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Hofstetter, Daniel
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Hofstetter, Daniel
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Collaborateur scientifique
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Dani_Hofstetter@Outlook.com
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Voici les éléments 1 - 10 sur 132
- PublicationMétadonnées seulementSi-Interdiffusion in heavily doped AIN-GaN-based quantum well intersubband photodetectors(2011)
; ; - PublicationMétadonnées seulementFrequency Noise and Linewidth of Mid-infrared Continuous-Wave Quantum Cascade Lasers: An Overview(Bellingham, WA: SPIE Press, 2013)
; ; ; - PublicationAccès libreMonolithically integrated interferometer for optical displacement measurement
; Dändliker, R.A monolithically integrated optical displacement sensor in the GaAs/AlGaAs material system has been developed, fabricated and characterized. The device was a double Michelson interferometer with an integrated light source, photodetectors, couplers and phase shifters. A key point of the work was the development of a single growth-step distributed Bragg reflector laser which served as the light source of the interferometer circuit. Special attention was also directed at the establishment of a bandgap-engineering technique (vacancy-enhanced disordering) allowing the definition of absorbing areas for the pumped laser section and the photodetector and transparent areas for the waveguiding sections and the grating section of the laser. The combination of the vacancy-enhanced disordering and the laser process enabled the fabrication of a fully integrated optical Michelson interferometer with quadrature signal detection. The maximal measurement distance with this double Michelson interferometer was 25 cm, and a maximal resolution of 20 nm was seen. Although using relatively simple standard processes, complex optical functions could be realized on a single chip. - PublicationMétadonnées seulementQuantum-cascade-laser structures as photodetectors(2002)
; - PublicationMétadonnées seulementEdge- and surface-emitting 10.1(2000)
; - PublicationMétadonnées seulementTerahertz intersubband emission in strong magnetic fields(2002)
; Faist, JérômeElectroluminescence in quantum-cascade structures based on vertical transitions is studied in a strong perpendicular magnetic field in the limit in which the cyclotron energy is larger than the intersubband transition energy. Cyclotron emission and a luminescence intensity enhancement up to a factor of 6 is observed in GaAs/AlGaAs and InGaAs/InAlAs vertical transition-based quantum-cascade structures. (C) 2002 American Institute of Physics. - PublicationMétadonnées seulementContinuous wave operation of a mid-infrared semiconductor laser at room temperature(2002)
; - PublicationMétadonnées seulementZnO Devices and Applications: A Review of Current Status and Future Prospects(2010)
; Morkoç, HadisZnO is an attractive material for applications inelectronics, photonics, acoustics, and sensing. In optical emitters, its high exciton binding energy (60 meV) gives ZnO an edge over other semiconductors such as GaN if reproducible and reliable p-type doping in ZnO were to be achieved, which currently remains to be the main obstacle for realization of bipolar devices. On the electronic side, ZnO holds some potential in transparent thin film transistors (TFTs) owing to its high optical transmittivity and high conductivity. Among the other promising areas of application for ZnO are acoustic wave devices, due to large electromechanical coupling in ZnO, and devices utilizing nanowires/nanorods such as biosensors and gas sensors and solar cells, since it is relatively easy to produce such forms of ZnO nanostructures, which have good charge carrier transport properties and high crystalline quality. Despite the significant progress made, there is still a number of important issues that need to be resolved before ZnO can be transitioned to commercial use, not to mention the stiff competition it is facing with GaN, which is much more mature in terms of devices. In this paper, recent progress in device applications of ZnO is discussed and a review of critical issues for realization of ZnO-based devices is given. - PublicationAccès libreLinewidth of a quantum cascade laser assessed from its frequency noise spectrum and impact of the current driver(2012-4-21)
; ; ; ; ; We report on the measurement of the frequency noise properties of a 4.6-μm distributed-feedback quantum-cascade laser (QCL) operating in continuous wave near room temperature using a spectroscopic set-up. The flank of the R(14) ro-vibrational absorption line of carbon monoxide at 2196.6 cm^−1 is used to convert the frequency fluctuations of the laser into intensity fluctuations that are spectrally analyzed. We evaluate the influence of the laser driver on the observed QCL frequency noise and show how only a low-noise driver with a current noise density below ≈1 nA/√Hz allows observing the frequency noise of the laser itself, without any degradation induced by the current source. We also show how the laser FWHM linewidth, extracted from the frequency noise spectrum using a simple formula, can be drastically broadened at a rate of ≈1.6 MHz/(nA/√Hz) for higher current noise densities of the driver. The current noise of commercial QCL drivers can reach several nA/√Hz , leading to a broadening of the linewidth of our QCL of up to several megahertz. To remedy this limitation, we present a low-noise QCL driver with only 350 pA/√Hz current noise, which is suitable to observe the ≈550 kHz linewidth of our QCL. - PublicationMétadonnées seulementLong-wavelength ((2001)
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