Couple light into photonic crystal fiber

[jlyu]

I have one hollow core fiber, the core is around 20um, Numerical Aperture is
0.03. The spot size of Ti:Sapphire laser is around 2~2.5mm. So I used focal
length 50mm. But only very few power can be achieved (6uw). I wonder
the reason. Could someone please give me some suggestions?

 

[Kim P. Hansen]

I have one hollow core fiber, the core is around 20um, Numerical Aperture is
0.03. The spot size of Ti:Sapphire laser is around 2~2.5mm. So I used focal
length 50mm. But only very few power can be achieved (6uw). I wonder
the reason. Could someone please give me some suggestions?

Hi There,

Maybe I can help you. Can you give a bit more information about the fiber you have? A 20µm core for a 800nm range hollow-core fibers sounds very big. Do you know if this is a 7 or a 19 cell design?

/Kim Hansen, NKT Photonics

 

[jlyu]

Actually, I do not think it belongs to 7 or 19 cell design. It is made by some other research group.

 

[Kim P. Hansen]

No worries. We would be happy to help even if the fiber is not made by us. Do you have a picture of the cross section of the fiber? Also, do you know what the loss in the fiber is at your laser wavelength?

 

[alphy]

There are a few possible reasons for the low power achieved in your experiment. One possibility is that the numerical aperture of your fiber is too small to efficiently couple the light from your laser into the fiber. A larger numerical aperture would allow for a wider range of angles of incident light to be coupled into the fiber, resulting in a higher power output. Another possibility is that the spot size of your laser may not be optimal for coupling into the fiber. Ideally, the spot size should be matched to the core size of the fiber for efficient coupling. You may want to try using a lens with a different focal length to achieve a better match.

Additionally, the quality of the fiber itself could also be a factor. If the fiber has impurities or defects, it could lead to losses and reduce the power output. It may be worth trying a different fiber or cleaning the current one to see if that improves the power output.

Another consideration is the alignment of the laser and the fiber. Even small misalignments can significantly reduce the power coupled into the fiber. Make sure that the laser and fiber are properly aligned and that the fiber is securely fixed in place.

Finally, it is important to consider the power limitations of the components in your setup. Your laser may not be able to output a higher power, or the fiber may not be able to handle higher powers without damage. It may be helpful to consult the specifications of your equipment to determine the maximum power that can be safely used.

In summary, there are several factors that could be contributing to the low power output in your experiment. It is important to carefully consider the numerical aperture, spot size, fiber quality, alignment, and power limitations to optimize the coupling of light into your photonic crystal fiber. I hope these suggestions are helpful in improving your results.