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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 40 for “"QCL"”.
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Design of high efficiency Mid IR QCL lasers
… high-efficiency Mid-IR quantum cascade lasers (QCL). This thesis explores "injector-less" designs for achieving lower voltage defects and improving wall plug efficiencies through highly strain-balanced structures and minimized injector regions. This work contains experimental design work for …
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The design and fabrication of an inp-based transistor-injected quantum cascade laser
… to these problems. While quantum cascade lasers (QCLs) present one appealing solution for these infrared sources, inherent limitations related to efficiency and operational control leave room for improvement. The transistor-injected quantum cascade laser (TI-QCL) presents a novel three-terminal …
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Towards terahertz dual-comb spectroscopy based on quantum cascade lasers
… 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 Laboratories at MIT …
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Long-wave infrared frequency combs based on quantum cascade lasers
… 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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Development of Broadband Semiconductor Laser Frequency Combs
Quantum Cascade Laser (QCL) is a compact, mature and flexible coherent radiation source in both terahertz (THz) and mid-infrared (midIR) frequency range. Many molecules have rotational-vibrational absorption bands in midIR, making QCL-based dual comb spectroscopy (DCS) systems the ideal tool for …
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High-resolution infrared spectroscopy of large molecules and water clusters using quantum cascade lasers
… been obtained using a quantum cascade laser (QCL) based infrared spectrometer coupled to a supersonic expansion source. The spectrometer operates near 8.5 μm and has been developed for the purpose of obtaining a high-resolution gas phase spectrum of C60 for use in astronomical observations of …
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Design and Characterization of Quantum-Cascade Lasers
From SIMS experiment, MBE-grown QCL structure exhibit high controllability and uniformity. The position of the PL peak is very close to the location predicted by our model. THz radiation from an MBE grown bound-to-continuum QCL is observed with the lasing wavelength of 104 mum. The …
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Novel Applications of Terahertz Quantum Cascade Lasers: Gas Spectroscopy, Active Control & Nearfield Imaging
… of Terahertz (THz) quantum cascade lasers (QCLs) in 2002, they have seen significant improvement in output power, operating temperature, and spectral coverage as well as having been widely applied to astronomical applications, imaging, and spectroscopy because of their high output power and …
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Novel waveguides for terahertz quantum cascade lasers
… 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 engineering has been a …
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Highly tunable room temperature quantum cascade lasers
… 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 pulse powers of >10mW. The …
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Terahertz imaging and quantum cascade laser based devices
… developed terahertz quantum-cascade laser (QCL) sources, along with commercial, focal plane array thermal detectors. The system uses a high power (48 mW) 4.3-THz QCL, which is also used to characterize the focal plane array, resulting in a noise equivalent power (NEP) of 320 pW/Hz. The …
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Terahertz laser frequency combs : devices and applications
… it has been shown that quantum cascade lasers (QCLs) are capable of forming a frequency comb state where dispersed cavity modes of the Fabry-Perot cavity are synchronized by third order nonlinearity. With proper dispersion engineering, we have shown that it is possible to create QCL frequency …
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New frontiers in THz quantum cascade lasers
… 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 systems, and they have …
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Laterally confined THz sources and graphene based THz optics
… spectrum. Terahertz quantum cascade lasers (THz QCLs) are one of the most compact, powerful sources of coherent radiation that bridge the terahertz gap. However, their cryogenic requirements for operation limit the scope of the applications. This is because of the electron-electron scattering and …
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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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Germanium on Silicon Integrated Photonics for the Mid-Wave Infrared
… flip-chip integration of quantum-cascade lasers (QCLs) are presented. Coupling between the QCL and the GOS waveguides is simulated and input tapers are designed. Test structures for QCL-waveguide coupling and external cavity QCL demonstration are designed. The predicted coupling from the QCL into …
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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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Study on dynamic behavior of ring-cavity quantum-cascade lasers with group velocity dispersion
Quantum cascade lasers (QCLs) have been the common mid-infrared sources because of their high output power and agile wavelength range owing to the intersubband transitions. Previous research on QCLs shows that the instability and dynamic behaviors are more complicated than conventional …
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Graphene Integrated Metamaterial Devices for Terahertz Modulation
… (THz-TDS) and THz quantum cascade lasers (THz-QCLs). A range of THz modulator architectures will then be discussed, focusing on the methods which involve converting passive metamaterial arrays into actively tunable devices, including the implementation of microelectromechanical systems (MEMS), …
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Development of Active Terahertz Modulators for use with Quantum Cascade Lasers and Near-Field Imaging of their Individual Resonators
… were coupled with THz quantum cascade lasers (QCLs). The phase modulators were integrated with a partially suppressed QCL to form an external cavity. The devices acted as optoelectronic mirrors. By changing the bias on the device, the reflected phase changed the effective length of the cavity …
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