The purpose of this thesis is to fabricate the In0.75Ga0.25As quantum dot (QD) lasers, and analyze the optical properties of laser devices to be applied to optical fiber communication systems. In laser materials, we grew 12-layer In0.75Ga0.25As QD strcutures by molecular-beam epitaxy (MBE) with S-K mode on GaAs substrate, which contains the cladding layer material Al0.5Ga0.5As (C433) Al0.25Ga0.75As (C486) and Al0.2Ga0.8As (C485) of the three structures, the emission wavelength of about 1.3£gm. In the waveguide design, the design of 2.2£gm ridge width waveguide, the purpose is to enable the single transmission mode in the waveguide, so that smaller dispersion losses. Using ridge waveguide and cleaved mirror as the formation of Fabry-Perot cavity laser. In the quantum dot laser characteristic, C485 in the cavity length is 3000£gm of threshold current is 80mA with a slope efficiency of 41.88mW/A, the main emission Peak at 1201nm, the second Peak at 1197nm, the third Peak at 1182nm ; however C486 cavity length is 3300£gm of threshold current is 120mA with a slope efficiency of 27.44mW/A, the main emission Peak at 1215nm, the second Peak at 1205nm. C485 of the threshold current density is 1212 A/cm2, C486 of the threshold current density is 1454 A/cm2.

In this work, the operating characteristics of quantum dot (QD) lasers with asymmetric barrier layers (ABLs) are studied. Several different cases are examined, in particular: 1) Effect of excited states on static and dynamic operating characteristics Within QDs, in addition to the lasing ground state, carriers can be captured into excited states, where they then decay into the ground state. This excited-state-mediated capture impacts the operating characteristics, limiting the maximum output power and modulation bandwidth. Three separate cases are considered: only indirect capture with electron-hole symmetry, both direct and indirect capture with electron-hole symmetry, and both direct and indirect capture of electrons but only indirect capture of holes. The impact of different parameters on the operating characteristics is studied, with values for maximizing the output power and modulation bandwidth being found. In addition, it is found that parasitic recombination in the active region in the space between QDs causes the output power to saturate at high injection currents for the cases of indirect capture for both electrons and holes and indirect capture for holes but direct and indirect capture for electrons, although the presence of the ABLs causes it to reach saturation at much lower currents. 2) QD laser with only a single ABL To be effective, the materials for ABLs must be carefully chosen to ensure that the band edges properly align to allow one carrier to enter the active region while preventing the other from overshooting it. Due to this requirement, it may arise that a suitable material only exists for one ABL but not the other. The performance of a QD laser with only a single ABL is considered and compared to a conventional QD laser. Specifically, the output power and characteristic temperature are calculated. While the single ABL laser only offers a negligible increase in output power compared to the conventional laser, it offers a considerable increase in characteristic temperature. 3) Analytical derivation of alpha factor in QD lasers with and without ABLs The alpha factor of a semiconductor laser describes the spectral linewidth broadening that occurs in semiconductor lasers due to changes in the refractive index due to the carrier density. While it has been studied experimentally, there has been little work done on deriving the alpha factor of QD lasers analytically. An expression for the alpha factor is found in this work using the real and imaginary parts of the complex susceptibility. For QD lasers with no inhomogeneous broadening, as well as ones with equilibrium filling of QDs with narrow line of QD size distribution, the alpha factor is independent of carrier density, and is therefore the same for any QD lasers, with or without ABLs. For QD lasers with equilibrium filling without a narrow line of QD size distribution, the alpha factor depends on carrier density, allowing for a potential difference between conventional and ABL QD lasers, however the difference between the two will be lessened. / Doctor of Philosophy / Semiconductor lasers are the most widely used laser, due in part to their ability to be controlled using electricity. Semiconductor lasers are used in a wide variety of consumer electronics, such as optical drives, as well as being used in fiber optic communications, where data is transmitted using the laser's light. Fiber optic communications transmit data by controlling the laser's output, where a high output (brighter light) represents a digital one, and a low output (dimmer light) represents a digital zero. Because semiconductor lasers can be directly controlled by changing the amount of current they receive, their output can easily be changed, allowing fast transfer of data. Despite their benefits, semiconductor lasers suffer from a drawback known as parasitic recombination. Parasitic recombination is a process that makes a significant portion of the current injected to generate useful light go to waste, which negatively impacts the laser's performance. One solution to parasitic recombination is the addition of asymmetric barrier layers (ABLs). By adding ABLs, parasitic recombination can be completely removed. In this work, several different cases of semiconductor quantum dot (QD) laser with ABLs are examined. Starting from a set of equations, the operating characteristics of the lasers in the different cases are found. First, the case of excited states is examined. The presence of excited states in semiconductor lasers impacts the rate that current can be converted to light, lowering their performance. By solving the starting rate equations, which describe the way different values change over time, the performance of the laser can be calculated. Specifically, the impact of several tunable parameters on the output power and modulation bandwidth are examined. The modulation bandwidth is how fast the laser output can be changed, which is equivalent to how fast data can be transmitted. Optimum values for the DC injection current, QD surface density (number of QDs per area), and laser cavity length are found.

This dissertation presents to our knowledge the first demonstration of a quantum well (QW) laser monolithically integrated with internal optical pump based on a light emitting diode (LED). The LED with high efficiency is operated in a thermoelectrophotonic (TEP) regime for which it can absorb both its own emitted light and heat. The LED optical pump can reduce internal optical loss in the QW laser, and enables monolithically integrated TEP heat pumps to the semiconductor laser. The design, growth and fabrication processes of the laser chip are discussed, and its experimental data is presented. In order to further increase the TEP laser efficiency the development of QDs as the active region for TEP edge emitting laser (EEL) is studied. The usage of QD as TEP laser's active region is significant in terms of its low threshold current density, low internal optical loss and high reliability, which are mainly due to low transparency in QD laser. The crystal growth of self-organized QDs in molecular beam epitaxial (MBE) system and characterization of QDs are mentioned. The design, growth, processing and fabrication of a QD laser structure are detailed. The characteristics of laser devices with different cavity length are reported. QD active regions with different amount of material are grown to improve the active region performance. Theoretical calculations based on material parameters and semiconductor physics indicate that with proper design, the combination of high efficiency LED in TEP regime with a QD laser can result in the integrated laser chip power conversion efficiency exceeding unity.