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  • 1.
    Carrasco, Irene
    et al.
    Univ Surrey, Adv Technol Inst, Dept Elect & Elect Engn, Guildford GU2 7XH, Surrey, England..
    Agazzi, Laura
    Univ Twente, MESA Inst, Integrated Opt Micro Syst, POB 217, NL-7500 AE Enschede, Netherlands..
    Loiko, Pavel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Pollnau, Markus
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics. Univ Surrey, Adv Technol Inst, Dept Elect & Elect Engn, Guildford GU2 7XH, Surrey, England.;Univ Twente, MESA Inst, Integrated Opt Micro Syst, POB 217, NL-7500 AE Enschede, Netherlands.
    Energy-Transfer Processes Among Non-Homogeneously Distributed Rare-Earth Ions and Impact on Amplification and Lasing2018In: 20th International Conference on Transparent Optical Networks, ICTON / [ed] Jaworski, M Marciniak, M, Institute of Electrical and Electronics Engineers (IEEE), 2018, article id 8473493Conference paper (Refereed)
    Abstract [en]

    Energy-transfer processes such as energy-transfer upconversion are often detrimental to the performance of rareearth- doped amplifiers and lasers on the typical luminescence transitions in the near-infrared spectral region between 1-2 mu m. In order to quantify the influence of these interionic processes on amplification and lasing, not only luminescence decay curves have to be measured, but also the population dynamics of the electronic level scheme need to be modeled. The usually encountered non-homogeneous ion distributions complicate the situation. Here we present a stochastic model of energy-transfer processes that takes a statistical ion distribution into account. The influence of energy-transfer upconversion and cross-relaxation on amplification and lasing on the 1.06 mm transition in Nd3+, the 1.53 mm transition in Er3+, or the 1.84 mm transition in Tm3+ under these conditions is investigated.

  • 2. Glazunov, I. V.
    et al.
    Skoptsov, N. A.
    Malyarevich, A. M.
    Yumashev, K. V.
    Loiko, Pavel
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Fotonik och mikrovågsteknik, FMI.
    Device for measurment of relaxation time of the bleached state of optical materials by the "pump-probe" method in sub-mu s time domain2016In: Devices and Methods of Measurements, ISSN 2220-9506, Vol. 7, no 1, p. 24-31Article in journal (Refereed)
    Abstract [en]

    The use of passive shutters to control the duration of the light pulses is an important aspect in the miniature and microchip lasers. One of the key spectroscopic characteristics which determine the properties of the material, which can be used as a passive shutter is relaxation time of its bleached state. We describe a device for determination of relaxation time of the bleached state in optical materials by the "pump-probe" method in the sub-mu s time domain. This device allows one to determine relaxation times for materials which absorb at the light wavelength of 1.5 mu m, e.g., materials doped with cobalt ions Co2+. The results of test examinations of the device are described, and the relaxation time of the bleached state of Co2+ ions is measured for a novel material - transparent glass-ceramics with Co2+:Ga2O3 nanophase - amounting to 190 +/- 6 ns.

  • 3.
    Loiko, P.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Pollnau, M.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics. Univ Surrey, Adv Technol Inst, Guildford GU2 7XH, Surrey, England..
    Stochastic Model of Energy-Transfer Processes Among Rare-Earth Ions2018In: FIBER LASERS AND GLASS PHOTONICS: MATERIALS THROUGH APPLICATIONS / [ed] Taccheo, S Mackenzie, JI Ferrari, M, SPIE-INT SOC OPTICAL ENGINEERING , 2018, article id 106831XConference paper (Refereed)
    Abstract [en]

    Energy-transfer processes strongly affect the performance of lanthanide-doped photonic devices. In this work, we introduce a simple stochastic model of energy-transfer processes and successfully apply it to the example of cross-relaxation (CR) and energy-transfer upconversion (ETU) in amorphous Al2O3:Tm3+ waveguides on silicon intended for lasers operating at similar to 2 mu m. The stochastic model is based on the rate-equation formalism and considers two spectroscopically distinct ion classes, namely single ions and ions with neighbours (pairs and clusters), with the corresponding ion fractions being dependent on the doping concentration. We prove that a more accurate description of the luminescence properties of amorphous Al2O3:Tm3+ is obtained when accounting for the presence of these distinct ion classes. Based on the developed model, we derive microscopic CR and ETU parameters of C-CR = 5.83 x 10(-38) cm(6)s(-1), C-ETU1 = 0.93 x 10(-40) cm(6)s(-1), and C-ETU2 = 7.81 x 10(-40) cm(6)s(-1), and determine the laser quantum efficiency eta(q) of excitation of Tm3+ ions in the upper laser level. For the maximum Tm3+ concentration of 5.0 x 10(20) cm(-3) studied experimentally in this investigation, eta(q) reaches 1.73. Furthermore, the transition cross-sections at the pump and laser wavelengths are determined. For the H-3(6) -> F-3(4) transition, the maximum stimulated-emission cross-section is sigma(e) = 0.47 x 10(-20) cm(2) at 1808 nm.

  • 4.
    Loiko, Pavel
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Ismail, Nur
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Bradley, Jonathan D. B.
    Götelid, Mats
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Pollnau, Markus
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Refractive-index variation with rare-earth incorporation in amorphous Al2O3 thin films2017In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 476, p. 95-99Article in journal (Refereed)
    Abstract [en]

    Rare-earth-doped amorphous aluminum oxide (Al2O3;RE3+) thin films are attractive materials for near-IR amplifiers and lasers that can be integrated with silicon-on-insulator waveguides or deposited onto CMOS-fabricated integrated optical structures. We characterize reactively co-sputtered Al2O3;Tm3+ films on silicon by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Raman spectroscopy. The refractive index is systematically studied for different Tm3+ concentrations. The resulting increase of refractive index is explained by analyzing the mechanism of incorporating Tm3+ ions into the amorphous Al2O3 network. Sellmeier dispersion formulas are presented.

  • 5.
    Loiko, Pavel
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Pollnau, Markus
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Stochastic Model of Energy-Transfer Processes Among Rare-Earth Ions. Example of Al2O3:Tm3+2016In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 46, p. 26480-26489Article in journal (Refereed)
    Abstract [en]

    Energy-transfer processes strongly affect the performance of lanthanide-doped photonic devices. In this work, we introduce a simple stochastic model of energy-transfer processes and successfully apply it to the example of cross-relaxation (CR) and energy-transfer upconversion (ETU) in amorphous Al2O3:Tm3+ waveguides on silicon intended for lasers operating at similar to 2 mu m. The stochastic model is based on the rate-equation formalism and considers two spectroscopically distinct ion classes, namely single ions and ions with neighbors (pairs and clusters), with the corresponding ion fractions being dependent on the doping concentration. We prove that a more accurate description of the luminescence properties of amorphous Al2O3:Tm3+ is obtained when accounting for the presence of these distinct ion classes. Based on the developed model, we derive microscopic CR and ETU parameters of C-CR = 5.83 X 10(-38) cm(6) s(-1), C-ETU1 = 0.93 x 10(-40) cm(6) s(-1), and C-Eru2 = 7.81 x 10(-40) cm(6) s(-1), and determine the laser quantum efficiency eta(q) of excitation of Tm3+ ions in the upper laser level. For the maximum Tm3+ concentration of 5.0 X 10(20) cm(-3) studied experimentally in this investigation, eta(q) reaches 1.73. Furthermore, the transition cross sections at the pump and laser wavelengths are determined. For the H-3(6) -> F-3(4) transition, the maximum stimulated-emission cross section is sigma(e) = 0.47 X 10(-20) cm(2) at 1808 nm.

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