Focusing of electromagnetic waves by paraboloid mirrors. II. Numerical results.
We present results of numerical computations obtained from a theory described in Part 1 of our current investigations [J. Opt. Soc. Am. A 17, 2081 (2000)]. We show that a segment of a paraboloid mirror produces an intensity distribution identical to that of a high-aperture lens. It is shown that when the convergence angle of the paraboloid is increased beyond the pi/2 limit, the lateral resolution in the direction orthogonal to the incident polarization improves, whereas in the other direction the resolution worsens. Numerical results show that paraboloid mirrors of high convergence angle exhibit dispersion; that is, when the focal length is altered by a quarter of the wavelength the intensity in the focus changes from its maximum to its minimum value. A focal shift is observed that, in the case of a paraboloid of low convergence angle is identical to the Fresnel shift. However, a focal shift is also observed at large convergence angles.
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Department of Engineering Science, University of Oxford, UK.
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