Diffractive Optical Elements (DOEs) are made for demanding industrial and consumer applications. These lithographically patterned elements provide complete phase control of transmitted light without limitations that refractive optics impose. A micro-thick active phase-transforming layer is directly etched into dielectrics on a fused silica substrate.
With the DOE’s ability to alter the transmitted laser light, it can produce nearly any beam intensity profile or beam shape to meet application requirements. DOEs can be made from different substrates including fused silica, plastic, zinc selenide, and germanium, allowing their use with UV, visible, and infrared lasers. In general, DOEs are designed for a specific laser wavelength and their performance depends on the wavelength.
In lithography and holographic lighting, DOEs are used in beam homogenization in mask projection systems, homogenous field illumination for normal and highly tilted planes, as well as structured pupil illumination. Also, DOEs are used to shape and split laser beams during welding, soldering, cutting, and drilling in laser material processing.
With diffractive optics, it is possible to implement a range of applications with minimal light loss. Diffractive microoptics can be found in production facilities for laser material processing, in areas like lighting, lithography, and printing technologies, in medical laser treatments and diagnostic instruments, as well as in measuring and metrology systems. DOEs are used for patterning light in work areas for custom illumination.
Benefits of DOEs
The use of DOEs in various applications generally offers the following benefits:
- Modern production methods and manufacturing experience make it possible for manufacturers to produce high-precision diffraction structures.
- Energy-efficiency. With DOEs, shaping and splitting of laser beams to control the intensity have become highly energy-efficient.
- Diffractive optics can replace refractive optics or combine with them.
- Customer-centricity. DOEs are tailored to the specific applications that customers require.
- With DOEs, users have the ability to control the phase across the aperture precisely and make complex intensity profiles.
Fabricating DOEs involves robust deep ultraviolet (DUV) photolithography and a reactive ion etch process. Robust volume fabrication methods are used to mass-produce wafer-scale DOE optics. DUV is ideal for fabricating high-performance flat lenses, phase plates, structured light splitters, pattern generators, beam splitters, or computer-generated holograms. Because there is no limitation to component size, it is ideal for fabricating micro-optical parts. In a single optical surface, multiple optical functions like collimation and beam splitting may be implemented. Also, the approach may be used for hybrid integration of a passive optical layer used for beam-shaping and an active layer that contains optical sources and detectors.