BMV Optical

Extremely demanding Gaussian Reflectivity Mirror (GRM) for Commercial application

First side of 1” diameter GRM the Gaussian profile coating must occupy the full surface
Second side of GRM must have a tri-wavelength design dielectric coating
GRM must have an extremely high laser damage threshold coating of 5J/cm² for 1ns
Solution required super polish for surfaces, advance cleaning methodology, new coating materials and redesign of mask design software
BMV met the customers specifications and exceeded the required laser damage threshold

Space bound optic for the International Space Station
Holes on each side must be aligned precisely with holes on opposite side
Because of large number of holes diamond wear on the drill was a serious problem in order to maintain very tight tolerance on diameter and depth of holes and hole position
Extremely time consuming alignment procedure and drilling of holes. Extremely time consuming metrology with CMM.
Material is high purity Fused Silica
Bi-Convex lens with each radius of curvature accurate to 1%
200 blind drilled holes per side
All hole diameters, spacing, depth and placement relative to a reference, accurate to 50µm

Customer Axicon Requirements Included:
- Precise Apex Angle (Tolerance = +/-0.1Degrees)
- Minimal decentration (Tolerance = +/-0.010mm)
- Extremely small Apex Rounding Diameter (>1.5mm)
- Two-sided broadband visible AR coating.
Special Design Considerations Included:
- Specialized high-speed part holder and blocking component had to be manufactured to ensure part decentration and Apex Angle specifications were still met under high lateral polishing forces.
- Part surface generation was made to a pre-polish quality to decrease the amount of total polishing time necessary, which was found to decrease overall surface zoning.
- High-speed equipment modifications had to be made to ensure that the software limitations of the machine wouldn’t result in uneven surface working conditions during Axicon polishing.
Unexpected Issues Included:
- Conventional polishing pad materials and configurations lead to badly damaged Apex tip.
- A non-conventional polishing pad shape was created to polish the Axicon surface in concert machine software modifications to prevent damage and Apex rounding from occurring to the Apex tip region.