• Ø25 mm Unmounted Filter
• Design Wavelength: 1550 nm
• Optical Density: 3.0
• Wavelength Range: 800 - 2700 nm
• Good Visible Wavelength Transmission (T_avg > 75% for 365 - 600 nm)
• Absorptive Glass Reduces Multiple Reflections

This Thorlabs' unmounted near infrared absorptive neutral density filter has an optical density of 3.0. This shortpass, heat-protective filter is designed to be transmissive in the visible region, allowing for passage of an alignment beam, and absorptive in the near infrared. Although optimized at 1550 nm, this optimization also leads to excellent performance at 1064 nm (see Specifications for details). This filter has a relatively flat spectral response from 1000 nm - 1600 nm and is an effective attenuator up to 2700 nm. It can also be used as heat absorbing filters, transmitting <2% above 4 µm.

This absorptive NIR ND filter is fabricated from Schott glass. This glass has a spectrally flat absorption coefficient from 1000 - 1600 nm. By varying the thickness of the glass, we are able to produce our entire line of NIR ND filters from just four types of Schott glass.

Please note that this product is not designed for use as laser safety equipment. For lab safety, Thorlabs offers an extensive line of safety and blackout products, including beam blocks, that significantly reduce exposure to stray light.

• Substrate: KG3
• Substrate Thickness: 2.0 mm
• Optical Density at 1064 nm: 3.18
• Transmission at 1064 nm: 0.07%
• Optical Density at 1550 nm: 2.88
• Transmission at 1550 nm: 0.13%
• Dimensions: Ø25 mm
• Dimension Tolerance: +0.0 / -0.25 mm
• Clear Aperture: 90% of Diameter
• Surface Flatness: λ/4 @ 633 nm
• Design Wavelength: 1550 nm
• Wavelength Range: 800 - 2700 nm
• Surface Quality: 40-20 Scratch-Dig
• Parallelism: <10 arcsec
• Optical Density Tolerance: ±5% @ 1550 nm
• Transmission: >75% Avg (365 - 600 nm)