The 721 Laser Spectrum Analyzer operates as a high-accuracy wavelength meter and a high-resolution spectrum analyzer resulting in the most complete spectral characterization of CW and high-repetition rate pulsed lasers. Absolute laser wavelength is measured to an accuracy as high as ± 0.2 parts per million, and the laser’s spectrum is determined to a resolution as high as 2 GHz. Continuous calibration with a built-in wavelength standard provides the reliable accuracy that is expected from Bristol Instruments. Two versions of the model 721 are available. The 721A is offered for the most demanding experiments, measuring absolute laser wavelength to the highest accuracy of ± 0.2 parts per million (± 0.0002 nm at 1000 nm). For experiments that are less exacting, the 721B is a lower-priced alternative, measuring laser wavelength to an accuracy of ± 0.75 parts per million (± 0.0008 nm at 1000 nm). The model 721 is available in several broad wavelength configurations to satisfy virtually any experimental requirement. These are the VIS (375-1100 nm), NIR (520-1700 nm), IR (1.3-5.0 µm), and MIR (2-12 µm). The laser under test enters the VIS and NIR systems through a pre-aligned fiber-optic input to ensure optimum alignment. The laser under test enters the IR and MIR systems through a free-space aperture, through which the internal HeNe reference laser is emitted as a visible tracer beam to facilitate alignment. The 721 Laser Spectrum Analyzer operates with a PC running under Windows. Software is provided for two modes of operation. The Wavelength Meter Mode is used to accurately measure absolute laser wavelength. The Spectrum Analyzer Mode is used to generate the spectrum of a laser. Spectral features are measured to a resolution as high as 2 GHz, and displayed in a graph with the wavelength axis calibrated to the specified accuracy of the instrument.