Polycrystalline Optical Windows
Large-aperture CVD windows to 150 mm for high-power laser and infrared systems.
CVD diamond transmits from 0.2 to 25 µm, covering the ultraviolet, visible, near-infrared and mid-infrared in a single material, and its refractive index runs from 2.91 at 0.2 µm to 2.38 at 100 µm, among the highest of any natural mineral. The polycrystalline grade is the large-aperture option, to 150 mm.
Transmittance figures below are not corrected for reflection losses.
- Ultra-wide transmission band
- High thermal conductivity
- Exceptional mechanical strength
- Ultra-high hardness
- Excellent high-temperature resistance and thermal stability
- Superior chemical inertness and radiation resistance
Specifications
| Transmittance, 8–25 µm (1 mm thick) | > 69 % |
|---|---|
| Transmittance at 633 nm (1 mm thick) | > 64 % |
| Refractive index at 10.6 µm | 2.376 |
| Refractive index at 1550 nm | 2.386 |
| Refractive index at 1064 nm | 2.392 |
| Absorption coefficient at 10.6 µm | < 0.07 cm⁻¹ |
| Absorption coefficient at 1.064 µm | 0.12 cm⁻¹ |
| Absorption, 3–5 µm | minimum 0.8 at 3.7 µm |
| Thermo-optic coefficient dn/dT | 9.6×10⁻⁶ K⁻¹ |
| Thermal conductivity at 300 K | > 1500 W·m⁻¹·K⁻¹ |
| Thermal expansion coefficient at 300 K | 1.0 ppm·K⁻¹ |
| Dielectric constant (35 GHz) | 5.68 ± 0.15 |
| Loss tangent at 145 GHz | 8 – 20 ×10⁻⁴ |
| Hardness | 81 ± 18 GPa |
| Fracture toughness | 8.5 MPa·m^½ |
| Young's modulus | 1050 GPa |
| Poisson's ratio | 0.1 |
| Specific heat capacity at 300 K | 0.502 J·g⁻¹·K⁻¹ |
| Surface roughness Ra | < 5 nm |
| Reference sizes | 25, 50, 75, 100, 125, 150 mm diameter (customisable) |
| Thickness | < 1 mm (customisable) |
Reference values from the producer datasheet. Dimensions marked customisable are set per order. Request a quote to have a specification confirmed against your drawing.
Applications
The polycrystalline grade is specified where the aperture, the power handling or the thermal load rules out every other window material.
- High-power laser transmission windows
- Infrared thermal imager windows and remote sensing detection windows
- Vacuum isolation windows for extreme-ultraviolet lithography
- Infrared imaging seeker heads
- Aero-engine optical sensor windows