Diffractive Elements Used to Correct Aberrations

A large number of lenses is often required to successfully correct aberrations when using classical optics.

Alternatively, many corrections can be made with a single diffractive element. This way, compact systems – light and reasonably priced – can be developed.

Plano lenses with an etched structure are used for achromatic correction. They are mainly used in CO₂ lasers where system alignments are done with a pilot laser. Due to the different wavelengths of both types of lasers there are different focal lengths, which can be corrected with DOEs.

Diffraction limited DOE lenses are commonly used in CO₂ laser systems.

Until now diffraction limited focussing of numerical apertures of NA < 1 could only be achieved with multiple or aspherical lenses.

If multiple lenses are used in laser optics then extremely high efficiency losses can be expected. Not only that, but extensive adjustment work is necessary. Through the application of diffractive elements theses restrictions no longer apply.

In addition to the options listed concerning beam correction, further DOEs can be produced upon request. Some examples include:

• Correction of astigmatism for laser diodes.
• Chromatic corrections for several wavelengths