Optical Gain Measurement of Quantum-dot Structures by Using a Variable-stripe-length Method with Current Injection
Date Issued
2004
Date
2004
Author(s)
Kao, Chien-Kai
DOI
en-US
Abstract
Gain spectrum measurement plays an important role in analysis of quantum-dot 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 new variable-stripe-length method with current injection to demonstrate the gain spectrum measurement of quantum-dot structures.
In this thesis, we measure four samples with different numbers of quantum-dot layers, C1511 (10 layers of quantum dots), C1512 (5 layers), C1513 (3 layers), and SH239 (15 layers), to discuss their modal gain in ground states and excited states. We observe the gain peak of the excited states surpasses that of the ground states, which is hardly observed by using Hakki-Paoli method due to the limited wavelength range. Furthermore, the transmission experiment is applied to measure internal loss (ξ). From our results, ξ of C1511, C1512 and C1513 are 1 cm-1, 1.35 cm-1, and 3.2 cm-1 respectively. We find that the optical mode loss does not increase as the layer number increases.
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 in QD lasers.
Subjects
量子點
光學增益
多段電激發
內部損耗
Internal loss
Quantum-dot Structures
Modal gain
Variable-stripe-length Method
Type
thesis
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