Industrial diamond window blanks with optical transmissivity for IR-applications are commercially available. The applicable wavelengths of current diamond optical window components basically include all wavelengths from X-ray, deep ultraviolet to microwave. Therefore, there is a great significance for the development of optical windows/fairings used in airborne, missile-borne, and shipborne infrared search and tracking systems, new weapons (such as power microwave weapons and high-energy laser weapons), dielectric windows for nuclear reactor ECRH, and traveling wave tubes for terahertz bands. More detailed product info, please see below:
1. Specifications of Diamond Windows
PAMP17032-DW
Ø2,5 mm x 0,5 mm, optical grade, double side polished: transmission rate>64% @ infrared light, and transmission rate is about 60%@ultraviolet and visible light;
Ø 4,0 mm x 1,0 mm, optical grade, double side polished;
PAM170417-DW
Ø6,0 mm x 1,0 mm Diamond window, optical clear material: transmission rate>65% @ infrared light, and transmission rate is about 50%@ultraviolet and visible light.
2. Properties Comparison among Typical Infrared Window Material
| Physical Properties | Band Gap Width(Eg/eV) | Absorption Coefficient (α) | Microhardness /(kg-mm-2) | Refractive Index (n) | Thermo-optical Coefficient (dn/dT/10-3K-1) | Thermal Conductivity (W-cm-1-K-1) | Thermal Expansion Coefficient (α/10-6K-1) |
| Diamond | 5.48 | 0.1-0.3 | 8300 | 2.38 | 1.0 | 20-22 | 1.3 |
| Si | 1.11 | 0.35 | 1150 | 3.42 | 13 | 1.63 | 2.56 |
| GaAs | 1.42 | 0.01 | 721 | 3.28 | 15 | 0.55 | 5.9 |
| Ge | 0.664 | 0.02 | 780 | 4.00 | 40 | 0.59 | 5.9 |
| Al2O3 | 9.9 | – | 190 | 1.63 | 1.3 | 0.35 | 5.8 |
| ZnSe | 2.7 | 0.005 | 137 | 2.40 | 6.4 | 0.19 | 7.6 |
| ZnS | 3.9 | 0.2 | 230 | 2.19 | 4.1 | 0.27 | 7.9 |
After comparison, it can be found that other infrared materials except diamond have a compromise between transmittance and mechanical strength. For example, as a window material for long-wave infrared, zinc sulfide is currently the most widely used infrared optical window material in the 8-12 μm band, but zinc sulfide has a soft texture and poor mechanical properties, and it is difficult to withstand harsh environments. In contrast, diamond IR window has good mechanical properties, chemical stability, and good optical permeability in the infrared band.
Furthermore, diamond has loss tangent @140GHz<10-5, dielectric constant 5.7 and dielectric strength 10,000KV/cm, so the proper diamond window film can output 2MW power without cooling device. The mechanical, thermal and optical properties make diamond material with the smallest photothermal distortion and the most ideal window material
3. About Ultra-thin Freestanding Diamond Window
Diamond optical window related components are prepared by microwave plasma chemical vapor deposition process, hot wire chemical vapor deposition process, DC arc plasma jet chemical vapor deposition process and other synthetic methods. They have different geometric structures and can be used under extreme conditions. Take the optical grade polycrystalline chemical vapor deposition (CVD) diamond window for example:
CVD diamond window is produced by chemical vapor deposition. After double-sided polishing, the color is transparent. The normal size diameter can reach more than 100mm and the thickness of 1mm, and the light transmittance can reach more than 60%. Among all infrared optical materials, CVD diamond film is the only one material that combines light transmittance, thermal shock, and high durability against raindrop and solid particle impact and chemical corrosion. More importantly, diamond’s extremely low thermal expansion coefficient and high thermal conductivity make diamond have excellent thermal vibration resistance and maintain good optical performance in high temperature environments, making diamond near infrared antireflective filter window the best infrared optical window material for service in harsh environments.
Optical grade CVD diamond window transmittace is shown in following diagrams:
Transmittance of Optical Grade CVD Diamond, 1mm Thick
Transmittance of Optical Grade CVD Diamond, 0.4mm Thick
Optical grade polycrystalline CVD diamond window can be applied in infrared, short wave UV, high power microwave device, CO2 laser exit window and output coupler. And the transparency can be improved by coating anti-inflection on the component.
For more information, please contact us email at victorchan@powerwaywafer.com and powerwaymaterial@gmail.com.