Wavelength meters use optical interferometry to measure a laser's absolute wavelength very accurately. Measurements are made in real-time resulting in the ability to automatically report and control laser wavelength. The wavelength and power level can be measured simultaneously with a single measurement. Once known, the next set of choices revolves around mounting a laser diode and choosing the. I want to know how to measure the wavelength of laser diodes ranging from visible to near infrared? (300 nm to 1100 nm) What type of instrument/meter do I need to use? spectrometer, spectrophotometer, wavelength meter, reflectometer, oscilloscope or what and how? This question recently came up on. To determine the wavelength of laser light using a plane diffraction grating and verify the principles of wave optics through diffraction phenomena. When monochromatic light passes through a diffraction grating, it produces a characteristic diffraction pattern due to the interference of light waves. It is often necessary to quantitatively assess the quality, performance, and characteristics of laser diodes. This is done through performing a series of experiments and obtaining certain significant parameters from which we can determine how well the laser diode is performing.