Fabry - Pérot Fringe Analyzer

Turn spectral fringes into film thickness and birefringence.

ANALYSIS INPUTSAssumes adjacent extrema and negligible index dispersion over each selected range.

FABRY–PÉROT CONDITION

4n d cos θₜ = mλ

OPTICAL MODEL

● Demo fringe families loaded

SPECTRAL UNIT

INCIDENCE ANGLE

deg

KNOWN THICKNESS

µm

ORDINARY PERMITTIVITY εₒ

EXTRAORDINARY PERMITTIVITY εₑ

KNOWN-VALUE UNCERTAINTY

POLARIZATION / OPTIC AXIS

45°

RETARDANCE WAVELENGTH

IMPORT AS DOWNLOAD TEST SPECTRUM

ENTER DIP POSITIONS AND MODES

ORDINARY DIP POSITIONS ORDINARY MODE NUMBERS · SAME ORDER EXTRAORDINARY DIP POSITIONS EXTRAORDINARY MODE NUMBERS · SAME ORDER

RESULTSCalculated from the current inputs and selected cavity convention.

SPECTRAL RESPONSE

O dips E dips

PER-DIP PERMITTIVITYEach dip is paired with the mode number entered in the same position.

ORDINARY / ISOTROPIC

DIP	POSITION	MODE m	ε

EXTRAORDINARY

DIP	POSITION	MODE m	ε

MODEL NOTE — In permittivity mode, each dip uses its assigned mode in Cn d cos θₜ = mλ, where C is 2 for full-cavity mode and 4 for half-cavity mode. The displayed ε is the arithmetic mean of the individual dip values. At oblique incidence the calculator applies Snell’s law separately to each principal phase index. In birefringent mode, O and E dip families must be identified independently; polarization angle reports expected intensity weights Iₒ ∝ sin²φ and Iₑ ∝ cos²φ, not a full Berreman simulation. The result is real ε under low-loss assumptions; complex ε requires additional intensity or phase data.