We report on novel concepts for reflective diffractive elements based on high-contrast gratings. To demonstrate
the possibilities for such devices reflective cavity couplers with three output ports are investigated. A diffracting
period is superposed to a highly reflective subwavelength grating in order to realize diffractive elements. This
superposition can be realized with a periodic depth, fill factor or period modulation of the reflector. Further, to
limit the total transmission of the device it is necessary to enhance its angular tolerance. We discuss different
approaches in order to realize this increased reflectivity in broad range of the angular spectrum. The contribution
focuses on the material combination silicon-silica, but the presented concepts also hold for other material
combinations with large index contrast and even for monolithic silicon structures.
In this work we present a wire grid polarizer with a working range down to 300 nm based on an amorphous silicon
grating. For the fabrication of gratings with periods of 120 nm and 140 nm electron beam lithography and ICP
etching were used. Furthermore the influence of the grating period on the optical properties was investigated.
The measured maximum value of the extinction ratio for a period of 140 nm and 120 nm is 177 at a wavelength
of 418 nm and 324 at a wavelength of 394 nm, respectively.
In this work we present a metal wire grid polarizer for the UV spectral region. The period of the aluminum grating is 100
nm. The grating was fabricated using a spatial frequency doubling technique. The process consist of electron-beamlithography,
sputter coating and various ion-beam- and ICP etching steps. The features of the fabricated aluminum wires
fulfill the theoretical demands with a height of 150 nm and a width of 35 nm. Optical parameters of the grating at 250 nm
wavelength are 42% transmittance and an extinction ratio of almost 15. The optical parameters are even improved with