Atomically Smooth Gold Microflake-Enabled Fiber-Tip Fabry-Perot Interferometer for Temperature and Pressure Sensing

Fiber-tipsensors based on the Fabry-Perot interferometer(FPI) are one of the most widely used devices for temperature andpressure measurements in space-confined scenarios. However, the depositedmetal films with a polycrystalline structure tend to form microcracksunder strain,which can undermine the optical quality factor and thus sensing performanceof these fiber-tip sensors. Here, we demonstrate an atomically smoothgold microflake (GMF)-enabled fiber-tip FPI sensor with a Q factor as high as 628. Benefiting from the high reflectivityand flexibility of GMFs and the elasticity of the PDMS spacer, thefiber-tip FPI can maintain stable sensing performance under largedeformation. For temperature sensing, the fiber-tip sensor exhibitsa linear response to the temperature in the range 28-40 & DEG;Cwith a sensitivity as high as 1.74 nm & DEG;C-1.To realize linear and sensitive pressure sensing, we design and fabricatea PDMS clamped-beam structure on the fiber tip using a soft lithographytechnique, achieving a sensitivity of 11.48 nm kPa(-1). Moreover, simultaneous measurement of the temperature and pressureis also demonstrated using the wavelength demodulation method. Thesimple and cost-effective fabrication of the clamped beam and thetransferable GMFs allow for the facile integration of high-qualityFP cavities on fiber tips, opening new opportunities for developingoptical sensors with miniaturized sizes.

Automated summary

Fiber-tip sensors based on the Fabry-Perot interferometer (FPI) are widely used for temperature and pressure measurements in confined spaces. By using an atomically smooth gold microflake (GMF) and a PDMS spacer, the fiber-tip sensor achieves a high Q factor of 628 and maintains stable sensing performance under large deformation. The sensor shows a linear response to temperature with a sensitivity of 1.74 nm℃-1 and a sensitivity of 11.48 nm kPa-1 for pressure sensing. Simultaneous measurement of temperature and pressure is also demonstrated using wavelength demodulation. The integration of high-quality FP cavities on fiber tips opens new opportunities for miniaturized optical sensors.