N-BK7 (equivalent to SCHOTT BK7) optical windows for visible and near-IR applications. The industry standard optical glass for general-purpose protective windows, beam enclosures, and observation ports with excellent optical homogeneity.
| Material | N-BK7 (equivalent to SCHOTT BK7 / K9) |
| Transmission Range | 330 - 2,100 nm |
| Refractive Index | Nd = 1.5168 |
| Diameter Range | 3mm - 200mm |
| Thickness Range | 0.5mm - 50mm |
| Surface Quality | 20-10 / 40-20 / 60-40 (MIL-PRF-13830B) |
| Surface Flatness | lambda/4 to lambda/10 @ 632.8nm |
| Parallelism | < 1 arc-min (standard) / < 10 arc-sec (precision) |
| Coating | AR / HR / BBAR / Uncoated |
Parameter Reference Guide
Typical Standard capability — available as shown
Available Alternative options exist — request quotation
Custom Per your drawing — quote after review
Subject to Review Depends on project specifics
Select the optimal optical material based on your wavelength, power, thermal environment and mechanical requirements.
Coatings are engineered around your specific wavelength and operating conditions.
We optimize specifications to match your system requirements — not over-specify. Tighter tolerances increase cost without always improving system performance. Typical manufacturing capabilities:
Every component undergoes 100% inspection before shipment with full documentation including interferometer reports, spectral curves, surface quality images and dimensional data.
Cost vs. performance: N-BK7 is the most economical optical window material for visible-NIR applications. Only upgrade to fused silica or sapphire when you specifically need UV transmission, higher LIDT, or extreme hardness.
Thickness selection: For standard beam enclosures, 2-3mm thickness is sufficient. For vacuum applications or larger diameter windows (>50mm), increase thickness to prevent bowing under pressure differential.
Parallelism: For windows in laser cavities, specify wedged windows to eliminate etalon effects. For general protective use, standard parallelism (<1 arc-min) is adequate.
Upload your drawing or describe your specification. Our engineering team will review and respond within 1 business day.
N-BK7 is the most economical window material. Use this guide to confirm it matches your needs.
| Your Need | This Material? | Note |
|---|---|---|
| UV needed (< 350nm) | No | Use UV fused silica |
| Visible-NIR (350-2000nm) | Yes ✓ | N-BK7 is standard |
| IR beyond 2.5um | No | Use ZnSe or Ge |
| Your Need | This Material? | Note |
|---|---|---|
| High-power laser (> 50W) | No | Use fused silica for higher LIDT |
| Low-power / non-laser | Yes ✓ | N-BK7 is adequate |
| Your Need | This Material? | Note |
|---|---|---|
| Abrasive / harsh | No | Use sapphire (Mohs 9) |
| Indoor / cleanroom | Yes ✓ | N-BK7 is sufficient |
Tell us your wavelength, application and operating conditions. PhotonEdge AI Optical Engineer can help you identify the key specifications before you request a quote.
Ask AI Optical Engineer → Request a QuoteTell us what you know. We'll help identify what you still need.
Upload Drawing / RFQ Request a QuoteContact us for exact pricing based on your specifications.
Specification Parameters
Typical Specifications shown on this page are standard capabilities. Available Options include alternative materials and coatings. Custom Specifications are available per your drawing. Requirements beyond standard capability are marked Subject to Engineering Review.
Upload your drawing or specifications. Our engineering team will review and respond within 1 business day.
When requesting a quote for this product, please specify the following parameters to help our engineering team provide an accurate quotation:
Not sure about specifications? Upload your drawing and our team will assist with engineering review.