Nonparaxial free-space diffraction from oblique end faces of single-mode optical fibers

We investigate free-space diffraction of light that emanates from obliquely cleaved end faces of single-mode fibers. Emphasis is placed on precise prediction of the wave-front sphericity of fiber-generating waves in the nonparaxial Fresnel propagation region spanning an entire hemispherical observation surface. Rayleigh-Sommerfeld scalar diffraction theory is used to produce an analytic closed-form solution with a nonparaxial approximation. The result allows the wave front's sphericity and the amplitude distribution of fiber-generating waves to be evaluated precisely with less computation than for existing numerical or infinite-series solutions.