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Hofstetter, Daniel

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Hofstetter, Daniel
Affiliation principale
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Ancien.ne collaborateur.trice
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https://libra.unine.ch/handle/123456789/472

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  • Publication
    Accès libre
    Continuous wave operation of quantum cascade lasers
    (2003)
    Beck, Mattias
    ;
    Hofstetter, Daniel 
    ;
    Aellen, Thierry
    ;
    Blaser, Stéphane
    ;
    Faist, Jérôme
    ;
    Oesterle, Ursula
    ;
    Gini Emilio
    Continuous wave (CW) operation of quantum cascade lasers is reported up to temperatures of 312 K. The devices were fabricated as buried heterostructure lasers and episide-down mounted for improved heat dissipation. Fabry–Perot lasers emitted 17 mW of continuous optical power at 292 K and still 3 mW at 311 K at λ=9.12 μm. Distributed feedback quantum cascade lasers showed CW single-mode operation up to 260 K at λ=9.0 μm with a side mode suppression rate better than 30 dB.
  • Publication
    Accès libre
    Distributed-feedback quantum cascade lasers emitting in the 9-μm band with InP top cladding layers
    (2002)
    Hofstetter, Daniel 
    ;
    Beck, Mattias
    ;
    Aellen, Thierry
    ;
    Faist, Jérôme
    ;
    Oesterle, Ursula
    ;
    Ilegems, Marc
    ;
    Gini Emilio
    ;
    Melchior, Hans
    Two different high performance quantum cascade distributed-feedback lasers with four quantum-well-based active regions and InP top cladding layers are presented. The first device, which emitted at 9.5 μm, was mounted junction down in order to get high average powers of up to 71 mW at -30°C and 30 mW at room temperature. The other device, which lased at 9.1 μm, was optimized for high pulsed operating temperatures and tested up to 150°C at 1.5% duty cycle. The emission of both lasers stayed single mode with more than 20-dB side-mode suppression ratio over the entire investigated power and temperature range.
  • Publication
    Accès libre
    Continuous wave operation of a 9.3 µm quantum cascade laser on a Peltier cooler
    (2001)
    Hofstetter, Daniel 
    ;
    Beck, Mattias
    ;
    Aellen, Thierry
    ;
    Faist, Jérôme
    ;
    Oesterle, Ursula
    ;
    Ilegems, Marc
    ;
    Gini Emilio
    ;
    Melchior, Hans
    High average power quantum cascade lasers at 9.3 µm using InP top cladding layers and both junction up and junction down mounting are presented. A 3 mm long, junction up mounted device emitted 54 mW average power at 30 °C and 11.5% duty cycle with a threshold current density of 3.72 kA/cm2. A similar, but only 1.5 mm long device with high reflection coating on both facets was mounted junction down and tested at even higher duty cycles. At –27 °C, we achieved continuous wave operation with a threshold current density of 3.3 kA/cm2.
  • Publication
    Accès libre
    Edge- and surface-emitting 10.1 μm quantum cascade distributed feedback lasers
    (2000)
    Hofstetter, Daniel 
    ;
    Faist, Jérôme
    ;
    Beck, Mattias
    ;
    Müller, Antoine
    ;
    Oesterle, Ursula
    We present measurement results on high-power low-threshold quantum cascade-distributed feedback lasers emitting infrared radiation at 10.16 μm. 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 μm, and for the surface emitter, a second-order grating with a period of 3.15 μm 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/cm2 (5.4 kA/cm2) and 2.1 kA/cm2 (5.6 kA/cm2) for edge and surface emitters, respectively.
  • Publication
    Accès libre
    A quantum cascade laser based on an n-i-p-i superlattice
    (2000)
    Faist, Jérôme
    ;
    Müller, Antoine
    ;
    Beck, Mattias
    ;
    Hofstetter, Daniel 
    ;
    Blaser, Stéphane
    ;
    Oesterle, Ursula
    ;
    Ilegms, Marc
    We demonstrate a quantum cascade laser with a novel injection concept. Periodic insertion of silicon- and beryllium-doped layers are used to control locally the internal electric field in the active region. This concept is demonstrated experimentally using an active region based on a periodic superlattice.
  • Publication
    Accès libre
    Surface-emitting 10.1 µm quantum-cascade distributed feedback lasers
    (1999)
    Hofstetter, Daniel 
    ;
    Faist, Jérôme
    ;
    Beck, Mattias
    ;
    Oesterle, Ursula
    We present measurement results on a surface-emitting quantum-cascade distributed feedback laser emitting infrared radiation at 10.1 µm. The use of a second order grating enabled the laser to emit about 25% of its total optical power from the grating. The beam radiated from the grating was at a very low divergence angle of about 1°×14°. As already presented in a previous paper, we simplified the processing by using a lateral current injection scheme avoiding epitaxial regrowth. At 85 K, the laser emitted 210 and 60 mW of pulsed power from facet and grating, respectively; at room temperature, the corresponding numbers were 70 and 18 mW. Threshold current densities of 2.1 kA/cm2 at 85 K and 5.6 kA/cm2 at room temperature were observed. The device showed single mode behavior for the entire temperature range and all investigated power levels. In addition, a constant temperature tuning coefficient of 0.06 cm–1/K was seen.
  • Publication
    Accès libre
    Demonstration of high-performance 10.16 µm quantum cascade distributed feedback lasers fabricated without epitaxial regrowth
    (1999)
    Hofstetter, Daniel 
    ;
    Faist, Jérôme
    ;
    Beck, Mattias
    ;
    Müller, Antoine
    ;
    Oesterle, Ursula
    We present measurement results on high-power low threshold quantum cascade distributed feedback lasers emitting infrared radiation at 10.16µm. A lateral current injection scheme allowed the use of a strongly coupled surface grating without metal coverage and epitaxial regrowth. Although this design resulted in a simplified processing, the fabrication of high performance devices was demonstrated. The laser emitted 230 mW of pulsed power at 85 K, and 80 mW at room temperature. Threshold current densities of 1.85 kA/cm2 at 85 K and 5.4 kA/cm2 at room temperature were observed. Since the spectrum showed single mode behavior for all temperatures and power levels of the operating range, this device will be ideal for optical sensor applications.
  • Publication
    Accès libre
    Continuous Wave Operation of a Mid-Infrared Semiconductor Laser at Room Temperature
    Beck, Mattias
    ;
    Hofstetter, Daniel 
    ;
    Aellen, Thierry
    ;
    Faist, Jérôme
    ;
    Oesterle, Ursula
    ;
    Ilegems, Marc
    ;
    Gini, Emilio
    ;
    Melchior, Hans
    Continuous 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.