Source: MDPI

Understanding Flat-Top Beams in Laser Technology

Overview

A flat-top beam, also known as a top-hat beam, is a type of light beam with a uniform intensity profile across its cross-section. This is different from Gaussian beams, where the intensity decreases smoothly from the center. Flat-top beams find applications in various laser technologies, such as semiconductor wafer processing and high-power frequency conversion.

Characteristics of Flat-Top Beams

Flat-top beams typically have smooth edges and can be approximated by supergaussian profiles rather than perfect rectangles. The order of the supergaussian profile determines the sharpness of the edges. While flat-top beams can be spatially coherent in theory, practical implementations often result in spatially incoherent beams with complex phase profiles.

Propagation of Flat-Top Beams

Unlike Gaussian beams, flat-top beams are not free-space modes, meaning their intensity profiles change during propagation. The rate of change depends on the sharpness of the edges. For larger beams with gradual intensity profiles, the shape may remain relatively stable over distances.

Generation of Flat-Top Beams

Flat-top beams are commonly created by first generating a Gaussian beam from a laser and then reshaping its intensity profile using specialized optical elements like beam homogenizers. Various techniques exist for transforming Gaussian beams into flat-top beams, each with unique characteristics regarding coherence, beam shape, and sensitivity to input parameters.

Conclusion

Flat-top beams play a crucial role in laser applications that require uniform intensity distribution. Understanding their characteristics, propagation behavior, and generation methods is essential for optimizing performance in diverse industrial and scientific settings.

Source: ResearchGate
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