UV-sapphire: High-quality MATERIAL meets precision machining for maximum transmission in deep UV.

In a joint project between KYBURZ SAPPHIRE – a specialist in precision machining of synthetic sapphire – and SAPPHCOM | SAPPHIRE COMPETENCE – the expert in sourcing synthetic sapphire – it was impressively demonstrated how crucial material quality and machining competence are for optical performance in the deep UV range.

For this purpose, UV-grade sapphire samples – characterized by high transparency in the UV wavelength range – were sourced from various crystal growers by SAPPHCOM.

To compare the UV transmission of the two materials, cylindrical raw material with a diameter of 29 mm and a thickness of 24.6 mm was provided. KYBURZ SAPPHIRE then ground, lapped, and precisely polished the samples to various thicknesses, ensuring that surface defects were eliminated and material quality could be accurately assessed.

The subsequent transmission measurements clearly show significant differences in UV transmission.

In general, synthetic sapphire offers excellent transmission over a wide wavelength range – from deep UV (\~200 nm) to the mid-infrared range (\~5000 nm).

However, the actual optical quality crucially depends on the purity of the raw material and the controlled crystal growth process.

The following factors influence the UV transmission of sapphire:

Examples of applications of sapphire in the UV range include:

·       Optics (Lenses, windows, prisms)

·       UV analysis windows in spectroscopy

·       High-pressure / high-temperature UV applications

·       UV measurement cells

·       Protective windows for UV lasers

·       UV lithography, including in microchip manufacturing

Results

Two types of sapphire (“S” and “R”) were examined for their UV transmission. The samples were ground to specific thicknesses, lapped, and precisely polished to make differences in material quality measurable.

1. Visable range (428 nm):

Both samples show a high transmission (>80 %).

• In the S samples, transmission decreases with increasing thickness – an indication of internal defects such as inclusions or scattering centers in the visible range.
• The R samples maintain constant transmission even at greater thicknesses → suitable for applications in the visible spectrum.

2. UV absorption edge (228 nm)
Transmission increases in both samples as thickness decreases.

• S samples exhibit a more favorable (lower) absorption edge → fewer UV-active defects.
• R samples display a “right-shifted” band edge → stronger UV absorption from 228 nm onward, indicating a significant influence of impurities or lattice defects.

3. Deep UV (<220 nm):

This is where the biggest differences become apparent:

• S samples achieve approximately 77% transmission at a thickness of 2 mm (at 200 nm) – even at 24 mm thickness, the transmission remains above 50%.
• R samples exhibit strong absorption: Nearly complete absorption from a thickness of \~14 mm onward, with only \~37% transmission at 220 nm (2 mm thickness) and less than 2% at 200 nm. 

Interpretation: The S samples clearly outperform in the deep UV range. Their transmission increases steadily with decreasing thickness – a typical behavior of high-quality material with a low absorption coefficient.

Conclusion: The combination of carefully selected raw material by SAPPHCOM and precise processing by KYBURZ SAPPHIRE leads to optimal UV-sapphire transmission.

While KYBURZ SAPPHIRE manufactures sapphire components with high dimensional accuracy and excellent polish, SAPPHCOM, as a specialized sapphire partner, provides the foundation: carefully selected raw material from controlled crystal growth with defined UV properties.

The result: Outstanding UV transmission combined with high surface quality – a genuine competitive advantage for applications in optics, sensing, and analysis.

Precision does not happen by chance – it results from the combination of the right material, the right processing partner, and the right supply chain.