# How to estimate how many wavelengths wide a laser is?

• ZedCar
In summary, the person is seeking assistance in estimating the width of a laser beam used in two experiments. They have produced two graphs but are unsure if they can be used to estimate the width. They have also mentioned using a "pure" monochromatic source or a spectrum analyzer to measure the difference-frequency term in Δw. They have suggested looking into Agilent and Anritsu for more information or referencing a classic introductory text on the topic.
ZedCar

## Homework Statement

I've conducted two laser experiments. One with single slit, and one with a double slit.

I've produced two graphs which look something like these;

Would anyone know how to go about roughly estimating how many wavelengths wide the laser beam used is?

Possibly from the graphs? (or maybe from other data)

Thank you.

## The Attempt at a Solution

You can't use your graphs since the resolution is totally inadequate. You're looking for slight flattening of the peaks and troughs on the interferogram & you won't see that.

I think you need a "pure" monochromatic source to mix with your laser. If the laser spectrum is extremely small ( < 10 GHz or so) you could theoretically mix the two sources onto a photodiode which woud then output an electrical frequency spectrum you could measure: {sin(wt) + sin(w + Δw)t}2 gives a term 2sin(wt)*sin(w + Δw)t which of course produces the difference-frequency term in Δw.

For a broader laser spectrum I can ony think of a \$100,000 spectrum analyzer. These use precision diffraction gratings, Fourier transforms & whatnot. I don't know enough about how they work. Agilent and Anritsu make them, you might go to their Websites.

For a somewhat lower monetary expenditure you might get hold of the classic introductory text: https://www.amazon.com/dp/0805385665/?tag=pfamazon01-20

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## 1. How do you measure the width of a laser?

The width of a laser can be measured using a technique called interferometry. This involves splitting the laser beam into two paths and recombining them to create an interference pattern. The width of the laser can then be determined by measuring the distance between the peaks of the interference pattern.

## 2. Can the width of a laser be accurately estimated without specialized equipment?

It is difficult to accurately estimate the width of a laser without specialized equipment such as an interferometer or a laser beam profiler. These tools are specifically designed for measuring the properties of laser beams and provide more precise measurements than other methods.

## 3. What factors can affect the width of a laser?

The width of a laser can be affected by several factors, including the type of laser used, the power and intensity of the laser, the quality of the optics used to produce the laser beam, and environmental conditions such as temperature and humidity. These factors can all impact the coherence and focus of the laser beam, which in turn affects its width.

## 4. Is there a standard unit of measurement for the width of a laser?

The most common unit of measurement for the width of a laser is the wavelength, typically measured in nanometers (nm). This is because the width of a laser is closely related to its wavelength. However, other units such as millimeters or microns may also be used depending on the specific application.

## 5. Are there any mathematical formulas or calculations for estimating the width of a laser?

Yes, there are several mathematical formulas and calculations that can be used to estimate the width of a laser. These may include the diffraction-limited beam width formula, the Gaussian beam width formula, or the Rayleigh range formula. However, these calculations may only provide an approximation and may not be as accurate as using specialized equipment for measurement.

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