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  • 1.
    Bjurshagen, Stefan
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Hellström, Jonas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pujol, Maria
    Fisica I Cristal-Lografia de Materials (FiCMA), Universitat Rovira I Virgili, Spain.
    Aguiló, Magdalena
    Fisica I Cristal-Lografia de Materials (FiCMA), Universitat Rovira I Virgili, Spain.
    Díaz, Francesc
    Fisica I Cristal-Lografia de Materials (FiCMA), Universitat Rovira I Virgili, Spain.
    Fluorescence dynamics and rate equations analysis in Er3+,Yb3+ doped double tungstates2006In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 45, no 19, p. 4715-4725Article in journal (Refereed)
    Abstract [en]

    The fluorescence dynamics in Er3+ and Yb3+ doped KGd(WO4)(2) and KY(WO4)(2) has been investigated. Lifetimes have been measured for the Yb(F-2(5/2)), Er(I-4(13/2)), and Er(S-4(3/2)) levels around 1, 1.5, and 0.55 mu m, respectively. The Yb(F-2(5/2)) lifetimes show a decreasing trend toward the limiting Er(I-4(11/2)) lifetime with increasing Er-to-Yb concentration ratio, whereas the Er(I-4(13/2)) lifetimes are mostly unaffected by the doping concentrations. A rate equation analysis has been performed to explain the observed behavior and gain is calculated for a continuous-wave laser at 1.53 mu m to find the optimum doping concentrations for high gain.

  • 2. Denker, B.
    et al.
    Galagan, B.
    Ivleva, L.
    Osiko, V.
    Sverchkov, S.
    Voronina, I.
    Hellström, Jonas E.
    KTH, Superseded Departments, Physics.
    Karlsson, Gunnar
    KTH, Superseded Departments, Physics.
    Laurell, Fredrik
    KTH, Superseded Departments, Physics.
    New crystalline material for 1.5 μm lasers: Yb,Er - Activated GdCa 4O(BO3)32004In: Advanced Solid-State Photonics: Proceedings volume, Optics Info Base, Optical Society of America, 2004, Vol. 94, p. 430-434Conference paper (Refereed)
    Abstract [en]

    A new crystalline medium for 1.5 μm Yb-Er lasers is proposed: GdCa 4O(BO3)3 (GdCOB). Its melting point allows crystal growth using platinum instead of iridium crucibles. Spectroscopic and laser tests of the new material are described. A maximum CW output power of 80 mW was achieved in a monolithic microchip cavity under laser diode pumping.

  • 3. Denker, B.
    et al.
    Galagan, B.
    Osiko, V.
    Sverchkov, S.
    Balbashov, A. M.
    Hellström, Jonas E.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Hot YAG:Yb3+:Er3+ crystal-a potential laser medium for high average power 1.5 μm lasers2006In: Advanced solid-state photonics 2006, Optical Society of America , 2006Conference paper (Refereed)
    Abstract [en]

    The near-IR spectroscopic properties of YAG:Yb:Er crystals were investigated at high temperatures. It is shown that at 600°-800°C temperatures they become close to their corresponding properties in Er,Yb: phosphate laser glasses.

  • 4. Denker, B.
    et al.
    Sverchkov, S.
    Galagan, B.
    Ivleva, L.
    Hellström, Jonas E.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Karlsson, Gunnar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Passive Q-switching-at 1.54-micrometer of a Er-Yb:GdCa4O(BO 3)3 laser with a Co :MgAl2O4 saturable absorber2005In: OSA Trends in Optics and Photonics Series, Volume 98, Optical Society of America, 2005, p. 364-366Conference paper (Refereed)
    Abstract [en]

    A train of Q-switched pulses is formed in a diode-pumped microchip laser consisting of an Er-Yb:GdCa4O(BC3)3 active and Co2+:MgAl2C4:Co passive element. The pulses' durations were in the range of 1.6-6 ns and maximum output power was 88.2 mW at 928 mW of absorbed power.

  • 5.
    Denker, Boris
    et al.
    General Physics Institute, Moscow.
    Galagan, Boris
    General Physics Institute, Moscow.
    Ivleva, L.
    General Physics Institute, Moscow.
    Osiko, V.
    General Physics Institute, Moscow.
    Sverchkov, Sergey
    General Physics Institute, Moscow.
    Voronina, I.
    General Physics Institute, Moscow.
    Hellström, Jonas
    KTH, Superseded Departments, Physics.
    Karlsson, Gunnar
    KTH, Superseded Departments, Physics.
    Laurell, Fredrik
    KTH, Superseded Departments, Physics.
    Luminescent and laser properties of Yb-Er:GdCa4O(BO3)3: a new crystal for eye-safe 1.5-µm lasers2004In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 79, no 5, p. 577-581Article in journal (Refereed)
    Abstract [en]

    We present for the first time 1.5-μm laser emission in Yb-Er:GdCa 4O(BO3)3 (GdCOB). The crystals were grown by the Czochralski method from platinum crucibles. Spectroscopic and laser tests of the crystals are described. A continuous-wave output power of 80 mW was achieved in a monolithic microchip cavity under laser-diode pumping.

  • 6.
    Denker, Boris
    et al.
    A.M.Prokhorov General Physics Institute, Moscow.
    Galagan, Boris
    A.M.Prokhorov General Physics Institute, Moscow.
    Osiko, V.
    A.M.Prokhorov General Physics Institute, Moscow.
    Sverchkov, S.
    A.M.Prokhorov General Physics Institute, Moscow.
    Balbashov, A.
    Moscow Power Engineering Institute.
    Hellström, Jonas
    KTH, School of Engineering Sciences (SCI), Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Physics.
    Yb3+,Er3+:YAG at high temperatures: energy transfer and spectroscopic properties2007In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 271, no 1, p. 142-147Article in journal (Refereed)
    Abstract [en]

    Energy transfer and spectroscopic properties at high temperatures have been investigated in Er,Yb:YAG crystals. It is shown that at elevated temperatures around 600-800 degrees C these characteristics become similar to those in the efficient 1.5 mu m laser medium - Er,Yb-doped phosphate glasses. (c) 2006 Elsevier B.V. All rights reserved.

  • 7.
    Hellström, Jonas
    KTH, School of Engineering Sciences (SCI), Physics.
    Novel materials for Yb and Er-Yb doped microchip lasers2006Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The objective of this thesis has been to investigate novel host material configurations for high-power end-pumped Er-Yb co-doped, or Yb doped microchip lasers and try to increase their performance. In Er-Yb co-doped systems, the main limitation is the thermal shortcomings of the phosphate glass host material. The thesis presents some novel results that contribute to the search for a crystalline replacement. In Yb doped systems, most end-pumped schemes reported have been using relatively low-power single-emitter diodes. The thesis presents experiments with Yb:KGW microchips end-pumped by high-power diode bars. Another common limitation of end-pumped Yb microchip lasers is the thermal lens that destabilizes the cavity and decreases the beam quality. The approach to reduce the thermal lens by using an athermal propagation direction has been evaluated and the results are presented in the thesis.

    In the search for a crystalline host material for Er-Yb systems, borates have been found increasingly interesting. Consequently, we started out by investigating Gadolinium-calcium-oxoborate, GdCOB, which could be grown in platinum crucibles. It was found that the cw performance of such monolithic microchips is quite comparable to glass hosts in terms of slope efficiency, but the threshold is significantly larger. As for Q-switched performance, which is essential to most Er-Yb applications, the first efficient Q-switched results with a crystalline host is presented in the thesis. Similar to the cw regime, the slope efficiencies are comparable to glass, while the threshold is quite high. However, the perhaps most important parameter, maximum output power before thermal fracture, is neither significantly improved nor worsened compared with phosphate glass. This is believed to be due to higher threshold and a stronger thermal expansion that negates the benefit of a thermal conductivity that is only 2-3 times higher. To find a host material that could withstand higher pump powers, we turned our attention to the double-tungstates KGW and KYW, which have higher thermal conductivity and higher cross-sections. They have, however, energy level lifetimes which differ significantly from glass or borates and as a consequence, a thorough spectroscopic investigation has been undertaken to optimize dopant concentrations. Laser experiments on crystals with dopant concentrations based on this investigation are expected in the near future.

    When pumping Yb:KGW with a high-power diode bar, we achieved output powers of 9 – 12.4 W under different experimental conditions with incident powers of 18.3 – 26 W. The incident power of 26 W in one design was enough to fracture the crystal. Using a crystal cut for propagation along an athermal direction and comparing it with an identical b-cut crystal, we found that the thermal lens in the athermally oriented crystal was about a factor two weaker at the same absorbed power.

  • 8.
    Hellström, Jonas
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    On diode-pumped solid-state lasers2007Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The research that is presented in this thesis can be divided into two major parts. The first part concerns longitudinally pumped, bulk Er-Yb lasers. In these lasers, the main limitation is the thermal shortcomings of the phosphate glass host material. From the laser experiments and the spectroscopic measurements on crystalline host materials, as well as an investigation to bring further light to the physical background of the involved dynamics, the thesis presents some novel results that contribute to the search for a crystalline replacement. The second part concerns novel laser concepts applied to Yb-doped double tungstate lasers. Different crystal orientations are investigated, such as an athermal orientation for reduced thermal lensing and a conical refraction orientation for complete polarization tuning. Furthermore, the introduction of volume Bragg gratings in the cavity enables wide spectral tuning ranges and extremely low quantum defects.

    Regarding the first part, the main results are the achievement of 15 % slope efficiency in a monolithic, continuous-wave Yb:GdCOB laser and the achievement of Q-switching of the same laser. The Q-switched pulse durations were around 5-6 ns and the Q-switched slope efficiency was 11.6 %. For both lasers, a maximum output power of 90 mW was obtained, which is close to ordinary glass lasers under similar conditions. A spectroscopic investigation into the Er,Yb-codoped double tungstates was also performed and the results have enabled mathematical modeling of the fluorescence dynamics in these materials. Finally, the temperature dependence of the dynamics in Er,Yb:YAG was studied and the results have given some insight into the physical background of the mechanisms involved.

    Regarding the second part, different end-pumped Yb:KReW laser cavities were constructed to demonstrate the different concepts. With a laser crystal cut for propagation along the athermal direction at 17º angle clockwise from the dielectric direction Nm, the thermal lens could be reduced by 50 %. In these experiments the maximum output power was 4 W at 60 % slope efficiency. In another cavity incorporating a volume Bragg grating in a retroreflector set-up, the wavelength could be continuously tuned between 997 - 1050 nm. The spectral bandwidth was 10 GHz and the peak output power was 3 W. The same output power could also be obtained at 1063 nm with the grating positioned as an output coupler instead. If, on the other hand, the grating was positioned as an input coupler, 3.6 W output power at 998 nm was obtained at a quantum defect of only 1.6 %. Furthermore, using a crystal oriented for propagation along an optic axis, internal conical refraction could be used to establish arbitrary control of the polarization direction as well as the extinction ratio. Even unpolarized light could be enforced despite the highly anisotropic medium. With this configuration, the maximum output power was 8.6 W at 60 % slope efficiency which equals the performance of a reference crystal with standard orientation. The completely novel concepts of laser tuning with Bragg grating retroreflectors, of low quantum defect through Bragg grating input couplers and of polarization tuning by internal conical refraction can all easily be applied to several other laser materials as well.

  • 9.
    Hellström, Jonas
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Bjurshagen, Stefan
    KTH, School of Engineering Sciences (SCI), Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Physics.
    Liu, Junhai
    Max-Born Institute, Berlin.
    Petrov, Valentin
    Max-Born Institute, Berlin.
    Griebner, Uwe
    Max-Born Institute, Berlin.
    Efficient Yb: KGW lasers end-pumped by high-power diode bars2006In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 82, no 2, p. 235-239Article in journal (Refereed)
    Abstract [en]

    The laser performance of Yb:KGW under end-pumping with high-power diode bars has been investigated. In one configuration, the pump is delivered through an optical fiber yielding a symmetric but unpolarized pump spot. In the second configuration, the pump is delivered through an optical lens system yielding a polarized but asymmetric pump spot. Both configurations resulted in a maximum optical to optical efficiency of 47% and a maximum power of 12.4 W has been generated with the fiber coupled pump source. The output power was limited by crystal fracture, which occurred at an estimated temperature gradient of 1.2 x 10(5) K/m. Thermal lensing and laser tuning characteristics are also investigated.

  • 10.
    Hellström, Jonas
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Bjurshagen, Stefan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicus, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laser performance and thermal lensing in high-power diode pumped Yb:KGW with athermal orientation2006In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 83, no 1, p. 55-59Article in journal (Refereed)
    Abstract [en]

    A comparative, experimental study of the high-power diode-pumped laser performance and thermal lensing properties between standard b-cut Yb:KGW and Yb:KGW cut along an athermal direction is presented. The results show that thermal lens properties in both the b-cut and the athermal direction-cut crystals are determined by anisotropic thermal expansion in Yb:KGW. Thermal gradients due to the pump beam cause thermal lensing even in the athermal direction-cut geometry. The thermal lens is much weaker and less astigmatic in the athermal direction-cut crystal, for the same absorbed power. These properties allow generation of better-quality laser beams with the athermal direction-cut crystal as compared to the b-cut crystal.

  • 11.
    Hellström, Jonas E.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Bjurshagen, Stefan
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Experimental investigation of the athermal orientation in Yb:KGW2006In: Advanced solid-state photonics 2006, Optical Society of America, 2006Conference paper (Refereed)
    Abstract [en]

    A comparative, experimental study between b-cut Yb:KGW and Yb:KGW cut along a proposed athermal direction is presented. The athermal direction gives a significantly weaker thermal lens, lower astigmatism and higher beam quality under lasing conditions.

  • 12.
    Hellström, Jonas E.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Bjurshagen, Stefan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Liu, J.
    Griebner, U.
    Petrov, V.
    Efficient Yb:KGW lasers end-pumped by high-power diode bars2006Conference paper (Refereed)
    Abstract [en]

    The generation of 12.4W of output power with optical-to-optical conversion efficiency of 47% and slope efficiency of 74% is demonstrated in Yb:KGW laser end-pumped with high-power diode bars. Thermal-lensing and laser tuning has been investigated.

  • 13.
    Hellström, Jonas E.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Jacobsson, Björn
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Finite beams in reflective volume Bragg gratings: theory and experiments2008In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 44, no 1, p. 81-89Article in journal (Refereed)
    Abstract [en]

    We present a theoretical model to describe finite beams incident on reflective volume Bragg gratings. We also give experimental results that verify our model. From these results, we identify certain properties of reflective volume Bragg gratings, such as beam waist, incidence angle and beam profile, that have direct impact on the design of laser cavities that include such gratings. We also show how these gratings can act as spatial mode filters.

  • 14.
    Hellström, Jonas E.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Jacobsson, Björn
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Quasi-two-level Yb:KYW laser with a volume Bragg grating2007In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 15, no 21, p. 13930-13935Article in journal (Refereed)
    Abstract [en]

    Using a volume Bragg grating as input coupler, we demonstrate an Yb:KYW laser with a very small quantum defect (1.6%) and an output power of 3.6 W. The laser was longitudinally diode-pumped at 982 nm and the laser wavelength was determined by the grating to 998 nm, with a laser bandwidth of 10 GHz (33 pm). Due to the low quantum defect, the laser should be readily scalable to 20 W or more without critical thermal effects.

  • 15.
    Hellström, Jonas E.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Jacobsson, Björn
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Tunable Yb:KYW Laser with a Volume Bragg Grating2007In: Optics InfoBase Conference Papers, 2007Conference paper (Refereed)
    Abstract [en]

    We demonstrate a tunable Yb:KYW laser, locked by a volume Bragg grating in a retroreflector geometry. The power was ~1 W within the tuning range from 1032 nm to 1048 nm.

  • 16.
    Hellström, Jonas
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Henricsson, H.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Exploiting conical refraction in Yb-doped double tungstate lasers [invited]2010Conference paper (Refereed)
  • 17.
    Hellström, Jonas
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Henricsson, Hanna
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Bünting, Udo
    Hannover Laser Cetrum.
    Haussman, D.
    Hannover Laser Centrum.
    Polarization-Tuning of Yb:KGW by Use of Internal Conical Refraction2008Conference paper (Refereed)
    Abstract [en]

    We demonstrate that both direction and extinction ratio of the polarization in an Yb:KGW laser can be arbitrarily controlled using conical refraction. No additional components are necessary. Output power was 8.6W and slope efficiency 60.5%.

  • 18.
    Hellström, Jonas
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Henricsson, Hanna
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Bünting, Udo
    Vision Crystal Technology AG, Germany.
    Haussman, Dirk
    Vision Crystal Technology AG, Germany.
    Polarization-tunable Yb:KGW laser based on internal conical refraction2007In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 32, no 19, p. 2783-2785Article in journal (Refereed)
    Abstract [en]

    Using internal conical refraction, we demonstrate an Yb:KGW laser where the polarization state can be arbitrarily altered without any additional cavity components. The extinction ratio can also be altered between 1:1 and 40:1. The maximum output power achieved was 8.6 W at a slope efficiency of 60.5% with respect to incident pump power. This equals the power performance of a standard Yb:KGW laser used for reference.

  • 19.
    Hellström, Jonas
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Jacobsson, Björn
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Tunable Yb: KYW laser with volume Bragg grating2007In: Advanced Solid-State Photonics (ASSP) 2007, Optical Society of America, 2007Conference paper (Refereed)
    Abstract [en]

    We demonstrate a tunable Yb:KYW laser, locked by a volume Bragg grating in a retroreflector geometry. The power was ~1 W within the tuning range from 1032 nm to 1048 nm.

  • 20.
    Hellström, Jonas
    et al.
    KTH, Superseded Departments, Physics.
    Karlsson, Gunnar
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Pasiskevicius, Valdas
    KTH, Superseded Departments, Physics.
    Laurell, Fredrik
    KTH, Superseded Departments, Physics.
    An optical parametric amplifier based on periodically poled KTiOPO4, seeded by an Er-Yb: glass microchip laser2001In: ADVANCED SOLID-STATE LASERS, PROCEEDINGS, 2001, Vol. 50, p. 650-655Conference paper (Refereed)
    Abstract [en]

    We report on an optical parametric amplifier in periodically poled KTiOPO4 at 1.54 mum, with an Er-Yb:glass microchip seed laser. The signal pulses reached 71 muJ, with pulse duration of 3 ns, corresponding to 66 dB gain.

  • 21.
    Hellström, Jonas
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Karlsson, Gunnar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Physics.
    Denker, Boris
    General Physics Institute, Moscow.
    Sverchkov, Sergey
    General Physics Institute, Moscow.
    Galagan, Boris
    General Physics Institute, Moscow.
    Ivleva, L.
    General Physics Institute, Moscow.
    Passive Q-switching at 1.54 µm of an Er-Yb:GdCa4O(BO3)3 laser with a Co2+:MgAl2O4 saturable absorber2005In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 81, no 1, p. 49-52Article in journal (Refereed)
    Abstract [en]

    We report, for the first time to our knowledge, efficient passive Q-switching of the 1.54-μm laser transition in an Er-Yb-doped crystalline medium. The laser configuration is a compact microchip design that is suitable for a range of practical applications such as range finding and lidar. The slope efficiency of 11.6%, pulse duration of 5-6 ns and average output power of 88 mW are all comparable with standard Er-Yb:glass lasers.

  • 22.
    Hellström, Jonas
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Denker, B.
    General Physics Institute, Moscow, Russia.
    Galagan, B.
    General Physics Institute, Moscow, Russia.
    Ivleva, L.
    General Physics Institute, Moscow, Russia.
    Sverchkov, S.
    General Physics Institute, Moscow, Russia.
    Horvath, V.
    General Physics Institute, Moscow, Russia.
    High-power end-pumped lasers with Yb:GdCa4O(BO3)3 and Yb:KGd(WO4)22007Conference paper (Refereed)
  • 23.
    Jacobsson, Björn
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Hellström, J. E.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Transversal mode transformation in reflective volume Bragg grating, theory and expeirments2007Conference paper (Other academic)
  • 24.
    Jacobsson, Björn
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Hellström, Jonas E.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Quasi-two-level Yb: KYW laser with a volume Bragg grating2008Conference paper (Refereed)
    Abstract [en]

    A volume Bragg grating is used as input coupler in an Yb:KYW laser to obtain lasing at 998 nm while diode-pumping at 982 nm. The power was 3.6 W with a bandwidth of 10 GHz.

  • 25.
    Jacobsson, Björn
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Hellström, Jonas E.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Quasi-Two-Level Yb:KYW Laser Using a Volume Bragg Grating2008Conference paper (Refereed)
  • 26.
    Jacobsson, Björn
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Hellström, Jonas E.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Transversal Mode Transformation in Reflective Volume Bragg Gratings, Theory and Experiments2007In: Optics InfoBase Conference Papers, 2007Conference paper (Refereed)
    Abstract [en]

    We present a theoretical model describing finite beams incident at volume Bragg gratings and confirm it experimentally. Reflectivity decreases with increasing incidence angle and decreasing beam size, and the transmitted transversal mode profile is transformed.

  • 27.
    Jacobsson, Björn
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Hellström, Jonas E.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Tunable Yb:KYW laser using volume Bragg grating in s-polarization2008In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 91, no 1, p. 85-88Article in journal (Refereed)
    Abstract [en]

    We report on a volume-Bragg-grating tunable Yb:KYW laser. By using s-polarized light on the grating, we obtain an output power of 3 W in a single beam, doubled compared to earlier p-polarization results. The laser tunability was from 996 nm to 1048 nm. Detailed measurements of the laser spectrum revealed a bandwidth of 10 GHz.

  • 28.
    Jacobsson, Björn
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Hellström, Jonas E.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Widely Tunable Yb:KYW Laser Locked by a Volume Bragg Grating2007In: 2007 CONFERENCE ON LASERS & ELECTRO-OPTICS/QUANTUM ELECTRONICS AND LASER SCIENCE CONFERENCE (CLEO/QELS 2007), NEW YORK: IEEE , 2007, p. 1099-1100Conference paper (Refereed)
    Abstract [en]

    We demonstrate a technique for laser tuning based on a volume Bragg grating. A peak power of 4.7 W, a bandwidth <0.1 nm and a 1000-1050 nm tuning range is achieved in an Yb:KYW laser.

  • 29.
    Jacobsson, Björn
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Hellström, Jonas E.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Widely tunable Yb:KYW laser with a volume Bragg grating2007In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 15, no 3, p. 1003-1010Article in journal (Refereed)
    Abstract [en]

    We demonstrate a narrowband, continuously tunable Yb: KYW laser locked by a volume Bragg grating at oblique incidence in a retroreflector configuration. The tuning range was 997 nm to 1050 nm (15 THz) with bandwidth < 0.1 nm and a maximum output power of 4.7 W. In a high- quality beam with M-2 < 1.3, the maximum output power was 1.7 W. We also demonstrate 3 W output power at 1064 nm from the same Yb: KYW laser with the grating at normal incidence.

  • 30.
    Pasiskevicius, Valdas
    et al.
    KTH, Superseded Departments, Physics.
    Freitag, Ingo
    Karlsson, Håkan
    KTH.
    Hellström, Jonas E.
    KTH, Superseded Departments, Physics.
    Laurell, Fredrik
    KTH, Superseded Departments, Physics.
    Low-threshold mid-infrared optical parametric oscillation in periodically poled KTiOPO42000In: Nonlinear Materials, Devices, and Applications, SPIE - International Society for Optical Engineering, 2000, p. 2-8Conference paper (Refereed)
    Abstract [en]

    In this work we demonstrate low-threshold oscillation in the mid-infrared spectral region with periodically poled KTiOPO4 (PPKTP) pumped at 1064 nm by a single-frequency Nd:YAG laser. The compact pump laser had a diode-pumped passively Q-switched monolithic ring cavity configuration and could generate up to 70 μJ, 2 ns pulses. With two PPKTP crystals having ferroelectric domain inversion periods of 37.8 μm and 38.5 μm, the temperature tuning bands for the signal (idler) of 1720-1750 nm (2790-2717 nm) and 1850-1920 nm (2510-2390 nm) have been obtained. The lowest oscillation threshold of 8.3 μJ was obtained in a cavity using two mirrors reflecting 99% at the signal and the idler wavelengths. The maximum OPO output power of 6 mW and the pump depletion of 39% was achieved by driving cavity close to stability limit for the idler field. The output power was substantially increased to 36 mW (6 μJ) by using output mirror with 90% reflectivity only in the signal band and optimizing pump focusing conditions. The external OPO efficiency in this case reached 21%.

  • 31.
    Tillman, Karl A.
    et al.
    University of Edinburgh.
    Reid, Derryk T.
    University of Edinburgh.
    Artigas, D.
    University of Edinburgh.
    Hellström, Jonas
    KTH, Superseded Departments, Physics.
    Pasiskevicius, Valdas
    KTH, Superseded Departments, Physics.
    Laurell, Fredrik
    KTH, Superseded Departments, Physics.
    Low threshold, high repetition frequency, femtosecond optical parametric oscillator based on chirped-pulse frequency conversion2004In: Ultrafast Optics IV / [ed] F. Kraus, G. Korn, P. Corcum, I. A. Walmsley, Springer Berlin/Heidelberg, 2004, 1, p. 385-392Chapter in book (Refereed)
1 - 31 of 31
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