Thorlabs BBSQ1‑E03 Broadband Dielectric Mirror

BBSQ1‑E03 is a broadband dielectric mirror manufactured by Thorlabs. It is part of their BBSQ series of square mirrors, and specifically:

• Square broadband dielectric mirror

• Size: 1″ × 1″ (square)

• Coating / wavelength range: Designed to reflect strongly over 750 nm to 1100 nm (near‑infrared)

• Substrate: Fused silica

• Thickness: ~6 mm

• Surface Quality: Typically 10‑5 scratch‑dig

• Clear Aperture: High (≈ > 90% of area)

These mirrors are used in optical setups where you need high reflectivity across a broad NIR band — for example in laser experiments, imaging systems, interferometers, or spectroscopy where you want to steer or fold beams without frequency‑selective behavior.