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

Abstract

a b s t r a c tThis 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 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. 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 and cost reduction of the laser assisted processes in manufacturing.

Multi-octave spanning, Watt-level ultrafast mid-infrared source

“…In order to compare the current performance of this system to other standard broadband infrared sources, we use the spectral brilliance as a figure of merit. The definition of the brightness describes the photon flux of the source (in ph s −1 ) inside a certain spectral window (usually defined as 0.1% of the bandwidth at each frequency), as well as the focusability and beam quality of the source (encompassing the focal spot size (mm 2 ) and divergence (Sr)) [59]. The total brightness of the source is then expressed in units of [ph s −1 mm −2 sr −1 /0.1% BW].…”

Coherent X-ray imaging across length scales

“…The brilliance of any beam of radiation cannot be changed once it has been produced [22]. This can be understood intuitively from Fig.…”

Towards Terawatt-Scale Spectrally Tunable Terahertz Pulses via Relativistic Laser-Foil Interactions

“…In contrast, since the THz spectrum from crystal-based sources depends primarily on the crystal, and the THz radiation from laser-induced plasmas in air and liquids is ultrabroadband, the opportunity to spectrally tune these sources is small. To characterize the average spectral intensity over the bandwidth, the parameter brightness temperature [49] T B is adopted and calculated as k B T B ¼ Peak power=½ðM 2 Þ 2 • Bandwidth, where M 2 is the beam quality factor. The T B evaluated for the presented source is nearly 2 orders of magnitude higher than previous sources.…”