In laser applications such as materials processing, environmental monitoring and confocal microscopy, understanding the laser's performance is critical. A laser that operates erratically as it drills holes in steel could fail to penetrate the metal or produce holes that are too large or too small. A laser whose output is misunderstood could produce misleading spectroscopic data. A laser whose power is even slightly too high could destroy a fragile biological specimen. Measuring optical power is often simple. You can obtain a valid reading by using the appropriate sensor and readout and by controlling any environmentally induced errors…