Optimizing Beam Size for Increased Diffraction Efficiency

In summary, to increase the diffraction efficiency of the AOM, the beam size of the laser needs to be reduced to 220um or less. This can be achieved by using longer focal length lenses, as they suffer from less aberration. Polarization control of the beam can also improve efficiency. Additionally, the laser beam should nearly fill the aperture of the AOM to maximize diffraction efficiency. The AOM's aperture may be too small for the laser beam, leading to lower transmission than expected.
  • #1
cks
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In order to increase the diffraction efficiency of the AOM, we need to reduce the beam size of the laser. According to the manual of my AOM, it needs to have the beam size of 220um to get more than 90% diffraction efficiency.

So, I decided to do so by putting a lens in front of it and another one at the back of AOM.

However, I'm not sure what is the focal length I should use for both the lenses?

I remember my professor used to tell me that longer focal length is better, but I forgot why is it the case? Is 50mm considered ok?
 
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  • #2
Long focal length singlets generally suffer from less aberration, that's the reason for the rule of thumb.

It's been a while since I used an AOD/AOM, but I was never able to get more than about 60% diffraction efficiency. Polarization control of the beam can help, also. And IIRC, I needed to nearly fill the aperture of the AOD to maximize the diffraction efficiency, not minimize the beam size- the spatial density grating within the crystal worked best when the beam size covered many periods.
 
  • #3
The aperture of the AOM is too small for my laser beam spot size, that was one of the reasons why I needed to focus the laser. The AOM is only able to pass through 87% of laser beam while it's not on. From the manual, it should have more than 95% transmission.
 

What is the purpose of optimizing beam size?

The purpose of optimizing beam size is to increase the diffraction efficiency, which is the percentage of light that is diffracted by a grating. This can improve the overall performance and sensitivity of optical systems.

What factors affect the optimal beam size?

The optimal beam size is affected by several factors, including the wavelength of light, the properties of the grating (such as groove spacing and depth), and the angle of incidence of the light.

How can I determine the optimal beam size for my specific system?

The optimal beam size can be determined through experimental testing and optimization, or through theoretical calculations using equations that take into account the factors mentioned above.

Can optimizing beam size improve the resolution of an optical system?

Yes, optimizing beam size can improve the resolution of an optical system by increasing the diffraction efficiency, which leads to a better quality and more precise diffracted image.

Are there any limitations to optimizing beam size?

There may be limitations to optimizing beam size, such as physical constraints of the grating or the limitations of the light source. Additionally, optimizing beam size may also affect the signal-to-noise ratio and require careful balancing with other factors in the system.

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