Download or read book High Power Mid infrared Quantum Cascade Laser Array for Standoff Photoacoustic Chemical Detection written by Xing Chen and published by . This book was released on 2013 with total page 364 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum cascade lasers (QCLs) are compact, portable, powerful semiconductor laser sources with emission wavelengths from mid-infrared (mid-IR) to terahertz (THz) regions of the electromagnetic spectrum. Mid-IR (i.e. wavelengths from 3 to 20 μm) QCLs are of great importance in a wide range of applications such as trace gas sensing, environmental monitoring, free space communication, medical diagnosis and so on. High power QCLs are particularly important to applications such as infrared counter measure (IRCM) and standoff chemical detections. In such applications, the system performances critically depend on the amount of power a QCL can produce. This dissertation includes two major studies: the first part of the dissertation includes design, fabrication and characterization of high power mid-IR QCL arrays; the second part involves standoff chemical detection using QCLs as laser sources and photoacoustic effect as sensing technologies.
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 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 Widely Tunable and High Power Mid Infrared Quantum Cascade Lasers written by and published by . This book was released on 2001 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Single mode cw and pulsed distributed feedback (DFB) QC lasers with wide current tuning and high single mode power, have been realized at lambda app. = 4.6 nm; 5.2 nm, 8 nm and 9.5-10 nm and their trace gas sensing ability (parts per billion in volume or less) has been demonstrated by a variety of spectroscopic techniques. These devices, free-running and stabilized, had cw linewidths of 1 MHz and 10 KHz, respectively. Optical powers in excess of 0.5W (1W) at 300K (200K) was obtained in 75-stage structures; the cw operating temperature was increased to 175K using epitaxial-side heat sinking. New chirped superlattice active region designs yielded greater optical power per stage and allowed extension of the operating wavelength to 19 nm. These longwavelength QCLs use metal semiconductor waveguides supporting a surface plasmon mode, which allows greater optical confinement, and hence lower thresholds than conventional semiconductor waveguides of nearly double thickness. A QCL lasing simultaneously at two or more widely spaced wavelengths and a bidirectional QCL emitting different wavelengths for opposite bias polanty were demonstrated. Gain switching and active modelocking of QC lasers at 5 and 8 nm gave pulse widths of 90 ps and a few ps, respectively.
Download or read book Spectroscopic Applications of Terahertz Quantum Cascade Lasers written by Tasmim Alam and published by Cuvillier Verlag. This book was released on 2020-10-29 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum cascade lasers (QCLs) are attractive for high-resolution spectroscopy because they can provide high power and a narrow linewidth. They are particularly promising in the terahertz (THz) range since they can be used as local oscillators for heterodyne detection as well as transmitters for direct detection. However, THz QCL-based technologies are still under development and are limited by the lack of frequency tunability as well as the frequency and output power stability for free-running operation. In this dissertation, frequency tuning and linewidth of THz QCLs are studied in detail by using rotational spectroscopic features of molecular species. In molecular spectroscopy, the Doppler eff ect broadens the spectral lines of molecules in the gas phase at thermal equilibrium. Saturated absorption spectroscopy has been performed that allows for sub-Doppler resolution of the spectral features. One possible application is QCL frequency stabilization based on the Lamb dip. Since the tunability of the emission frequency is an essential requirement to use THz QCL for high-resolution spectroscopy, a new method has been developed that relies on near-infrared (NIR) optical excitation of the QCL rear-facet. A wide tuning range has been achieved by using this approach. The scheme is straightforward to implement, and the approach can be readily applied to a large class of THz QCLs. The frequency and output stability of the local oscillator has a direct impact on the performance and consistency of the heterodyne spectroscopy. A technique has been developed for a simultaneous stabilization of the frequency and output power by taking advantage of the frequency and power regulation by NIR excitation. The results presented in this thesis will enable the routine use of THz QCLs for spectroscopic applications in the near future.
Download or read book A Contribution to Active Infrared Laser Spectroscopy for Remote Substance Detection written by Jarvis, Jan-Philip and published by KIT Scientific Publishing. This book was released on 2017-12-04 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work we present a stand-off, long wave infrared (LWIR) spectroscopy system for remote detection of hazardous substances. The principle is based upon wavelength selective illumination using External Cavity Quantum Cascade Lasers, that are tunable in the LWIR wavelength range from 7.5 - 10 μm, in which most chemical substances exhibit a highly characteristic absorption behaviour.
Download or read book Widely Tunable and SI traceable Frequency comb stabilised Mid infrared Quantum Cascade Laser written by Dang Bao An Tran and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The thesis consists in developing a high-resolution mid-infrared spectrometer traceable to primary frequency standards and providing a unique combination of resolution, tunability, detection sensitivity and frequency control. A quantum cascade laser (QCL) emitting at 10.3 μm is phase locked to an optical frequency comb stabilized to a remote 1.55 μm ultra-stable reference developed at LNE-SYRTE, monitored against primary frequency standards and transferred to LPL via an active noise compensated fibre link. This results in a 0.1 Hz QCL linewidth, a stability below 10−15 at 1 s and an uncertainty on its absolute frequency below 4 × 10−14. Moreover, the setup allows the QCL to be widely scanned over 1.4 GHz while maintaining the highest stabilities and precision. This QCL was used to carry out saturated absorption spectroscopy of several molecules in a compact multipass cell. We demonstrated statistical uncertaintyon line-center frequencies at the kHz level and sub-10 kHz systematic uncertainty. We have recorded several singular K-doublets and many rovibrational transitions of methanol, in particular weak transitions and weak doublets - unreported so far. Precise parameters modelling trioxaneh ave been determined with only a few tens of rovibrational transitions recorded at unprecedented accuracy. The quadrupole hyperfine structure of an ammonia transition has been resolved for thefirst time. This setup constitutes a key element for the project aiming at the first observation of parity violation in molecules currently held at LPL, and, more generally, for various fields of physics, from atmospheric and interstellar physics to fundamental physics beyond the standard model.
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 0 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 The Application of Quantum Cascade Lasers to Mid infrared Gas Sensing written by Paul Richie Black and published by . This book was released on 2011 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis explains the development of a quantum cascade laser based gas sensor and the verification of performance of the resulting product. The capability to detect trace levels of multiple species in varying physical conditions, specifically high temperature is shown.Optical designs capable of allowing the measurement technique to be used in a variety of applications have been developed, specifically multi-pass gas absorption cells. The accurate, precise and high speed analysis of the resulting data is made possible by spectral analysis algorithms. These developments and techniques were then applied to high temperature spectroscopic measurements. Spectra recorded at Rutherford Appleton Laboratory were used to calibrate high temperature measurements. The performance of the technology was thoroughly tested at the National Physical Laboratory. The resulting sensors have since been used to study the exhaust gases produced by a variety engine types ranging from cars to ships as well as atmospheric measurements.
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 Distributed Feedback Quantum Cascade Laser Arrays for Chemical Sensing written by Benjamin Guocian Lee and published by . This book was released on 2009 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt: Achieving overlapped beams at extended distances can be important for a number of applications envisioned for DFB-QCL arrays, particularly remote sensing. Using the technique of spectral beam combining, the total angular divergence of the DFB-QCL array was reduced to less than 2 milliradians, which is 40 times better than without beam combining. Using the beam-combined array, absorption spectroscopy was performed at a distance of 6 m from the laser chip. An ultra-broadband DFB-QCL array was developed to further increase the coverage and tuning range. The array emitted in a range over 220 cm -1 near 9 μm wavelength, operated pulsed at room temperature.
Download or read book Characterization of Mid infrared Quantum Cascade Lasers written by David Patrick Burghoff and published by . This book was released on 2009 with total page 99 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum cascade lasers provide some of the highest output powers available for light in the mid-infrared range (from 3 to 8 m). As many of their applications require portability, designs that have a high wall-plug efficiency are essential, and were designed and grown by others to achieve this goal. However, because a large fraction of these devices did not operate at all, very few of the standard laser measurements could be performed to determine their properties. Therefore, measurements needed to be performed that could non-destructively probe the behavior of QCLs while still providing useful information. This thesis explores these types of measurements, all of which fall into the category of device spectroscopy. Through polarization-dependent transmission and photovoltaic spectroscopy, a large portion of the quantum mechanical bandstructure could be determined, along with many of the parameters characterizing crystal growth quality. In addition, high-resolution transmission spectroscopy was used to find the properties of the QCL waveguide. In order to find the correspondence between theory and experiment, bandstructure simulations were performed using a three-band p model, and two-dimensional electromagnetic simulations were performed to describe the laser's optical properties. These simulations were found to be in relatively good agreement with the device measurements, and any discrepancies were found to be consistent with problems in the growth and fabrication.
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.
Download or read book Applications for Quantum Cascade Lasers and Detectors in Mid infrared High resolution Heterodyne Astronomy written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum cascade (QC) structures, for both emitting and detecting mid-infrared radiation, are powerful devices for spectroscopy. QC lasers (QCLs), which have been built for nearly 15 years, already play the leading role in certain wavelength regions. QC detectors (QCDs) are a fairly new development, which has been evolving from the QCL research. In high-resolution heterodyne spectrometers for astronomy, such as the Cologne tuneable heterodyne infrared spectrometer (THIS), QC devices help to open new windows to space as discussed in this paper. We will briefly review the use of QC devices in THIS, show recent results in measuring planetary atmospheric dynamics and give an outlook to astronomical goals for the future.
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 0 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 High power and Narrow linewidth Optimizations of Mid infrared Quantum Cascade Lasers written by Ilia Sergachev and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
