Europe, UK, Asia & RoW: [email protected] +44 (0)1622 859444 | USA & Canada: [email protected] +1 401-583-7846


Our technical experts are here to assist you. For optical solutions to suit your needs

click here


KRS5 (Thallium Bromide-Iodide) is used for transmission in the visible and IR spectrums. The material has relatively low absorbance in the Mid-IR range, wide transparency, a low solubility in water and a comparatively high refractive index, making it desirable in internal reflection components. KRS5 has a tendency to cold flow over time.

KRS5 is used primarily for Attenuated Total Reflection (ATR) prisms in IR spectroscopy and as IR windows and lenses. Examples of KRS5 applications include transmission windows for gas and liquid sample cells in Fourier Transform Infra-Red (FTIR) spectrophotometers. KRS5 has a broad transmittance of 0.6 – 40µm, peaking at over 68% between 2-25μm, and has a hardness of HK40. It is used as a substrate for infra-red holographic polarizers. The refractive index varies from about 2.68 at 0.6µm to about 2.2 at 40µm. The soft surface requires a coating to prevent the crystal from being scratched and dissolved by water.

Thallium Bromine-Iodide is considered toxic and must be handled with extreme care.

Knight Optical supply a range of quality KRS5 optical components including KRS5 windows, KRS5 prisms, and KRS5 blanks either from stock or custom made to your specification for a range of applications. Every component is individually tested by our highly skilled technicians in our state of the art metrology lab to ensure all components meet our high quality standards.

Contact our multilingual technical sales team and discover how Knight Optical’s high quality KRS5 optical components and service can improve your instrumentation and supply chain experience.

Our 2018/2019 Catalogue

Inside Knight Optical’s catalogue you’ll find details of the industries we serve as well as the many other services we can offer. It also showcases hundreds of our most popular products, supported by useful technical information, to help you choose the right part for your application.
Click below to view our digital catalogue now.

view our catalogue