Diffractive optical elements or DOEs are unique types of optical phase components that manipulate the light beam’s phase based on the diffractive principle, whereas conventional mirrors and lenses use the principle of reflection and refraction to modify the phase of the incoming light waves. In simple words, these optical elements are one type of beam shaper that shape the light beam and modify its intensity distribution. But why do we need to shape the light beams or laser beams? The answer is straightforward: many applications that involve the use of laser beams require beams to have a unique intensity distribution pattern, instead of the Gaussian distribution pattern where a substantial amount of energy gets wasted. Some major applications that involve modified laser beams are medical-aesthetic treatments, communication, sensing, imaging, printing, additive manufacturing, and material processing.
To modify the input laser beam’s phase, DOEs involve a custom-made micro-structure that ultimately changes the laser beam’s shape, amplitude, and profile. Nowadays, the fabrication of DOEs has become industrially viable due to the tremendous development of microfabrication methods and modern advanced technology.
Diffractive Optical Elements: Useful Characteristics
The main useful characteristics of DOEs are that these optical elements are smaller, thinner, and lightweight in comparison to conventional optical elements (refractive elements or reflective elements). This characteristic makes DOEs more efficient to integrate. Other notable characteristics of DOEs are absolute angular accuracy, longevity under high laser power and harsh conditions, and some other effective optical characteristics such as high LDT.
Different Types of DOE Applications
Beam Splitting:
When it comes to splitting an input laser beam into multiple output laser beams with specific intensities, DOEs can be useful. Beam-splitting DOEs also help you to organize the output beams’ pattern into a specific shape, for instance, hexagon, square, round, line, or any other anticipated shape. The applications of beam-splitting DOEs include laser micromachining, medical aesthetic treatments, and laser scribing. To get a desired intensity, separation angles, order numbers, and wavelength between UV and IR, one can custom design a beam-splitting DOE.
Beam Shaping:
DOEs can also be used to manipulate the input laser beam and produce a well-structured laser beam with consistent intensity. These beam-shaping DOEs can help develop a spot of any desired shape, including round, square, and other random shapes. Some major applications of beam-shaping DOEs are spectroscopy, 3D imaging, and medical diagnostics. The use of these DOEs is evident in diffractive diffusers, broadband diffusers, and analytical beam shapers.
Beam Foci:
When it comes to changing the focal properties of an input laser beam, beam foci DOEs have significant applications. Beam foci DOEs help us to get multiple foci with accurate focal separations from a single laser focus, to modify the depth of focus, and to concentrate multiple wavelengths on a single focus plane. Laser glass cutting, light-sheet microscopy and cytometry are some useful applications of beam foci DOEs.
