John McCauley, Ophir
As for products that measure a laser's performance, the application can be tricky and sometimes overwhelming, especially if the user is unfamiliar with a specific measurement product, the respective laser system or both. This article will detail why a laser's performance is important for industrial laser materials processing, and will serve as a guide for the right and wrong ways to apply, ascertain, evaluate, and take action on the laser performance data gathered.
Understanding all of this ultimately will help determine the efficiency of your laser. It also will be beneficial if you've had problems with your laser system but didn't know where to start troubleshooting, or if you've spent more time than should have been required to develop any specific laser application.
When discussing laser applications, regardless of how the laser is used, it is imperative to understand how the laser is interacting with the material being processed. Power density typically is expressed in W/cm² and represents the measurement of how the laser is interacting with the material to which it is applied. This measurement is determined by evaluating two key laser performance characteristics.
First, the output power directed at the material being processed is measured by assessing how much laser light is being supplied by the entire laser system. This quantification can be a measure of continuous wave power if the laser is not pulsed or, if the laser is pulsed, an average power measurement (if pulse energy is measured, the term for how the laser is applied to the material is "energy density"). Secondly, the measurement of the diameter of the focused laser spot is taken to determine the area in which the laser's focus has been concentrated.
If either of these measurements changes, it can affect how the laser is interacting with the material being processed. These two characteristics can change for a number of reasons, which is why it's important to measure them often. For example, if the turning mirrors or any other optics in the beam's path become contaminated, two things could happen. For one, laser output power could drop, resulting in a decrease in overall power density. Alternatively, the location of the laser's focused spot could fluctuate, resulting in a change in power density. In either event, the laser is not interacting with the process as it was designed to do.