| Summary: | 碩士 === 國立臺灣大學 === 光電工程學研究所 === 93 === Gain spectrum measurement plays an important role in analysis of semiconductor electro-optic devices. Traditionally, the Hakki-Paoli method is used to measure the modulation depth of the Fabry–Perot mode spectrum of lasers below threshold. In this study, we introduce a variable-stripe-length method with current injection and a multi-section device method to demonstrate the gain spectrum measurement of quantum-dot and quantum-well structures.
In this thesis, we discuss the modal gain in ground states and excited states of quantum-dot and quantum-well samples. We can observe the modal gain in ground and excited states at the same time, which is hardly observed by using Hakki-Paoli method due to the limited wavelength range. Furthermore, we measure the modal absorption of quantum-dot and quantum-well structures by multi-section devices and the internal loss (αi) can be extracted from modal absorption spectrum.
Based on the results in our measurement and analysis, the contribution of excited states to the gain spectra, especially under higher excitation, will be demonstrated. This will cause lasing emission wavelength to shift from ground states to excited states. The internal loss obtained from modal absorption is the quite same as that from traditional method used by different cavity lengths. These results demonstrate the reliability of the multi-section method.
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