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  • Resultat 1-10 av 258
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  • Fu, Ying, et al. (författare)
  • Energy band structure and spectral gain characteristics of dilute-nitride zinc blende InGaNAs quantum wells embedded in GaAs and GaNAs barriers
  • 2006
  • Ingår i: Journal of Applied Physics. - 00218979. ; 100:7
  • Tidskriftsartikel (refereegranskat)abstract
    • The spectral gain characteristics of dilute-nitride zinc blende InxGa1-xNyAs1-y quantum wells embedded in GaNy1As1-y1 barriers have been investigated experimentally and theoretically. Two samples, both with the gain peak at 1300 nm, were studied for comparison. One has a high nitrogen concentration in the quantum well with the surrounding barriers being pure GaAs. The other has a lower and uniform nitrogen concentration in the quantum well and the barriers (GaNAs barriers). Measurements show the redshift of the gain peak induced by the incorporation of nitrogen and difference in the spectral gain characteristics. The energy band structures and spectral gain characteristics are analyzed theoretically using the standard eight-band k center dot p theory. It is shown that the introduction of nitrogen atoms in the GaAs barriers reduces the barrier height for the central quantum well so that the energy sublevels in the conduction band becomes condensed. The condensation of the conduction-band energy sublevels reduces the peak gain and makes the gain spectrum narrower, in agreement with measurements.
  • Han, T.T., et al. (författare)
  • Structural analysis of dilute-nitride zinc blende InxGa1−xNyAs1−y cluster by a semiempirical quantum chemistry study
  • 2007
  • Ingår i: Journal of Applied Physics. - 0021-8979. ; 101:12, s. 123707-1-123707-6
  • Tidskriftsartikel (refereegranskat)abstract
    • We have studied the total energy of a series of dilute-nitride zinc blende Inx Ga1-x Ny As1-y cluster configurations using a semiempirical quantum chemistry method. It was found that In-N bonding is favorable from an energy point of view when the N atom is substitutional (replacing an As atom at the regular zinc blende lattice site) and the In mole fraction is smaller than 25%. In-N bonding is always favorable when the N atom is interstitial. Furthermore, an analysis of the incorporation of N-N pairs showed that substitutional incorporation is favored over interstitial. In addition, the dissociation of a N-N pair was found to depend on the local environment, being either In rich or In-free, along the dissociation trajectory when the average In mole fraction is high. The theoretical results are in agreement with experimental results.
  • Kakanakova-Georgieva, Anelia, et al. (författare)
  • Mg-doped Al0.85Ga0.15N layers grown by hot-wall MOCVD with low resistivity at room temperature
  • 2010
  • Ingår i: physica status solidi (RRL) – Rapid Research Letters. - 1862-6254. ; 4:11, s. 311-313
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on the hot-wall MOCVD growth of Mg-doped AlxGa1-xN layers with an Al content as high as x similar to 0.85. After subjecting the layers to post-growth in-situ annealing in nitrogen in the growth reactor, a room temperature resistivity of 7 k Omega cm was obtained indicating an enhanced p-type conductivity compared to published data for AlxGa1-xN layers with a lower Al content of x similar to 0.70 and a room temperature resistivity of about 10 k Omega cm. It is believed that the enhanced p-type conductivity is a result of reduced compensation by native defects through growth conditions enabled by the distinct hot-wall MOCVD system.
  • Lindberg, Hans, 1977-, et al. (författare)
  • Improved spectral properties of an optically pumped semiconductor disk laser using a thin diamond heat spreader as an intracavity filter
  • 2005
  • Ingår i: IEEE Photonics Technology Letters. - 1041-1135. ; 17:7, s. 1363-1365
  • Tidskriftsartikel (refereegranskat)abstract
    • This letter describes an optically pumped high-power InP-based semiconductor disk laser with a thin (50 mu m) diamond heat spreader bonded to the surface of the gain chip. The diamond heat spreader performs the multiple functions of heat removal, spectral filtering, and wavelength stabilization by utilizing the high thermal conductivity and the low thermooptic coefficient of diamond, along with the large free-spectral range of a thin intracavity etalon. A pump-power-limited output power of 680 mW at 1.55 mu m is demonstrated at a heat sink temperature of -30 degrees C, and 140 mW at room temperature. The spectral width was measured to be less than 0.08 nm and the spectral drift with temperature and pump power as low as 0.03 nm/degrees C and 0.14 nm/W, respectively.
  • Lindberg, Hans, 1977-, et al. (författare)
  • InP-based optically pumped VECSEL operating CW at 1550 nm
  • 2004
  • Ingår i: IEEE Photonics Technology Letters. - 1041-1135. ; 16:2, s. 362-364
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a vertical external-cavity surface-emitting laser operating at 1550 run. The laser comprises an InGaAsP-based gain element, with a resonant periodic gain structure on top of a distributed Bragg reflector, and a high reflectivity spherical mirror as the external reflector. Optical pumping is achieved using a 1250-nm fiber Raman laser. A maximum continuous output power of 70 mW was obtained under multitransverse mode operation at 233 K. Under single-mode operation, we obtained a maximum power of 60 mW with a beam quality factor M-2 less than 1.1.
  • Lindberg, Hans, 1977-, et al. (författare)
  • Optically pumped VECSEL operating at 1550 nm
  • 2004
  • Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. ; s. 25-33
  • Konferensbidrag (refereegranskat)abstract
    • We present the design and characteristics of an optically pumped vertical external cavity surface emitting laser emitting near 1550 nm. The InP-based laser was grown by Metalorganic vapor-phase epitaxy including an InGaAsP gain element and an InP/InGaAsP mirror. The gain element comprises 20 strain compensated quantum wells on top of a distributed Bragg reflector. As an external mirror we used a concave spherical mirror, which also provides the outcoupling of light. Gain is achieved by optical pumping with a high power, 1250 nm fiber Raman laser focused on the gain chip. Essential for achieving high output power is to reduce the temperature of the gain material and this is accomplished by bonding an intra-cavity silicon heat spreader to the surface of the gain element. The maximum output power is 260 mW at multi transverse mode operation and 230 mW at single transverse mode operation with a near Gaussian beam profile (M2=1.22) at 240 K. At room temperature the output power was limited to 12 mW. The maximum output power greatly depends on the operating temperature and studies of pump induced thermal effects show that thermal lensing imposes limitations on the attainable power.
  • Lindberg, Hans, 1977-, et al. (författare)
  • Single-frequency operation of a high-power, long-wavelength semiconductor disk laser
  • 2005
  • Ingår i: Optics Letters. - 0146-9592. ; 30:17, s. 2260-2262
  • Tidskriftsartikel (refereegranskat)abstract
    • An optically pumped, high-power, single-frequency semiconductor disk laser is demonstrated. A thin (50 mu m) diamond bonded to an InGaAsP gain chip provides the combined functions of heat removal and spectral filtering, thus eliminating the need for the additional intracavity etalons that are usually employed for single-frequency operation. In a short cavity (4 mm) configuration we obtained a maximum output power of 470 mW at 0 degrees C and 170 mW at 20 degrees C in a near-diffraction-limited beam (M-2 < 1.2). The emission wavelength was 1549 nm and the linewidth was less than 200 MHz.
  • Söderberg, Emma, 1980-, et al. (författare)
  • High speed, high temperature operation of 1.28-μm singlemode InGaAs VCSELs
  • 2006
  • Ingår i: Electronics Letters. - 0013-5194. ; 42:17, s. 978-979
  • Tidskriftsartikel (refereegranskat)abstract
    • Singlemode 1.28 μm InGaAs VCSELs, with a higher-order mode suppression >30 dB in the temperature range 25-85°C, have been fabricated using an inverted surface relief technique for relaxed fabrication tolerances. High performance 2.5 and 10 Gbit/s modulation is demonstrated in the same temperature range.
  • Söderberg, Emma, 1980-, et al. (författare)
  • Suppression of higher order transverse modes and oxide modes in 1.3 µm InGaAs VCSELs by an inverted surface relief
  • 2007
  • Ingår i: IEEE Photonics Technology Letters. ; 19
  • Tidskriftsartikel (refereegranskat)abstract
    • It is shown, by a systematic variation of design parameters, that the use of an inverted surface relief is very effective for suppressing higher order transverse modes in oxide confined 1.3-mu m InGaAs vertical-cavity surface-emitting lasers (VCSELs). Single-mode emission is achieved for a large variety of oxide aperture and surface relief diameters, with optimum designs, having a surface relief with a diameter half of that of the oxide aperture, producing 1.1-1.3 mW of single-mode power. It is also shown that the anti-phase layer employed to enable the use of an inverted surface relief is effective for suppressing oxide modes that otherwise appear in oxide confined VCSELs with a large detuning between the gain peak and the cavity resonance.
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