Calculate focused spot size - Gaussian FWHM

In summary, the website calculates the spot size (Gaussian FWHM) for a plane wave using the formula 2*wavelength*f/(pi*d0), where f is the focal length of the lens and d0 is the collimated beam diameter before the lens. However, for calculating the spot size of a Gaussian, one would need to refer to laser optics textbooks or other sources for more detailed and approximate formulas.
  • #1
eliasds
4
0
http://www.calctool.org/CALC/phys/optics/f_NA

Does anyone know how they calculate the spot size (Gaussian FWHM) at this website?

For a plane wave, the focused spot size it approx=2*wavelength*f/(pi*d0)
f=focal length of lens
d0=collimated beam diameter before lens

but how do you calculate the spot size of a gaussian?
 
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  • #2
If you're asking how to derive the formulas used on the website, you'll have to look it up and wade through the details on your own - laser optics textbooks often go through it, and I bet it's in Born and Wolfe in one form or another, but generally it's a relatively simple and approximate formula that you just use.
 
  • #3
Anyone else have a more detailed answer?
 

1. What is the definition of "focused spot size"?

Focused spot size refers to the size of the smallest point of a laser beam after it has been focused to a tight spot. It is typically measured as the full width at half maximum (FWHM) of a Gaussian beam.

2. How is the focused spot size calculated?

The focused spot size can be calculated using the formula FWHM = 2.355 * λ / (π * NA), where λ is the wavelength of the laser and NA is the numerical aperture of the focusing lens. This formula assumes a Gaussian beam profile.

3. What is the significance of the Gaussian beam profile in calculating focused spot size?

The Gaussian beam profile is commonly used in laser optics because it closely matches the natural spreading of light in free space. This allows for more accurate calculations of the focused spot size, as the beam is not perfectly collimated.

4. Can the focused spot size be adjusted?

Yes, the focused spot size can be adjusted by changing the wavelength of the laser or the numerical aperture of the focusing lens. These parameters can be adjusted to achieve a smaller or larger spot size, depending on the application.

5. What are some factors that can affect the accuracy of the calculated focused spot size?

The accuracy of the calculated focused spot size can be affected by factors such as the quality of the focusing lens, the presence of aberrations in the optics, and the beam quality of the laser. It is important to consider these factors when calculating the focused spot size for a specific application.

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