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  • Publication
    Accès libre
    Frequency noise of free-running 4.6 μm distributed feedback quantum cascade lasers near room temperature
    The frequency noise properties of commercial distributed feedback quantum cascade lasers emitting in the 4.6 μm range and operated in cw mode near room temperature (277 K) are presented. The measured frequency noise power spectral density reveals a flicker noise dropping down to the very low level of <100 Hz2/Hz at 10 MHz Fourier frequency and is globally a factor of 100 lower than data recently reported for a similar laser operated at cryogenic temperature. This makes our laser a good candidate for the realization of a mid-IR ultranarrow linewidth reference.
  • Publication
    Accès libre
    Quantum Cascade Detectors
    (2009)
    Giorgetta, Fabrizio R.
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    Baumann, Esther
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    Graf, Marcel
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    Yang, Quankui
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    Manz, Christian
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    Köhler, Klaus
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    Beere, Harvey E.
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    Ritchie, David A.
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    Linfield, Edmund
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    Davies, Alexander G.
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    Fedoryshyn, Yuriy
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    Jackel, Heinz
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    Fischer, Milan
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    Faist, Jérôme
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    This paper gives an overview on the design, fabrication, and characterization of quantum cascade detectors. They are tailorable infrared photodetectors based on intersubband transitions in semiconductor quantum wells that do not require an external bias voltage due to their asymmetric conduction band profile. They thus profit from favorable noise behavior, reduced thermal load, and simpler readout circuits. This was demonstrated at wavelengths from the near infrared at 2 μm to THz radiation at 87 μm using different semiconductor material systems.
  • Publication
    Accès libre
    Short wavelength (4 µm) quantum cascade detector based on strain compensated InGaAs/InAlAs
    (2008)
    Giorgetta, Fabrizio R.
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    Baumann, Esther
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    Théron, Ricardo
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    Pellaton, M. L.
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    Fischer, M.
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    Faist, Jérôme
    We report on a quantum cascade detector based on nearly strain compensated InGaAs/InAlAs pseudomorphically grown on InP substrate and detecting light at short wavelengths around 4 µm. The background limited infrared performance (BLIP) condition is met at a temperature of 108 K with a high detectivity of D*BLIP =1.2×1011 Jones.
  • Publication
    Accès libre
    16.5 µm quantum cascade detector using miniband transport
    (2007)
    Giorgetta, Fabrizio R.
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    Baumann, Esther
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    Graf, Marcel
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    Ajili, Lassaad
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    Hoyler, Nicolas
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    Faist, Jérôme
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    Krötz, Peter
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    Sonnabend, Guido
    The authors report on an InP based photovoltaic quantum cascade detector operating at 16.5 µm and using miniband-based vertical transport. This concept allowed the construction of a longitudinal optical phonon extraction stair with two rungs without touching on a high device resistance. At 10 K, they observed a responsivity of 1.72 mA/W and a Johnson noise limited detectivity of 2.2×109 Jones. Altogether, this design resulted in detection at temperatures of up to 90 K with a lower bandwidth limit of 200 MHz imposed by the measurement setup.
  • Publication
    Accès libre
    Room temperature, continuous wave operation of distributed feedback quantum cascade lasers with widely spaced operation frequencies
    (2006)
    Wittmann, Andreas
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    Faist, Jérôme
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    Hvozdara, Lubos
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    Blaser, Stéphane
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    Gini Emilio
    Lasing properties of room temperature, continuous wave operated distributed feedback (DFB) quantum cascade lasers are reported. A bound-to-continuum active region was used to generate a broad gain spectrum. As a result, first-order DFB lasers employing different periods allowed us to achieve single mode continuous wave emission at several wavelengths ranging from 7.7 to 8.3 µm at a temperature of +30 °C. The frequency span corresponds to 8% of the center frequency.
  • Publication
    Accès libre
    InP-based quantum cascade detectors in the mid-infrared
    (2006)
    Graf, Marcel
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    Hoyler, Nicolas
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    Faist, Jérôme
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    We present two InP-based quantum cascade detectors (QCDs) in the mid-infrared wavelength range. Their narrow band detection spectra are centered at 5.3 and 9 µm. A vertical intersubband transition followed by a carefully designed extraction cascade, which is adapted to the LO-phonon energy, leads to 10 K responsivities R of 3.2 and 9.0 mA/W and background limited detectivities D*BLIP of 2×108 and 3×109 Jones, for the 5.3 and the 9 µm devices, respectively. Detection has been observed up to device temperatures of 300 K (RT), albeit reasonable performance is restricted to temperatures below 150 K (5.3 µm) and 70 K (9 µm). Designed for zero bias operation, QCDs do not produce any dark current and therefore do not suffer from dark current noise and capacitance saturation at long integration times, making them ideal devices for large focal plane arrays.
  • Publication
    Accès libre
    A THz quantum cascade detector in a strong perpendicular magnetic field
    (2006)
    Scalari, Giacomo
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    Graf, Marcel
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    Faist, Jérôme
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    Beere, Harvey
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    Ritchie, David
    A 3.6 THz quantum cascade detector is studied under the influence of a strong magnetic field applied perpendicularly to the plane of the layers. Modulation of lifetimes based on elastic intersubband scattering processes is observed, leading to an increase of the responsivity for particular values of the applied magnetic field.
  • Publication
    Accès libre
    Microfluidic tuning of distributed feedback quantum cascade lasers
    (2006)
    Diehl, Laurent
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    Lee, Benjamin G.
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    Behroozi, Peter
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    Loncar, Marko
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    Belkin, Mikhail
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    Capasso, Federico
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    Aellen, Thierry
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    Beck, Mattias
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    Faist, Jérôme
    In this Letter, we report the tuning of the emission wavelength of a single mode distributed feedback quantum cascade laser by modifying the mode effective refractive index using fluids. A fabrication procedure to encapsulate the devices in polymers for microfluidic delivery is also presented. The integration of microfluidics with semiconductor laser (optofluidics) is promising for new compact and portable lab-on-a-chip applications.
  • Publication
    Accès libre
    23 GHz operation of a room temperature photovoltaic quantum cascade detector at 5.35 µm
    (2006) ;
    Graf, Marcel
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    Aellen, Thierry
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    Faist, Jérôme
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    Hvozdara, Lubos
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    Blaser, Stéphane
    We present a room temperature operated 5.35 µm quantum cascade detector which was tested at high frequencies using an optical heterodyne experiment. Two slightly detuned continuous wave distributed feedback single mode quantum cascade lasers were used to generate a beating signal. The maximum frequency at which the resulting microwave signal could be detected was 23 GHz. The cutoff behavior of our device was modeled with a simple RLC circuit and showed excellent agreement with the experimental data.
  • Publication
    Accès libre
    Ozone detection by differential absorption spectroscopy at ambient pressure with a 9.6 µm pulsed quantum-cascade laser
    (2004)
    Jiménez, R.
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    Taslakov, M.
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    Simeonov, V.
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    Calpini, B.
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    Jeanneret, F.
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    Beck, Mattias
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    Faist, Jérôme
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    van den Bergh, H.
    We report direct absorption spectroscopic detection of ozone at ambient pressure with a pulsed, DFB quantum-cascade laser (QCL) tuned within 1044–1050 cm-1 by temperature scanning. Wavelength calibration curves were derived from FTIR and CO2 spectra and interpreted with respect to the heat transfer from the heterostructure to the sink. The laser linewidth (~0.13 cm-1 FWHM) was found to decrease with temperature, probably as a result of operation at constant current. Spurious spectral features due to baseline inaccuracies were successfully filtered out from the QCL O3 spectra using differential absorption. Reference O3 concentrations were obtained by applying the same method to UV spectra, simultaneously measured with a differential optical absorption spectrometer (DOAS). Column densities retrieved from QCL spectra are in fairly good agreement (±20%) with the DOAS values above 28 ppmm. The estimated QCL lowest detectable, absolute and differential absorptions, (7×10-3 and 2×10-3, respectively), entail effective detection limits of 14 and 25 ppmm, respectively. Ongoing improvements in the acquisition system should allow the achievement of detection limits at the level of commercial open-path DOAS systems (~2 ppm m) in the near future. Our results demonstrate the applicability of the differential absorption method to QCL spectroscopy at ambient pressure, and encourage its use for open path detection.