In this monograph, the authors address the physics and engineering together with the latest achievements of efficient and compact ultrafast lasers based on novel quantum-dot structures and devices. Their approach encompasses a broad range of laser systems, while taking into consideration not only the physical and experimental aspects but also the much needed modeling tools, thus providing a holistic understanding of this hot topic.

Written by a team of European experts in the field, this book addresses the physics, the principles, the engineering methods, and the latest developments of efficient and compact ultrafast lasers based on novel quantum-dot structures and devices, as well as their applications in biophotonics. Recommended reading for physicists, engineers, students and lecturers in the fields of photonics, optics, laser physics, optoelectronics, and biophotonics.

This thesis deals with the dynamics of state-of-the-art nanophotonic semiconductor structures, providing essential information on fundamental aspects of nonlinear dynamical systems on the one hand, and technological applications in modern telecommunication on the other. Three different complex laser structures are considered in detail: (i) a quantum-dot-based semiconductor laser under optical injection from a master laser, (ii) a quantum-dot laser with optical feedback from an external resonator, and (iii) a passively mode-locked quantum-well semiconductor laser with saturable absorber under optical feedback from an external resonator. Using a broad spectrum of methods, both numerical and analytical, this work achieves new fundamental insights into the interplay of microscopically based nonlinear laser dynamics and optical perturbations by delayed feedback and injection.

The book addresses issues associated with physics and technology of injection lasers based on self-organized quantum dots. Fundamental and technological aspects of quantum dot edge-emitting lasers and VCSELs, their current status and future prospects are summarized and reviewed. Basic principles of QD formation using self-organization phenomena are reviewed. Structural and optical properties of self-organized QDs are considered with a number of examples in different material systems. Recent achievements in controlling the QD properties including the effects of vertical stacking, changing the matrix bandgap and the surface density of QDs are reviewed. The authors focus on the use of self-organized quantum dots in laser structures, fabrication and characterization of edge and surface emitting diode lasers, their properties and optimization with special attention paid to the relationship between structural and electronic properties of QDs and laser characteristics. The threshold and power characteristics of the state-of-the-art QD lasers are demonstrated. Issues related to the long-wavelength (1.3-mm) lasers on a GaAs substrate are also addressed and recent results on InGaAsN-based diode lasers presented for the purpose of comparison.

An accessible yet rigorous introduction to nanophotonics, covering basic principles, technology, and applications in lighting, lasers, and photovoltaics. Providing a wealth of information on materials and devices, and over 150 color figures, it is the 'go-to' guide for students in electrical engineering taking courses in nanophotonics.

André Röhm investigates the dynamic properties of two-state lasing quantum dot lasers, with a focus on ground state quenching. With a novel semi-analytical approach, different quenching mechanisms are discussed in an unified framework and verified with numerical simulations. The known results and experimental findings are reproduced and parameter dependencies are systematically studied. Additionally, the turn-on dynamics and modulation response curves of two-state lasing devices are presented.

Recently, nonpolar InGaN/GaN optoelectronic structures have been widely studied for applications in ultrafast communication, solid-state lighting, solar cell, sensing, photonic integrated circuits and quantum cryptography. When grown in a core-shell architecture (where the nonpolar, multiple disk active region is radially grown on the sidewall of a hexagonal GaN nanowire), these devices exhibit superior properties that mainly arise from the availability of a larger active region. Recently, the viability of using such architectures in electrically injected, low-threshold single-nanowire laser operating at room temperature has been experimentally demonstrated. In contrast, axially (or expitaxially) grown disk-in-wire structures suffer from a smaller gain-volume and, thus, have failed to produce optically pumped lasing emissions. From fundamental physics point of view, the benefits of using nonpolar m-axis and a-axis oriented InGaN/GaN in the active region are as follows: a) lesser degree of lattice mismatch, resulting in a weaker strain field; b) absence of spontaneous (pyroelectric) polarization; c) smaller piezoelectric polarization, induced internal potential, and electric field in the carrier transport direction; d) stronger overlap of conduction electron and valence hole wavefunctions; e) elimination or reduction of quantum-confined stark effect (QCSE); f) higher transition probability (emission probability) and quantum efficiency; g) higher degree of polarized emission with spectral stability; and h) higher injection efficiency by reducing carrier overflow in a thicker active region. Nevertheless, nonpolar structures exhibit a small internal potential, which mainly arise from non-zero off-diagonal strain components. In addition, even when the active region is completely relaxed in such structures, there remains a small degree of anisotropy that originates from the fundamental symmetry lowering at the material interfaces. In this dissertation, we make efforts to: a) investigate the effects of atomistic strain distributions in realistic multiple dot-in-nanowire In0.08Ga0.92N/GaN structures, as reported in some recent experiments; b) compare the emission characteristics of c-axis and m-axis oriented optical structures (i.e. laser structure); c) explore possibility of improving optical transition probability (rate) via engineering the optical cavity spacer dot size, aspect ratio, Indium mole fraction, and crystal growth direction for precise control over nanowire geometry and high material quality, d) numerically investigate and demonstrate lasing from nonpolar p-i-n core−shell InGaN/GaN multiple quantum dots in nanowires under electrical injection at room temperature, e) carry out detailed numerical investigation with a goal to optimize optical gain, lasing threshold, dynamic response, and device performance of these ultrafast laser structures, and f) explore viability of nonpolar architecture for nanolaser for providing a route forward for integrable, electrically injected nanowire laser for novel nanophotonic applications. The core simulations are performed with an augmented version of the open-source NEMO 3-D software that uses a fully-atomistic valence force-field (VFF) for strain distributions and empirical sp3s*-spin tight-binding model to compute the electronic structure. Both linear and nonlinear components of internal polarization field have been included using a recently proposed first-principles based polarization model. When compared to conventional c-plane based polar structures, the nonpolar device, overall, exhibits a much weaker (yet non-zero) internal potential and improved emission characteristics. In particular, we have found that the m-plane structure exhibits a much smaller (peak ~18.5 mV) internal potential than the c-plane counterpart (peak ~242 mV). However, the fundamental atomicity in the active region results in pronounced anisotropy in the emission characteristic. The energy bandgap is found to be little larger (3.24 eV) in the m-plane structure than in the c-plane device (3.15 eV). With a stronger wavefunction overlap, m-plane clearly offers a higher optical transition probability. Yet, the overall yield in these nonpolar structures suffers from the presence of a strong localization of wavefunctions, which confines the carriers (electrons and holes) in just one (lowest) quantum disk. As for design optimization, it is found that increasing the spacer size (i.e. disk separation) leads to a higher transition rate. Furthermore, detailed analysis has been presented comparing the performance of c-plane, m-plane and the a-plane based InGaN disk-in-wire structures as they show promise in novel optoelectronic applications. It is found that the magnitude of the net polarization potential in the non-polar m-plane and a-plane structures is much smaller (~5 mV) than the polar c-plane counterpart (~129 mV). This particular finding eventually leads to the formation of strongly localized wavefunctions and higher optical transition probabilities in non-polar wurtzite structures. As for the terminal device characteristics, it is found that the disk-in-wire LED in the a-plane orientation offers the highest internal quantum efficiency (IQE) as well as the smallest efficiency droop characteristics.