The range of the accuracy of scalar diffraction theory and effective medium theory for binary rectangular groove phase grating is evaluated by the comparison of diffraction efficiencies predicted from scalar theory and effective medium theory, respectively, to exact vector results calculated by Fourier modal method. The effect of element parameters (depth, period, index of refraction, angle of incidence, and fill factor) on the accuracy of scalar treatment and effective medium theory is quantitatively determined. Generally, it is found that the scalar method is valid when the normalized period is more than fourfold wavelength of incident light at normal incidence. The error of transmittances between vector method and scalar method increases as the incident angle and refractive index increase. Furthermore, when the higher diffraction orders other than zero-th order are not to propagate, the effective medium theory is accurate to evaluate the transmittance of grating at normal incidence. The error of transmittances between effective medium method and rigorous vector theory increases as the incident angle and refractive index increase. Also, the error of diffraction efficiencies between the simple methods and the vector method on the polarization state of incident light is clearly demonstrated.
Standard measuring condition of d/0 structure has been widely applied on spectrophotometer. Ordinarily, in order to
eliminate the impact of light source fluctuation, the inner surface of integrating sphere is selected as reference in the
design of integrating sphere system. This design ensures the temporal stability of measurement. But the reflected light of
inner surface and diffuse reflection light of sample are both detected as reference signal. It greatly impacts repeatability
and error of indication. This paper improves d/0 measuring condition configuration with LEDs light source, and finds the
method to reduce the error considering light source and integrating sphere. Then this paper simulates the configuration
and establishes experiment for it. The results indicates that this configuration can effectively revise the error which
carried by the diffuse light.
In this paper ,the advantages and disadvantages of the methods to achieve White LED are reviewed, and
phosphor-converted white LEDs are discussed in detail. In the case of blue chip exciting YAG phosphor to get white
LED, use Mie scattering theory to construct physical model, then analyze how the package, concentration, thickness and particle size of phosphor work on extraction efficiency, spatial Chroma uniformity and color temperature of white LED. The conclusion of this paper advances the application of LED solid-state light source. In the end, the paper puts forward the direction and focus of phosphor research.
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