Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 50 for “"Quantum Cascade Lasers"”.
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Terahertz quantum cascade lasers
… power. This thesis details the development of quantum cascade lasers (QCLs) that operate in the terahertz with photon energies below the semiconductor Reststrahlen band. Photons are emitted via electronic intersubband transitions that take place entirely within the conduction band, where the …
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Electrically tunable terahertz quantum cascade lasers
… (MEMS) assisted electrically tunable terahertz quantum cascade lasers (THz QCLs) are designed and demonstrated. Two MEMS tuner devices are proposed to achieve electrically tunable THz QCLs. One is the electrostatic comb drive actuated tuner design and the other one is a two-stage flexure design …
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Development of terahertz quantum-cascade lasers
… remarkable development of mid-infrared ( ... ) quantum-cascade lasers (QCLs) in the past decade, this thesis describes the development of electrically-pumped terahertz quantum-cascade lasers in GaAs/AlsGal_.As heterostructures that span a spectral range of 1.59 - 5.0 THz ( ... ). A …
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Trace gas spectrometry using quantum cascade lasers
… swept laser. A bench mounted two channel quantum cascade laser absorption spectrometer was used during experiments to observe and reduce nonlinear effects that arise from tuning the lasers during the absorption of light by several atmospherically important gases. These gases include the …
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Highly tunable room temperature quantum cascade lasers
… was conducted into the feasibility of novel Quantum Cascade Laser (QCL) technology to replace Optical Parametric Oscillator based light sources in real-time video-rate gas imaging systems. Such a laser must produce pulses of >5ns in duration at a repetition rate of at least 5kHz with peak …
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Design and Characterization of Quantum-Cascade Lasers
… temperature is extracted to be 144 K, while the quantum efficiency is found to be around 8-13% with the tunability of 2 nm/K. Both the lasing energy transition and the threshold current density are in good agreement with our calculation.
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Novel waveguides for terahertz quantum cascade lasers
… first demonstration in 2002, terahertz (THz) quantum cascade lasers (QCLs) have proven to be one of the most reliable sources of this type of radiation. Advances have been made in increasing maximum operating temperature, shaping the beam and tuning the frequency and bandwidth. Waveguide …
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New frontiers in THz quantum cascade lasers
… and powerful THz sources. The invention of THz quantum cascade lasers (QCL) held great promise to bridge the gap between semiconductor electronic and photonic devices. However, the demanding cooling requirements for THz QCL have been a hard brake in the race for achieving compact and portable …
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Characterization of mid-infrared quantum cascade lasers
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. …
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n-type silicon-germanium based terahertz quantum cascade lasers
Terahertz quantum cascade lasers (THz QCLs) have many potential applications, including detection of skin tumours, and of illicit drugs and explosives. To date, all THz QCLs use III–V compound semiconductors, but silicon (Si)-based devices could offer significant benefits. The high thermal …
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Design, Fabrication, and Characterization of Terahertz Quantum Cascade Lasers
We also perform an experimental study of the role of the substrate on the optical and electrical properties. We find that the effect of the substrate thickness on the laser performance is dependent on other waveguide parameters. In particular, if the plasma layer is thick enough, the role of the …
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Discrete frequency mid-infrared spectroscopic imaging using quantum cascade lasers
… substantive changes due to rapid developments in quantum cascade lasers (QCL) in terms of their output power, beam stability, and wavelength tuning range. In this dissertation, we present the research and development of several state-of-the-art microscopy systems that have advanced what was …
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Towards room-temperature Terahertz Quantum Cascade Lasers : directions and design
Terahertz Quantum Cascade Lasers (THz QCLs) are arguably the most promising technology today for the compact, efficient generation of THz radiation. Their main limitation is that they require cryogenic cooling, which dominates their ownership cost. Therefore, achieving room-temperature operation is …
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Analysis of the electron transport properties in quantum cascade lasers
Recently, the operating frequency range of quantum-cascade lasers (QCLs) has been extended from the mid-infrared to the far-infrared beow the Reststrahlen band (THz frequencies). Especially for THz QCLs, a detailed understanding of the dynamics of the electron transport is essential in order to …
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Characterization and analysis of highly diagonal Terahertz Quantum Cascade Lasers
… is essential for establishing Terahertz Quantum Cascade Lasers (THz QCLs) as practical sources of THz radiation. Temperature performance is hypothesized to be limited by upper laser level lifetime reduction due to non-radiative scattering, particularly by longitudinal optical phonons. To …
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Towards terahertz dual-comb spectroscopy based on quantum cascade lasers
… To achieve better performance of THz quantum cascade laser (QCL) frequency combs, several broadband homogeneous and heterogeneous gain media are characterized, and corresponding dispersion compensators are designed. All THz QCL frequency combs are fabricated in Microsystems Technology …
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Long-wave infrared frequency combs based on quantum cascade lasers
Ever since the invention of quantum cascade laser (QCL), the performance and the flexibility in design has made it a desirable source for a wide range of applications, such as trace-chemical sensing, health monitoring, frequency metrology, noninvasive imgaing and infrared countermeasures. The LWIR …
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