Real-time spectral interferometric system based on fs laser fabricated on-fiber micro F-P interferometer for transient temperature sensing

Miniaturized spectral interferometers combining high-speed operation and sufficient spectral resolution are critically needed for advancing applications in imaging, sensing, and precision metrology. While existing systems face limitations in real-time measurement capabilities due to the constrained sampling rates of conventional instruments like optical spectrum analyzers, we propose a breakthrough solution through the integration of dispersion Fourier transform (DFT) technology into spectral sensing. This work demonstrates a DFT-based real-time micro-interferometer fabricated directly on optical fibers, capable of capturing transient spectral interference dynamics. The on-fiber micro spectral interferometer is a passive air-filled Fabry-Perot (F-P) microresonator, which is fabricated by using the two-photon-polymerization-based femtosecond laser direct writing technology. The proof of the principle of our real-time micro spectral interferometric system is validated by monitoring the steady ambient temperature change and transient temperature change. Experimental characterization revealed a temperature sensitivity of approximately 75 pm/°C with a 40 MS/s (million samples per second) sampling rate. This performance enables single-shot real-time spectral measurements, demonstrating significant potential for applications requiring high-speed photonic sensing, including but not limited to industrial process monitoring and biomedical diagnostics.