demagnification imaging improved by mask in a hyperlens photolithography system

Hyperlens, composed by curved dielectric-metal layers, are often used in photolithography systems to realize demagnification imaging in subwavelength scale. most studies are focused on the design of the hyperlens for resolution enhancement. here, we show the demagnification imaging can also be improved by the mask. it is found that the demagnification ratio can be increased by 14.5 % when a silver rather than a chromium mask is used. an image with a half-pitch resolution of about one tenth of the operating wavelength can be achieved if the mask material and thickness are properly selected. the image contrast can also be promoted by introducing a phase-shifting layer on the top of the mask.