Thermal and optical characterization of high power laser diodes

Daniel J Konopa, Purdue University

Abstract

Semiconductor lasers have become one of the most ubiquitous classes of lasers due to their efficiency, ease of modulation, size, and other factors. As these devices are quite small and can reach impressive optical densities, waste heat dissipation becomes a key consideration in many applications. Thermally induced effects such as spectral shift, broadening, and inefficiency can drastically degrade device performance for a desired application. This study attempts to quantify and analyze the thermal effects in laser diodes through a two-part approach. First, modeling of the temperature profile throughout the laser package is used to gain insight into the heat propagation. The model agrees to within 0.6 degrees Celsius of the experimental values withing four seconds after laser turn-on. This simulation gives insights into the heat dissipation of the device and also highlights the importance of choosing proper materials for spreading heat from the laser. The second part of this study consists of a statistically designed run of experiments is used to gather multiple performance characteristics and statistically correlate the effect of input variables onto those characteristics. Data taken included temperature rise of the device, relative spectral power, and beam quality images. The resulting analysis provides a comprehensive picture of how the device responds to thermal perturbations and what the consequence of those responses are. Statistically determined parameters from the experiment, such as the wavelength dependence on coolant temperature, were found to agree to within 1\% of the manufacturer's specifications.

Degree

M.S.E.C.E.

Advisors

Fisher, Purdue University.

Subject Area

Electrical engineering

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