Direct Laser Writing Facility for Fabrication of Submicron Mask

Direct laser writing technique has become a well-established, multi-functional and flexible method for fabricating high quality diffractive optical elements. We propose and build a maskless direct laser writing system with the ability to produce a sub-micron feature size. The high precision lithography is realized by using the astigmatic autofocus method. The minimum feature size of the system, breaking through the diffraction limit with the chromium layer, can achieve 300 nm with the 405 nm blue laser. A 50×50 mm² chromium grating mask with a period of 1 μm and line width of 300 nm is fabricated. This facility will be useful for the fabrication of large-scale submicron diffraction optical elements in the future.