Precision Manufacturing of Super-Polished Optics Application Note

To Enable High-Power Laser Application

One of the technology engines in high value-add photonics service is in the area of high-power lasers and applications, ranging from scientific to precision material processing. High-power laser optics and precision optics applications require stringent optics quality. Such manufacturing processes put up new capabilities including materials development, polishing techniques, coating techniques as well as metrology technologies. This application note specifically describes our new capability of super-polishing.

Operation Principle

A super-polishing capability for optics can produce extremely smooth surfaces on windows, mirrors, and other flat optics of various sizes, thicknesses, and materials. Super-polished surfaces are referring to surfaces with a roughness of less than 1nm. The whole super-polishing processing included a multi-axis spindling polishing plus a magnetic abrasive polishing, as shown in Fig. 1. After fabrication, an atomic force microscope (AFM) was used to measure the surface roughness over an area of interest, as shown in Fig. 2. The measured roughness average value is less than 5 Å.

Super-Polished Optics 1
Figure 1. A two-step process of super-polishing technique
Super-Polished Optics 3
Figure 2. Atomic force microscope and surface roughness measurement.

The above-mentioned super-polishing process is applicable to various types of optical materials. Some commonly used materials and their properties are listed in Table 1.

MaterialIndex (588nm)Transmission (um)Optical UniformityStress Uniformity (nm/cm)
H-K9L1.51640.33- 2.12x10e-62
JGS11.45860.185- 2.58x10e-62-4
Heraeus 3131.45860.185- 2.5<10e-5≤5
Corning 79801.45860.185- 2.5≤5
Table 1. List of some typical optical glass materials for super-polishing.

Applications of super-polished optics

With the new capabilities in super-polished optics, the power handling of mirrors/lenses/windows has been dramatically increased.

This extends new markets, especially in the area of:

  • Cavity-enhanced absorption spectroscopy (CEAS)
  • Ring laser gyroscope (RLG)
  • Green HeNe laser for confocal microscopy and flow cytometry
Super-Polished Optics 5
Figure 3. Application of high-quality optics. Courtesy of photos: Raycus,
SIOM and Temasek Research Lab

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