Study on the sensitivity of optical cavity length to light power fluctuation

The length stability of optical cavities is vital in ultra-stable, cavity-stabilized laser systems. Using finite element analysis, we study the length deviation of optical cavities due to thermal expansion and thermo-refractive effects when the incident light power is changed. The simulated fractional length sensitivity of a 7.75-cm-long football cavity to the power fluctuation of incident light is 5 × 10^-14/μW, which is in agreement with the experimental results found by measuring the frequency change of a cavity-stabilized laser when the incident light power is changed. Based on the simulation, the cavity sensitivity to light power fluctuation is found to depend on the cavity size and material.