Localized Beams and Localized Pulses: Generation Using the Angular Spectrum

The Bessel beam has a long history, dating back to Airy and Rayleigh. This chapter clearly stated the propagation invariance of Bessel beams. It investigates the properties of electromagnetic Bessel beams, generated by illumination of a narrow annulus by a plane-polarized wave. In order to investigate how the cross section of a Bessel beam transforms with defocus from a Bessel beam to an annulus, the chapter considers the case of a pupil that is an annulus convolved with a Gaussian beam, which is now known as a Bessel-Gauss(ian) (BG) beam. A pulsed Bessel beam can be generated by integrating Bessel beams of different frequency over an assumed spectral distribution. Localized waves have numerous potential applications, and of these the applications in biological and medical imaging are important examples. The Bessel beams can improve spatial resolution when compared with using a circular pupil of the same dimension. Controlled Vocabulary Terms Bessel functions; biomedical imaging; electromagnetic wave polarisation; image processing; laser theory