INTRODUCTIONOptical lithography is the primary tool for the fabrication of micro/nanostructures in micro-electronic and opto-electronic applications,which has fueled the explosive growth of the semiconductor industry.Over the past several decades,the resolution of optical lithography has shrunk from ～1 μm to ～38 nm with a single exposure,accompanied by a reduction in the light wavelength from 436 nm to 193 nm.As a result of the classic diffraction limit established by Abbe and Rayleigh in the 1870s [1],further improvements in the resolution call for shorter wavelengths (such as 13.5 nm for extreme-ultraviolet (EUV) lithography)and more complex processes (such as multiple exposure/patteming),as well as a much higher cost,which is not easily affordable for customized requirements.In addition,current lithography systems are mainly built on the needs of the semiconductor industry and may not be suitable for the ever-changing nanoscale research and development.