Diffractive optics are making their way into industry. The areas of applications range from bio technology via printing, material processing, sensing, contact-less testing to technical optics and optical metrology. Diffractive optics provide value-add to laser systems. By incorporating diffractive optical elements (DOE) in the optical field of a laser beam, the beam’s “shape” can be controlled and changed flexibly according to application needs.
The base here is the microstructure of the DOE which acts like a router for photons directing their way to propagate through free space. A Diffractive Optical Element utilizes a surface with a complex microstructure for its optical function. The micro-structured surface relief profile has two or more surface levels. The surface structures are either etched in fused silica or other glass types, or embossed in various polymer materials.
The technical discipline of diffractive optics provides methods to design and implement DOE microstructures in order to manipulate light and photons and by this implement a desired function. Remarkable progress in DOE design and implementation has been achieved within the last few years. Fabrication techniques have been proven to be reliable and cost-efficient. DOE have been shown to be effective in various technical applications. In some cases DOE have even opened the doors to new solutions.
Design Example: Combined Laser Aiming Device
DOEs realize a non imaging pattern generation which makes a high sharpness possible at any position of a beam. This qualifies DOEs to be the perfect solution for any laser aiming application in which a display of a specific pattern is needed.
Diffractive Optical Elements – Advantages
- DOEs guarantee a distinct aim pattern at any position of the target field because the pattern is produced by the diffraction of laser light and not by projecting an image.
- Pattern generating Diffractive Optical Elements can be produced for different wavelents. Thereby DOEs provide an unique solution for combined visible and infrared targeting devices.
- DOEs enable an easy and cost effective customization of targeting patterns (e.g. for cross-hair determination in teams).
Diffractive optics can realize almost the same optical functions as refractive optics such as lenses, prisms or aspheres, but they are much smaller and lighter. DOEs are not limited to laser applications; partially coherent light from LEDs or other light sources can also be modulated.
Types of Diffractive Optical Elements
- Beam Splitters:
Diffract the original laser beam into a certain number of beams with a specific direction and intenisty.
- Fourier Holograms:
A special version of Beam Splitters where special patterns, like images, are realised by diffraction in the optical far field.
- Beam Shapers:
Map a certain phase function onto the laser beam in order to modify its propagation. Classical application is a Top-hat generation.
These elements can be seen as special scattering plates, where the light will be diffused to a certain geometry mostly to generate a homogenious illumination.