Divergence angle of light exiting a nano-etched single mode fiber

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SUMMARY

The discussion focuses on calculating the divergence angle of light exiting a nano-etched single mode fiber with a numerical aperture (NA) of 0.12 at a wavelength of 830 nm. The fiber features a silver-coated tip with a 200 nm diameter hole, which acts as a point source. The presence of this small aperture introduces complexities in determining the cone of light emitted, particularly due to diffraction effects. The user seeks methods to accurately compute the light's divergence angle considering these factors.

PREREQUISITES
  • Understanding of single mode fiber optics
  • Knowledge of numerical aperture (NA) and its implications
  • Familiarity with diffraction principles, particularly single-slit diffraction
  • Basic skills in optical calculations and geometry
NEXT STEPS
  • Research methods for calculating light divergence in optical fibers
  • Learn about the impact of aperture size on diffraction patterns
  • Explore the principles of numerical aperture in fiber optics
  • Investigate simulation tools for modeling light propagation in fibers
USEFUL FOR

Optical engineers, fiber optic researchers, and students studying photonics or optical communications will benefit from this discussion.

melnop
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I am working with a single mode fiber at 830 nm with a NA of 0.12 (http://www.thorlabs.com/thorcat/19600/P3-830A-FC-2-AutoCADPDF.pdf). One end has a fiber tip coated in silver with a small hole of 200 nm diameter to essentially create a point source. My advisor told me that the fiber has a few modes when the light traveling through is shorter than 830 nm. I know that the acceptance angle may be calculated easily for a normal fiber, but I'm not sure how the small hole will affect things.

How could I calculate the cone of light that is coming out of the silvered end?

(I have included a diagram for clarity)
 

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