A high-power, short wavelength, computer-controlled laser diode characterization tester was developed to measure the specialized electro-optical characteristics required for optical data storage applications. The tester design goals were achievements of high accuracy, repeatability, stability, and throughput of all the measured characteristics. To accomplish these goals, optimization of thermal, mechanical, and electro-optical factors of the tester were required. The laser diode used for this work was packaged with a back-facet photodiode in a TO-5 can, and was mounted on a specialized electro-satic discharge (ESD) protected, grounded heatsink, temperature-controlled, brass block mount. The laser diode fixture was mounted on computer-controlled micropositioning stages for fast and repeatable measurements. The data was acquired by a digitizing oscilloscope and sent to an IBM-PC AT on an IEEE-488 bus. The tester capability allows the following measurements: First, the continuous wave (CW) optical power, forward voltage, and back-facet diode sensitivity are measured. An optical power limiter and a maximum current setting are used as a precaution. Second, the peak lasing wave-length in the optical spectrum are measured at a given low and high power. Third, the parallel and perpendicular profiles of the far-field pattern are also measured at a given low and high power. For each profile, the full-width at half-maximum (FWHM), pointing direction, and relative ripple magnitude are calculated using a Gaussain least-square fit to the data. Fourth, the astigmatic length and its shift from low to high power, and the near-field profiles are measured. Fifth, the polarization ratios are measured for a given numerical aperture objective. In these measurements, the collimating and focusing optics are corrected for the operating wavelength of the laser diode. Sixth, the temperature dependence of all the above characteristics is measured, and different important parameters such as the characteristic temperature and wavelength temperature sensitivity are calculated. The repeatability and accuracy of each of the measurements are statistically analyzed using control laser diodes.