Diffractive Optical Elements: Exploring Different Options and Applications

Diffractive optics modulate light by diffraction. They are micro-structured optical elements fabricated by etching in fused silica or embossing in various polymer materials. They feature unique properties that let them realize optical functions that are otherwise hard or impossible with traditional optics. Diffractive optics have benefits that include reduced weight and size; however, their main feature is their ability to act like optical wavefront processors by forming beam splitters, beam shapers, Fourier holograms, and different grating structures.

Diffractive Optical Elements

Holographic diffractive optical elements (DOEs) come in standard designs for common beam shapes. Also, they can be customized to a certain application for optimum performance. Highly efficient multi-level holographic kinoform designs can efficiently convert the incident laser beam into the required image in the output field. As a result, the energy losses associated with binary diffractive structures are reduced.

Reactive DOEs can be produced for CO2 lasers for some applications including beam splitting and complex heat profiles for welding applications. Some manufacturers also have transmissive DOEs, which are fabricated in fused silica to fit most standard lens holders. Some DOEs are available for custom wavelengths in specific applications. They include reflective beam splitters that produce a total of 81 individual spots for a 3µm source and pattern-generating DOEs for a UV laser.

Optical Diffusers

Optical diffusers are a type of DOE that transforms a single or multi-mode input beam into a well-defined output beam. They use various methods for diffusing light. They include holographic diffusers, greyed glass diffusers, and opal diffusers. These diffusers are made to different specifications determined based on the application. Generally, optical diffusers are found in an array of technical applications including bar code scanning, aerospace and military, imaging systems, computer screens and other monitors, optical sensing, and more. Often, the diffuser material is fused silica or GaN.

Adjustable Function Beam Shaping

DOEs are passive elements. Although this quality is an advantage in a lot of applications, it poses a limitation for others. In some applications, the flexibility of making different optical functions on the same optical path is a benefit that DOEs don’t have. This problem is addressed by developing a new method for adjustable function beam shaping. Such elements have more than one optical function on the same surface but on various areas. They make it possible to design an active beam shaping system that enjoys all the benefits of diffractive optics including accuracy, quality, and compactness while allowing for flexible shaping.

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