Bristol Instruments said its 621-series laser wavelength meters from offer accurate, real-time wavelength information for continuous-wave (CW) lasers. Two versions are available: The model 621A is for the most demanding experiments, measuring absolute wavelength to an accuracy as high as ± 0.0001 nm. For experiments that are less exacting, the model 621B is a lower-priced alternative. This system measures laser wavelength to an accuracy of ± 0.001 nm. The accuracy of the 621 is guaranteed, because it is continuously calibrated with a built-in HeNe laser wavelength standard. The 621 system also offers an unprecedented level of reliability, versatility and convenience. Operational wavelength ranges from 350 nm to 5 um are available to satisfy any experimental requirement. Optical power is measured to provide a more complete analysis of laser performance. Measurements are made at a rate as high as 10 Hz, resulting in instantaneous reporting.