined as the average energy flowing through the unit area within unit time in light vector theory. Light intensity in the cross section perpendicular to the optical axis (z-axis) is equivalent to the z-component of the average Poynting vector. Also light intensity is traditionally defined as the square of the absolute value of the complex amplitude of light vibration. This research compared the two light intensity definitions in detail and analyzed the validity of the traditionally defined light intensity I.In the study of light beam energy transmission, the energy concentration degree,η, oflight beam is a very important physical unit to describe the characterization of energy transmission. Using plane wave circular aperture diffraction as an example, this researchstudied the changes ofηwith diameter of diffraction holeρ₀, propagation distance zand light spot radius r and found how to obtain the largest energy concentration degree by controlling these three factors.