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Non-Gaussian beam single mode coupling!

  • 24 March 2023
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Searched and read the KB articles and some threads here for the single mode fiber couplings. All of them were talking about how to couple laser beam (Gaussian beam) into single mode fibers. I am wondering if anybody here have done single mode fiber coupling with Non-Gaussian beam? Are there any tools and operands can be used for analysis the coupling efficiency? It seems to me that the POP and Single Mode Fiber Coupling tool are all designed for Gaussian beam. Please advise! 

Best regards,

Bob  

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Best answer by Jeff.Wilde 24 March 2023, 19:37

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Jeff.Wilde
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Have you tried using POP?  It may work for you.  It is not restricted to Gaussian beams.  You can define the starting beam in a wide variety of ways, and then select the receiving fiber to be Gaussian single-mode.

 

Regards,
Jeff

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Jeff,

Thank you so much for the direction!  I am going to have a try on it by selecting the tog hat or multimode beam type. 

Best regards,

Bob

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Hi Jeff,

 

I have tried the POP by selecting the top hat for the input beam type, but it seemed still need to input the waist information. I haven’t tried other beam type yet but I found the Single Mode Fiber Coupling tool gives some reasonable coupling efficiency (much closer to lab measured number than POP does!) if I selected “Ignore source fiber” like in this screenshot. But not sure if that’s correct since I ignored the source fiber.

Best regards,

Bob

Jeff.Wilde
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Hi Bob,

As explained in the help documentation, the Waist X and Waist Y values for a Top Hat beam are simply the x & y radius values. 

 

I don’t know what your optical path looks like or what your actual lab source is, so I can’t really say much more about how to best model your setup.  However, generally speaking, both POP and Fiber Coupling can yield meaningful results, although the POP version is more flexible but can take longer to execute.  The Fiber Coupling analysis is based on tracing rays to the exit pupil in order to find the wavefront used in the overlap integral calculation:

 

When you ignore the source fiber, it requires your source to be properly defined via the System Aperture (type, size and apodization).  

Regards,

Jeff

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Jeff,

Thank you so much for the advices! In fact, the setup in our lab, input beam is pretty fast (f /# < 1), so based on the help document about POP, it may not accurate enough to use POP. And I don’t have X, Y beam radius values either. So, I will focus on the Single Mode Fiber Coupling tool now. Really appreciate your helps!

Best regards,

Bob

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