intensity of a light equation point source

This meaning is obviously quite different from that of intensities in optical physics. In radiometry, the radiant intensity is understood to be the radiant flux (or radiant power) per unit solid angle, which leads to units of W/sr (watts per steradian). Intensities in Radiometry Radiant flux per unit area or per unit solid angle – that detail makes a big difference! The radiation pressure of light incident on a surface is proportional to the optical intensity.īeam profilers can be used for measuring the shape of the intensity profile of a laser beam.10 14 W/cm 2 or higher in a gas, high harmonic generation can occur. Extremely high peak intensities can be achieved with amplified ultrashort pulses.Laser-induced damage of a medium may occur for intensities above a certain damage threshold, which however can usually only be reached with optical pulses, and then depends on the pulse duration.The refractive index change via the Kerr effect in a transparent medium is the nonlinear index times the local intensity.Strong saturation of an optical transition in the steady state occurs when the intensity exceeds the saturation intensity. In conjunction with transition cross-sections, intensities govern the rates of optical transitions, e.g.Optical intensities with the meaning as used in optical physics are relevant in various situations: The peak intensity can then vary, and may occur at locations at some distance from the beam axis. In a multimode laser beam, generated in a laser where higher-order transverse resonator modes are excited, the shape of the transverse intensity profile can undergo significant changes as the relative optical phases of the modes change with time. The equation can be verified by integrating the intensity over the whole beam area, which must result in the total power. Which is two times higher than is often assumed. It is sometimes called optical energy flux.įor a monochromatic propagating wave, such as a plane wave or a Gaussian beam, the local intensity is related to the amplitude of the electric field via The intensity is the product of photon energy and photon flux. The units of the optical intensity (or light intensity) are W/m 2 or (more commonly) W/cm 2. of a laser beam at some location, is generally understood to the optical power per unit area, which is transmitted through an imagined surface perpendicular to the propagation direction. An example is that the intensity noise of a laser normally refers to noise (fluctuations) of its optical power rather than e.g. Such uses of the term should be avoided, but in certain contexts they are nevertheless very common. Sometimes, what is actually meant is for example an optical power, an irradiance or a radiant intensity – these are examples of very different quantities which should not be confused. In other cases, intensities are meant to be quantitative measures, but used in quite inaccurate ways. Such non-quantitative statements rarely create a risk of misunderstanding. An actual numerical value is not specified in such cases. For example, such a statement could be “high intensity laser beams are used for laser material processing” – just like “the sun is very bright today”. The term intensity is often used in a non-quantitative way.

Non-quantitative and Inaccurate Meanings of Intensity Certainly, for quantitative reference it is important to clearly indicate which meaning of intensity is used. However, we must deal with literature using the term in different ways, as explained in the following sections. One may recommend using optical intensity only in a non-quantitative way and only use well-defined radiometric quantities like radiant intensity and irradiance for quantitative references.

The term optical intensity (or just intensity) is quite common in optical physics and technology, but it is somewhat problematic, since it is used with substantially different meanings.

Intensity of a light equation point source