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  • 51.
    Holmgren, Stefan
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Ultrashort single-shot pulse characterization with high spatial resolution using localized nonlinearities in ferroelectric domain walls2007In: Optics letters, ISSN 0146-9592, Vol. 32, no 11, p. 1545-1547Article in journal (Refereed)
    Abstract [en]

    Second-order nonlinearities localized in the regions adjacent to the ferroelectric domain wall in KTiOPO4 are used to realize a single-shot noncollinear frequency-resolved optical gating arrangement for ultrashort pulse characterization with high spatial resolution. Cerenkov phase matching is utilized to achieve spectral dispersion and makes the same nonlinear crystal applicable over wide spectral ranges from the visible to the mid-infrared.

  • 52.
    Jacobsson, Björn
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    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.
    Narrowband and tunable ring optical parametric oscillator with a volume Bragg grating2007In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 32, no 22, p. 3278-3280Article in journal (Refereed)
    Abstract [en]

    We demonstrate a tunable nanosecond optical parametric oscillator with a narrowed signal spectrum. This was done by use of a volume Bragg grating based retrorefiector, which makes the tuning simple and yields a compact design. Using periodically poled KTiOPO4 as the nonlinear medium, we generated 0.42 mJ of signal energy at 760 nm with a tuning range of 5 nm (2.6 THz) and a bandwidth of 0.25nm (130 GHz) when the oscillator was pumped at 532 nm with 1.3 mJ of energy.

  • 53.
    Jacobsson, Björn
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    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 Ring Optical Parametric Oscillator with a Volume Bragg Grating2007In: 2007 CONFERENCE ON LASERS & ELECTRO-OPTICS/QUANTUM ELECTRONICS AND LASER SCIENCE CONFERENCE (CLEO/QELS 2007), NEW YORK: IEEE , 2007, p. 1085-1086Conference paper (Refereed)
    Abstract [en]

    We demonstrate a new technique for locking and narrowing the wavelength of a ring optical parametric oscillator with a volume Bragg grating at an angle in a retroreflector design.

  • 54.
    Jang, Hoon
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Strömqvist, Gustav
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Control of forward stimulated polariton scattering in periodically-poled KTP crystals2013In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 21, no 22, p. 27277-27283Article in journal (Refereed)
    Abstract [en]

    We report suppression of forward stimulated polariton scattering (SPS) in chi((2)) structured media. Periodic poling in KTiOPO4 (KTP) leads to the destructive interference of phonon-polariton waves, which is responsible for the dependence of the SPS threshold on the poling period. This was confirmed by comparing the SPS thresholds in periodically-poled KTP (PPKTP) crystals with different poling periods. Further confirming the physical picture, we studied the changes in the Stokes power distribution as a function of the rotation angle of the PPKTP crystal.

  • 55.
    Jang, Hoon
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Strömqvist, Gustav
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Control of forward stimulated polariton scattering in periodically poled nonlinear crystals2012In: 2012 Conference on Lasers and Electro-Optics, CLEO 2012, IEEE , 2012, p. 6325627-Conference paper (Refereed)
    Abstract [en]

    Periodic poling in KTP leads to periodic phase reversal of the polaritons generated in Cherenkov phase-matched direction. This is responsible for the dependence of stimulated Raman scattering threshold on crystal rotation angle and poling period.

  • 56.
    Jang, Hoon
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Strömqvist, Gustav
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Zukauskas, Andrius
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Enhanced Backward Stimulated Raman Scattering in Periodically Poled KTiOPO42012Conference paper (Refereed)
  • 57.
    Jang, Hoon
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Viotti, Anne-Lise
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Strömqvist, Gustav
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Zukauskas, Andrius
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Counter-propagating parametric interaction with phonon-polaritons in periodically poled KTiOPO42017In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 25, no 3, p. 2677-2686Article in journal (Refereed)
    Abstract [en]

    Strongly enhanced backward stimulated polariton scattering (BSPS) is demonstrated in periodically-poled KTiOPO4 (KTP) crystals with a high power-conversion efficiency up to 70%. We study the physical mechanism of such counter-propagating parametric interaction with phonon-polaritons in χ(2) modulated structures. BSPS is a three-wave mixing that is distinguished from backward stimulated Raman scattering (BSRS), while a strong absorption at large polariton wave-vectors can still make BSPS display certain characteristics of BSRS such as self-compression of the Stokes pulse. We also compare BSPS with counter-propagating parametric oscillation in the near- and mid-infrared range, providing an estimation of the fabrication error margin to expect the outcome of their competition in the same device.

  • 58.
    Jang, Hoon
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Zukauskas, Andrius
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Highly efficient backward stimulated polariton scattering in periodically poled KTiOPO42015In: CLEO: Science and Innovations 2015, 2015Conference paper (Refereed)
    Abstract [en]

    X(2)-nonlinearity enhanced by crystal lattice contribution in the THz-region is behind backward stimulated polariton scattering with efficiencies exceeding 50% in PPKTP where forward scattering process is suppressed. 10-times compression of counter-propagating signal is observed.

  • 59.
    Jenkins, Amelia
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Canalias, Carlota
    KTH.
    Pasiskevicius, Valdas
    KTH.
    Who needs mirrors?2007In: Nature Photonics, ISSN 1749-4885, E-ISSN 1749-4893, Vol. 1, no 8, p. 484-484Article in journal (Other academic)
  • 60.
    Johansson, Sandra
    et al.
    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.
    Bjurshagen, Stefan
    KTH, School of Engineering Sciences (SCI), Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Koch, Ralf
    An all solid-state UV source based on a frequency-quadrupled, passively Q-switched 946 nm laser2007In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 15, no 2, p. 449-Article in journal (Refereed)
    Abstract [en]

    We report a 236 nm light source with 20 mW of average power based on critically phase-matched second-harmonic generation in a beta-barium borate crystal at room temperature. The fundamental light source was a passively Q-switched 946 nm Nd: YAG laser tunable from 10-38 kHz and with a pulse length of 16 ns. In the generation of 473 nm light, periodically poled KTP and BiBO was compared in terms of conversion efficiency and stability.

  • 61.
    Kianirad, Hoda
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Domain wall motion in stoichiometric LiTaO3 induced by low-energy electron beam2019In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118Article in journal (Refereed)
    Abstract [en]

    Scanning electron microscopy was used to study the mobility of domain walls in vapor-transport equilibrated stoichiometric LiTaO3. By using low-acceleration voltage, switching occurs solely for polarization pointing-up domains, resulting in fast domain-wall motion. When the incoming electron beam was more energetic with larger penetration depth, the switching instead occurred for polarization pointing down domains. Our results are discussed in terms of the interaction of the scanning electron beam with the polarization-screening charges at the crystal surface.

  • 62.
    Kianirad, Hoda
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Domain wall motion in stoichiometric LiTaO3 induced by low-energy electron beam2019In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 115, no 5, article id 052901Article in journal (Refereed)
    Abstract [en]

    Scanning electron microscopy was used to study the mobility of domain walls in vapor-transport equilibrated stoichiometric LiTaO3. By using low-acceleration voltage, switching occurs solely for polarization pointing up domains, resulting in fast domain-wall motion. When the incoming electron beam was more energetic with larger penetration depth, the switching instead occurred for polarization pointing down domains. Our results are discussed in terms of the interaction of the scanning electron beam with the polarization-screening charges at the crystal surface.

  • 63.
    Kianirad, Hoda
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Lindgren, Gustav
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Peña, A.
    Zukauskas, Andrius
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Ménaert, B.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Boulanger, B.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Stabilization of domain structures in Rb-doped KTiOPO 4 for high-temperature processes2019In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 114, no 5, article id 052904Article in journal (Refereed)
    Abstract [en]

    A way to stabilize the domain structure in periodically poled Rb-doped KTiOPO 4 samples at high-temperatures is presented. The domain contraction along the b-crystallographic axis that is observed when crystals are annealed at high temperatures is suppressed when the ends of the domains along the b-axis are diced away. Additionally, the thermal stability of self-assembled domain gratings with a sub-μm average periodicity of 650 ± 200 nm and a domain-width of 225 ± 75 nm in mm-thick samples is investigated, and it is shown that the key factor for the domain stability is the domain width rather than the interdomain distance.

  • 64.
    Kianirad, Hoda
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Zakauskas, Andrius
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Domain dynamics in Stoichiometric Lithium Tantalate revealed by etching and on-line Second Harmonic Generation2015Conference paper (Refereed)
    Abstract [en]

    Periodically poled LiTaO3 has a shorter cut-off wavelength than KTP and LiNbO3, which makes this material attractive for UV generation. However, the standard congruent material suffers strongly from photorefractive damage which has limited its use in the UV. It is expected that stoichiometric LiTaO3 (SLT) would make a superior material in this context, as the defect concentration, which directly relates to the damage, is strongly reduced. Close to perfectly stoichiometric crystals can be obtained by post growth diffusion of Li2O into the crystal at high temperatures to compensate the Li2O deficiency, so called vapour transport equilibrated (VTE) SLT [1]. The coercive field is drastically reduced for SLT which facilitates the way for fabricating QPM devices [2]. However lower defects and reduced coercive field might cause instability for charged domain walls (DW) or walls that are not in their lowest energy state. Since the stability mechanism for VTE SLT is not very well known, its investigation would lead to improvement in device fabrication with short period and also helps to understand the DW dynamics.

     

    In this work, we study the impact of chemical etching after poling on domain stability of SLT. We show that chemical etching right after poling induced DW movement without any external field. We demonstrate that when the original DW configuration is head-to-head (HH) or tail-to-tail (TT), the DW movement results in backswitching or merging with neighboring domians, respectively. Our finding are monitored by in situ SHG during etching followed by characterization of the domain structure with optical microscopy. We also show that this behavior is independent of the domain orientation with respect the crystallographic axes.

  • 65.
    Kianirad, Hoda
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Zukauskas, Andrius
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Domain dynamics in stoichiometric lithium tantalate revealed by wet etching and on-line second harmonic generation2017In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 121, no 18, article id 184103Article in journal (Refereed)
    Abstract [en]

    The effect of chemical etching on the stability of domains in periodically poled stoichiometric lithium tantalate is studied by on-line second harmonic generation and microscopy. It is found that wet etching directly after poling leads to domain-wall movement, resulting in back-switching or domain merging. Head-to-head domains tend to backswitch, while tail-to-tail domains merge. For samples where the domain structure stabilized for longer time, no domain motion is observed when etched.

  • 66.
    Kianirad, Hoda
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Zukauskas, Andrius
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Domain engineering using Si-electrode stamp2016Conference paper (Refereed)
  • 67.
    Kianirad, Hoda
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Zukauskas, Andrius
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    On the stability of periodically poled Lithium Tantalate2014Conference paper (Refereed)
  • 68.
    Kianirad, Hoda
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Zukauskas, Andrius
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Frisk, Thomas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Contact poling of Rb:KTiOPO4 using a micro-structured silicon electrode2015In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 23, no 2, p. 636-641Article in journal (Refereed)
    Abstract [en]

    A contact poling technique for domain engineering of ferroelectrics using a micro-structured silicon electrode is demonstrated on Rb:KTiOPO4. High quality QPM gratings were reproducibly fabricated. The silicon electrode is reusable and the technique potentially suitable when complex structures with sub-mu m features are to be domain engineered, which otherwise is incompatible with conventional photolithography. A non-negligible domain broadening was seen and attributed to a low nucleation rate using this type of electrode. However, under the appropriate poling conditions, this could be exploited to obtain a QPM grating with a short pitch (2 mu m), equal to half of the electrode period.

  • 69.
    Kianirad, Hoda
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Zukauskas, Andrius
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Frisk, Thomas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Contact poling of RKTP using a micro-structured silicon electrode2014Conference paper (Other academic)
  • 70.
    Kianirad, Hoda
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Zukauskas, Andrius
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Frisk, Thomas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Contact poling of RKTP with silicon pillars2013In: 2013 Conference on Lasers and Electro-Optics Europe and International Quantum Electronics Conference, CLEO/Europe-IQEC 2013, IEEE Computer Society, 2013, p. 6800873-Conference paper (Refereed)
    Abstract [en]

    Quasi-phase-matching (QPM) is a method to get tailored efficient second order nonlinear interactions [1]. Several techniques exist for fabrication of periodic domain structures in ferroelectric crystals for QPM frequency conversion. By far, electric field poling using lithographically patterned electrodes on the z-face of the crystal is the most common one [2]. High-quality periodically inverted ferroelectric domain structures in flux grown KTiOP 4 (KTP) crystals were fabricated already in the late 90's using this technique [3], and recently periodic domain sizes of few hundred nanometers were fabricated in 1 mm thick samples thanks to the quasi-one dimensional structure of KTP. It has recently also been shown that a slight Rb doping of the KTP crystal (RKTP) facilitates the periodic poling [4]. However, fabrication of two-dimensional (2D) domain structures in RKTP has not yet been investigated. A disadvantage with the lithographic patterning is that each sample needs to be patterned individually, which is tedious and time consuming. Moreover, when it comes to the small domain features, which are required by the next generation of nonlinear optical devices, a more versatile poling technique has to be developed due to the limitations of conventional photolithography. Structured silicon has been investigated as an alternative electrode for formation of 1D domains by contact poling in LiNb3 [5]. However, these electrodes were fabricated by wet etching and the sample thickness was limited to ∼200 μm.

  • 71.
    Kores, Cristine C.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Mutter, Patrick
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Kianirad, Hoda
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Quasi-phase matched second harmonic generation in periodically poled Rb-doped KTiOPO4 ridge waveguide2018In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 26, no 25, p. 33142-33147Article in journal (Refereed)
    Abstract [en]

    A 10.8 mu m wide ridge waveguide was fabricated by diamond-blade dicing in an ion-exchanged periodically poled Rb-doped KTiOPO4 sample. The waveguide was used to generate blue second harmonic light at 468.8 nm in the TM(00 )mode through first order Type I quasi-phase matching, exploiting the large d(33) coefficient of the crystal. It was evaluated using a cw Ti:Sapphire laser, and 6.7 mu W of blue light was generated with 5.8 mW of fundamental radiation at 933.8 nm coupled through the waveguide. The results presented here pave the way for efficient nonlinear processes in a waveguide format. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

  • 72.
    Kortsdottir, Katrin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Wreland Lindström, Rakel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Dominiguez Fernandez, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Hydrogen fuel impurities: The effect of CO2 and hydrocarbons at the anode of a PEM fuel cell2011In: Proceedings of EFC2011, 2011, p. EFC11159-Conference paper (Refereed)
    Abstract [en]

    Hydrogen fuel produced by reforming contains, in addition to hydrogen, CO2, CO, sulphur compounds and small hydrocarbons in varying amount. The effect of CO2 and a few example hydrocarbons has been studied on traditional PEM fuel cell anodes by cyclic voltammetry and constant load experiments. In addition, Electrochemical Impedance Spectroscopy and Mass Spectrometry have been employed to aid in the analysis. The effect of adsorption potential, cell temperature, humidity of the feed gases and concentrations of selected impurities has been studied.

  • 73. Lagatsky, A. A.
    et al.
    Brown, C. T. A.
    Sibbett, W.
    Holmgren, Stefan J.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    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.
    Rafailov, E. V.
    Efficient doubling of femtosecond pulses in aperiodically and periodically poled KTP crystals2006Conference paper (Refereed)
    Abstract [en]

    Efficient doubling of femtosecond pulses from a mode-locked Yb:KYW laser in periodically poled and aperiodically poled KTP is reported. Second-harmonic conversion efficiencies of up to 58% have been achieved and 354-fs pulses generated at 522nm.

  • 74. Lagatsky, A. A.
    et al.
    Brown, C.T.A.
    Sibbett, W.
    Holmgren, Stefan J.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    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.
    Rafailov, E. U.
    Efficient Doubling of Femtosecond Pulses in Aperiodically and Periodically Poled KTP Crystals2007In: Optics express, ISSN 1094-4087, Vol. 15, no 3, p. 1155-1160Article in journal (Refereed)
    Abstract [en]

    Efficient doubling of femtosecond pulses in periodically and aperiodically poled KTP crystals is demonstrated by employing the quasi-phasematched frequency conversion technique. Conversion efficiencies as high as 60% were achieved using either aperiodically or periodically poled KTP nonlinear crystals in an extracavity, single-pass configuration using a diode-pumped femtosecond Yb:KYW laser as the pump source. The temporal characteristics of the frequency-doubled pulses as a function of focusing conditions in a "thick" nonlinear crystal regime have been investigated experimentally and pulses as short as 177 fs have been generated at around 520 nm under strong focusing conditions using a KTP crystal with aperiodic poling.

  • 75.
    Laurell, Fredrik
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Calmano, Thomas
    Mueller, Sebastian
    Zeil, Peter
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Huber, Guenter
    Laser-written waveguides in KTP for broadband Type II second harmonic generation2012In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 20, no 20, p. 22308-22313Article in journal (Refereed)
    Abstract [en]

    Femto-second laser writing was used to fabricate waveguides in a z-cut KTP sample with losses below 0.8 dB/ cm. They were used for efficient, broad bandwidth, Type II birefringent second harmonic generation to the green. The temperature and wavelength bandwidth were, 28 degrees C.cm and 0.85 nm.cm, respectively.

  • 76.
    Laurell, Fredrik
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Calmano, T.
    Müller, S.
    Huber, G.
    Laser written waveguides in KTP for broadband Type II frequency doubling2012In: Proceedings ECIO 2012, 2012Conference paper (Refereed)
    Abstract [en]

    Femto-second laser writing was used to fabricatewaveguides in KTP with losses below 0.8 dB/cm. They were usedfor efficient broad bandwidth, Type II frequency doubling of cwTi-sapphire laser radiation at 1080.4 nm.

  • 77.
    Laurell, Fredrik
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Hirohashi, Junji
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Wang, Shunhua
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Periodically poled nonlinear materials - engineered for applications and away from damage2007In: Advanced Solid-State Photonics 2007, Optical Society of America, 2007Conference paper (Refereed)
    Abstract [en]

    Periodic poling issues and damage measurements for important ferroelectrics like KTP, KNbO3 and undoped and MgO-doped stoichiometric LiNbO3 and LiTaO3 will be presented together with suggestions on how optimize choose and use these materials.

  • 78.
    Laurell, Fredrik
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Functional microlasers2007Conference paper (Refereed)
  • 79.
    Laurell, Fredrik
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Functional nonlinearoptics using periodically poled ferroelectrics2007Conference paper (Refereed)
  • 80.
    Laurell, Fredrik
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Physics.
    Periodically poled crystals with submicrometerdomain gratings: fabrication, evaluation and applications2005Conference paper (Refereed)
  • 81.
    Laurell, Fredrik
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Physics.
    Tailoring ferroelectric crystals2005Conference paper (Refereed)
  • 82.
    Laurell, Fredrik
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Zukauskas, Andrius
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Liljestrand, Charlotte
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Nanodomain Engineered Ferroelectrics for Nonlinear Optical Applications2013In: Progress In Electromagnetics Research Symposium, 2013Conference paper (Other academic)
  • 83.
    Laurell, Fredrik
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Müller, S.
    Calmano, T.
    Metz, P.
    Kränkel, C.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Liljestrand, Charlotte
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Huber, G.
    A fs-laser written waveguide in periodically poled Rb: KTiOPO4 forefficient second harmonic generation2014Conference paper (Refereed)
  • 84.
    Laurell, Fredrik
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Gallo, Katia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Nonlinear optics in 1D and 2D domain engineered crystals2011Conference paper (Refereed)
  • 85.
    Laurell, Fredrik
    et al.
    KTH, Superseded Departments, Physics.
    Pasiskevicius, Valdas
    KTH, Superseded Departments, Physics.
    Canalias, Carlota
    KTH, Superseded Departments, Physics.
    Wang, S.
    Periodic domain engineering in KTP2004Conference paper (Refereed)
  • 86.
    Laurell, Fredrik
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Strömqvist, Gustav
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Modifying of stimulated Raman scattering by electric field poling of ferroelectric crystals2009Conference paper (Refereed)
  • 87.
    Liljestrand, Charlotte
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Chemical Patterning by ion exchange of Rubidium doped KTiOPO4 for electric field periodic poling2015In: Optics and Photonics Sweden 2015, 2015Conference paper (Other academic)
  • 88.
    Liljestrand, Charlotte
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Chemical Patterning of Rubidium doped KTiOPO4 for electric field periodic poling2014In: Optics and Photonics Sweden 2014, Gothenburg, November 11-12, 2014, 2014Conference paper (Other academic)
  • 89.
    Liljestrand, Charlotte
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Coercive Field Engineering in Bulk Rb-doped KTiOPO42016Conference paper (Refereed)
  • 90.
    Liljestrand, Charlotte
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Ion-Exchange Induced Coercive Field Gratings for QPM Devices in Rb-doped KTP2016In: 2016 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO), IEEE conference proceedings, 2016Conference paper (Refereed)
    Abstract [en]

    We demonstrate 3.16 mu m periodic poling in RKTP using a coercive field grating induced by ion-exchange. The process results in a linear refractive index change over the sample thickness, adding extra tunability to the QPM device.

  • 91.
    Liljestrand, Charlotte
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Periodic poling of Rb-doped KTiOPO4 by coercive field engineering2016In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 24, no 13, p. 14682-14689Article in journal (Refereed)
    Abstract [en]

    We demonstrate fine-pitch periodic poling of bulk Rb-doped KTiOPO4 using a coercive field grating induced by ion-exchange. These samples were used for quasi phase matched (QPM) second harmonic generation at 795 nm with a normalized conversion efficiency of 1.7% W−1cm−1. Additionally, the ion-exchange introduced a refractive index change over the sample thickness resulting in a phasematching wavelength shift of 0.21 nm, adding extra tunability to the QPM device.

  • 92.
    Liljestrand, Charlotte
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Zukauskas, Andrius
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    A highly efficient mirrorless optical parametricoscillator pumped by nanosecond pulses2017In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794Article in journal (Refereed)
  • 93.
    Liljestrand, Charlotte
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Zukauskas, Andrius
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Highly efficient mirrorless optical parametric oscillator pumped by nanosecond pulses2017In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 42, no 13, p. 2435-2438Article in journal (Refereed)
    Abstract [en]

    A highly efficient mirrorless optical parametric oscillator (MOPO), pumped by narrowband nanosecond pulses at 1064 nm, is demonstrated. The MOPO is based on quasi-phase-matched parametric interaction of counter-propagating photons in 1-mm-thick periodically poled Rb-doped KTiOPO4 crystal with a period of 755 nm. It generates a co-propagating signal at 1740 nm and a counter-propagating idler at 2741 nm, achieving mJ-level output with a total signal-and-idler conversion efficiency of 47%. Both generated waves present narrow spectral bandwidths, thanks to the unique properties of the counter-propagating nonlinear interaction. The high conversion efficiency, inherently narrow spectral width, and simplicity of the optical setup make the MOPO an attractive alternative to conventional co-propagating optical parametric oscillators.

  • 94.
    Liljestrand, Charlotte
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Zukauskas, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Mirrorless optical parametric oscillator pumped by nanosecond pulses2017In: Optics InfoBase Conference Papers, Optics Info Base, Optical Society of America, 2017, Vol. Part F82Conference paper (Refereed)
  • 95.
    Lindgren, G.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Conductive atomic force microscopy studies of charged domain walls in KTiOPO42018In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 8, no 8, article id 085214Article in journal (Refereed)
    Abstract [en]

    We study the conductive properties of charged domain walls in KTiOPO4 using conductive atomic force microscopy. We show that the region of increased conductivity at the domain wall broadens when the wall is in motion, extending from the initial wall position to the final wall position. When wall motion stops, the conductive region attains a narrow width. The magnitude of the conductivity of charged domain walls is four times larger than that of the surrounding domains, as is the case at stationary wall. We investigate

  • 96. Lindgren, Gustav
    et al.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Conductive properties of charged domain walls in motion in KTiOPO4In: Article in journal (Refereed)
  • 97.
    Lindgren, Gustav
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Domain wall conductivity in KTiOPO4 crystals2017In: APL Materials, ISSN 2166-532X, Vol. 5, no 7, article id 076108Article in journal (Refereed)
    Abstract [en]

    We study the local ionic conductivity of ferroelectric domain walls and domains in KTiOPO4 single-crystals. We show a fourfold increase in conductivity at the domain walls, compared to that of the domains, attributed to an increased concentration of defects. Our current-voltage measurements reveal memristive-like behavior associated with topographic changes and permanent charge displacement. This behavior is observed for all the voltage sweep-rates at the domain walls, while it only occurs for low frequencies at the domains. We attribute these findings to the redistribution of ions due to the applied bias and their effect on the tip-sample barrier.

  • 98.
    Lindgren, Gustav
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Enhanced Domain Wall Conductivity and Memristivity in KTiOPO42016Conference paper (Refereed)
  • 99. Lindgren, Gustav
    et al.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Levlev, Anton
    Vasudevan, Rama
    Ovchinnikova, Olga
    Jesse, Stephen
    Kalinin, Sergei
    Direct evidence of ionic migration during local ferroelectric switchingIn: Article in journal (Refereed)
  • 100.
    Lindgren, Gustav
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Ievlev, A.
    Jesse, S.
    Ovchinnikova, O. S.
    Kalinin, S. V.
    Vasudevan, R. K.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Elasticity Modulation Due to Polarization Reversal and Ionic Motion in the Ferroelectric Superionic Conductor KTiOPO42018In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 38, p. 32298-32303Article in journal (Refereed)
    Abstract [en]

    The coupling between ionic degrees of freedom and ferroelectricity has received renewed attention in recent years, given that surface electrochemical processes have been shown to be intrinsically linked to ferroelectric phase stability in ultrathin ferroelectric films. However, the coupling between bulk ionic transport and local polarization switching has received less attention, as typically the bulk ionic mobilities are low for common ferroelectrics at room temperature. Here, we use the coupled band-excitation method in conjunction with site-correlated time-of-flight secondary ion mass spectrometry, to determine the coupling between ferroelectric switching and ionic motion in single crystal KTiOPO4. The local scanning probe measurements indicate a substantial softening, as determined by resonant frequency changes, during reversal of polarization along one direction. These changes are correlated with the mass spectrometry measurements, showing a polarization-dependent accumulation of K ions at the polar surfaces, thus corroborating their role in the screening process. These studies shed light on the interplay between ionic dynamics and bulk ferroelectric switching and have implications for studies on domain wall conductivity, chemical switching, and bulk and surface-screening phenomena. 

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