Fabrication of Achromatic Infrared Wave Plate by Direct Imprinting Process on Chalcogenide Glass

An achromatic infrared wave plate was fabricated by forming a subwavelength grating on the chalcogenide glass using direct imprint lithography. A low toxic chalcogenide glass (Sb--Ge--Sn--S system) substrate was imprinted with a grating of 1.63-μm depth, a fill factor of 0.7, and 3-μm period using glassy carbon as a mold at 253 °C and 3.8 MPa. Phase retardation of the element reached around 30° at 8.5--10.5 μm wavelengths, and the transmittance exceeded that of a flat substrate over 8 μm wavelength. Fabrication of the mid-infrared wave plate is thereby less expensive than that of conventional crystalline wave plates.