High-Accuracy Laser Wavelength Meter - The model 621A is offered for the most demanding experiments, measuring absolute wavelength to the highest accuracy of ± 0.2 ppm.
Two versions of the 621 series are available. For experiments that are less exacting, the model 621B is a lower-priced alternative.

• Accuracy ± 0.2 ppm for 621A Model
• Accuracy ± 0.75 ppm (± 1 ppm for MIR and XIR)for 621B Model
• Operation available from 375 nm to 12 μm