Design of transmission multilayer polarizer for soft X-ray using a merit function.
A new method of designing soft X-ray transmission multilayer polarizer for use at a single wavelength using a merit function has been eveloped. A merit function of product of p-transmittance throughput and logarithm of transmittance polarization ratio was chosen. Characteristics of Mo/Si multilayer calculated using the merit function at 13.0 nm have been compared with those calculated using the traditional method by the present authors and those reported so far. The merit function has given the most optimal results of throughput of 30.0% and polarization ratio of 202. The polarizers of much higher polarization ratio or much larger p-transmittance can be designed by choosing the number of layers and optimizing the thickness of each layer to maximize the merit function. Using this method, the roughness effect has been studied on Mo/Si and La/B multilayer polarizers at 13.0 nm and 6.7 nm, respectively. It was found that the influence of roughness is crucial in shorter wavelength region.