![]() Consequently, flat top lasers do not have a peak irradiance. 6 Other lasers have flat top beam profiles which, unlike Gaussian beams, have a constant irradiance profile through the cross-section of the laser beam and a quick drop off in intensity. Most laser beams have a Gaussian beam profile, so irradiance and fluence are both highest on the optical axis of the laser and decrease as deviation from the axis increases. ![]() Volumetric values are typically more applicable to these situations and is an important distinction that must be understood to avoid miscommunication. This is particularly important for laser cutting and welding applications because the depth of laser penetration must be considered as opposed to simply encountering the surface. However, in optical sciences the terms are typically used to describe a two-dimensional area, unless described as “volumetric.” Power density, energy density, fluence, and irradiance are often used interchangeably in the optics industry, which can be completely inaccurate, especially if it is not clear if the metric is a two- or three-dimensional value. In most scientific disciplines, including chemistry and electrical engineering, “power density” and “energy density” typically describe a three-dimensional volume. Table 1: Definitions of common metrics used to describe laser beams and other electromagnetic radiation. Power over a three-dimensional volume, which considers the depth of laser penetration into a sample in applications like materials processing.Įnergy over a three-dimensional volume, which considers the depth of laser penetration into a sample in applications like materials processing. The maximum optical energy reached over the duration of a laser pulse. The maximum irradiance, or optical power density, reached over the duration of a laser pulse. Linear power density is only applicable to flat top beams and must be adjusted for Gaussian beams. Linear distribution of a flat top beam’s power describing the laser-induced damage threshold (LIDT) of continuous wave (CW) lasers through total power divided by 1/e 2 beam diameter. Power per unit area, also known as irradiance.Įnergy per unit area, also known as fluence. Potential energy stored in electromagnetic radiation, found by integrating power with respect to time. MetricĮnergy of light per unit time, such as the energy delivered by a laser beam. Table 1 defines power density, energy density, and other related terms as they relate to laser optics. These two terms are often used interchangeably but have different meanings. Power and energy densities are two important concepts to understand when dealing with laser optics.
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