Deep-IR Crystal — Toxic Handling Required
KRS-5 (Thallium Bromo Iodide)
Very broad deep-IR transmission for ATR prisms, windows and specialist infrared optics
KRS-5 is a thallium bromo-iodide mixed crystal with very broad infrared transmission and a high refractive index. It is used extensively for ATR prisms, spectroscopy windows and specialist infrared lenses, and can be paired with germanium in thermally compensated IR systems. KRS-5 is mechanically soft and contains toxic thallium salts, so fabrication, cleaning and disposal require controlled handling.
Is this material right for your application?
Use When:
Extremely broad mid- to far-IR transmission is required
FTIR spectroscopy spans wide wavelength ranges
Optical flexibility outweighs mechanical strength
Toxic material handling protocols are in place
Components can be encapsulated
Avoid When:
Toxic materials cannot be safely handled
Mechanical strength or hardness is required
Environmental exposure is unavoidable
Regulatory constraints limit material choice
Consider Alternatives:
KRS-6 – improved durability
ZnSe – safer handling and better robustness
Germanium (Ge) – LWIR optics without toxicity
Explore Related Optical Materials
KRS-6 (Thallium Bromo Chloride)
Zinc Selenide (ZnSe)
Germanium (Ge)
Material specifications and frequently asked questions
FAQ
Q1. What wavelength range is KRS-5 used for?
KRS-5 has representative transmission from approximately 0.6 to 40 µm.
Q2. Where is KRS-5 commonly used?
It is used for ATR prisms, FTIR windows and specialist broadband infrared optics.
Q3. Is KRS-5 moisture-sensitive?
KRS-5 has low but non-zero water solubility. It should be kept dry and handled carefully.
Q4. Is KRS-5 hazardous?
Yes. It contains toxic thallium salts, so fabrication, handling and disposal require appropriate controlled procedures.
Very soft material and easily scratched
Contains thallium; controlled handling is required
Not suitable for humid or harsh environments