Fiber photonics is an innovative technology enabling cost-effective fabrication of diffractive optical elements (DOE) directly on the facet of an optical fiber. The diffractive elements control the wavefront of light coming out of the fiber to perform different optical functions, for example, optical vortex generation, light splitting or focusing. The main advantage of the fiber photonics technology is that the diffractive element is always connected to the light source – optical fiber. This makes the use of such devices extremely easy. Simply connect the fiber to a fiber coupled laser, and the desired light profile comes out of the other end. No free-space optics is required. There is no need to worry about the input beam shape because the fiber mode profile always remains the same. This makes fiber photonics devices very stable and reliable.
The key to the technology is fiber nanoimprint. The new imprinting process, developed by aBeam Technologies, transfers a perfect replica of a 3D structure from silicon mold onto a fiber’s edge. The nanoimprint technology provides reproducibility and nanoscale resolution. In addition, nanoimprint allows us to choose the material for the diffractive element. While optical elements made out of common materials with refractive index ~1.5 perform well in the air, they do not provide enough refractive index contrast if immersed in liquids. However, we can use our proprietary materials with the refractive index as high as 2.05, allowing immersion operation.
The mold fabrication is also different. Conventional DOE either has only two height levels, which limits optical performance or use multimask fabrication procedure which is difficult and expensive. In contrast, we make our molds using grayscale lithography technique. Our diffractive elements have 256 height levels and we fabricate all of them in a single process.
Advantages of having diffractive optics on fiber:
- Easy to use – no assembly or alignment
- Ultimate optical performance through free-form design
- Optical stability
- Reproducible fabrication
- High refractive index – immersion compatible
- Compact – the diffractive element is smaller than 125x125x5 µm