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Development of an order of magnitude better bromide broadband IR polarizer and acousto-optic tunable filter



Organisational Unit
Implementation progress
25 January 2023

Duration: 18 months


The main objective of this activity is to develop the technology of crystal growth and testing of mercurous bromide (Hg2Br2) single crystals potentially suitable for broadband infrared (SWIR, LWIR) polarization otic and an acousto-optics, incl. the acousto-optic tunable filter (AOTF). The crystal exhibits unique optical characteristics in the full 0.5 -30 μm spectral range: broad optical transmission, high birefringence, extremely low velocity of acoustic wave propagation and high coefficient of acousto-optical interaction. It is a very promising and completely new material for new type of hi-powerful polarizers and acousto-optical tuneable filters (AOTF) working in far thermal infrared regions.

A present optical market offers only wiregrid or holographic type IR polarizers with very low or limited extinction ratios (ER) and very low optical load resistance, which limits the final performance and efficiency of the product. From our experience, we expect an order of magnitude higher ER compared to the competition. In the case of AOTF there is literally no competition. Calcite-based polarization optics is applicable in a range of 0.3 - 2.5 μm at best and AOTFs based on paratellurite about 0.33 - 5 μm.

The optical elements based on mercurous bromide are very promising components of future hi-tech IR optical systems in Earth and Space applications. Mercurous halides are the only group of crystals, which was originally developed in the Czech Republic and the Czech company BBT-Materials Processing, s. r. o. (hereinafter "BBT"). BBT is still the only one worldwide to be able to produce and supply other world-unique crystal (mercurous chloride) in a sufficient quality quality and therefore has all the prerequisites to successfully address the development of technologies related to the growth and testing of mercury bromide single crystals.

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Development of an order of magnitude better bromide broadband IR polarizer and acousto-optic tunable filter