Fabry-Perot Cavity: Frequency Separation Explained

In summary, the "refresher assignment" for the new semester includes a selection of short questions, one of which asks about the frequency separation between neighbouring transmission peaks in an air-spaced Fabry Perot. This is determined by the free spectral range, which is equal to the speed of light divided by twice the cavity length (1 cm in this case) and is 0.15 GHz. The person asking for help is struggling to find concise information on this topic and is looking for guidance and resources.
  • #1
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As "refresher assignment" for the new semester I have been given a selection of very short questions,
the only one I am having trouble with is the followng:

QUESTION
An air-spaced fabry perot consists of two exactly parallel reflecting surfaaces, separated by a distance of 1 cm. What is the frequency separation between neighbouring transmission peaks?

...In truth I have not until reading this question even heard of a Fabry Perot and am having trouble finding concise information in the literature that will allow me to answer this question... As I say these are very short revision questions so I assume the answer is no more than a line or two... Any nudges in the right direction would be great, also any advice on good introductory online material on this subject would be useful
 
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  • #2
.ANSWERThe frequency separation between neighbouring transmission peaks in an air-spaced Fabry Perot is determined by the free spectral range (FSR) of the Fabry Perot which is equal to the speed of light divided by twice the cavity length (1 cm in this case). Therefore, the FSR of this Fabry Perot is 0.15 GHz.
 

1. What is a Fabry-Perot cavity and how does it work?

A Fabry-Perot cavity is an optical resonator that consists of two highly reflective parallel mirrors separated by a small distance. Light can enter the cavity through one of the mirrors and bounce back and forth between the mirrors, creating standing waves. This amplifies the light and results in a highly focused beam.

2. What is the frequency separation in a Fabry-Perot cavity and why is it important?

The frequency separation in a Fabry-Perot cavity refers to the difference in frequency between two consecutive resonance peaks. This is important because it determines the spectral resolution of the cavity, or how well it can differentiate between different frequencies of light. A smaller frequency separation results in a higher spectral resolution.

3. How is the frequency separation in a Fabry-Perot cavity calculated?

The frequency separation of a Fabry-Perot cavity can be calculated using the formula Δf = c/2nl, where c is the speed of light, n is the refractive index of the medium between the mirrors, and l is the distance between the mirrors. This formula assumes that the mirrors are perfectly parallel and have 100% reflectivity.

4. What factors can affect the frequency separation in a Fabry-Perot cavity?

The frequency separation in a Fabry-Perot cavity can be affected by the reflectivity of the mirrors, the refractive index of the medium between the mirrors, and the distance between the mirrors. Imperfections in the mirrors or misalignment of the mirrors can also impact the frequency separation.

5. How is the frequency separation in a Fabry-Perot cavity used in scientific research?

The frequency separation in a Fabry-Perot cavity is used in a variety of scientific research applications, including spectroscopy, laser stabilization, and cavity-enhanced absorption and emission measurements. It allows for precise measurement and analysis of the frequencies of light, which can provide valuable information about the properties of materials and molecules.

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