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TECHSPEC® components are designed, specified, or manufactured by Edmund Optics. TECHSPEC® components are designed, specified, or manufactured by Edmund Optics. Learn More
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λ/4 N-BK7 Precision Windows

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  • Circular and Rectangular Sizes from 2mm to 200mm
  • 8 Broadband Anti-Reflection Coating Options Available
  • World's Largest Selection of Standard N-BK7 Windows
  • Also Available with Ultra-Thin N-BK7 Windows

TECHSPEC® λ/4 N-BK7 Precision Windows are ideally suited for industrial and low-power laser applications. The high tolerance design yields minimal beam distortion and scatter. Broadband coating options extend the range of these precision windows through the visible and near-infrared spectra. TECHSPEC® λ/4 N-BK7 Precision Windows are offered in circular and rectangular sizes ranging from 2mm to 200mm.

Note: New additions to this product family may be specified with a transmitted wavefront distortion (TWD) specification instead of a surface flatness. For more information on the difference between these two specifications, see our application note on Understanding Optical Windows. 

Common Specifications

Bevel:
Protective as needed
Clear Aperture (%):
90
Edges:
Fine Ground
Knoop Hardness (kg/mm2):
610
Poisson's Ratio:
0.206
Young's Modulus (GPa):
82
Abbe Number (vd):
64.17
Index of Refraction (nd):
1.516
Surface Quality:
60-40
Density (g/cm3):
2.51

Products

Technical Information

N-BK7

Typical transmission of a 3mm thick, uncoated N-BK7 window across the UV - NIR spectra.

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Typical transmission of a 3mm thick N-BK7 window with MgF2 (400-700nm) coating at 0° AOI.

The blue shaded region indicates the coating design wavelengh range, with the following specification: 

Ravg ≤ 1.75% @ 400 - 700nm (N-BK7)

Data outside this range is not guaranteed and is for reference only.

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Typical transmission of a 3mm thick N-BK7 window with VIS-EXT (350-700nm) coating at 0° AOI.

The blue shaded region indicates the coating design wavelengh range, with the following specification: 

Ravg ≤ 0.5% @ 350 - 700nm

Data outside this range is not guaranteed and is for reference only.

Click Here to Download Data

Typical transmission of a 3mm thick N-BK7 window with VIS-NIR (400-1000nm) coating at 0° AOI.

The blue shaded region indicates the coating design wavelengh range, with the following specification: 

Rabs ≤ 0.25% @ 880nm
Ravg ≤ 1.25% @ 400 - 870nm
Ravg ≤ 1.25% @ 890 - 1000nm

Data outside this range is not guaranteed and is for reference only.

Click Here to Download Data

Typical transmission of a 3mm thick N-BK7 window with VIS 0° (425-675nm) coating at 0° AOI.

The blue shaded region indicates the coating design wavelengh range, with the following specification: 

Ravg ≤ 0.4% @ 425 - 675nm

Data outside this range is not guaranteed and is for reference only.

Click Here to Download Data

Typical transmission of a 3mm thick N-BK7 window with YAG-BBAR (500-1100nm) coating at 0° AOI.

The blue shaded region indicates the coating design wavelengh range, with the following specification: 

Rabs ≤ 0.25% @ 532nm
Rabs ≤ 0.25% @ 1064nm
Ravg ≤ 1.0% @ 500 - 1100nm

Data outside this range is not guaranteed and is for reference only.

Click Here to Download Data

Typical transmission of a 3mm thick N-BK7 window with NIR I (600 - 1050nm) coating at 0° AOI.

The blue shaded region indicates the coating design wavelengh range, with the following specification: 

Ravg ≤ 0.5% @ 600 - 1050nm

Data outside this range is not guaranteed and is for reference only.

Click Here to Download Data

Typical transmission of a 3mm thick N-BK7 window with NIR II (750 - 1550nm) coating at 0° AOI.

The blue shaded region indicates the coating design wavelengh range, with the following specification: 

Rabs ≤ 1.5% @ 750 - 800nm
Rabs ≤ 1.0% @ 800 - 1550nm
Ravg ≤ 0.7% @ 750 - 1550nm

Data outside this range is not guaranteed and is for reference only.

Click Here to Download Data

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Custom

Edmund Optics offers comprehensive custom manufacturing services for optical and imaging components tailored to your specific application requirements. Whether in the prototyping phase or preparing for full-scale production, we provide flexible solutions to meet your needs. Our experienced engineers are here to assist—from concept to completion.

Our capabilities include:

  • Custom dimensions, materials, coatings, and more
  • High-precision surface quality and flatness
  • Tight tolerances and complex geometries
  • Scalable production—from prototype to volume

Learn more about our custom manufacturing capabilities or submit an inquiry here.