Large Precision N-BK7 Optical Window 75mm Diameter

large plano-parallel optical window (optical flat) in excellent, clean condition (clear aperture_95%) from surplus lab/industrial stock. This is a rugged, thick-substrate precision piece with outstanding polish, clarity, and no visible scratches, chips, haze, or coating damage.

Key Specifications:

• Material: N-BK7 glass (Schott or equivalent borosilicate crown glass) – excellent visible/NIR transmission, low inclusions, and high homogeneity.

• Diameter: 75mm (exact precision fit for 3-inch mounts).

• Thickness: 12.5mm – significantly thicker than standard windows for superior mechanical rigidity, thermal stability, and high-power laser handling (ideal for demanding beam paths or viewports).

• Surfaces: Both sides precision polished and plano-parallel.

• Coating: Single-sided broadband anti-reflection (BBAR) dielectric coating, optimized for visible wavelengths (~400-700nm typical). Reduces reflection on the coated face for higher transmission

• Condition: Within clear aperture of 95%, Excellent – pristine surfaces, vibrant coating intact, finely beveled edges for safe handling. Minor crack mark outside the clear aperture does not affect performance.

Perfect for:

• High-power visible laser systems (beam sampling, enclosures, or turning paths)

• Optical experiments, interferometry, or spectroscopy setups

• Rugged viewports or protective elements in industrial/lab environments

• DIY telescope, projector, or imaging projects needing maximum durability and throughput