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Träfflista för sökning "swepub ;pers:(Larsson Anders);pers:(Larsson Anders 1957)"

Sökning: swepub > Larsson Anders > Larsson Anders 1957

  • Resultat 41-50 av 348
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41.
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42.
  • Berland, Kristian, 1983, et al. (författare)
  • Temperature stability of intersubband transitions in AlN/GaN quantum wells
  • 2010
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 97:4, s. 043507-
  • Tidskriftsartikel (refereegranskat)abstract
    • Temperature dependence of intersubband transitions in AlN/GaN multiple quantum wells grown with molecular beam epitaxy is investigated both by absorption studies at different temperatures and modeling of conduction-band electrons. For the absorption study, the sample is heated in increments up to 400 degrees C. The self-consistent Schroumldinger-Poisson modeling includes temperature effects of the band gap and the influence of thermal expansion on the piezoelectric field. We find that the intersubband absorption energy decreases only by similar to 6 meV at 400 degrees C relative to its room temperature value.
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43.
  • Bickham, S., et al. (författare)
  • Low cutoff G.657-compatible fiber for data center interconnects operating in the 1064 and 1310 nm windows
  • 2020
  • Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 11286
  • Konferensbidrag (refereegranskat)abstract
    • Optical interconnects in data centers have traditionally used 850 nm GaAs-based vertical-cavity surface-emitting lasers (VCSELs) in combination with multimode fiber, having a reach up to 100 m in length. Longer links typically use standard single-mode fiber in conjunction with either InP-based edge-emitting lasers or silicon photonic transmitters operating in the 1310 nm or 1550 nm window. Single-mode GaAs-based VCSELs operating at 1064 nm offer another path for achieving longer system reach. Potential advantages of these VCSELs include better power efficiency, modulation speeds reaching 50 Gbps and large-scale fabrication volumes. The longer wavelength is also beneficial due to the lower attenuation and chromatic dispersion of optical fibers at that wavelength. However, one practical issue for single-mode transmission is that the G.657 standard for single-mode fiber requires that the 22-meter cable cutoff wavelength be less than 1260 nm, and these fibers are typically few-moded at 1064 nm. The large differences between the group velocities of the LP01 and LP11 modes can lead to degradation of the system performance due to multi-path interference if the higher order modes are present. To resolve this quandary, we have designed and validated the performance of a new optical fiber which is single-moded at wavelengths less than 1064 nm, but also has G.657-compliant mode field diameter and dispersion characteristics that enable it to be used in the 1310 nm window.
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44.
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45.
  • Borgentun, Carl, 1979, et al. (författare)
  • Direct measurement of the spectral reflectance of OP-SDL gain elements under optical pumping
  • 2011
  • Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 19:18, s. 16890-16897
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on a direct measurement method for acquiring highly precise reflectance spectra of gain elements for semiconductor disk lasers under optical pumping. The gain element acts as an active mirror, and the active mirror reflectance (AMR) was measured with a weak and tunable probe beam coincident on the gain element with a high-power pump beam. In particular, we measured the spectral AMR of a gain element designed to have a broad and flat AMR spectrum by being anti-resonant at the center wavelength and employing a parametrically optimized anti-reflection structure. We were able to confirm that this sophisticated gain element performs according to design, with an almost constant AMR of ~103% over a wavelength range of nearly 35 nm, very well matching the simulated behavior. Such gain characteristics are useful for optically pumped semiconductor disk lasers (OP-SDLs) designed for broadband tuning and short-pulse generation through mode-locking. The measurement technique was also applied to a conventional resonant periodic gain element designed for fixed wavelength OP-SDL operation; its AMR spectrum is markedly different with a narrow peak, again in good agreement with the simulations.
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46.
  • Borgentun, Carl, 1979, et al. (författare)
  • Full characterization of a high-power semiconductor disk laser beam with simultaneous capture of optimally sized focus and farfield
  • 2011
  • Ingår i: Applied Optics. - 1559-128X .- 2155-3165. ; 50:12, s. 1640-1649
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on a beam characterization method that is based on the simultaneous measurement of the focus field and the farfield, thus avoiding problems with beam fluctuations during the measurement. By using reflections from both sides of a planoconvex lens, the method implements two branches of an optical system working simultaneously. Also, by letting the planoconvex lens be antireflection treated, and by allowing for both of the reflected fields to fill large and approximately equal areas on a camera detector array, the method significantly lowers the intensity onto the detector array, thus minimizing the need for additional disturbing attenuation filters to avoid camera saturation. In the numerical retrieval of the phase distribution, based on the measured intensity distributions of the focus and farfield, iterative propagation between the two branches is performed. The phase retrieval uses the two-step algorithm for the numerical field propagation conveniently providing an arbitrary choice of sampling distance in each plane.
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47.
  • Borgentun, Carl, 1979, et al. (författare)
  • Full characterization of a semiconductor laser beam by simultaneous capture of the near- and far-field
  • 2010
  • Ingår i: Conference Digest - IEEE International Semiconductor Laser Conference. - 0899-9406. - 9781424456833 ; , s. 127-128
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • We present a new measurement technique for fully characterizing a semiconductor laser beam. The reflections from both surfaces of a planoconvex lens are used to simultaneously capture the near- and far-field. The optical phase is then retrieved using the Gerchberg-Saxton algorithm with improved numerical operations.
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48.
  • Borgentun, Carl, 1979, et al. (författare)
  • Optically pumped high-power semiconductor disk laser with gain element engineered for wide tunability
  • 2010
  • Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. - 9780819481931 ; 7720:1, s. 772014-8
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • The layer structure of the gain element in an optically pumped semiconductor disk laser (OP-SDL) was designed for wide tunability. This was achieved by a parametric optimization of the structure, which in effect balanced the spectrally varying influence of the gain of the quantum wells, the longitudinal distribution of the standing wave lasing field in the structure, and the degree of resonance in the subcavity formed between the distributed Bragg reflector at the bottom and the air-semiconductor interface at the top. The quality measure in the optimization was the spectral reflectance of the gain element for light incident from the external cavity at low power. This unsaturated reflectance was compared to its target function, which was constant at a specified value larger than unity over a wide, prescribed wavelength range. The fabricated gain element was used in a linear OP-SDL with a rotatable intra-cavity birefringent filter for wavelength tuning. The design principles for achieving wide tunability were experimentally validated by the strong agreement between measurements and simulations of the spectral threshold pump intensity. Furthermore, tuning experiments at high pump powers were performed showing that the lasing wavelength could be tuned from 967 nm to 1010 nm with a maximum output power of 2.6 W.
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49.
  • Borgentun, Carl, 1979, et al. (författare)
  • Optimization of a Broadband Gain Element for a Widely Tunable High-power Semiconductor Disk Laser
  • 2010
  • Ingår i: IEEE Photonics Technology Letters. - 1041-1135 .- 1941-0174. ; 22:13, s. 978-980
  • Tidskriftsartikel (refereegranskat)abstract
    • The layer structure of the gain element in an optically pumped semiconductor disk laser was parametrically optimized with respect to a target function specifying a desired unsaturated reflectance over a desired wavelength range at a constant pump intensity. Spectral threshold pump intensity measurements confirmed the efficacy of the design, showing a much wider low-threshold regime than a conventional non-broadband gain element, in good agreement with simulations. This evaluation avoids the possible influence of additional factors under high power operation. Nonetheless, having a high and nearly constant broadband unsaturated reflectance at low pump intensity is a key to obtain good high power performance, as evidenced by the obtained continuous tuning from 967 nm to 1010 nm with a maximum output power of 2.6 W.
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50.
  • Borgentun, Carl, 1979, et al. (författare)
  • Widely Tunable High-Power Semiconductor Disk Laser With Nonresonant AR-Assisted Gain Element on Diamond Heat Spreader
  • 2011
  • Ingår i: IEEE Photonics Journal. - 1943-0655. ; 3:5, s. 946-953
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on an optically pumped semiconductor disk laser with a wide wavelength tuning range and a high peak output power. This was achieved using a combination of efficient thermal management and a broadband gain element (GE) with carefully engineered spectral gain characteristics. For heat removal, a flip-chip bonding scheme on diamond was used. To provide high active mirror reflectance over a large wavelength region, the layered structure of the GE formed a nonresonant subcavity assisted by an antireflective structure. A peak output power of more than 7.5 W and a tuning range of 32 nm around the center wavelength of 995 nm were obtained.
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