In selecting quartz window plates, numerous individuals prioritize factors such as cost and delivery time. However, they frequently neglect to consider several crucial parameters that govern the performance of the product. This can lead to scenarios where the light transmittance falls short of the standard or the anti-damage threshold proves insufficient for subsequent applications. In order to solve this problem, it is first necessary to consider the supplier’s actual control ability with regard to material purity, surface quality and coating process.

Firstly, the purity of the material is of the utmost importance. The presence of metal ion impurities in general-grade quartz glass results in the formation of a strong absorption band in the ultraviolet region. This characteristic leads to a significant reduction in transparency in the deep ultraviolet wavelength. High-purity fused quartz has an extremely low total metal impurity content, thus ensuring a high transmittance over a wide spectral range from deep ultraviolet to near-infrared. Furthermore, the accuracy of processing directly impacts the surface quality. During the milling, grinding and fine polishing processes of quartz plates, effective control of surface roughness is paramount to avoid the generation of scattering centres and stress concentration points. It is highly probable that these points will be damaged by high-power laser irradiation, which will reduce the service life of the components. Thirdly, the coating process is paramount to ensuring optimum performance. The reflection loss can be further reduced and the transmittance of a specific wavelength can be improved by using electron beam evaporation or ion-assisted deposition to deposit an anti-reflection film on the surface of the window.

2. Key parameters and verification methods

To evaluate the quality of quartz windows, the following three key parameters can be focused on.

(1) Material purity and ultraviolet transmittance

The transmittance of high-purity quartz windows at a wavelength of 193nm should generally be greater than 90%. This is the primary indicator for determining whether it is suitable for deep ultraviolet laser systems.

(2) Surface quality

The inspection includes surface finish and indicators of both scratches and pitting. For instance, in the case of window plates used in laser systems, scratch-pitting is typically required to achieve a standard of 40-20 or higher.

(3) Coating performance and anti-damage threshold

For laser applications, it is essential that the coating on the surface of the window demonstrates sufficient resistance to laser damage.

4. Typical application scenarios and applicable boundaries

(1) Laser system

The window is required to have both an extremely high laser damage resistance threshold and a low absorption rate, in order that it can function as the emission window of the laser light source or the protective window of the internal optical path.

(2) Spectral analysis instrument

When selecting a sample cell or beam entry window, it is essential to choose a material with high transmittance over a broad spectral range. When selecting the type, the primary focus is on the transmittance curve of the material in the target analysis spectral range.

(3) Aerospace and scientific research optics window

Optical systems utilized in extreme environments necessitate the use of materials exhibiting high uniformity, low thermal expansion coefficient, and radiation resistance.

(4) Semiconductor manufacturing equipment

For instance, it is vital that the observation windows of photolithography machines and etching equipment demonstrate resistance to plasma erosion and be free from particle release. When selecting a type, it is essential to consider the chemical stability of the material and the surface treatment method.

(5) Biomedical optical instruments

In the optical pathways of fluorescence microscopes and nucleic acid detectors, it is essential that the windows have high transmittance for both excitation and emission light of specific wavelengths.