Spotlight Summary by Brynmor Davis
The non-diffracting nature of truncated Hermiteâ€“Gaussian beams
Established families of standard beam profiles are extremely useful when characterizing the propagation of light; and this paper makes a new and useful connection between two widely used beam classes. Hermite-Gaussian beams are ubiquitous when studying rectangular propagation profiles, and cosine beams are of great interest because they are "diffraction free" (meaning the beam shape does not change as it propagates). In practice, the infinite energy and extent of a pure cosine beam means compromises must be made for physical realization, including limiting its extent. The resulting truncated cosine beam still maintains a consistent structure as it propagates, but now over only a limited distance.
In this paper the authors recognize that higher-order Hermite-Gaussian beams (those with a large number of peaks and valleys in the profile) can be approximated by an expression including a cosine factor. In fact, these asymptotic approximations of Hermite-Gaussian beams can be matched to truncated cosine beams to produce similar beam profiles. The degree of similarity, as a function of various beam parameters, is explored in the paper; and case studies compare how diffraction alters the beams as they propagate. The authors convincingly argue that in many circumstances a Hermite-Gaussian beam may exhibit a more desirable approximation to diffraction-free propagation than a truncated cosine. More generally, this paper establishes an important connection between the canonical rectangular beam pattern (Hermite-Gaussian) and diffraction-free propagation.
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In this paper the authors recognize that higher-order Hermite-Gaussian beams (those with a large number of peaks and valleys in the profile) can be approximated by an expression including a cosine factor. In fact, these asymptotic approximations of Hermite-Gaussian beams can be matched to truncated cosine beams to produce similar beam profiles. The degree of similarity, as a function of various beam parameters, is explored in the paper; and case studies compare how diffraction alters the beams as they propagate. The authors convincingly argue that in many circumstances a Hermite-Gaussian beam may exhibit a more desirable approximation to diffraction-free propagation than a truncated cosine. More generally, this paper establishes an important connection between the canonical rectangular beam pattern (Hermite-Gaussian) and diffraction-free propagation.
Article Reference
The non-diffracting nature of truncated Hermiteâ€“Gaussian beams
- J. Opt. Soc. Am. A 37(11) C1-C6 (2020)
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