Voici les éléments 1 - 10 sur 132
- PublicationMétadonnées seulementSi-Interdiffusion in heavily doped AIN-GaN-based quantum well intersubband photodetectors(2011)
; ; ;Martin, Denis ;Grandjean, Nicolas ;Kotsar, YuliaMonroy, EvaWe demonstrate the effect of rapid thermal annealing on heavily Si-doped AlN/GaN quantum wells. After 1000 °C annealing during 5, 10, and 20 min, the dominant effect was interdiffusion of Si rather than intermixing between the Al and Ga atoms. Both their original value and the magnitude of the changes after annealing reveal that intersubband absorption and photovoltage are related to two different optical transitions as follows: absorption occurs in the 1 to 2 intersubband transition, whereas photovoltage is due to a subsequent process from the 1 to 2 and the manifold of 2 to higher order transitions. © 2011 American Institute of Physics.
- PublicationMétadonnées seulementFrequency Noise and Linewidth of Mid-infrared Continuous-Wave Quantum Cascade Lasers: An Overview(Bellingham, WA: SPIE Press, 2013)
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- 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)
; ;Beck, MattiasFaist, JérômeWe evaluated two different quantum-cascade-laser structures as photodetectors. The first device was a 5.3 mum two-phonon-resonance structure, and the second one a 9.3 mum bound-to-continuum transition laser. The 5.3 mum structure had a peak responsivity of 120 muA/W at 2200 cm(-1) and functioned up to 325 K. On the other hand, the 9.3 mum device also worked up to 297 K but had a lower responsivity of 50 muA/W at 1330 cm-1. Since the absorption peak of these devices can be shifted by applying an external bias, we envision interesting applications in free-space optical telecommunications. (C) 2002 American Institute of Physics.
- PublicationMétadonnées seulementEdge- and surface-emitting 10.1(2000)
; ;Faist, Jérôme ;Beck, Mattias ;Muller, AntoineOesterle, UrsulaWe present measurement results on high-power low-threshold quantum cascade-distributed feedback lasers emitting infrared radiation at 10.16 mu m. A lateral current injection scheme allowed the use of a strongly coupled surface grating without metal coverage and epitaxial re-growth. Although this design resulted in a simplified processing, the fabrication of high-performance edge- and surface-emitting devices was demonstrated. For the edge-emitting laser, we used a standard first-order grating with a period of 1.57 mu m, and for the surface emitter, a second-order grating with a period of 3.15 mu m was used. Maximal output powers in excess of 200 mW at 85 K and 70 mW at 300 K were achieved for both configurations. The threshold current densities at 85 K (300 K) were 1.85 kA/cm(2) (5.4 kA/cm(2)) and 2.1 kA/cm(2) (5.6 kA/cm(2)) for edge and surface emitters, respectively. (C) 2000 Elsevier Science B.V. All rights reserved.
- PublicationMétadonnées seulementTerahertz intersubband emission in strong magnetic fields(2002)
;Blaser, Stéphane ;Rochat, Michel ;Beck, Mattias ;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)
;Beck, Mattias ; ;Aellen, Thierry ;Faist, Jérôme ;Oesterle, Ursula ;Ilegems, Marc ;Gini, EmilioMelchior, HansContinuous wave operation of quantum cascade lasers is reported up to a temperature of 312 kelvin. The devices were fabricated as buried heterostructure lasers with high-reflection coatings on both laser facets, resulting in continuous wave operation with optical output power ranging from 17 milliwatts at 292 kelvin to 3 milliwatts at 312 kelvin, at an emission wavelength of 9.1 micrometers. The results demonstrate the potential of quantum cascade lasers as continuous wave mid-infrared light sources for high-resolution spectroscopy, chemical sensing applications, and free-space optical communication systems.
- PublicationMétadonnées seulementZnO Devices and Applications: A Review of Current Status and Future Prospects(2010)
;özgür, ümit ;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)
;Rochat, Michel ; ;Beck, MattiasFaist, JérômeRoom-temperature operation of long-wavelength, Fabry-Perot and single-mode quantum-cascade lasers at lambda approximate to 16 mum is reported. Multimode emission with pulsed peak power up to 400 mW at -40 degreesC and 220 mW at 30 degreesC is demonstrated. Single-mode emission up to 60 mW peak power has been achieved at 30 degreesC. (C) 2001 American Institute of Physics.