Focusing of electromagnetic waves by paraboloid mirrors. II. Numerical results

We present results of numerical computations obtained from a theory describ ed in Part 1 of our current investigations [J. Opt. Sec. Am. A 17, 2081 (20 00)]. We show that a segment of a paraboloid mirror produces an intensity d istribution identical to that of a high-aperture lens. It is shown that whe n the convergence angle of the paraboloid is increased beyond the pi /2 lim it, the lateral resolution in the direction orthogonal to the incident pola rization improves, whereas in the other direction the resolution worsens. N umerical results show that paraboloid mirrors of high convergence angle exh ibit 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 m inimum value. A focal shift is observed that, in the case of a paraboloid o f low convergence angle is identical to the Fresnel shift. However, a focal shift is also observed at large convergence angles. (C) 2000 Optical Socie ty of America [S0740-3232(00)01811-1].