Download or read book High Performance Mid infrared emitting Quantum Cascade Lasers written by Jeremy Daniel Kirch and published by . This book was released on 2017 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt: The active region of conventional Quantum Cascade Lasers (QCLs) is composed of quantum wells and barriers of fixed alloy composition. As a consequence, they suffer severe carrier leakage from the upper laser level, as evidenced by low characteristic-temperature values for both the threshold current density and the slope efficiency, over a wide range of heatsink temperatures above room temperature. Here, we describe three methods by which the performance of these devices can be substantially increased. First, to suppress carrier leakage, the energy separation between the upper laser level and the next-higher energy state in the active region, E54 (or E43), needs to be increased; to this end, we propose 4.8μm-emitting, step-tapered active-region (STA) QCLs for nearly complete suppression of carrier leakage. Secondly, we introduce an 8-9μm-emitting STA-QCL design, which also employs a miniband-like carrier extraction scheme to ensures rapid depopulation of the lower laser level. We call the fast, carrier-extraction scheme resonant extraction (RE) since it involves resonant-(tunneling)-extraction not only from lower active-region levels but also from the lower laser level. When both the STA concept and miniband-like carrier extraction scheme are applied, in so-called STA-RE QCLs, it is shown that record-high internal differential efficiency hid values of ~ 86% can be achieved, by comparison to the prior state-of-the-art values of 57 to 67%. Furthermore, the fundamental upper limit for hid is shown be ~ 90%. With this improvement to internal differential efficiency, the wall-plug efficiency, hwp of mid-infrared-emitting QCLs should be ~34% higher than previously predicted, with hwp reaching values in excess of 40% for 4.6μm-emitting QCLs. Preliminary results from 5.0μm-emitting STA-RE QCLs are shown. Lastly, we show how single QCL emitters can be monolithically beam-combined to create High-Index-Contrast Photonic-Crystal (HC-PC) lasers as a means to coherently scale a QCL's output power while maintaining high beam quality, even under continuous-wave (CW) operating conditions. We present one such structure, which provided an output power of 5.5 W in a far-field beam pattern with lobewidths ~1.65 times the diffraction limit, and 82% energy contained in the central lobe. Methods to further improve on this result are also discussed.
Download or read book Mid Infrared and Terahertz Quantum Cascade Lasers written by Dan Botez and published by Cambridge University Press. This book was released on 2023-09-14 with total page 552 pages. Available in PDF, EPUB and Kindle. Book excerpt: Learn how the rapidly expanding area of mid-infrared and terahertz photonics has been revolutionized in this comprehensive overview. State-of-the-art practical applications are supported by real-life examples and expert guidance. Also featuring fundamental theory enabling you to improve performance of both existing and future devices.
Download or read book High Power and Efficient Mid infrared Emitting Quantum Cascade Lasers written by Suraj Suri and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mid infrared Quantum Cascade Lasers for Chaos Secure Communications written by Olivier Spitz and published by Springer Nature. This book was released on 2021-05-15 with total page 179 pages. Available in PDF, EPUB and Kindle. Book excerpt: The mid-infrared domain is a promising optical domain because it holds two transparency atmospheric windows, as well as the fingerprint of many chemical compounds. Quantum cascade lasers (QCLs) are one of the available sources in this domain and have already been proven useful for spectroscopic applications and free-space communications. This thesis demonstrates how to implement a private free-space communication relying on mid-infrared optical chaos and this requires an accurate cartography of non-linear phenomena in quantum cascade lasers. This private transmission is made possible by the chaos synchronization of two twin QCLs. Chaos in QCLs can be generated under optical injection or external optical feedback. Depending on the parameters of the optical feedback, QCLs can exhibit several non-linear phenomena in addition to chaos. Similarities exist between QCLs and laser diodes when the chaotic dropouts are synchronized with an external modulation, and this effect is known as the entrainment phenomenon. With a cross-polarization reinjection technique, QCLs can generate all-optical square-waves. Eventually, it is possible to trigger optical extreme events in QCLs with tilted optical feedback. All these experimental results allow a better understanding of the non-linear dynamics of QCLs and will extend the potential applications of this kind of semiconductor lasers.
Download or read book Nonlinear Photonics in Mid infrared Quantum Cascade Lasers written by Louise Jumpertz and published by Springer. This book was released on 2017-08-31 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents the first comprehensive analysis of quantum cascade laser nonlinear dynamics and includes the first observation of a temporal chaotic behavior in quantum cascade lasers. It also provides the first analysis of optical instabilities in the mid-infrared range. Mid-infrared quantum cascade lasers are unipolar semiconductor lasers, which have become widely used in applications such as gas spectroscopy, free-space communications or optical countermeasures. Applying external perturbations such as optical feedback or optical injection leads to a strong modification of the quantum cascade laser properties. Optical feedback impacts the static properties of mid-infrared Fabry–Perot and distributed feedback quantum cascade lasers, inducing power increase; threshold reduction; modification of the optical spectrum, which can become either single- or multimode; and enhanced beam quality in broad-area transverse multimode lasers. It also leads to a different dynamical behavior, and a quantum cascade laser subject to optical feedback can oscillate periodically or even become chaotic. A quantum cascade laser under external control could therefore be a source with enhanced properties for the usual mid-infrared applications, but could also address new applications such as tunable photonic oscillators, extreme events generators, chaotic Light Detection and Ranging (LIDAR), chaos-based secured communications or unpredictable countermeasures.
Download or read book Mid Infrared and Terahertz Quantum Cascade Lasers written by Dan Botez and published by Cambridge University Press. This book was released on 2023-06-30 with total page 551 pages. Available in PDF, EPUB and Kindle. Book excerpt: A state-of-the-art overview of this rapidly expanding field, featuring fundamental theory, practical applications, and real-life examples.
Download or read book High Efficiency and High Power Mid Wave Infrared Cascade Lasers written by and published by . This book was released on 2009 with total page 65 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum cascade laser (QCL) performance continues to improve towards the requirements of applications such as infrared counter measures. However, key metrics, such as wall-plug efficiency (WPE), are still not fully met. DARPA's EMIL program continues to support progress in QCLs, and this report summarizes the Princeton team's work during Phase I of this program. Although the work systematically addressed all major facets of efficiency, the greatest advancements involved injection designs, which improved almost all efficiency components. Strain compensated QCLs with heterogeneous injectors produced low voltage defect. The active core consisted of interdigitated undoped and doped injectors followed by nominally identical optical transitions. The undoped injectors were designed with reduced voltage defect while the doped injector designs were more conventional. The measured average voltage defect was less than 79 meV. At 80 K, a 2.3 mm long, back facet high reflectance coated laser had an emission wavelength of 4.7 micrometers and output 2.3 W pulsed power with 19% peak WPE. Other QCLs emitting at 4.2 micrometers featured a low voltage defect and short injector with only four quantum wells. Devices with a voltage defect of 20 meV and a record voltage efficiency of 91% were demonstrated for pulsed operation at 180 K. Voltage efficiencies of greater than 80% were exhibited at room temperature. WPEs ranging from 21% at cryogenic temperatures to 5.3% at room temperature were achieved. Interface roughness effects were analyzed as in homogeneous broadening, explaining the temperature dependent QCL gain spectra and suggesting improved designs. Specifically, density-matrix theory revealed benefits from stronger coupling between injector and upper laser level that led to low-temperature pulsed QCLs nearing 50% WPE.
Download or read book Mid Infrared Quantum Cascade Lasers written by Alfredo Bismuto and published by LAP Lambert Academic Publishing. This book was released on 2012-02 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work describes the work performed by the author at the ETH Zurich, under the supervision of Prof. Jerome Faist on the optimization of high performance quantum cascade lasers (QCLs) in the Mid-IR spectral region. The main factors influencing laser performance have therefore been analyzed. In particular the optimization of the laser design in order to improve the electron tranport and the optical gain. In addition a detailed analysis of the fabrication process is performed and a novel process scheme is presented for buried heterostructure lasers.
Download or read book Solid State Mid Infrared Laser Sources written by Irina T. Sorokina and published by Springer Science & Business Media. This book was released on 2003-09-04 with total page 600 pages. Available in PDF, EPUB and Kindle. Book excerpt: This collection of authoritative reviews by leading experts provides a broad and instructive introduction to the most advanced techniques for generating coherent light in the mid-infrared region of the spectrum. With a wealth of up-to-date references – also available online.
Download or read book Laser based Mid infrared Sources and Applications written by Konstantin L. Vodopyanov and published by John Wiley & Sons. This book was released on 2020-06-25 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt: An important guide to the major techniques for generating coherent light in the mid-infrared region of the spectrum Laser-based Mid-infrared Sources and Applications gives a comprehensive overview of the existing methods for generating coherent light in the important yet difficult-to-reach mid-infrared region of the spectrum (2–20 μm) and their applications. The book describes major approaches for mid-infrared light generation including ion-doped solid-state lasers, fiber lasers, semiconductor lasers, and laser sources based on nonlinear optical frequency conversion, and reviews a range of applications: spectral recognition of molecules and trace gas sensing, biomedical and military applications, high-field physics and attoscience, and others. Every chapter starts with the fundamentals for a given technique that enables self-directed study, while extensive references help conduct deeper research. Laser-based Mid-infrared Sources and Applications provides up-to-date information on the state-of the art mid-infrared sources, discusses in detail the advancements made over the last two decades such as microresonators and interband cascade lasers, and explores novel approaches that are currently subjects of intense research such as supercontinuum and frequency combs generation. This important book: • Explains the fundamental principles and major techniques for coherent mid-infrared light generation • Discusses recent advancements and current cutting-edge research in the field • Highlights important biomedical, environmental, and military applications Written for researchers, academics, students, and engineers from different disciplines, the book helps navigate the rapidly expanding field of mid-infrared laser-based technologies.
Download or read book High Power High Beam Quality Mid infrared Quantum Cascade Lasers written by Jae Ha Ryu and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Coherent power scaling of quantum cascade lasers (QCLs) for high-power, single-mode continuous-wave (CW) operation has proven to be quite a difficult task - while the device volume could be scaled for higher output power, many other factors such as beam quality and thermal resistance are negatively impacted if the device design is not carefully considered. The main objective of this work has been to develop methods for realizing high continuous-wave (CW) output power QCLs with high beam quality and minimal beam steering. One attractive approach for tackling this problem is the use of resonant leaky-wave-coupled antiguided phase-locked laser arrays. This dissertation focusses on two approaches to achieve high coherent power: 1) one alternate to the resonant leaky-wave-coupled antiguided phase-locked array concept, so called 'reverse-taper'laser; and 2) one combining grating-coupled surface-emitting lasers (GCSELs) with resonant leaky-wave-coupled antiguided phase-locked arrays, where each array element is coupled in both the lateral and longitudinal direction; thus, has a potential for multi-watt -CW surface-emitted output powers with good beam quality and narrow spectral linewidth. The novel geometry reverse-taper QCL device can scale the output power while maintaining good beam quality and beam stability - the tapered region scales the output power, while the emitting facet is located at the narrow-end taper section, which provides mode filtering by suppressing high-order spatial modes. A small degree of collimated-beam centroid movement (
Download or read book Quantum Cascade Lasers written by Jérôme Faist and published by Oxford University Press. This book was released on 2013-03-14 with total page 321 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book describes the physics, fabrication technology, and applications of the quantum cascade laser.
Download or read book Mid infrared emitting Quantum Cascade Lasers on Metamorphic Buffer Layers written by Ayushi Rajeev and published by . This book was released on 2019 with total page 107 pages. Available in PDF, EPUB and Kindle. Book excerpt: When using conventional substrates, such as InP and GaAs, the materials constituting the superlattice (SL) core region of the quantum cascade laser (QCL) are constrained by strain-induced critical-thickness limitations. Metamorphic buffer layers (MBLs) can serve as "virtual substrates" with a designer-chosen surface lattice constant, thus expanding the compositional-design space for a variety of device structures, including short-wavelength QCLs. An optimized short-wavelength (3.4 [mu]m) single-phonon-resonant (SPR)+ miniband extraction QCL design, grown on an [InxGa1-xAs] MBL, is presented along with the optical and thermal device considerations in play. MBLs can be grown with a variety of graded regions such as linear composition grade from GaAs to [InxGa1-xAs] or by employing dislocation filters between Si substrate and InP. QCL and test superlattices' regrowth on these MBLs with the corresponding materials and device analysis, is presented in this work. In addition to the materials limitation for the design of QCL devices, the requirement to have the constituent layers (1-5 nm) to be precisely controlled in the various compositions and thicknesses, is a challenge. Interfacial grading in strained SLs is studied via atom probe tomography for SLs with various layer thicknesses and relative lattice strains. The tip reconstructions are analyzed by fitting the interfaces to diffusion profiles. Mechanisms possible for the observed interdiffusion profile, such as surface segregation and/or bulk diffusion, are discussed. With an understanding of the compositional gradient at the interfaces, together with optimized QCL designs and regrowth on the MBLs, short-wavelength QCLs with high performances can be achieved.
Download or read book Mid Infrared Quantum Dot Quantum Cascade Laser written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In the framework of a microscopic model for intersubband gain from electrically pumped quantum-dot structures we investigate electrically pumped quantum-dots as active material for a mid-infrared quantum cascade laser. Our previous calculations have indicated that these structures could operate with reduced threshold current densities while also achieving a modal gain comparable to that of quantum well active materials. We study the influence of two important quantum-dot material parameters, here, namely inhomogeneous broadening and quantum-dot sheet density, on the performance of a proposed quantum cascade laser design. In terms of achieving a positive modal net gain, a high quantum-dot density can compensate for moderately high inhomogeneous broadening, but at a cost of increased threshold current density. By minimizing quantum-dot density with presently achievable inhomogeneous broadening and total losses, significantly lower threshold densities than those reported in quantum-well quantum-cascade lasers are predicted by our theory.
Download or read book Highly Efficient and Reliable Quantum Cascade Lasers written by Benjamin Knipfer and published by . This book was released on 2021 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mid-infrared (mid-IR) quantum cascade lasers (QCLs) have been commercially available for low power applications, however, while the desire for higher power devices is present, the efficiency and reliability are severe limitations. This work takes a multi-faceted approach to improving the reliability and efficiency of QCLs including: the identification and mitigation of failure mechanisms under high power continuous wave (CW) and quasi-continuous wave (QCW) operation, optical and thermal modeling of devices to further reduce active region heating, verification of these models using charge-coupled device (CCD) based thermoreflectance, and the introduction of interface roughness (IFR) engineered devices to reduce IFR scattering and leakage. Atom probe tomography (APT) is also employed to investigate the amount of aluminum and gallium incorporation in thin InAlAs barriers and InGaAs wells. It was found that thin layers with thicknesses less than 2 nm require an intentional aluminum or gallium overshoot in the gas phase during growth to grow the targeted compositions. This was verified when the overshoot in thin barriers resulted in the convergence of modeled and experimental emitting wavelengths. APT was also used to interrogate a few key interfaces within a 40 stage strain-compensated QCL emitting near 4.6 [mu]m. This interrogation yielded both in-plane and axial IFR parameters for barriers of high and low aluminum incorporation, and in turn high and low strain, respectively. It was found that the barrier with the highest aluminum target had a nearly 50% larger root mean square (RMS) roughness when compared to the shorter barriers. As the IFR scattering is proportional to the square of both the RMS roughness and in-plane correlation length, this finding has a significant impact on the IFR scattering and leakage. The variable IFR parameters, axial correlation length, graded interfaces, graded lattice constants, graded conduction band edge, and quaternary alloy disorder (AD) scattering have been incorporated into a scattering model. Results from this model suggest lower global lifetimes and significantly reduced transition efficiencies which results in lower IFR leakage, however, if electronic temperatures from software using non-equilibrium Green's function (NGEF) is incorporated, leakage currents remain high.
Download or read book 2 d Coherent Power Scaling of Mid infrared Quantum Cascade Lasers written by Christopher Andrew Sigler and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Scaling the continuous-wave (CW) power of quantum cascade lasers (QCLs) beyond ~5 W has proven difficult, and beam-quality degradation is common when scaling the device volume for high power. The primary objective of this work was to develop methods for spatially-coherent power scaling of mid-infrared-emitting QCLs to high CW powers. Two approaches were investigated: 1) resonant leaky-wave-coupled antiguided phase-locked laser arrays; and 2) grating-coupled surface-emitting lasers (GCSELs). These two approaches can be combined to realize high surface-emitted powers in a spatially and temporally coherent beam pattern. Optical and thermal models of planarized leaky-wave-coupled phase-locked QCL arrays were coupled together to investigate the influence of thermal lensing on modal behavior. Self-focusing under thermally-induced index variations across the array were found to impact the field profile and promote multi-moding due to gain spatial hole burning. Two techniques were found to mitigate this effect: 1) employing anti-resonant reflective-optical waveguide terminations outside the array; and 2) chirping the element width across the array to obtain identical optically-equivalent widths under CW operation, eliminating thermal lensing at a particular operating condition. Five-element phase-locked arrays of 4.7 μm-emitting QCLs were demonstrated which operate in a near-diffraction-limited beam (primarily in the in-phase array mode) to 5.1 W peak pulsed power, in agreement with simulations. Spectrally resolved near- and far-field measurements indicate that the wide spectral bandwidth of the QCL core promotes multi-mode operation at high drive levels. An optimized array design was identified to allow sole in-phase mode operation to high drive levels above threshold, indicating that full spatial coherence to high output powers does not require full temporal coherence for phase-locked laser arrays. Lastly, a novel method for obtaining a single-lobed beam pattern from transverse magnetic (TM)-polarized GCSELs is proposed: resonant coupling of the optical mode of a QCL to the antisymmetric surface plasmon mode of a 2nd-order distributed feedback metal/semiconductor grating results in strong antisymmetric-mode absorption. Lasing in the symmetric mode, resulting in a single-lobed far-field beam pattern from the substrate emission, is strongly favored around resonance. For infinite-length devices, the symmetric mode has negligible absorption loss while still being efficiently outcoupled by the grating.
Download or read book Quantum Cascade Lasers and Optical Metamaterials written by Matthew Escarra and published by LAP Lambert Academic Publishing. This book was released on 2013-01 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum cascade (QC) lasers have application in areas such as medical diagnostics and homeland security. Optical metamaterials have novel interactions with light and potential application for sub-wavelength imaging and optical cloaking. This work first explores new approaches to designing QC lasers. High performance QC lasers are described with a voltage defect of only 19 meV, resulting in record voltage efficiency. Lasers with ultra-strong coupling attain 50% wall-plug efficiency. The thermoelectric effect is measured for the first time within QC lasers, informing further performance enhancements. This work then describes two efforts to improve mid-IR metamaterials. Negative refraction bandwidth and dispersion properties are improved through the use of multiple-metamaterial stacks. QC gain regions are added to these metamaterials to reduce their absorption loss. Finally, QC lasers are developed for trace gas sensing of CO2 isotopes, and a techno-economic model is used to value improved CO2 isotope-based sequestration leakage monitoring. QC laser applications in non-invasive tissue measurements, inter-planetary sensors, C60 spectroscopy, and IR countermeasures are also examined.
