Light emitting diodes and semiconductor lasers belong to almost any curriculum in the field of physics, optics or photonics programs at universities. The physics concepts are usually introduced in Bachelor programs, but a real deep understanding which is also based on laboratory experiments is seldomly acquired before studying in Master programs. Here we present some laboratory experiments for students of a photonics Master program at our University of Applied Sciences. Students are required to study the transitions from LEDs to semiconductor lasers in a four step investigation. First they record the diode characteristic of output power versus current. This helps to identify the pure LED regime, the transition region and the pure laser regime of the devices. Second they study the spatial characteristics of the commercial LED / laser devices with or without additional lenses. Third, laser dimensions are measured with microscopy and fourth the changes of the emissions spectra while increasing the injection current from LED to laser are measured with high accuracy using a Fourier Transform Infrared spectrometer. Here we present and discuss exemplary results of the first two steps and briefly mention the subsequent ones.
© 2019 SPIE, ICO, IEEE, OSAPDF Article
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