1″Diameter x 5mm Thick Silicon Substrate Interference Bandpass Filter – LOT OF 4

SiW 25×5-RAR (“SiW” = Silicon substrate/window; “25×5” = 25mm diameter x 5mm thickness; “RAR” = Rear Anti-Reflection coating; likely custom/research lab origin) – LOT OF 4

Specifications:

• Diameter: 1″

• Thickness: 5 mm

• Substrate: High-quality silicon (Si) – inherently opaque in visible/near-IR (absorbs below ~1.1 µm)

• Type: Narrowband dielectric interference bandpass filter optimized for mid-infrared (mid-IR)

• Coatings: Multilayer dielectric on both sides

• Front side: Primary interference stack – highly reflective/mirror-like in visible light (shows specular highlights, gradients, and clear reflections under angles)

• Rear side: Broadband anti-reflection (AR) coating – uniformly matte black appearance for maximum passband transmission, reduced ghosts, and minimal stray light

• Visual Blocking: Completely blocks visible light

• Condition: Like-new/excellent

Recommended Orientation: Mount with the reflective/mirror-like front side (specular highlights/reflections) facing the incident beam/source for optimal performance (rejects out-of-band light early via reflection, minimizes heat/substrate absorption).

Applications: High-performance mid-IR filter with exceptional visible/near-IR rejection, ideal for:

• Mid-IR spectroscopy and spectrophotometry

• Laser line isolation/selection (e.g., CO2 lasers, quantum cascade lasers)

• Gas detection, flame sensing, or environmental monitoring

• Thermal imaging, pyrometry, or plasma diagnostics

• Research/industrial systems requiring precise IR bandpass with total visible blocking

Rare surplus find—perfect for labs needing affordable, high-quality IR optics.