Ivar Kjelberg - Academia.edu (original) (raw)

Papers by Ivar Kjelberg

An ion trap resonator, typically used for mass spectrometry, as introduced by Zajfman et al. [1],... more An ion trap resonator, typically used for mass spectrometry, as introduced by Zajfman et al. [1], uses a pair of opposite facing electrostatic mirrors and lenses to capture ions resonating between them (Figure 1). The electrostatic mirrors reflect the injected ions in the trap, while the lenses focus the ions and create a stable bunch with low ion particle diffusion. Another interesting phenomenon, that is observed in this resonator if certain criteria are met [2], is the existence of a synchronized state of the ions. This phenomenon leads to even lower diffusion rates in the trap, and makes very long measurements possible. In this study a smaller version of the trap is built in 2D axisymmetric geometry, and simulations are done using COMSOL Multiphysics software to optimize its performance. Figure 1 shows half of the 2D model of the device and the different electrodes. Simulations are done using the AC/DC Electric Circuit "cir", Electrostatics "es", Charged Part...

2017 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), 2017

Wavelength tuneable lasers for 40G and 100G coherent optical communications systems need to meet ... more Wavelength tuneable lasers for 40G and 100G coherent optical communications systems need to meet stringent requirements on narrow linewidth emission across the entire tuning range, with typical values of 300–500 kHz required in commercial systems. Higher capacities can be achieved in next generation systems by employing higher order modulation formats such as 16QAM or 64QAM. However, such systems have even more stringent linewidth requirements [1]. For example, square 64QAM transmission at data rate 40Gbit/s (the baud rate is 6.7G symbols / second) demands a laser with 1 kHz linewidth. Although linewidths as low as 70 kHz and even lower have been demonstrated in free-running Discrete Mode Laser Diodes (DMLD), further (active) linewidth reduction is required. This can be achieved by introducing a phase modulator on chip and applying a Pound-Drever-Hall (PDH) technique to stabilize on an optical reference cavity for instance. In the usual implementation of the PDH technique an external acousto-optic modulator (AOM) is used for active phase noise correction (Figure 1 (a), compare blue and red curves). This worsens significantly the intensity noise (Figure 1 (b)) rendering the laser unsuitable for QAM applications. In this talk we will report a DMLD laser with on-chip integrated frequency modulator based on Joule heating and showing zero residual amplitude modulation (RAM) (Figure 1 (a) and (b) green curves show preliminary stabilization results). DMLDs with integrated phase modulators are highly interesting for coherent optical communications and other applications demanding actively narrowed linewidth emission while offering an economic approach with a focus on high volume manufacturability of monolithic semiconductor lasers [2].

Physical Review Letters, 1989

AD 2 O far-infrared laser emitting 0.5J in 1.4 μs at 385 μm and a heterodyne receiver system comp... more AD 2 O far-infrared laser emitting 0.5J in 1.4 μs at 385 μm and a heterodyne receiver system comprising a Schottky barrier diode mixer with a noise temperature of 8000° K (double sideband) were used in a Thomson scattering experiment to measure the ion temperature ...

IEEE Journal of Quantum Electronics, 1985

The effects of buffer gas additives on the performance of an optically pumped D 2 0 laser operati... more The effects of buffer gas additives on the performance of an optically pumped D 2 0 laser operating at 385 pm have been investigated both experimentally and by numerical simulation. Three gases, sulphur hexafluoride, carbon tetrafluoride, and n-hexane, were found to produce an increase of up to 40 percent in the pumping efficiency, as well as significant lengthening of the far infrared pulse. Under optimum conditions, 2.6 J in a 1 ps long pulse have been obtained. The buffer gases are shown to eliminate the vibrational deexcitation bottleneck, which in pure D20 leads to an accumulation of population in the upper vibrational level and, hence, a reduction in the efficiency of absorption of the pump beam. Comparison of the observed buffer gas effects with the predictions of a numerical simulation code based on a rate equation model gives information about the constants for vibrational and rotational relaxation rates due to D20-D20 and D,O-buff er gas collisions.

IEEE Journal of Quantum Electronics, 1988

Note: Proc. 11th Int. Conference on Infrared and Millimeter Waves, Pisa, Italy, October 1986, 261... more Note: Proc. 11th Int. Conference on Infrared and Millimeter Waves, Pisa, Italy, October 1986, 261 - 263 (1986) Reference CRPP-CONF-1986-003 Record created on 2008-05-13, modified on 2016-08-08

Applied Physics B Photophysics and Laser Chemistry, 1982

1985 Tenth International Conference on Infrared and Millimeter Waves, 1985

Collective Thomson Scattering from thermal density fluctuations using a pulsed, high power far-in... more Collective Thomson Scattering from thermal density fluctuations using a pulsed, high power far-infrared laser offers several advantages as a means to measure the ion temperature in a tokamak plasma /1/. In order to demonstrate the feasibility of such a measurement, an experiment has been set up at the TCA Tokamak of the CRPP. A similar study has been carried out before by Woskoboinikow et al. on Alcator C of the M.I.T., Cambridge, Massachusetts /2/.

The Point Ahead Angle Mechanism (PAAM) for ESA’s Laser Interferometer Space Antenna (LISA) missio... more The Point Ahead Angle Mechanism (PAAM) for ESA’s Laser Interferometer Space Antenna (LISA) mission will compensate the out-of-plane point-ahead angle between three satellites flying 5 million kilometres apart. The PAAM consists of a mirror supported by flexures allowing the mirror to rotate with a maximum stroke of ±1 mrad. The mirror is actuated in 0.14 μrad steps by two redundant linear Piezo LEGS ® actuators driving a sine-bar. Since the actuators are self-locking, a special lever performing the role of a linear mechanical differential is used to provide redundancy. The design uses high-precision flexures to minimise mirror parasitic piston displacements in the picometres range. The angle is driven in closed loop using two capacitive sensors. This paper presents the mechanism at the design stage of an elegant breadboard (EBB) ready for tests. The performance requirements are summarized, then the overall concept of the mechanism is described, at last the key aspects of the detaile...

Ground-based and Airborne Telescopes VI, 2016