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

In summary, the speaker has a question about using a FP-cavity for spectrometry. They explain that the maxima of the FP-cavity occur when the distance of the cavity is changed by a multiple of λ/2 and this can be used to look at the spectrum of light. They mention that the spacing between the maxima changes when doing spectroscopy because the FSR naturally changes with the distance of the cavity. The speaker has not seen a reference mentioning this and is concerned about their understanding.
  • #1
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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  • #2
I understand it now, I figured out how to derive it. Finally some success.
 

1. What is a Fabry-Perot spectrometer?

A Fabry-Perot spectrometer is a type of interferometer used to measure the wavelengths of light in a given spectrum. It consists of two partially reflective mirrors separated by a small distance, which creates an interference pattern that can be used to measure the wavelengths of light passing through the instrument.

2. How does a Fabry-Perot spectrometer work?

A Fabry-Perot spectrometer works by using the interference pattern created by the two partially reflective mirrors to measure the wavelengths of light. As light passes through the instrument, it is reflected back and forth between the mirrors, creating a series of constructive and destructive interference patterns. By analyzing these patterns, the wavelengths of light can be calculated.

3. What are the advantages of using a Fabry-Perot spectrometer?

One advantage of using a Fabry-Perot spectrometer is its high resolution. The interference pattern created by the mirrors allows for very precise measurements of the wavelengths of light, making this instrument useful for studying fine details in a spectrum. Additionally, Fabry-Perot spectrometers are compact and relatively easy to use, making them a popular choice for many scientific applications.

4. What are some common applications of Fabry-Perot spectrometers?

Fabry-Perot spectrometers have a wide range of applications in various fields of science. They are commonly used in astronomy to study the composition of stars and galaxies, as well as in atmospheric science to measure the chemical composition of the Earth's atmosphere. They are also used in chemistry, physics, and engineering for various research and analysis purposes.

5. Are there any limitations to using a Fabry-Perot spectrometer?

One limitation of using a Fabry-Perot spectrometer is its sensitivity to environmental factors such as temperature and vibrations. These can affect the accuracy and precision of the measurements, so it is important to carefully control these variables during experiments. Additionally, Fabry-Perot spectrometers are generally limited to measuring light in the visible and near-infrared ranges, so they may not be suitable for studying longer or shorter wavelengths of light.

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