In the far-ultraviolet (UV) region, optical materials are dispersive and absorbing. The previous successful design method utilized in the visible band should be re-examined. We report on the design and fabrication of a far-UV reflective broadband filter based on dielectric materials lanthanum fluoride (LaF3) and magnesium fluoride (MgF2). Extended bandwidth technology is utilized in designing this filter. The obtained filter has a high reflectance in the working wavelength range of 140-180 nm, meanwhile, with good suppression in shorter and longer wavelength regions. In 2016, this filter was employed in a wide-angle aurora imager (WAAI) installed in the Feng Yun III satellite that will be launched in China.
Keywords: LaF3; Lanthanum fluoride; MgF2; broadband; filter; magnesium fluoride.