Diffractive optical elements (DOEs) are visual elements that create an image by refracting light. They do this differently than typical lenses, which use refraction and reflection to form doubles. The following is a list of a few types of diffractive optical elements.
- Holographic Optical Element (HOE):
This type of DOE is created by recording the interference pattern formed when two laser beams are superimposed. This creates a holographic surface with features smaller than one wavelength of light, which allows for fine control over beam propagation without influencing chromatic aberration.
- Diffractive Grating Spatial Light Modulator (DGSLM) :
A DGSLM type of DOE uses a micro-mirror array to create an image. This type of DOE can modulate light in tiny increments, making it ideal for high-resolution displays and imaging systems.
- Surface Relief DOE:
A surface relief DOE is created by etching a pattern into a thin film. This type of DOE can control the direction and intensity of light passing through it.
- Volume DOE:
A volume DOE is a type of DOE fabricated by engraving or embossing a pattern into a bulk material. This type of DOE can control the distribution and intensity of light passing through it.
- Bragg Grating:
A Bragg grating is a volume DOE that uses periodic grooves in material to diffract light. This type of DOE can control the spectrum and direction of light passing through it.
- Optically Resonant Structures:
This type of DOE uses a structure with specific dimensions to control the direction and intensity of light passing through it. This can be done by controlling both phase and group delay and reducing Fresnel reflections at surfaces.
- Asymmetric Transmission DOE:
This type of DOE uses a non-uniform transmission profile to diffract light. This can control the direction and intensity of light passing through it.
- Homogenizing Diffractive Optical Element (HDOE):
An HDOE is a type of DOE used to create a uniform distribution of light across an input surface. This can be useful for eliminating hotspots and improving image quality.
- Angularly-selective DOE:
An angularly selective DOE is a volume or surface relief optical element that can reflect light in one angular direction while transmitting light at different angles. This can be used for beam steering, polarized lighting, and adaptive optics applications.
Conclusion
It should be noted that DOEs are not limited to the types listed above. Many other types of DOEs can be used for specific applications. For example, there are DOEs made from plastic or glass specifically designed for use in LED lighting systems.