Fabry Perot Etalon Calculator
Calculate ideal equal-mirror cavity free spectral range, exact Airy half-height finesse and normalized detuned transmission.
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Result
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Calculation steps
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How to calculate
Use a lossless symmetric plane-parallel cavity at fixed internal angle and extract the exact Airy half-height width.
FSR=c/(2nL cosθ); Airy F=4R/(1−R)²; finesse=π/(2asin(1/√F))
Worked example
A 1 cm air cavity at normal incidence has FSR 14.9896229 GHz. Its resonance-normalized transmission is one at zero frequency detuning.
Assumptions and input details
Equal mirrors, fixed real index, no dispersion/group-index correction, absorption, coating phase, walkoff or actual cavity mode matching. Reflectance ≥0.2 ensures a half-maximum width exists. Detuning is reduced modulo the FSR numerically; ratio is limited to 1e9.
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