  Fiber optic all-optical thermometry is a promising technology to track
temperature at a micro-scale while designing efficient and reliable
microelectronic devices and components. In this work, we demonstrate a novel
real-time ratiometric fiber optic thermometry technique based on
silicon-vacancy (SiV) diamond that shows the highest temperature resolution
(22.91 KHz^(-1/2) Wcm^(-2)) and spatial resolution (~7.5 um) among all-optical
fiber-based thermosensors reported to date. Instead of analyzing the spectral
features of temperature-dependent SiV signal, coming from SiV micro-diamond
fixed on the fiber tip, an alternative parallel detection method based on
filtering optics and photon counters is proposed to read out the sample
temperature in real-time. The signal collection efficiency of the fiber is also
investigated numerically with semi-analytic ray-optical analysis and then
compared with our experimental study. We finally demonstrate the performance of
the thermosensor by monitoring the temperature at distinct locations in a
lab-built graphite-based microheater device. Our work introduces a
reconfigurable method for temperature monitoring in microelectronic,
microfluidic devices, or biological environments and unlocks a new direction
for fiber-based all-optical thermometry research.
