Comparison of optical performance between fused silica wedge prisms and BK7(K9) wedge prisms
Parameter	UV Fused Silica	Optical Glass BK7
Transmission Range	170 nm -2.1 μm (deep UV to NIR)	350 nm - 2.0 μm (VIS is dominant)
UV transmittance@200nm	>90% (Thickness=1mm)	<10% (strong absorption)
Refractive Index@587.6nm	1.458	1.517
Dispersion (νd)	67.8 (low dispersion)	64.2 (moderate dispersion)
Birefringence	No (isotropic)	No (isotropic)
Laser Induced Damage Threshold	Higher (suitable for high-energy ultraviolet lasers)	Relatively low (especially prone to damage in the ultraviolet band)

When is a BK7 (K9) wedge prism the more suitable choice?
The working band is visible(400-700 nm) or near-infrared (700-2000 nm). The budget is limited and no ultraviolet or ultra-high thermal stability is required. It is used for low-power laser or ordinary optical adjustment (such as laboratory optical path calibration).