Summary Description

AMTIR is a medium refractive index material (2.4981 @ 10 microns) with good long wavelength transmission in the infrared spectral region. The primary use is as an acid resistant window or ATR element. In this application it will typically perform well in a pH range of 1–9. Although AMTIR contains arsenic and selenium it is considered safe to handle.

Advantages

• Very low water solubility
• Good chemical resistance, particularly acids
• Good spectral range
• Good refractive index match with diamond
• Dispersion makes possible using as achromatic lens when coupled with germanium

Disadvantages

1. Expensive

Physical Data

Melting Point: 405 °C
Density: 4.4 g/cm³
Solubility in H₂O: 0 g/100 g at 20 °C
Hardness: 170 kg/mm²
Appearance: Red clear

Mid-IR Transmission – 1 mm thick AMTIR window

Mid-IR Transmission – 2 mm thick AMTIR window

Refractive Index¹

Specific index listed; Generic: 2.4981 @ 10 microns

Typical Uses

• ATR elements
• Perhaps the main use of AMTIR is in infrared imaging systems
• The following physical properties are particularly important in this application and, in combination are unique to AMTIR:
  1. It is an amorphous, glasslike material with extreme homogeneity
  2. The refractive index is much lower than Ge and can be used in a lens doublet with Ge in an achromat to cover a wide spectral range
  3. It is similar to Ge in physical properties
  4. It can be fabricated into exotic aspherical shapes using diamond turning
  5. It is also relatively easy to polish to a figure of ¼ wave in the visible with good scratch/dig characteristics
  6. BBAR coatings are available using designs similar to those used for ZnSe optics
• The AMTIR and AMTIR/Ge achromatic lenses are used in military FLIR, thermal imaging and low power laser systems

Spectral Range

Short Wavelength Limit: 11,000 cm^-1 (1 mm)
Long Wavelength Limit: 593 cm^-1 (1 mm), 625 cm^-1 (4 mm)

Coatings

AMTIR can be coated with a BBAR (broad band anti-reflective) coating. AMTIR may also be hard coated.

Notes

Short and Long Wavelength Ranges for which transmissivity is greater than 50% of stated crystal thickness.

1. Amorphous Materials Inc. website