Abstract: A high-sensitive micro-force measurement method based on photonic crystal micro-cavity was proposed. Firstly， an M-typed beam was proposed as the sensing head， thus the resonance wavelength drift of the micro-cavity will only be affected by holes refractive index of photonic crystal micro-cavity when force was applied on this system， which could greatly improve the linearity and measurement range of sensor. Then， the structure of photonic crystal micro-cavity with micro-ring structure was optimized， and the quality factor of 7100 was obtained. Finally， the wavelength demodulation system based on fiber loop ring-down was built， with proper selection and design of experimental apparatuses， and the wavelength demodulation sensitivity could reach to 90μs/nm. Therefore， it was demonstrated that the measurement sensitivity of 194.616μs/μN could be obtained by using our proposed micro-force measurement system.

Key words: photonic crystal micro-cavity, M-typed beam, micro-force sensor, fiber loop ring-down, quality factor