Laser Machine World for Laser Technology and Laser Products

Since laser intensity noise often sets the performance limits of experiments, it is important to characterize it for good results. Low noise, high sensitivity photoreceivers are invaluable when making such measurements. Optical receivers provide an ideal solution for this application. They combine scatter-grain noise-limited performance, high conversion gain, and wide bandwidth to make noise measurements easy to perform.   Figure 1 shows a typical setup for measuring laser intensity noise. The laser output is attenuated to unsaturate the photodetector and focus it onto the photoreceiver. It is important to ensure that the photodetector is not overfilled. This can lead to undesired noise coupling as mechanical vibrations cause the photodetector to see varying amounts of laser light. These acoustic frequencies will give false peaks in the amplitude noise spectrum.   The output of the photodetector is then sent to the spectrum analyzer. It is very common for the equivalent input ...

Power and energy density are two important concepts to understand when dealing with laser optics. These two terms are often used interchangeably but have different meanings   In most scientific disciplines, including chemical and electrical engineering, "power density" and "energy density" usually describe three-dimensional volumes. However, in the optical sciences, these terms are usually used to describe two-dimensional regions unless they are described as "volumes". Power density, energy density, fluence, and irradiance are often used interchangeably in the optical industry, which can be completely inaccurate, especially when it is not clear whether the metric is a 2D or 3D value. This is particularly important for laser cutting and welding applications, where the depth of laser penetration must be considered, rather than simply touching a surface. Volume values are often more applicable in these situations and are an important distinction that must be...