Pre-stress-assisted nanoimprint lithography for fabricating high-density diffraction gratings

This study presents a pre-stress-assisted nanoimprint lithography (NIL) method for fabricating high-density flexible diffraction gratings. Compared to conventional NIL methods, this method offers the advantage of producing gratings with smaller periods than that of the master mould. First, a polydimethylsiloxane (PDMS) film is patterned by NIL, and is adhered to a flat PDMS substrate under pre-stress tension. Then, patterned PDMS gratings with small periods are obtained when the pre-stress tension is released. The grating periods can be controlled by the degree of the pre-stress tension. In the experiment, flexible diffraction gratings with periods of 3-4 μm are obtained, and the largest reduction ratio of the grating period is approximately 25%. Experimental results primarily verify the effectiveness of the proposed method for fabricating high-density diffraction gratings. Highlights (1) A pre-stress assisted NIL method for fabricating high-density diffraction gratings is proposed. (2) The periods of the diffraction gratings can be controlled by adjusting the degree of the pre-stress tension during the fabrication process. (3) A biggest grating-period reduction ratio of about 25% is obtained in the experiment.