= Simin Feng
{c}
\b[Simin Feng] is the first-listed author, with <Herbert G. Winful>, of the 2001 primary paper <Physical origin of the Gouy phase shift by Simin Feng and Herbert G. Winful>. The full published byline supplies the name; the paper lists a University of Michigan affiliation and a Lucent Technologies present-address note. These identify the contribution at publication without inferring a present appointment or attaching an unverified namesake's portrait.<Physical origin of the Gouy phase shift by Simin Feng and Herbert G. Winful>[Printed p.485, author byline and address note]{ref}
The paper connects the <Gouy phase> with transverse confinement and the <angular spectrum representation> of a wave. Its analysis treats a finite beam as a superposition of <plane waves> with different transverse <wave vector> components and obtains the Gaussian phase contribution.<Physical origin of the Gouy phase shift by Simin Feng and Herbert G. Winful>[Equations1–12, pp.485–486]{ref}
An original one-coordinate example makes the localization issue quantitative. At a waist, let the field amplitude be $U(x)\propto e^{-x^2/w_0^2}$. Its <Fourier transform> has amplitude $\widetilde U(k_x)\propto e^{-w_0^2k_x^2/4}$. Normalizing the squared magnitudes as distributions gives
$$
\operatorname{Var}(x)=\frac{w_0^2}{4},\qquad
\operatorname{Var}(k_x)=\frac1{w_0^2},\qquad
\Delta x\,\Delta k_x=\frac12.
$$
For stipulated $w_0=100\,\mathrm{\mu m}$, the position spread is $50\,\mathrm{\mu m}$ and the transverse-wavenumber spread is $10^4\,\mathrm{m^{-1}}$. Halving the waist halves the first and doubles the second. The distributions here are constructed from field amplitudes; no single-photon counting experiment is assumed.
This <Fourier localization of a Gaussian beam> is part of the mathematics underlying the paper's focusing analysis. It also explains why a perfectly transverse-localized beam cannot retain the single propagation direction of an infinite <plane wave>. A field model, its phase convention and its transverse geometry must accompany any numerical phase claim.
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