Diffractive Optical Elements

DOEs can be integrated into optical systems in various ways. Flexible calculation methods and differing manufacturing procedures allow for the realization of a multitude of optical functions.

Often, optical testing of aspherical surfaces utilizing interferometers or SHSLab is only possible by the use of DOEs. At least, many test setups can be simplyfied by DOEs which work as null-lenses, but also can fulfil beam splitting and recombination tasks.

Moreover, DOEs can be used for laser beam-shaping. As an example, it is possible to perform a Gauss-mode to flat-top transformation of a laser beam for applications in materials processing.

Due to the working principle of diffractive optics, achromatization and other wavelength-dependend functions can be realized by DOEs. Also for optical interconnects or for shearing-interferometry it is potentially advantageous to utilize DOEs for beam splitting and recombination.

The principle of DOEs (also called computer-generated holograms, CGHs for some applications) is based on diffraction of light. The transition from a refractive to a diffractive optical element can graphically be understood by removing material which causes a phase delay of a multiple of the used wavelength. Hence, a diffractive element has a wavelength dependency which has to be taken into account for a particular application. This dependency can be actively used for wavelength filtering or for achromatization. Compared to their refractive pedants, DOEs are only thin, structured elements which means savings of space an weight.

For calculation of the structures of DOEs we use our extensive design software, which has been developed during many years. By means of this software tool, we can encode simple optical elements like lenses, gratings but also more complex functions described by polynomials, for example. We have included iterative Fourier methods (IFTA) a well as geometrical calculation methods like inverse ray-tracing (IRT).

Depending on the particular application, we offer different possibilities of realizing the required function in a DOE. The plainest form of a DOE is a binary amplitude or phase mask which is made from a glas substrate coated with chromium and photo resist. For higher demands on efficiency the wavefront information can be encoded in a multi-level or quasi-contineous phase mask. The possibility of repositioning the mask in the lithography system allows embedding marks for adjusting or enables amplitude and phase stuctures on the same mask positioned with lithographic accuracy.
Besides design and fabrication of DOEs, we also offer layout of optical systems using DOEs. Moreover, DOEs can be used as null-lenses in setups including our wavefront sensor SHSLab for testing strongly aspherical lenses.
Further information and request forms can be found in the download section .