Abstract
AbstractGlass microspheres embedded with Nd3+‐doped nanoperovskites based on yttrium orthoaluminate are synthesized and used as optical vacuum sensor. Under 532 nm excitation, the microspheres show two emission bands centered at 820 and 890 nm, corresponding to the 2H9/2,4F5/2 → 4I9/2 and 4F3/2 → 4I9/2 transitions. When the microspheres are heated by laser excitation in air (ambient conditions), the positions of the Stark level transitions shift toward red or blue spectral regions. Additionally, the full width at half maximum of these peaks increases. Furthermore, due to the specific geometry of the microspheres, it is possible to trap the emitted light inside the microsphere resonator, in the form of whispering‐gallery‐modes (WGM). When the microspheres are heated, these resonant modes present higher shifts toward lower energies than those for the Stark levels. As pressure decreases, the thermal exchange (convection process) between the microsphere and the surrounding air molecules decreases, which leads to an increase on the temperature of the microsphere. Based on this effect, the response of the WGM spectral positions as a function of pressure level is used to calibrate the luminescent microspheres as optical vacuum sensors. Relative sensitivity and limit of detection are obtained and compared with other optical vacuum sensors.
Published Version
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