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High efficiency geometric-phase polarization fan-out grating on silicon
Optics Express
|October 19, 2017
Summary
We developed a novel geometric-phase grating for efficient coherent beam combining at 1550 nm. This polarization fan-out grating offers high diffraction efficiency and tolerance to fabrication errors, suitable for infrared applications.
Area of Science:
- Optics and Photonics
- Nanotechnology
- Materials Science
Background:
- Coherent beam combining is crucial for high-power laser systems.
- Existing methods for fabricating fan-out gratings face challenges in efficiency, cost, and scalability.
- Geometric-phase gratings offer a promising alternative for precise phase control.
Purpose of the Study:
- To design, fabricate, and characterize a 1-by-5 geometric-phase polarization fan-out grating.
- To achieve efficient coherent beam combining at 1550 nm.
- To demonstrate a fabrication method tolerant to errors and suitable for large areas.
Main Methods:
- Utilized deep-UV interference lithography on silicon for grating fabrication.
- Controlled grating phase profile via local orientation of binary subwavelength structures.
- Characterized diffraction efficiency and polarization properties at 1550 nm.
Main Results:
- Achieved a theoretical diffraction efficiency of 87% and experimental efficiency of 85.7%.
- Demonstrated high tolerance to fabrication errors due to phase control mechanism.
- Verified the grating's suitability for polarization-controlled fan-out.
Conclusions:
- The developed geometric-phase fan-out grating is a cost-effective, efficient solution for coherent beam combining.
- Deep-UV interference lithography provides a scalable and high-performance fabrication route.
- The grating shows potential for high-power infrared laser applications.
