$M^2$ as a Quantitative Measure for Beam Quality
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arXiv
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| Format: | Preprint |
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2025
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| _version_ | 1866910907947286528 |
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| author | Lausch, Filipp Pecile, Vito F. Heckl, Oliver H. |
| author_facet | Lausch, Filipp Pecile, Vito F. Heckl, Oliver H. |
| contents | Beam quality is a fundamental aspect for evaluating the performance of laser sources. $M^2$-measurements serve as the gold standard for beam quality assessment since the 1990s. The measured $M^2$-parameter indicates similarity to the pure fundamental Gaussian mode, characterized by the ideal $M^2=1$, by describing a beams' divergence. $M^2$-values close to 1 are considered to correspond to nearly fundamental sources. However, in terms of the higher-order mode contribution of a laser, it acts as a qualitative measure that does not permit a quantitative statement. Here, we introduce a framework to assess the fundamental mode content of a laser beam using $M^2$-measurements and establish a direct link between beam quality and its mode composition. Our results significantly enhance the utility of $M^2$-measurements in evaluating laser sources, coupling efficiencies, focusing performance, and long-distance propagation. This repositions $M^2$ from a qualitative figure to a quantitative tool in modern photonics. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2501_10345 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | $M^2$ as a Quantitative Measure for Beam Quality Lausch, Filipp Pecile, Vito F. Heckl, Oliver H. Optics Beam quality is a fundamental aspect for evaluating the performance of laser sources. $M^2$-measurements serve as the gold standard for beam quality assessment since the 1990s. The measured $M^2$-parameter indicates similarity to the pure fundamental Gaussian mode, characterized by the ideal $M^2=1$, by describing a beams' divergence. $M^2$-values close to 1 are considered to correspond to nearly fundamental sources. However, in terms of the higher-order mode contribution of a laser, it acts as a qualitative measure that does not permit a quantitative statement. Here, we introduce a framework to assess the fundamental mode content of a laser beam using $M^2$-measurements and establish a direct link between beam quality and its mode composition. Our results significantly enhance the utility of $M^2$-measurements in evaluating laser sources, coupling efficiencies, focusing performance, and long-distance propagation. This repositions $M^2$ from a qualitative figure to a quantitative tool in modern photonics. |
| title | $M^2$ as a Quantitative Measure for Beam Quality |
| topic | Optics |
| url | https://arxiv.org/abs/2501.10345 |