Broadband attenuation, 350 nm to 2000 nm
Metallic neutral density coating
Low wavefront distortion
UV grade fused silica
For lower power applications
Our metallic neutral density coatings provide broadband attenuation for lower power applications. The coating is deposited on one side of an ultra-pure UV grade fused silica substrate providing excellent transmission from the ultraviolet to the near-infrared. These precision polished substrates have flatness less than 1λ–2λ. The second polished side is uncoated.
These filters are available individually or in a set of eight. The set consists of a logical assortment of filters packaged in a protective hardwood case. All filters are permanently marked with the optical density and are shipped with a transmission curve.
Our unique assortment of filters permits easy selection of any desired density, from 0–8 with 0.1 OD resolution by using individual or combinations of filters. Optical density (OD) is defined by the relationship:
OD = -log(T) or T = 10-OD
where T is transmission (0≤T≤1). The density of a series of filters, unlike transmission, is additive. Custom densities can therefore be obtained by stacking filters, however stacking an excessive number of filters can lead to numerous unwanted back reflections.
Due to the absorptive nature of the metallic coating, use with high-power lasers should be avoided. Power levels less than 30 W/cm2 are advised. For attenuation of high-energy lasers our Model 935 variable attenuator is recommended (High-Energy Variable Attenuators).
| Material | UV grade fused silica |
| Surface Flatness |
25.4 mm Round: ≤1λ at 632.8 nm over the clear aperture 50.8 mm Square: ≤2λ at 632.8 nm over the clear aperture |
| Clear Aperture | ≥central 80% of dimensions |
| Surface Quality | 60-40 scratch-dig |
| Dimensions | ±0.25 mm |
| Thickness | 0.118 (3.0) ±0.25 [in. (mm)] |
| Wedge | ≤3 arc min |
| Chamfers | 0.25–0.76 mm face width x 45° ±15° |
| Angle of Incidence | 0° |
| Optical Density at 632.8 nm | 0.03 ±2.5%, 0.1 ±8%, 0.2 ±7%, 0.3 ±6%, 0.4 ±5% at 0.5 ±4% |
| Usable Wavelength Range | 350 - 2000 |
| Durability | MIL-C-48497A, adhesion, humidity, moderate abrasion, and solubility requirements |
| Cleaning |
Non-abrasive method, acetone or isopropyl alcohol on lens tissue recommended (see How to Clean Optics) |
| Damage Threshold | 30 W/cm2 CW, typical; not recommended for pulsed laser use |