Comparison between BK7 penta prism and fused silica penta prism
Properties	BK7 Penta Prism	Fused Silica Penta Prism
Transmission range	350nm - 2.0μm	185nm - 2.1μm
Ultraviolet performance	Poor (strong absorption below 350nm)	Excellent (high deep ultraviolet transmittance)
Thermal stability	Generally (with higher thermal expansion)	Excellent (low thermal expansion)
Laser damage threshold	Lower (5J/cm² @1064nm, 10ns)	High (10 J/cm²)
Cost	Lower	Higher
Applicable scene	Conventional applications of visible	Ultraviolet, high-power lasers, extreme environments

FAQ about BK7 penta prism
Q1: Can BK7 penta prisms be used with UV lasers?
→ Not recommended. BK7 exhibits strong absorption in the <350nm wavelength. For UV applications, use a fused silica penta prism instead.

Q2: Is coating necessary?
→ If the angle of incidence exceeds the critical angle (about 41° for BK7), no coating is needed. Otherwise, a high-reflectivity (HR) coating is required.

Q3: Can it handle high-power lasers?
→ Suitable only for low-power lasers (<1 W CW). For high-power applications, consider fused silica prisms or those with laser-grade HR coatings.