Calomel (mercurous chloride) is a tetragonal crystal material which is transparent from visible (0.38µm) up to mid-thermal region (20µm) and exhibits very strong birefringence (Δn=0,55). These two parameters make it a great candidate for infrared polarization optics as polarizers, beamsplitting cubes, etc. Calomel IR components find place in every application requiring a high degree of IR polarization, like spectroscopy, astronomy, optical laboratories, R&D institutions, chemical industry, etc.


Calomel has a large potential to be used also as an acousto-optical modulator. Its high AO figure of merit and extremely low velocity of acoustic waves are key parameters for the AOTF. Currently used AO units on the market are limited by the transparency of material used up to the limit of 5µm. Calomel, as a material transparent up to 17-20µm brings new opportunity for the acoustic frequency modulated filters, especially targeting the area around 8-10µm or longer.


Our group is the first in the world to develop a technique of preparing single crystals of mercurous halides. Our greatest progress has been made in the area of single crystals of mercurous chloride – CALOMEL Hg2Cl2 – and its functional elements. In 1969, the first CALOMEL single crystal was produced. From that time, we have gained valuable experience in the production and processing of this material.

Mercurous Chloride molecules
Material highlights
  • Discovered in 1969
  • Broadband spectral range from VIS to TIR (0.38-20µm)
  • Very high indices of refraction
    (n0 = 1.973 ne = 2.656 @589nm)
  • Extremely high values for acousto-optical figures of merit M2
  • Extremely low velocity of elastic wave propagation (347 m/s)
  • High value of birefringence (four times higher than calcite and positive)
Main application areas
  • IR Polarization optics (MWIR polarizers, waveplates)
  • IR Scramblers (optical depolarizers)
  • AO devices and components (acousto-optical elements)
  • Custom products (wedges, plates, prisms, windows, etc.)
  • Laser applications
  • Infrared spectroscopy (sample characterization)
Optical transmission

Calomel boule