Why Are Thulium-Doped Mixed Sesquioxide Ceramics So Important in Solid-State Lasers?


Solid-state lasers are currently used in a wide range of areas, from medicine to defense, optical communications to remote sensing. Lasers operating in the near- and mid-infrared wavelengths (1.5–2.3 µm) have become extremely valuable due to their ability to overlap with molecular fingerprint regions and cover atmospheric transparency windows. One of the most notable developments in this field has been the thulium (Tm³⁺)-doped mixed sesquioxide ceramics (Lu, Sc, Y)₂O₃.

The Importance of Thulium Ions
Thulium ions (Tm³⁺), along with Ho³⁺ ions, are one of the most researched rare earth elements in laser physics. This is due to their strong laser emission at wavelengths of 1.5 µm, 1.9 µm, and 2.3 µm.

The 1.5 µm wavelength is used in optical communication systems,

The 1.9 µm emission is used in medical, surgical, and eye safety applications,

The 2.3 µm laser light is used in gas sensors and biomedical measurements.

Furthermore, thulium-doped materials can be easily pumped with commercially available, high-efficiency diode lasers (in the 790–800 nm band), making them more economical and applicable.

Why Mixed Sesquioxide Ceramics?

In laser technology, not only single crystals but also mixed ceramics are attracting great interest. This is because these materials offer advantages such as:

High thermal conductivity

Wide transparency range (0.22–8 µm)

High refractive index

Suitable spectral width for short pulse durations

Ability to handle high doping concentrations

For example, laser pulses as short as 180 femtoseconds at 2070 nm have been achieved with Tm:Lu₂O₃ ceramics. Pulse durations of up to 54 fs (femtoseconds) have also been achieved with Tm:(Lu₂/₃Sc₁/₃)₂O₃ ceramics. These values ​​are crucial for the development of ultrashort pulsed laser systems.

Uses in Medicine and Technology
The advantages of infrared lasers lead to their use in many sectors:

Medicine:

The 2 µm region is considered "eye-safe" because it is absorbed by the eye. Therefore, it can be safely used in ophthalmology and laser surgery.

The 2.09 µm and 2.02 µm wavelengths allow for precise microsurgery on tissues because they strongly absorb water.

Industry and Defense:

Material processing and laser cutting systems,

Remote sensing and gas detection (e.g., methane, carbon dioxide measurements).

Communications:

The 1.5 µm band is used in fiber optic communication systems.

It can serve as a pump source for erbium-doped fiber amplifiers.

Mid-Infrared Sources:

These lasers are ideal for pumping optical parametric oscillators (OPOs). This allows for the generation of new laser wavelengths between 3 and 12 µm.

Looking Ahead
Research shows that the full potential of thulium-doped mixed sesquioxide ceramics has still not been explored. Advances in manufacturing techniques are resulting in more transparent, more homogeneous, and stronger ceramics. These advances could lead to revolutionary applications in both medical and defense technologies in the future.

✅ Conclusion: Thulium-doped (Lu, Sc, Y)₂O₃ mixed sesquioxide ceramics stand out in solid-state lasers with their advantages such as high efficiency, wide tunability, and eye safety. Their applications range from non-invasive diagnostics and surgical procedures in medicine to materials processing in industry, optical communications, and gas detection. These materials are predicted to become the heart of more compact, safer, and more powerful laser systems in the coming years.