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Investigations Of Quantum Dot Lasers
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Book Synopsis Investigations of Quantum Dot Lasers by :
Download or read book Investigations of Quantum Dot Lasers written by and published by . This book was released on 2000 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: A detailed theoretical and experimental study of the application of quantum dot active regions to edge-emitting lasers and electro-optic modulators was undertaken. The theoretical work included calculation of the bandstructure and electronic properties of self-assembled quantum dots, carrier scattering rates and the oscillator strength and gain of interband and intersubband transitions. Experimental work included growth of self-organized dots and active devices, their fabrication and characterization. Very narrow PL linewidths in the dots were achieved (approx. 19 meV) by the incorporation of buried stressor dots. The dynamics of hot carriers and carrier relaxation rates were characterized by differential transmission spectroscopy. It was established from a variety of measurements and calculations that electron-hole scattering is the dominant carrier relaxation mechanism in quantum dots. Modulation bandwidth measurements on QD lasers at cryogenic temperatures (f-3dB approx. 30 GHz at T = 100K) confirmed the role of electron-hole scattering. The electron-optic coefficients of quantum dots was measured for the first time and a QD modulator has been demonstrated. Bistability and gain switching has also been observed and characterized. The unique carrier dynamics in quantum dots is favorable for the realization of intersubband emitters and detectors, and these have been investigated.
Book Synopsis Quantum Dot Lasers by : Victor Mikhailovich Ustinov
Download or read book Quantum Dot Lasers written by Victor Mikhailovich Ustinov and published by . This book was released on 2003 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Investigation of Quantum Dot Lasers by :
Download or read book Investigation of Quantum Dot Lasers written by and published by . This book was released on 2004 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the first demonstration of room-temperature operation of self-assembled quantum dot (QD) lasers about a decade ago, there have been great strides in improving the characteristics and performance of these lasers. They currently match or surpass the performance of quantum well lasers. However, there are unique problems that limit the performance of conventional separate confinement heterostructure (SCH) QD lasers compared to what is expected from "ideal" lasers with near singular density of states. In the study reported here, unique insights and solutions to these problems are demonstrated and reliable quantum dot lasers that surpass quantum well lasers in performance characteristics are developed. By utilizing the concepts of tunnel injection and p-doping, 1.0 micrometer and 1.3 micrometer quantum dot lasers with high differential gain, modulation bandwidth ^25GHz, a factor less than unity, and zero chirp have been achieved. This final report summarizes the successful design, fabrication, and characterization of high performance 1.0 micrometer QD-Distributed-Feedback (DFB) lasers, 1.0 micrometer QD-Tunnel-Injection lasers (undoped and p-doped), and 1.3 micrometer p-doped QD lasers. The authors have demonstrated record performance of these unique devices in terms of differential gain, modulation bandwidth, temperature dependence, chirp, and linewidth enhancement factor. (16 figures, 14 refs.).
Book Synopsis Quantum Dot Devices by : Zhiming M. Wang
Download or read book Quantum Dot Devices written by Zhiming M. Wang and published by Springer Science & Business Media. This book was released on 2012-05-24 with total page 375 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum dots as nanomaterials have been extensively investigated in the past several decades from growth to characterization to applications. As the basis of future developments in the field, this book collects a series of state-of-the-art chapters on the current status of quantum dot devices and how these devices take advantage of quantum features. Written by 56 leading experts from 14 countries, the chapters cover numerous quantum dot applications, including lasers, LEDs, detectors, amplifiers, switches, transistors, and solar cells. Quantum Dot Devices is appropriate for researchers of all levels of experience with an interest in epitaxial and/or colloidal quantum dots. It provides the beginner with the necessary overview of this exciting field and those more experienced with a comprehensive reference source.
Book Synopsis Quantum Confined Laser Devices by : Peter Blood
Download or read book Quantum Confined Laser Devices written by Peter Blood and published by Oxford University Press. This book was released on 2015 with total page 433 pages. Available in PDF, EPUB and Kindle. Book excerpt: The semiconductor laser, invented over 50 years ago, has had an enormous impact on the digital technologies that now dominate so many applications in business, commerce and the home. The laser is used in all types of optical fibre communication networks that enable the operation of the internet, e-mail, voice and skype transmission. Approximately one billion are produced each year for a market valued at around $5 billion. Nearly all semiconductor lasers now use extremely thin layers of light emitting materials (quantum well lasers). Increasingly smaller nanostructures are used in the form of quantum dots. The impact of the semiconductor laser is surprising in the light of the complexity of the physical processes that determine the operation of every device. This text takes the reader from the fundamental optical gain and carrier recombination processes in quantum wells and quantum dots, through descriptions of common device structures to an understanding of their operating characteristics. It has a consistent treatment of both quantum dot and quantum well structures taking full account of their dimensionality, which provides the reader with a complete account of contemporary quantum confined laser diodes. It includes plenty of illustrations from both model calculations and experimental observations. There are numerous exercises, many designed to give a feel for values of key parameters and experience obtaining quantitative results from equations. Some challenging concepts, previously the subject matter of research monographs, are treated here at this level for the first time. To request a copy of the Solutions Manual, visit http: //global.oup.com/uk/academic/physics/admin/solutions.
Book Synopsis Quantum Dot Lasers on Silicon by : Bozhang Dong
Download or read book Quantum Dot Lasers on Silicon written by Bozhang Dong and published by Springer Nature. This book was released on 2023-02-04 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides guidelines and design rules for developing high-performance, low-cost, and energy-efficient quantum-dot (QD) lasers for silicon photonic integrated circuits (PIC), optical frequency comb generation, and quantum information systems. To this end, the nonlinear properties and dynamics of QD lasers on silicon are investigated in depth by both theoretical analysis and experiment. This book aims at addressing four issues encountered in developing silicon PIC: 1) The instability of laser emission caused by the chip-scale back-reflection. During photonic integration, the chip-scale back-reflection is usually responsible for the generation of severe instability (i.e., coherence collapse) from the on-chip source. As a consequence, the transmission performance of the chip could be largely degraded. To overcome this issue, we investigate the nonlinear properties and dynamics of QD laser on Si in this book to understand how can it be applied to isolator-free photonic integration in which the expensive optical isolator can be avoided. Results show that the QD laser exhibits a high degree of tolerance for chip-scale back-reflections in absence of any instability, which is a promising solution for isolator-free applications. 2) The degradation of laser performance at a high operating temperature. In this era of Internet-of-Thing (IoT), about 40% of energy is consumed for cooling in the data center. In this context, it is important to develop a high-temperature continuous-wave (CW) emitted laser source. In this book, we introduce a single-mode distributed feedback (DFB) QD laser with a design of optical wavelength detuning (OWD). By taking advantage of the OWD technique and the high-performance QD with high thermal stability, all the static and dynamical performances of the QD device are improved when the operating temperature is high. This study paves the way for developing uncooled and isolator-free PIC. 3) The limited phase noise level and optical bandwidth of the laser are the bottlenecks for further increasing the transmission capacity. To improve the transmission capacity and meet the requirement of the next generation of high-speed optical communication, we introduce the QD-based optical frequency comb (OFC) laser in this book. Benefiting from the gain broadening effect and the low-noise properties of QD, the OFC laser is realized with high optical bandwidth and low phase noise. We also provide approaches to further improve the laser performance, including the external optical feedback and the optical injection. 4) Platform with rich optical nonlinearities is highly desired by future integrated quantum technologies. In this book, we investigate the nonlinear properties and four-wave mixing (FWM) of QD laser on Si. This study reveals that the FWM efficiency of QD laser is more than ten times higher than that of quantum-well laser, which gives insight into developing a QD-based silicon platform for quantum states of light generation. Based on the results in this book, scientists, researchers, and engineers can come up with an informed judgment in utilizing the QD laser for applications ranging from classical silicon PIC to integrated quantum technologies.
Book Synopsis Nonlinear and Nonequilibrium Dynamics of Quantum-Dot Optoelectronic Devices by : Benjamin Lingnau
Download or read book Nonlinear and Nonequilibrium Dynamics of Quantum-Dot Optoelectronic Devices written by Benjamin Lingnau and published by Springer. This book was released on 2015-12-14 with total page 203 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis sheds light on the unique dynamics of optoelectronic devices based on semiconductor quantum-dots. The complex scattering processes involved in filling the optically active quantum-dot states and the presence of charge-carrier nonequilibrium conditions are identified as sources for the distinct dynamical behavior of quantum-dot based devices. Comprehensive theoretical models, which allow for an accurate description of such devices, are presented and applied to recent experimental observations. The low sensitivity of quantum-dot lasers to optical perturbations is directly attributed to their unique charge-carrier dynamics and amplitude-phase-coupling, which is found not to be accurately described by conventional approaches. The potential of quantum-dot semiconductor optical amplifiers for novel applications such as simultaneous multi-state amplification, ultra-wide wavelength conversion, and coherent pulse shaping is investigated. The scattering mechanisms and the unique electronic structure of semiconductor quantum-dots are found to make such devices prime candidates for the implementation of next-generation optoelectronic applications, which could significantly simplify optical telecommunication networks and open up novel high-speed data transmission schemes.
Book Synopsis Dynamics of Quantum Dot Lasers by : Christian Otto
Download or read book Dynamics of Quantum Dot Lasers written by Christian Otto and published by Springer Science & Business Media. This book was released on 2014-01-21 with total page 301 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Self-Assembled Quantum Dots by : Zhiming M Wang
Download or read book Self-Assembled Quantum Dots written by Zhiming M Wang and published by Springer Science & Business Media. This book was released on 2007-11-29 with total page 470 pages. Available in PDF, EPUB and Kindle. Book excerpt: This multidisciplinary book provides up-to-date coverage of carrier and spin dynamics and energy transfer and structural interaction among nanostructures. Coverage also includes current device applications such as quantum dot lasers and detectors, as well as future applications to quantum information processing. The book will serve as a reference for anyone working with or planning to work with quantum dots.
Book Synopsis Quantum Dots for Quantum Information Technologies by : Peter Michler
Download or read book Quantum Dots for Quantum Information Technologies written by Peter Michler and published by Springer. This book was released on 2017-06-01 with total page 457 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book highlights the most recent developments in quantum dot spin physics and the generation of deterministic superior non-classical light states with quantum dots. In particular, it addresses single quantum dot spin manipulation, spin-photon entanglement and the generation of single-photon and entangled photon pair states with nearly ideal properties. The role of semiconductor microcavities, nanophotonic interfaces as well as quantum photonic integrated circuits is emphasized. The latest theoretical and experimental studies of phonon-dressed light matter interaction, single-dot lasing and resonance fluorescence in QD cavity systems are also provided. The book is written by the leading experts in the field.
Book Synopsis The Physics and Engineering of Compact Quantum Dot-based Lasers for Biophotonics by : Edik U. Rafailov
Download or read book The Physics and Engineering of Compact Quantum Dot-based Lasers for Biophotonics written by Edik U. Rafailov and published by John Wiley & Sons. This book was released on 2013-12-30 with total page 349 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis High Power Ultra-short Pulse Quantum-dot Lasers by : Daniil Nikitichev
Download or read book High Power Ultra-short Pulse Quantum-dot Lasers written by Daniil Nikitichev and published by . This book was released on 2012-08-12 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, novel multi-section laser diodes based on quantum-dot material are designed and investigated which exhibit a number of advantages such as low threshold current density; temperature-insensitivity and suppress carrier diffusion due to discrete nature of density of state of quantum-dots. The spectral versatility in the range of 1.1 μm - 1.3 μm wavelengths is demonstrated through novel mode-locking regimes such as dual-wavelength mode-locking, wavelength bistability and broad tunability. Moreover, broad pulse repetition rate tuning using an external cavity configuration is presented. A high peak power of 17.7 W was generated from the quantum-dot laser as a result of the tapered geometry of the gain section of the laser has led to successful application of such device for two-photon imaging. Dual-wavelength mode-locking is demonstrated via ground (?=1180 nm) and excited (?=1263 nm) spectral bands with optical pulses from both states simultaneously in the 5-layer quantum-dot two-section diode laser. The widest spectral separation of 83 nm between the modes was achieved in a dual-wavelength mode-locked non-vibronic laser. Power and wavelength bistability are achieved in a mode-locked multi-section laser which active region incorporates non-identical QD layers grown by molecular beam epitaxy. As a result the wavelength can be electronically controlled between 1245 nm and 1290 nm by applying different voltages to the saturable absorber. Mode-locked or continuous-wave regimes are observed for both wavelengths over a 260 mA - 330 mA current ranges with average power up to 28 mW and 31 mW, respectively. In mode-locked regime, a repetition rate of 10 GHz of optical pulses as short as 4 ps is observed. Noticeable hysteresis of average power for different bias conditions is also demonstrated. The wavelength and power bistability in QD lasers are potentially suitable for flip-flop memory application. In addition, a unique mode-locked regime at expense of the reverse bias with 50 nm wavelength tuning range from 1245 nm to 1290 nm is also presented. Broad repetition rate tunability is shown from quantum-dot external cavity mode-locked 1.27 μm laser. The repetition rate from record low of 191 MHz to 1 GHz from fundamental mode-locking was achieved. Harmonic mode-locking allows further to increase tuning up to 6.8 GHz (34th-order harmonic) from 200 MHz fundamental mode-locking. High peak power of 1.5 W can be generated directly from two-section 4 mm long laser with bent waveguide at angle of 7° at 1.14 GHz repetition rate without the use of any pulse compression and optical amplifier. Stable mode-locking with an average power up to 60 mW, corresponding to 25 pJ pulse energy is also obtained at a repetition frequency of 2.4 GHz. The minimum time-bandwidth product of 1.01 is obtained with the pulse duration of 8.4 ps. Novel tapered quantum-dot lasers with a gain-guided geometry operating in a passively mode-locked regime have been investigated, using structures that incorporated either 5 or 10 quantum dot layers. The peak power of 3.6 W is achieved with pulse duration of 3.2 ps. Furthermore, the record peak power of 17.7 W and transform limited pulses of 672 fs were achieved with optimized structure. The generation of picosecond pulses with high average power of up to 209 mW was demonstrated, corresponding to 14.2 pJ pulse energy. The improved optical parameters of the tapered laser enable to achieve nonlinear images of fluorescent beads. Thus it is for the first time that QD based compact monolithic device enables to image biological samples using two-photon microscopy imaging technique.
Book Synopsis Quantum Dot Based Mode-locked Semiconductor Lasers and Applications by : Jimyung Kim
Download or read book Quantum Dot Based Mode-locked Semiconductor Lasers and Applications written by Jimyung Kim and published by . This book was released on 2010 with total page 115 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation, self-assembled InAs/InGaAs quantum dot Fabry-Pérot lasers and mode-locked lasers are investigated. The mode-locked lasers investigated include monolithic and curved two-section devices, and colliding pulse mode-locked diode lasers. Ridge waveguide semiconductor lasers have been designed and fabricated by wet etching processes. Electroluminescence of the quantum dot lasers is studied. Cavity length dependent lasing via ground state and/or excited state transitions is observed from quantum dot lasers and the optical gain from both transitions is measured. Stable optical pulse trains via ground and excited state transitions are generated using a grating coupled external cavity with a curved two-section device. Large differences in the applied reverse bias voltage on the saturable absorber are observed for stable mode-locking from the excited and ground state mode-locking regimes. The optical pulses from quantum dot mode-locked lasers are investigated in terms of chirp sign and linear chirp magnitude. Upchirped pulses with large linear chirp magnitude are observed from both ground and excited states. Externally compressed pulse widths from the ground and excited states are 1.2 ps and 970 fs, respectively. Ground state optical pulses from monolithic mode-locked lasers e.g., two-section devices and colliding pulse mode-locked lasers, are also studied. Transformed limited optical pulses (~4.5 ps) are generated from a colliding pulse mode-locked semiconductor laser. The above threshold linewidth enhancement factor of quantum dot Fabry-Pérot lasers is measured using the continuous wave injection locking method. A strong spectral dependence of the linewidth enhancement factor is observed around the gain peak. The measured linewidth enhancement factor is highest at the gain peak, but becomes lower 10 nm away from the gain peak. The lowest linewidth enhancement factor is observed on the anti-Stokes side. The spectral dependence of the pulse duration from quantum dot based mode-locked lasers is also observed. Shorter pulses and reduced linear chirp are observed on the anti-Stokes side and externally compressed 660 fs pulses are achieved in this spectral regime. A novel clock recovery technique using passively mode-locked quantum dot lasers is investigated. The clock signal (~4 GHz) is recovered by injecting an interband optical pulse train to the saturable absorber section. The excited state clock signal is recovered through the ground state transition and vice-versa. Asymmetry in the locking bandwidth is observed. The measured locking bandwidth is 10 times wider when the excited state clock signal is recovered from the ground state injection, as compared to recovering a ground state clock signal from excited state injection.
Book Synopsis Numerical Modeling of Narrow-linewidth Quantum Dot Lasers by : Bjelica, Marko
Download or read book Numerical Modeling of Narrow-linewidth Quantum Dot Lasers written by Bjelica, Marko and published by kassel university press GmbH. This book was released on 2017-01-01 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: The quantization of the active laser medium has enabled numerous advances in fiber-optic communications, e.g., higher efficiency of laser diodes, higher modulation bandwidth, lower spectral linewidth of the emitted signal. In recent years the quantum dot lasers have demonstrated a strong potential to continue this trend, therefore, by progressing from standard quantum well to quantum dot designs, it can be expected that the quantum dot lasers will play an increasingly important role in future fiber-optic communications. The research work presented in this dissertation seeks to further develop the quantum dot laser designs and improve the understanding of complex operating conditions affecting the laser linewidth. This is achieved by developing a comprehensive laser simulator, that was applied to design and simulation of edge-emitting lasers and laser arrays. As a result, the optimized laser diodes have demonstrated a significantly lower linewidth compared to equivalent quantum well designs. Due to their narrow linewidth, the realized photonic devices can be a viable solution for high bit rate fiber-optic networks.
Book Synopsis Quantum Semiconductor Devices and Technologies by : Tom Pearsall
Download or read book Quantum Semiconductor Devices and Technologies written by Tom Pearsall and published by Springer Science & Business Media. This book was released on 2013-11-27 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt: stacked QD structure and is useful for examining the possibility of all optical measurement of stacked QD layers. Optical absorption spectra of self-assembled QDs has been little reported, and further investigation in necessary to study hole-burning memory. 2.5 Summary This chapter describes recent advances in quantum dot fabrication tech nologies, focusing on our self-formed quantum dot technologies including TSR quantum dots and SK-mode self-assembled quantum dots. As is described in this chapter, there are many possible device applications such as quantum dot tunneling memory devices, quantum dot fioating-dot gate FETs, quantum dot lasers, and quantum dot hole-burning memory devices. The quantum dot laser applications seem to be the most practicable among these applications. However, many problems remain to be solved before even this application becomes practical. The most important issue is to of self-assembled quantum dots more pre control the size and position cisely, with an accuracy on an atomic scale. The confinement must be enough to keep the separation energy between quantized energy levels high enough to get high-temperature characteristics. The lasing oscillation frequency should be fixed at 1.3 f.lITl or 1.5 f.lITl for optical communication. Phonon bottleneck problems should be solved by the optimization of device structures. Fortunately, there is much activity in the area of quantum dot lasers and, therefore, many breakthroughs will be made, along with the exploration of other new application areas.
Book Synopsis Noise, Dynamics and Squeezed Light in Quantum Dot and Interband Cascade Lasers by : Shiyuan Zhao
Download or read book Noise, Dynamics and Squeezed Light in Quantum Dot and Interband Cascade Lasers written by Shiyuan Zhao and published by Springer Nature. This book was released on with total page 245 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Photonics of Quantum-dot Nanomaterials and Devices by : Ortwin Hess
Download or read book Photonics of Quantum-dot Nanomaterials and Devices written by Ortwin Hess and published by World Scientific. This book was released on 2012 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt: 1. Introduction to photonic quantum dot nanomaterials and devices. 1.1. Physical properties of quantum dots. 1.2. Active semiconductor gain media. 1.3. Quantum dot lasers. 1.4. Laser cavities -- 2. Theory of quantum dot light-matter dynamics. 2.1. Rate equations. 2.2. Maxwell-Bloch equations. 2.3. Quantum luminescence equations. 2.4. Quantum theoretical description -- 3. Light meets matter I: microscopic carrier effect. 3.1. Dynamics in the active charge carrier plasma. 3.2. Dynamic level hole burning. 3.3. Ultrashort nonlinear gain and index dynamics. 3.4. Conclusion -- 4. Light meets matter II: mesoscopic space-time dynamics. 4.1. Introduction: transverse and longitudinal mode dynamics. 4.2. Influence of the transverse degree of freedom and nano-structuring on nearfield dynamics and spectra. 4.3. Longitudinal modes. 4.4. Coupled space-time dynamics. 4.5. Conclusion -- 5. Performance and characterisation: properties on large time and length scales. 5.1. Introduction. 5.2. Spatial and spectral beam quality. 5.3. Dynamic amplitude phase coupling. 5.4. Conclusion -- 6. Nonlinear pulse propagation in semiconductor quantum dot lasers. 6.1. Dynamic shaping of short optical pulses. 6.2. Nonlinear femtosecond dynamics. 6.3. Conclusion -- 7. High-speed dynamics. 7.1. Mode-locking in multi-section quantum dot lasers. 7.2. Dependence of pulse duration on injection current, bias voltage and device geometry. 7.3. Radio frequency spectra of the emitted light. 7.4. Short-pulse optimisation. 7.5. Conclusion -- 8. Quantum dot random lasers. 8.1. Spatially inhomogeneous semiconductor quantum dot ensembles. 8.2. Coherence properties. 8.3. Random lasing in semiconductor quantum dot ensembles. 8.4. Conclusion -- 9. Coherence properties of quantum dot micro-cavity lasers. 9.1. Introduction. 9.2. Radial signal propagation and coherence trapping. 9.3. Influence of disorder. 9.4. Conclusions
