Improving the intensity of a focused laser beam

Sofiane Haddadi; Michael Fromager; Djelloul Louhibi; Abdelkrim Hasnaoui; Ali Harfouche; Emmanuel Cagniot; Kamel Äit-Ameur

doi:10.1117/12.2075578

3 March 2015 Improving the intensity of a focused laser beam

Sofiane Haddadi, Michael Fromager, Djelloul Louhibi, Abdelkrim Hasnaoui, Ali Harfouche, Emmanuel Cagniot, Kamel Äit-Ameur

Author Affiliations +

Proceedings Volume 9343, Laser Resonators, Microresonators, and Beam Control XVII; 93431R (2015) https://doi.org/10.1117/12.2075578
Event: SPIE LASE, 2015, San Francisco, California, United States

Abstract

Let us consider the family of symmetrical Laguerre-Gaus modes of zero azimuthal order which will be denoted as LG_p0 . The latter is made up of central lobe surrounded by p concentric rings of light. The fundamental mode LG₀₀ is a Gaussian beam of width W. The focusing of a LG_p0 beam of power P by a converging lens of focal length f produces a focal spot keeping the LG_p0 -shape and having a central intensity I₀= 2PW²/(λf)²whatever the value of the radial order p. Many applications of lasers (laser marking, laser ablation, …) seek nowadays for a focal laser spot with the highest as possible intensity. For a given power P, increasing intensity I₀ can be achieved by increasing W and reducing the focal length f. However, this way of doing is in fact limited because the ratio W/f cannot increase indefinitely at the risk of introducing a huge truncation upon the edge of the lens. In fact, it is possible to produce a single-lobed focal spot with a central intensity of about p times the intensity I₀. This result has been obtained by reshaping (rectification) a LG_p0 beam thanks to a proper Binary Diffractive Optical Element (BDOE). In addition, forcing a laser cavity to oscillate upon a LG_p0 can improve the power extract due to a mode volume increasing with the mode order p. This could allow envisaging an economy of scale in term of laser pumping power for producing a given intensity I₀. In addition, we have demonstrated that a rectified LG_p0 beam better stand the lens spherical aberration than the usual Gaussian beam.

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Sofiane Haddadi, Michael Fromager, Djelloul Louhibi, Abdelkrim Hasnaoui, Ali Harfouche, Emmanuel Cagniot, and Kamel Äit-Ameur "Improving the intensity of a focused laser beam", Proc. SPIE 9343, Laser Resonators, Microresonators, and Beam Control XVII, 93431R (3 March 2015); https://doi.org/10.1117/12.2075578

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KEYWORDS

Gaussian beams

Monochromatic aberrations

Laser applications

Collimation

Laser marking

Laser resonators

Binary data

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