Does the Fabry Perot spectrometer's free spectral range change with distance?

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SUMMARY

The Fabry Perot (FP) spectrometer's free spectral range (FSR) is defined as c/2d, where c is the speed of light and d is the cavity distance. As the distance d changes, the FSR also changes, leading to variations in the spacing between the maxima observed during spectroscopy. This relationship is crucial for accurately interpreting spectral data. The discussion confirms that the FSR is indeed dependent on the cavity distance, which is a fundamental aspect of using FP-cavities in spectrometry.

PREREQUISITES
  • Understanding of Fabry Perot cavity principles
  • Knowledge of the speed of light (c) and its implications in optics
  • Familiarity with the concept of free spectral range (FSR)
  • Basic principles of spectroscopy
NEXT STEPS
  • Study the derivation of free spectral range in Fabry Perot interferometers
  • Explore the impact of cavity length variations on spectral measurements
  • Learn about advanced spectrometry techniques using FP-cavities
  • Investigate applications of FSR in different optical systems
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Optical engineers, physicists, and researchers involved in spectroscopy and optical measurement techniques will benefit from this discussion.

Niles
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Hi

I have a question regarding doing spectrometry using a FP-cavity. For a fixed wavelength, the successive maxima of the FP-cavity occur when the distance of the cavity is changed by a multiple of λ/2. This we can use to look at the spectrum of light in the cavity by changing the distance. In my book it is stated that these maxima are separated by the free spectral range (FSR), which in frequency is given by c/2d.

However, the FSR naturally changes with the distance d of the cavity. Does that mean that the spacing between the maxima changes when doing spectroscopy? The reason why I ask is because I have not seen a reference mentioning this, so I am worried that I might be wrong.Niles.
 
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