Boltzmann Thermometry at Cryogenic Temperatures Exploiting Stark Sublevels in Er³⁺/Yb³⁺-Codoped Yttrium Oxide...

Area of Science:

• Nanotechnology
• Materials Science
• Quantum Optics

Background:

• Reliable luminescent nanothermometers are crucial for quantum technologies and superconducting systems.
• Lanthanide-doped materials are widely used but often optimized for room temperature.
• Cryogenic temperature monitoring requires specialized, high-spatial-resolution tools.

Purpose of the Study:

• To demonstrate an optical Boltzmann thermometer for cryogenic applications using Er³⁺/Yb³⁺ codoped yttria nanoparticles.
• To investigate the use of individual Stark sublevels for enhanced thermometric performance.
• To validate theoretical predictions regarding thermometric performance and energy gap calibration.

Main Methods:

• Utilizing Er³⁺/Yb³⁺ codoped yttria (Y₂O₃) nanoparticles as the thermometric material.
• Exploiting individual Stark sublevels within the ⁴S_3/2 manifold of Er³⁺ ions.
• Applying the Luminescence Intensity Ratio (LIR) method to specific Stark transitions for temperature sensing.

Main Results:

• Demonstrated effective operation across a temperature range of 25–175 K.
• Achieved high thermal sensitivity up to 1.22% K^-1 at 100 K.
• Reached a temperature resolution as fine as 0.6 K, confirming theoretical predictions.

Conclusions:

• Individual Stark sublevels enable effective cryogenic thermometry in Er³⁺/Yb³⁺:Y₂O₃ nanoparticles.
• Thermometric performance is not solely dependent on spectral line separation when using Stark transitions.
• This work provides a foundation for designing advanced cryogenic thermometers using rare-earth-doped materials.