How to find the FWHM-diameter of the SH beam?

In summary, the conversation discusses the generation of a second harmonic (SH) beam from a Gaussian laser beam with a 1064 nm wavelength and 5 mm FWHM-diameter. The SH beam has a wavelength of 532 nm and co-propagates with the fundamental laser beam. The FWHM-diameter of the SH beam can be calculated using the equation dFWHM = ω(z)√2ln2, with the key factor being that the SH beam is proportional to the square of the incoming field.
  • #1
telekom90
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0

Homework Statement


Assume a Gaussian laser beam ( 1064 nm wavelength) having an FWHM-diameter(intensity) of 5 mm. By transmission through a thin nonlinear crystal, a new wave is generated that is proportional to the square of the incoming field (and therefore radiates at twice the frequency, or 532nm wavelength). This second harmonic (SH) beam co-propagates with the fundamental laser beam. What is the FWHM-diameter of the SH beam?

Homework Equations



dFWHM = ω(z)√2ln2

The Attempt at a Solution


λ =1064nm, dFWHM=5 mm##, ## λSH=532 nm .
I can't solve this problem because I don't know how to relate this equation "dFWHM=ω(z)√2ln2= 5mm " with the FWHM-diameter of second harmonic (SH) beam?!
 
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  • #2
The key word is
telekom90 said:
that is proportional to the square of the incoming field
.
 

1. What is FWHM-diameter and why is it important in SH beam measurements?

FWHM-diameter stands for full width at half maximum diameter, which is a measure of the width of a Gaussian-shaped beam at the point where its intensity is half of its maximum value. This is important in SH beam measurements because it gives an indication of the beam's spatial extent and can be used to determine the beam's spot size and focus.

2. How do you calculate the FWHM-diameter of an SH beam?

To calculate the FWHM-diameter of an SH beam, you will need to measure the beam's intensity profile using a power meter or camera. Then, you can use the equation FWHM = 2.355 * σ, where σ is the standard deviation of the Gaussian distribution of the beam's intensity.

3. What factors can affect the FWHM-diameter of an SH beam?

The FWHM-diameter of an SH beam can be affected by factors such as the quality and alignment of the optical components, the beam's wavelength and polarization, and any aberrations in the beam's path. Environmental factors such as temperature and air turbulence can also impact the beam's FWHM-diameter.

4. How can I improve the accuracy of my FWHM-diameter measurements?

To improve the accuracy of FWHM-diameter measurements, it is important to use high-quality optical components and ensure proper alignment. It can also be helpful to take multiple measurements at different points along the beam's path and average the results. Additionally, minimizing environmental factors and using a power meter or camera with a high-resolution detector can also improve accuracy.

5. Are there any other methods for determining the size of an SH beam besides FWHM-diameter?

Yes, there are other methods for determining the size of an SH beam, such as using knife-edge or scanning techniques. However, FWHM-diameter is a commonly used method because it is relatively simple and provides a good estimate of the beam size. It is also important to note that different methods may give slightly different results, so it is best to use multiple techniques to confirm the size of the SH beam.

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