PUMA User's Manual Version 1.0

 H. PLANA M. ROSADO  L GUTIERREZ   H CASTANEDA  ARIAS R. LANGARICA  A. BERNAL

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I. Introduction
 

I.1. Description of a Fabry Perot interferometer
 

The Fabry Perot (FP) interferometer is composed by two semi reflective mirrors separated by a certain thickness of air. With a parallel monochromatic light beam the FP will produce a system of interference rings located at infinity. Figure I.1 gives a basic view of a FP interferometer light beam path.

Figure I.1

Where l is the wavelength of the light beam, e the spacing between the 2 plates, n the refractive index of the medium and i the inclination of the beam.
 

I.2. Definitions and basic (but useful) formulae

The luminous intensity transmitted is given by:

 

Figure I.2 Airy function for different finesse

I.3. The scanning Fabry Perot

In a scanning FP, the spacing e between the 2 plates is not constant anymore. The etalon will act like a turnable filter scanning along the Free Spectral Range. The figure I.3 is giving an excellent illustration of how the scanning FP produces a profile in each pixel of the receptor (Georgelin Y.P. in CFHT MOS/SIS User Manual).

Figure I.3 How a Scanning FP produce profiles

The FP will scan across all the free spectral range with a step given by: nb of channel ~ 2*Finesse. At the end we will deal with a data cube: x, y and the spacing e who is related to the wavelength. Through the Doppler relationship the wavelength can be related to the velocity.

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