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Levelling the focal spot intensity of the focused Gaussian beam
V.V. Kotlyar, S.N. Khonina
Image Processing Systems Institute of RAS

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Pages: 42-51.

Full text of article: Russian language.

Abstract:
The paper considers the possibility of levelling the intensity of a Gaussian beam in the focusing plane (with a minimum increase of the diffraction spot size) using a simple phase optical element. A new criterion is introduced, according to which the degree of levelling the light beam intensity is considered not as the degree of proximity to the function with the constant intensity in some area of the focusing plane, but as the degree of reaching the maximum energy in the area where the beam intensity decreases to a particular level (for example, to 60% of the maximum value). This work uses numerical examples to show that the intensity of the Gaussian beam within the minimum diffraction spot can be levelled efficiently by using a simple binary DOE shaped as a cylindrical (or rectangular) step, the height and radius of which depend on the radius of the beam waist and the distance to it. The article uses a model example of replacing a phase DOE with a discontinuous phase by a continuous amplitude spatial filter, to show that it is possible to increase the share of energy falling into the circle, where the intensity decreases by 40%, from 40% to 65%. In this case, the radius of such a circle is doubled.

Citation:
Kotlyar VV, Khonina SN Levelling the focal spot intensity of the focused Gaussian beam. Computer Optics 1998; 18: 42-51.

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