Computer-generated holograms (CGHs) are important for many tasks in modern optics. High efficiencies rely on an
increasing number of phase steps which usually complicates the fabrication process. In this paper, we demonstrate an
effective medium approach which uses binary subwavelength structures instead of a conventional surface relief profile to
generate a specific phase pattern. Consequently, the fabrication process is simplified to one exposure and one etching
step independent from the number of phase levels. This offers new perspectives in designing large-scale highly efficient
diffractive elements with large deviation angles. For demonstration, a highly off-axis 3-level CGH for a projection screen
application is designed, fabricated and experimentally evaluated.
Subwavelength structures open up the possibility to create an artificial index material which enables the realization of
high-efficient diffractive structures. This can be used to generate optical elements with nearly arbitrary phase profiles.
We demonstrate the realization of computer-generated holograms based on this effective medium approach. High
diffraction efficiencies can be realized by multi-phase-level modulation based on two-dimensional binary nanostructures.
The fabrication is performed by one lithographical step using a high-speed e-beam writer which allows high-resolution
patterning even on large areas. A diffractive element in the visible range is experimentally demonstrated using the
presented effective index approach.
We report on multi-channel detection of ultrashort THz pulses by a linear array of 16 photoconductive dipole antennas.
The dipole antennas built on low-temperature grown GaAs are excited by a line focus of fs-pulses. By the parallel
detection of a complete line of ultrashort THz pulses, the measurement speed of THz ultrashort pulse time domain
systems can be accelerated by an order of magnitude. For demonstration, the THz beam profile along the line detector is
determined, and its spectral dependence of the electric field distribution is compared and verified by wave-optical