| 11. |
- Fu, Ying, et al.
(författare)
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Energy band structure and spectral gain characteristics of dilute-nitride zinc blende InGaNAs quantum wells embedded in GaAs and GaNAs barriers
- 2006
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 100:7
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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.
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| 12. |
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| 13. |
- Lindberg, Hans, 1977, et al.
(författare)
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High-power optically pumped 1550-nm VECSEL with a bonded silicon heat spreader
- 2004
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Ingår i: IEEE Photonics Technology Letters. - 1041-1135 .- 1941-0174. ; 16:5, s. 1233-1235
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Tidskriftsartikel (refereegranskat)abstract
- We present an optically pumped 1550-nm vertical-external-cavity surface-emitting laser with improved output power and operating temperature using a bonded heat spreader. 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. Heat transport is enhanced by a Si heat spreader bonded to the InGaAsP surface by liquid capillary bonding. Optical pumping is achieved using a 1250-nm fiber Raman laser. A maximum continuous output power of 250 mW was obtained under multitransverse mode operation at 240 K. Under operation in the fundamental near-Gaussian mode, we obtained a maximum power of 230 mW with a beam quality factor (M-2) of 1.22. At room temperature, the output power was limited to 12 mW.
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| 14. |
- Lindberg, Hans, 1977, et al.
(författare)
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InP-based optically pumped VECSEL operating CW at 1550 nm
- 2004
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Ingår i: IEEE Photonics Technology Letters. - 1041-1135 .- 1941-0174. ; 16:2, s. 362-364
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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.
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| 15. |
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| 16. |
- Westbergh, Petter, 1981, et al.
(författare)
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Single mode 1.3 ÎŒm InGaAs VCSELs for access network applications
- 2008
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Ingår i: Semiconductor Lasers and Laser Dynamics III. - : SPIE. ; 6997, s. 69970Y-1-8-
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Konferensbidrag (refereegranskat)abstract
- GaAs-based VCSELs emitting near 1.3 Όm are realized using highly strained InGaAs quantum wells and a large detuning of the cavity resonance with respect to the gain peak. The VCSELs have an oxide aperture for current and optical confinement and an inverted surface relief for suppression of higher-order transverse modes. The inverted surface relief structure also has the advantage of suppressing oxide modes that otherwise appear in VCSELs with a large detuning between the cavity resonance and the gain peak. Under large signal, digital modulation, clear and open eyes and error free transmission over 9 km of single mode fiber have been demonstrated at the OC-48 and 10 GbE bit rates up to 85°C. Here we review these results and present results from a complementary study of the RF modulation characteristics, including second order harmonic and third order intermodulation distortion, relative intensity noise (RIN), and spurious free dynamic range (SFDR). RIN levels comparable to those of single mode VCSELs emitting at 850 nm are demonstrated, with values from -140 to -150 dB/Hz. SFDR values of 100 and 95 dB·Hz2/3 were obtained at 2 and 5 GHz, respectively, which is in the range of those required in radio-over-fiber systems.
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| 17. |
- Appelgren, Patrik, et al.
(författare)
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Disruption mechanisms in electrified solid copper jets
- 2011
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Ingår i: Journal of applied mechanics. - : ASME International. - 0021-8936 .- 1528-9036. ; 78:2
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Tidskriftsartikel (refereegranskat)abstract
- Interaction between a solid copper jet and an electric current pulse is a complex process that has been experimentally studied by letting a jet created by a shaped charge device pass through an electrode configuration consisting of two aluminum plates with a separation distance of 150 mm. When the jet bridged the electrodes, which are connected to a charged pulsed power supply, current pulses with amplitude up to 250 kA were passed through the jet. By using flash X-ray diagnostics, the disruption of the electrified jets could be studied. In this paper, the disruption of the electrified jets is discussed and compared with disruption phenomena observed in electrically exploded metal rods in a static setup. Necks are naturally formed along a stretching jet, and in the experiments with current interaction these necks explode electrically. In the static experiments, the metal rods have small notches distributed along the rod to resemble the necks of the jet. When two neighboring necks or notches explode, the shock of the explosion compresses the intermediate jet or rod segment axially and the material is forced out radially. The disruption phenomena in the jet and rod experiments are similar with rapid expansion of the metal at explosion and at comparable velocities.
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| 18. |
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| 19. |
- Appelgren, Patrik, et al.
(författare)
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Small helical magnetic flux compression generators : Experiments and analysis
- 2007
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Ingår i: PPPS-2007 - Pulsed Power Plasma Science 2007. - : IEEE. - 1424409144 - 9781424409143 ; , s. 1151-1154
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Konferensbidrag (refereegranskat)abstract
- This paper presents experimental results with helical magnetic flux-compression generators (FCGs). FCGs convert the chemical energy bond in explosives into electric energy. The generator had an initial inductance of 23 μH and was operated into a load of 0.2 μH. The generator is charged with 0.27 kg of high-explosives (PBXN-5). Various types of diagnostics were used to monitor the operation of the generator, including current probes, optical fibres, and piezo gauges. The results are analysed and the expansion of the armature compared with hydrodynamic simulations.
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| 20. |
- Appelgren, Patrik, et al.
(författare)
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Studies of Electrically-Exploded Conductors for Electric Armour Applications
- 2009
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Ingår i: Acta Physica Polonica. A. - 0587-4246 .- 1898-794X. ; 115:6, s. 1072-1074
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents experimental studies of current interaction with static copper rods. The results of the static experiments are used to discuss the effects responsible for the disruption of shaped-charge jets in electric armour. These effects include ohmic heating of, and current diffusion into, the rod as well as radial magnetic forces.
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