Quartz is an important optical material, which can be used to manufacture most ultraviolet, visible, and near-infrared optical lenses, such as microlens arrays, diffractive optical elements DOE, spiral phase plates, lenses, etc. A quartz substrate is also the most commonly used type of substrate for coating. Many mirrors, femtosecond laser lenses, and filters all use quartz substrates. In the terahertz band, quartz crystal is also a commonly used material, which can be used as a raw material to produce terahertz lenses, quartz prisms, terahertz window mirrors, quartz wave plates, and so on.
Natural quartz, also called quartz glass, is synthesized by some processes to form fused silica (Fused silica), which is the most common and important optical component material. Compared with natural quartz, synthetic fused silica has higher radiation hardness and higher absolute transmittance. It can have excellent optical performance in ultraviolet, visible light, near-infrared, infrared band, and terahertz band.
According to the transmittance of different bands, the quartz transmittance is classified as follows: JGS1 Extreme ultraviolet optical quartz glass185- 2500nmJGS2 UV optical quartz glass220- 2500nmJGS3 Infrared optical quartz glass260- 3500nm.
Quartz transmission spectrum:
We have provided two pictures, representing the transmittance of fused silica and the transmittance of natural quartz. Both transmission spectrum curves have included the calculation of Fresnel reflection loss (1-R)2, and the top curve in the transmission diagram Indicates the loss of Fresnel reflection. Regardless of fused silica or natural quartz, the cause of transmission loss in the 250nm~2800nm band is reflection, and there is almost no absorption.
The above figure shows the transmission spectra of several commercial fused silica. It can be seen that they have high transmittance at 185-2600nm. Depending on the model, the transmission spectra are slightly different. For example, some models are still in the deep ultraviolet band of 165nm. It has a transmittance of more than 80%, some models have an absorption peak near 2800nm, and some models can maintain a transmittance of greater than 80% until 3500nm.
The following figure shows the transmission spectrum of natural quartz. Natural quartz can only guarantee a high transmittance in the 270nm~2600nm range, and the transmittance in the ultraviolet band is much lower than that of fused silica.
The reflectivity of natural quartz and fused quartz are basically the same, both are less than <10%. Among them, the wavelength near the ultraviolet is close to 10%. As the wavelength increases, the reflectivity of quartz slowly decreases, and it is about 6% in the near-infrared band.
The transmittance of quartz crystal in the terahertz band (Z cut Crystal Quartz)
Quartz crystals can also be used in terahertz bands with wavelengths exceeding 50 μm. In the wave band from 120μm to 1000μm, the transmittance of the quartz crystal is >70%. In addition, the terahertz window mirror made of z-cut quartz crystal has high transmittance in both the visible light range and the terahertz band. With the assistance of HeNe lasers, the optical system can be easily adjusted without changing the light polarization state.
Ultraviolet transmittance and transmission spectrum of optical quartz glass, JGS1, JGS2, and JGS3
Grade and name of optical quartz glass
| Brand | Name | Application spectrum band range (μm) |
| JGS1 | far ultraviolet optical quartz glass | 0.185~2.5 |
| JGS2 | UV optical quartz glass | 0.220~2.5 |
| JGS3 | infrared optical quartz glass | 0.260~3.5 |
JGS1 Far Ultraviolet Optical Quartz Glass Classification
| Transmittance of 10mm thick blank (%) | ||||||
| Category | 0.185μｍ | 0.200μｍ | 0.220μｍ | 0.240μｍ | 0.300μｍ | 0.185~1.2μｍ |
| 1 | ＞85 | ＞85 | ＞85 | ＞87 | ＞90 | no absorption peak |
| 2 | ＞70 | ＞80 | ＞80 | ＞80 | ＞85 | no absorption peak |
| 3 | ＞70 | ＞70 | ＞70 | ＞80 | Absorption peak allowed |
JGS2 UV Optical Quartz Glass Classification
| Transmittance of 10mm thick blank (%) | |||
| Category | 0.220μｍ | 0.240μｍ | 0.300μｍ |
| 1 | ＞80 | ＞75 | ＞80 |
| 2 | ＞75 | ＞70 | ＞75 |
| 3 | ＞65 | ＞70 |
JGS3 infrared optical quartz glass classification
| Transmittance of 10mm thick blank (%) | |||||
| Category | 2.0μｍ | 2.5μｍ | 2.7μｍ | 2.8μｍ | 0.2－2.8μｍ |
| 1 | ＞90 | ＞90 | ＞90 | ＞85 | no absorption peak |
| 2 | ＞85 | ＞85 | ＞85 | ＞85 | no absorption peak |
| 3 | ＞80 | ＞80 | ＞75 | ＞75 | Absorption peak allowed |
Based on the above information, the UV transmission spectrum of optical quartz glass is as follows:
Reference data of physical and chemical properties of optical quartz glass
Hardness (Mohs): 5.5
Coefficient of linear expansion (-60~120℃): 2.1×10-7
Melting point (℃): 1700
Refractive index: 1.4585±4×10-4
Central dispersion: 0.00674±4×10-5
Dispersion coefficient: 68.0
