Large diameter aspheres for fiber collimation

14. February 2017

Aspheres offer the great advantage to accomplish monochromatic imaging tasks with one optical element where multiple lens elements would otherwise be needed. 

Main advantages of aspheres are:

-  less spherical aberrations

-   larger aperture

-   less weight

-   less transmission loss

-   no internal ghosts

The combination of high purity fused silica and low absorption coatings decreases thermal shift. The capability of Sill Optics MRF machines allows production of aspheres up to diameter 180 mm, sometimes restricted by curvature. Measurement setup (interferometric wavefront test, tactile and optical 3D profilometry) enables us to ensure a surface quality of 0.2 µm PV and 0.05 µm RMSi depending on material and geometry. Even sagittal heights up to 21 mm are measurable enabling the production and test of very steep radii at certain diameters.

This adds up to a perfect option for a fiber collimation system. For example a collimator for 1550 nm with a focal length of f = 275 mm and a clear aperture of 120 mm in diameter can be created just with one aspheric lens element and still be nearly diffraction limited. The mechanical housing includes a practical solution for the fiber mounting with possible precision adjustment in X, Y and Z direction. Custom design to your requirements in NA, focal length, size and other parameters is always an option. Please feel free to contact us.