Working equation for a Fabry-Perot cavity based optical pressure standard

Abstract

From basics of Fabry-Perot (FP) resonator and roundtrip phase, a complete working equation for a FP cavity based optical pressure standard (OPS) is derived and presented which includes corrections of reflection phase-shift, diffraction and pressure-induced distortion. The correction from diffraction, i.e. Gouy phase, is negligible. To operate an OPS as a primary standard, two unknown parameters, i.e. mirror dispersion coefficient 𝝐 𝜶 and pressure distortion coefficient 𝒅 𝒎 , in the working equation should be determined independently. Methods to determine 𝝐 𝜶 and 𝒅 𝒎 are described and applied to an OPS developed at the National Institute of Metrology (NIM), China. Thermodynamic effect observed in the determination of 𝒅 𝒎 is also discussed.