Diffractive Optical Elements (DOE): Beam Splitter & Shaper Application Note
Author: Vincent
Beam Splitter & Shaper: Modifying lasers through diffraction
DOE technologies are emerging in the optics industry. Its applications range from technical optics such as scanning and metrology to bioimaging and printing. DOEs are added to laser systems to control the incident beam’s phase and amplitude and to ‘shape’ the beam to a desired output pattern with distinctive functionality. It uses a surface complex microstructure to direct photons for specific functions.
Operation Principle
A DOE beam splitter is used to split a collimated incident beam into multiple beams. The power is shared between the resultant beams. These beams form a 1xN array (1-dimension) or MxN array (2- dimension) depending on the setup. Resultant beams exit the beam splitter with separation angle θ (Figure 1). For an odd number of beams (N), there is a desired beam that falls on the 0-order. For an even number of beams, there is no beam on the 0-order. To achieve well-defined spots at the desired working distance, focusing lenses are often used, as seen in Figures 1 and 2.
| Series Module | DOE-355-1×3 | DOE-355-1X4 |
| Wavelength* | 355nm | 355nm |
| Beam Mode | SM or MM | SM or MM |
| Number of Spots* | 1×3 | 1×4 |
*DOE can be customized to a preferred wavelength, spot size, focal length, and divergent angle of the beam.
A DOE beam shaper setup typically consists of a laser, a DOE beam shaper, a scan system/lens, and the working surface (Figure 3). The beam shaper DOE distributes the energy of a Gaussian beam spot to a Top-Hat profile with uniform intensity. This ensures an even laser irradiation on the working surface. The top-hat profile is identified by a sharp transition area that generates a clear boundary between treated and untreated regions. The output profile can either be rectangular or circular, (Figure 4).
| Series Module | DOE-9.4-150×200 | DOE-SCAN-1064-163 |
| Beam Mode | SM TEM00 with M2 < 1.5 | SM TEM00 with M2 < 1.5 |
| Element Type | Window | Window |
| Shape | Rectangular | Circular |
Applications
Being able to modify and isolate the resultant beam has proved useful in uses such as scanning the surface of the skin or implementing perforation on cigarette filters.
The systems could be used in, but not limited to the following application scenarios:
- Fibre Optics
- Laser Display
- Laser Scribing
- Laser Welding
- Laser Applications for Medical Purposes