Spectrum Compression of Gaussian Pulse from Central Obstructed Slit in the Far-Field^*

Abstract

The far-field diffraction characteristics of a time-dependent Gaussian pulse incident on a slit with a central obstruction are studied both theoretically and numerically. It can be shown that the central obstruction will cause the diffraction spectrum to be compressed compared with the slit without an obstruction. Also, the diffracted spectral intensity distributions with red/blue shifts of the maximum are presented.

Side-lobeless far-field spectrum of a short pulse from a circular aperture with Gaussian form of transmittance

“…(10).Fig. 3illustrates this property for different values of source bandwidth g( ¼ 1/o 0 t), and this property also can be found under other aperture dispersion cases[1][2][3][4][5][6][7][8][9][10][11][12][13]. The blue shift of the maximum of the spectral intensity I(0,o) is dependent on the source bandwidth g( ¼ 1/o 0 t).…”

“…It is also noted that Eq. (1) is usually used for a monochromatic incident field, U 0 (p 0 ,t) ¼ U 0 (p 0 ,o)e Àjot , with a single frequency o and the constant complex amplitude U 0 (p 0 ,o), but it is also applicable for a broad-band incident pulse [1][2][3][4][5][6][7][8][9][10][11][12][13], which can be superposed by monochromatic fields via the Fourier integral [15]. For a circular aperture with Gaussian form of transmittance, as shown in Fig.…”

“…In this work, we study the spectral characteristics of a time-dependent Gaussian pulse when it is incident on a circular aperture function with Gaussian form transmittance. It can be shown that the resultant diffracted intensity is completely free of the side-lobes, which appear in most of the aperture dispersion cases [1][2][3][4][5][6][7][8][9][10][11][12][13]. This side-lobeless effect can give important applications for optical engineering or optical communication where the side-lobes are not wanted.…”

“…It also includes the red or blue shift of the spectrum maximum or the distortion of the incident pulse's spectrum [1][2][3][4][5][6][7][8][9][10][11][12][13]. However, due to the oscillating properties of the aperture function in the spectral domain, as explained later, there are always some side-lobes found in the resultant diffraction spectrum [3][4][5][6][7][8][9][10][11][12][13]. Some of our previous papers tried to reduce or depress the side-lobes effect (the apodization effect) with specific aperture function [1,2].…”

Spectrum Compression of Gaussian Pulse from Annular Aperture in Far-Field

“…The topic ''aperture dispersion'', that is, the spectral changes of a short pulse resulting from aperture diffraction has gained more interest lately. [1][2][3][4][5][6][7][8][9][10][11] It includes the red or blue shift of the spectrum maximum or the distortion of the incident pulse's spectrum. It is well known that an aperture with a central obstruction can reduce the diffraction pattern width for a constant-intensity light wave; hence, it is used to enhance the resolving power of image-forming systems.…”