Understanding laser beam brightness: A review and new prospective in material processing

•A review on the correct terminology for Laser beam ‘radiance’ is presented.•All existing equations published in literature were reviewed.•A new modified equation was proposed and applied for the determination of laser beam radiance.•Effects of laser beam brightness to affect material processing was reviewed addressing gaps in knowledge.•Modification of radiance to influence laser design, and beam characterization was discussed.

This paper details the importance of brightness in relation to laser beams. The ‘brightness’ of lasers is a term that is generally not given much attention in laser applications or in any published literature. With this said, it is theoretically and practically an important parameter in laser-material processing. This study is first of a kind which emphasizes in-depth, the concept of brightness of lasers by firstly reviewing the existing literature and the progress with high brightness laser-material processes. Secondly, the techniques used to enhance the laser beam brightness are also reviewed. In addition, we review the brightness fundamentals and rationalize why brightness of lasers is an important concept. Moreover, an update on the analytical technique to determine brightness using the current empirical equations is also provided. A modified equation to determine the laser beam brightness is introduced thereafter. work The modified equation in turn is a new parameter called “Radiance Density”. Furthermore, research studies previously conducted to modify laser design to affect laser beam brightness are also discussed. The paper not only involves a review of the techniques used to improve laser beam brightness but also reviews how bright lasers can be employed to enhance/improve laser process capabilities leading to cost reduction of the laser assisted processes in areas such as manufacturing.