Acousto-optic devices based on TeO₂ crystals: space spectrometry, medicine, and quantum systems. (Review)

Tellurium dioxide (TeO₂, paratellurite) remains a key material in photonics thanks to its high acousto-optic figure of merit, birefringence, and wide transparency. Devices based on TeO₂ - modulators, deflectors, and tunable filters - are widely used for beam control, spectral selection, and polarization. This review article examines in detail three major domains where TeO₂-based devices have become critical: space spectrometry, medicine, and quantum technologies. In space exploration, acousto-optic tunable filters (AOTFs) fabricated from TeO₂ are implemented in flagship instruments such as ESA’s NOMAD on ExoMars, NASA’s SuperCam on the Perseverance rover, and China’s Chang’e spectrometers. These instruments enable high-resolution, in spectral analyses of planetary surfaces and atmospheres, providing insights into mineralogy, volatiles, and habitability. In the medical domain, Acousto-optic frequency shifters (AOFS) and fiber-based laser Doppler vibrometers exploit TeO₂ to achieve precise, non-invasive measurements of middle ear ossicle vibrations, offering clinicians a novel diagnostic tool in otology. These systems, benefiting from the safety and versatility of telecom-band radiation, illustrate how AO devices can address unmet clinical needs. The translation of TeO₂-based devices into medicine highlights the interdisciplinary role of acousto-optics, bridging physics, engineering, and healthcare.Quantum technologies represent perhaps the most transformative frontier. Here, TeO₂-based acousto-optic modulators and deflectors are indispensable for photon-level control: fast frequency shifting, phase stabilization, routing, and generation of spatial modes of light. Their ability to integrate into bi-frequency interferometers and multi-channel quantum networks places them at the foundation of the emerging quantum internet, quantum communication protocols, and scalable quantum computing. Overall, such promising application areas require not only scaling up crystal production but also continuous improvement of their quality. The purpose of this review is to demonstrate concrete examples of how TeO₂ devices are applied across such diverse fields, underlining their continued importance for next-generation photonics.