What are the optical properties of OD6 bandpass filters?
Optical Density	OD6 (T≤ 0.0001%) Only 1 out of every 1 million photons transmits through the resistive band region.
Tpeak	>90%
FWHM	Narrow band: 3-25 nm (e.g. laser line filters)
Broadband	30-100 nm (e.g. fluorescence imaging)
Cut-on/Cut-off Slope	The steeper the transition zone, the more selective the filter (e.g., only a few nanometers from OD6 to 90% transmission)

What are the characteristics of the structure of the OD6 bandpass filter?
Multi-layer Dielectric Coating: tens to hundreds of layers of high/low refractive index materials (e.g., Ta₂O₅/SiO₂) are deposited alternately for precise wavelength control.
Hard Coating: enhanced abrasion resistance and chemical stability for long-term use.
Substrate Materials: BK7 glass (general purpose), fused silica (UV applications), sapphire (high durability).