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  • 1.
    Bjurshagen, Stefan
    et al.
    KTH, Superseded Departments, Physics.
    Evekull, D.
    Acreo AB, Kista.
    Koch, R.
    Acreo AB, Kista.
    Efficient generation of blue light by frequency doubling of a Nd:YAG laser operating on 4F3/2 → 4I9/2 transitions2003In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 76, no 2, p. 135-141Article in journal (Refereed)
    Abstract [en]

    Efficient room-temperature operation of F-4(3/2) --> I-4(9/2) transitions in diode-end-pumped Nd:YAG lasers at 946 nm and 938.5 nm is reported. 7.0-W continuous-wave output power at 946 nm and 3.9 W at 93 8.5 nm have been obtained. An analytical model has been developed for the quasi-three-level laser including the influence of energy-transfer upconversion. Frequency doubling of these transitions in periodically poled KTP generated blue light at 473 nm and 469 nm. Both single-pass extra-cavity as well as intracavity schemes have been investigated.

  • 2. Cai, Y.
    et al.
    Chen, Yuntian
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Eyyuboglu, H. T.
    Baykal, Y.
    Propagation of laser array beams in a turbulent atmosphere2007In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 88, no 3, p. 467-475Article in journal (Refereed)
    Abstract [en]

    The propagation of phase-locked and non-phase-locked laser array beams of radial and rectangular symmetries in a turbulent atmosphere are investigated based on the extended Huygens-Fresnel integral. The beamlet used in our paper for constructing the laser array beams is of elliptical Gaussian mode. Analytical formulae for the average irradiance of phase-locked and non-phase-locked radial and rectangular laser array beams are derived through vector integration and tensor operation. The irradiance properties of these laser array beams in a turbulent atmosphere are studied numerically. It is found that both phase-locked and non-phase-locked radial and rectangular laser array beams eventually become circular Gaussian beams in a turbulent atmosphere, which is much different from their propagation properties in free space. The propagation properties are closely related to the parameters of laser array beams and the structure constant of the turbulent atmosphere.

  • 3. Cai, Y.
    et al.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Propagation of a Laguerre-Gaussian beam through a slightly misaligned paraxial optical system2006In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 84, no 3, p. 493-500Article in journal (Refereed)
  • 4.
    Chen, Zhihui
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Yu, Z. -Y
    Liu, Y. -M
    Lu, P. -F
    Fu, Ying
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Multiple beam splitting to free space from a V groove in a photonic crystal waveguide2011In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 102, no 4, p. 857-861Article in journal (Refereed)
    Abstract [en]

    We present multiple-beam splitting to free space from a V groove in a two-dimensional photonic crystal waveguide (PCW) with a few additional dielectric rods at the exit of the PCW. Numerical study shows that 'one-beam-in to two-beams-out' (one-to-two, also denoted as Y-shaped), one-to-three, and one-to-five beam splittings can be easily realized over a wide bandwidth, and the split beams have remarkable properties such as symmetric energy distributions and high directional transmissions. Off-axis directional emission can also be achieved by simple displacements of the additional rods at the exit of the PCW.

  • 5.
    Coetzee, R. S.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Zheng, X.
    Sun Yat Sen Univ, Sch Phys, Guangzhou 510275, Guangdong, Peoples R China..
    Fregnani, L.
    Univ Pavia, Dipartimento Ingn Ind & Informaz, Via Ferrata 5, I-27100 Pavia, Italy..
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Narrowband, tunable, 2 A mu m optical parametric master-oscillator power amplifier with large-aperture periodically poled Rb:KTP2018In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 124, no 6, article id 124Article in journal (Refereed)
    Abstract [en]

    A high-energy, ns, narrow-linewidth optical parametric oscillator and amplifier system based on large-aperture periodically poled Rb:KTP is presented. The 2 A mu m seed source is a singly resonant OPO locked with a transversely chirped volume Bragg grating, allowing a wavelength tuning of 21 nm and output linewidth of 0.56 nm. A maximum output energy of 52 mJ and conversion efficiency of 36% was obtained from the amplifier for a pump energy of 140 mJ. The high-energy and the robust and narrow dual-wavelength spectra obtained make this system an ideal pump source for difference frequency generation-based THz generation schemes.

  • 6.
    Coetzee, Riaan Stuart
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Zheng, Xionghua
    School of Physics, Sun Yat-Sen University.
    Fregnani, Luigi
    Universita di Pavia.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Narrowband, tunable, 2 μm optical parametric master-oscillator power amplifier with large-aperture periodically poled Rb:KTP2018In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649Article in journal (Refereed)
    The full text will be freely available from 2020-01-01 15:22
  • 7.
    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.

  • 8. Eismann, U.
    et al.
    Gerbier, F.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Zukauskas, Andrius
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Trenec, G.
    Vigue, J.
    Chevy, F.
    Salomon, C.
    An all-solid-state laser source at 671 nm for cold-atom experiments with lithium2012In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 106, no 1, p. 25-36Article in journal (Refereed)
    Abstract [en]

    We present an all-solid-state narrow-linewidth laser source emitting 670 mW output power at 671 nm delivered in a diffraction-limited beam. The source is based on a frequency-doubled diode-end-pumped ring laser operating on the 4F 3/2 → 4I 13/2 transition in Nd:YVO 4. By using periodically poled potassium titanyl phosphate (ppKTP) in an external buildup cavity, doubling efficiencies of up to 86% are obtained. Tunability of the source over 100 GHz is accomplished. We demonstrate the suitability of this robust frequency-stabilized light source for laser cooling of lithium atoms. Finally, a simplified design based on intracavity doubling is described and first results are presented.

  • 9. Garcia-Cortes, A.
    et al.
    Serrano, M. D.
    Zaldo, C.
    Cascales, C.
    Stromqvist, G.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Nonlinear refractive indices of disordered NaT(XO4)(2) T=Y, La, Gd, Lu and Bi, X=Mo, W femtosecond laser crystals2008In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 91, no 3-4, p. 507-510Article in journal (Refereed)
    Abstract [en]

    The nonlinear refractive index (n(2)) of several NaT(WO4)(2) (T = Y, La, Gd, Lu and Bi) and NaY(MoO4)(2) femtosecond laser crystals has been measured using the z-scan technique. These tetragonal crystals with structural local disorder present significant n(2) values, which should allow their efficient laser pulsed operation by Kerr-lens mode locking, especially NaBi(WO4)(2), 68x10(-16) cm(2)/W (for sigma light), which is about twice than for the others. This difference is attributed to the high polarizability associated with the lone electron pair of Bi3+.

  • 10. Hakkarainen, T.
    et al.
    Setala, T.
    Friberg, Ari. T.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Near-field imaging of point dipole with silver superlens2010In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 101, no 4, p. 731-734Article in journal (Refereed)
    Abstract [en]

    Making use of exact and quasistatic expressions for the field in near-field imaging of a point dipole by a thin silver slab, we calculate the point-spread function and the associated image resolution. We show that the resolution, which depends on the silver slab thickness and the dipole orientation, generally is better than the conventional diffraction limit and can be as high as lambda/8. The results substantially agree with recent theoretical and experimental studies on 2D objects.

  • 11. Hassinen, T.
    et al.
    Tervo, J.
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Cross-spectral purity of the Stokes parameters2011In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 105, no 2, p. 305-308Article in journal (Refereed)
    Abstract [en]

    We extend the concept of cross-spectral purity from the spectral density to the polarization properties of electromagnetic fields by considering the polarization Stokes parameters. We show that purity conditions similar to those in the case of electromagnetic cross-spectral purity can be derived for all the Stokes parameters. Furthermore, we introduce a situation of strict cross-spectral purity which leads to the equality of the degrees of coherence for electromagnetic fields in the space-time and space-frequency domains.

  • 12.
    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.

  • 13.
    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.

  • 14.
    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.

  • 15.
    Henriksson, Markus
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Sjöqvist, L
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Narrow linewidth 2 mu m optical parametric oscillation in periodically poled LiNbO3 with volume Bragg grating outcoupler2007In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 86, p. 497-501Article in journal (Refereed)
    Abstract [en]

    An optical parametric oscillator using a periodically poled LiNbO3 crystal and a volume Bragg grating output coupler is presented. Signal and idler wavelengths of 2008 and 2264 nm were generated from the 1064 nm Nd:YVO4 pump laser. The Bragg grating was reflecting in a narrow band around 2008 nm, creating a purely singly resonant cavity. Signal and idler linewidths of approximately 0.44 and 0.72 nm, respectively, were measured. This is a reduction of 80 and 60 times compared to when using a mirror as output coupler. A total output energy of 156 mu J was measured with 47% slope efficiency.

  • 16.
    Henriksson, Markus
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Tiihonen, Mikael
    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.
    Mid-infrared ZGP OPO pumped by near-degenerate narrowband type-I PPKTP parametric oscillator.2007In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 88, no 1, p. 37-41Article in journal (Refereed)
    Abstract [en]

    The total pulse energy of the signal and idler in a near-degenerate type-I periodically poled KTiOPO4 (PPKTP) optical parametrical oscillator (OPO) was spectrally confined within a 2 nm spectral bandwidth at 2.13 mu m. This was achieved by using a volume Bragg grating as the output coupler. Both the signal and the idler from the PPKTP OPO were then simultaneously used to pump a mid-infrared ZnGeP2 (ZGP) OPO. The 2 nm bandwidth was narrower than the ZGP crystal acceptance bandwidth and, thus, made efficient conversion in the second OPO possible. A total slope efficiency of 10% from 1.06 mu m to the 3.5-5 mu m region was demonstrated, generating 250 mu J in the mid-IR with only 3.6 mJ of 1.06 mu m pump energy. This corresponds to a Nd:YAG pump to mid-IR conversion efficiency of 7%.

  • 17.
    Hirohashi, Junji
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Physics.
    Quasi-phase-matched frequency conversion in KNbO3 structures consisting of 90-degree ferroelectric domains2005In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 81, p. 761-763Article in journal (Refereed)
    Abstract [en]

    Periodic 90° domain structure with 18.6 μm periodicity was fabricated by applying a 200 V/mm electric field over (1̄01)-cut KNbO3 plate. The blue light generation by quasi-phase-matched frequency doubling in this periodic 90° domain structure is demonstrated. The 90° domain structure completely compensates for a Poynting vector walk-off of the second-harmonic beam. Moreover, these structures exhibit amphoteric Poynting vector refraction properties, i.e., the refraction can be negative or positive depending on the angle of incidence at the 90° domain boundary.

  • 18.
    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.

  • 19. Kajari, E.
    et al.
    Harshman, N. L.
    Rasel, E. M.
    Stenholm, Stig
    KTH, School of Engineering Sciences (SCI), Physics.
    Süssmann, G.
    Schleich, W. P.
    Inertial and gravitational mass in quantum mechanics2010In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 100, no 1, p. 43-60Article in journal (Refereed)
    Abstract [en]

    We show that in complete agreement with classical mechanics, the dynamics of any quantum mechanical wave packet in a linear gravitational potential involves the gravitational and the inertial mass only as their ratio. In contrast, the spatial modulation of the corresponding energy wave function is determined by the third root of the product of the two masses. Moreover, the discrete energy spectrum of a particle constrained in its motion by a linear gravitational potential and an infinitely steep wall depends on the inertial as well as the gravitational mass with different fractional powers. This feature might open a new avenue in quantum tests of the universality of free fall.

  • 20. Kaminski, C. F.
    et al.
    Bai, X. S.
    Hult, J.
    Dreizler, A.
    Lindenmaier, S.
    Fuchs, Laszlo
    Flame growth and wrinkling in a turbulent flow2000In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 71, no 5, p. 711-716Article in journal (Refereed)
    Abstract [en]

    High-speed planar laser-induced fluorescence (PLIF) and 3-D large eddy simulations (LES) are used to study turbulent flame kernel growth, wrinkling and the formation of separated flame pockets in methane/air mixtures. Turbulence was effected by a set of rotary fans situated in a cylindrical enclosure. Flame wrinkling was followed on sequential 2-D OH images captured at kHz repetition rates. Under stoichiometric conditions and low turbulence levels the flame kernel remains singly connected and close to spherical in shape. By increasing turbulence or reducing the stoichiometry of the mixture the formation of separated pockets could be observed and studied. The mechanisms behind these phenomena are investigated qualitatively by LES of a level-set G-equation describing the flame surface propagation in turbulent flows.

  • 21. Karlsson, G.
    et al.
    Laurell, Fredrik
    KTH, Superseded Departments, Physics.
    Tellefsen, J.
    Denker, B.
    Galagan, B.
    Osiko, V.
    Sverchkov, S.
    Development and characterization of Yb-Er laser glass for high average power laser diode pumping2002In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 75, no 1, p. 41-46Article in journal (Refereed)
    Abstract [en]

    A new strong erbium laser glass (SELG) based on a boro-alumo-phosphate composition is reported. We discuss the synthesis and chemical properties together with spectroscopic and thermo-mechanical data. The new glass composition shows excellent laser performance and withstands high-average power pump radiation. We present laser results at 1.54 mum from flashlamp and laser pumping. In tests with laser-diode pumped Q-switched Er-Yb microchip lasers, we have achieved up to 150 mW of average output power and generated 1.2 kW in peak power. Co2+:MgAl2O4 was here used as the saturable absorber.

  • 22. Korkishko, Y. N.
    et al.
    Fedorov, V. A.
    Alkaev, A. N.
    Laurell, Fredrik
    KTH, Superseded Departments, Physics.
    Second-order optical non-linearity of proton exchanged lithium tantalate waveguides2001In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 73, no 06-maj, p. 519-522Article in journal (Refereed)
    Abstract [en]

    A detailed correlation between the fabrication conditions, crystallographic phase state of HxLi1-xTaO3 waveguides and second-order optical non-linearity has been investigated by using reflected SHG measurements from the polished waveguide end face. The non-linearity, strongly reduced after the initial proton exchange, is found to be restored and even increased after annealing. However, this apparent increase in the non-linearity is accompanied by a strong degradation of the quality of the SHG reflected beam in the region of the initial as-exchanged waveguide due to beam scattering. The high temperature proton exchange technique has been shown to produce high-quality alpha -phase waveguides with essentially undegraded non-linear optical properties. There is no phase transition when the alpha -phase waveguides are fabricated by direct exchange. This phase presents the same crystalline structure as that of LiTaO3 and maintains the excellent non-linear properties of the bulk material. The results obtained are important for the design fabrication and optimization of guided-wave non-linear optical devices in LiTaO3.

  • 23. Marchev, Georgi
    et al.
    Dallocchio, Paolo
    Pirzio, Federico
    Agnesi, Antonio
    Reali, Giancarlo
    Petrov, Valentin
    Tyazhev, Aleksey
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Thilmann, Nicky
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Sub-nanosecond, 1-10 kHz, low-threshold, non-critical OPOs based on periodically poled KTP crystal pumped at 1,064 nm2012In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 109, no 2, p. 211-214Article in journal (Refereed)
    Abstract [en]

    We employed a 9-mm long periodically poled KTiOPO4 (PPKTP) crystal in an optical parametric oscillator (OPO) to generate sub-nanosecond idler pulses around 2.8 mu m. With a 1-cm long OPO cavity in a singly resonant configuration and double pass pumping by 1-ns pulses at 1,064 nm, the maximum idler energy reached 110 mu J at 1 kHz. Pumping with 500 ps pulses at 1-10 kHz, resulted in an idler energy of similar to 50 mu J and the shortest pulse duration of similar to 250 ps, ever reported for an OPO. The corresponding quantum conversion efficiencies were 32.5 and 34.9 %, respectively.

  • 24. Martin, M. J.
    et al.
    Benyattou, T.
    Orobtchouk, R.
    Talneau, A.
    Berrier, A.
    Mulot, M.
    Anand, Srinivasan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Evidence of Bloch wave propagation within photonic crystal waveguides2006In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 82, no 1, p. 9-12Article in journal (Refereed)
    Abstract [en]

    We report in this paper results obtained from characterizations of photonic band gap waveguide, using near field optical microscopy. We will show evidence of a Bloch wave propagating within our W1 photonic crystal waveguides (PCWs) structure, using a 2D Fourier transform approach. The processed image will then be compared to simulations obtained from plane wave method. This comparison exhibits that near-field measurements, using tapered optical fibers as probes, are mainly sensitive to the electric field propagating within the structure.

  • 25.
    Mei, L.
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Guan, Z. G.
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Zhou, H. J.
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Lv, J.
    Zhu, Z. R.
    Cheng, J. A.
    Chen, F. J.
    Lofstedt, C.
    Svanberg, Sune
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Somesfalean, Gabriel
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Agricultural pest monitoring using fluorescence lidar techniques Feasibility study2012In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 106, no 3, p. 733-740Article in journal (Refereed)
    Abstract [en]

    The fluorescence of different types of planthopper (Hemiptera) and moth (Lepidoptera), which constitute important Chinese agricultural pests, was investigated both in situ in a laboratory setting and remotely using a fluorescence light detection and ranging (lidar) system operating at a range of about 50 m. The natural autofluorescence of different species, as well as the fluorescence from insects that had been dusted with fluorescent dye powder for identification were studied. Autofluorescence spectra of both moths and planthoppers show a maximum intensity peak around 450 nm. Bleaching upon long-time laser illumination was modest and did not affect the shape of the spectrum. A single dyed rice planthopper, a few mm in size, could be detected at 50 m distance by using the fluorescence lidar system. By employing various marking dyes, different types of agricultural pest could be determined. We suggest that lidar may be used in studies of migration and movement of pest insects, including studies of their behavior in the vicinity of pheromone traps and in pheromone-treated fields.

  • 26.
    Meiser, Niels
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Marcinkevicius, Saulius
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Transient behaviour of quantum-dot saturable absorber mirrors at varying excitation fluence2014In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 116, no 4, p. 919-927Article in journal (Refereed)
    Abstract [en]

    We present results from studying the carrier dynamics in self-assembled InAs/GaAs quantum-dot saturable absorbers intended for mode-locking of solid-state lasers. Four samples are examined, featuring controlled variations in the resonance condition of the electric field inside the absorber, the number of quantum-dot (QD) layers and the thickness of the GaAs barriers between these QD layers. Pump-probe experiments are conducted at a wide range of excitation fluences and reveal a fast relaxation component of the initial bleaching at low excitation fluences, while a slowly relaxing induced transparency becomes dominant at higher excitation fluences. Time-resolved photoluminescence measurements reveal a large and slowly relaxing induced transparency due to a capture of excess carriers from the barrier bands into the QDs and a slow radiative recombination there. The resonance condition as well as the thickness of the barriers between the QD layers can be used to control the relaxation behaviour. The fastest response is obtained in a structure with an increased number of QD layers at each individual anti-node of the electric field, which is attributed to the appearance of efficient non-radiative recombination channels and capture centres. These centres are probably related to dislocations and other defects appearing in thick QD stacks.

  • 27.
    Meiser, Niels
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Seger, Kai
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Jang, Hoon
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Rafailov, Edik
    Krestnikov, Igor
    Gigahertz repetition rate mode-locked Yb:KYW laser using self-assembled quantum dot saturable absorber2013In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 110, no 3, p. 327-333Article in journal (Refereed)
    Abstract [en]

    Fundamental mode-locking is achieved in a 1.036 GHz cavity using a semiconductor quantum dot saturable absorber mirror with a fast relaxation time component of down to 550 fs. The dispersive cavity delivers 1.7 ps wide pulses with spectra supporting sub-picosecond pulse durations and an MA(2) of 1.3. An average output power of up to 339 mW at wavelengths around 1,032 nm is achieved and the saturable absorber's damage threshold is identified as a limitation for further power scaling.

  • 28.
    Meiser, Niels
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Seger, Kai
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Zukauskas, Andrius
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Cascaded mode-locking of a spectrally controlled Yb: KYW laser2014In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 116, no 2, p. 493-499Article in journal (Refereed)
    Abstract [en]

    Self-starting and stable mode-locking of an Yb:KYW laser in the picoseconds pulse regime has been achieved by exploiting a positive cascaded Kerr lens in periodically poled KTP. The use of a volume Bragg grating (VBG), for locking the output spectrum of the laser, was essential to achieve a stable mode-locked operation in this wide gain bandwidth laser material. The laser emitted stable, nearly transform-limited pulses with a duration of 16 ps, at a repetition rate of 210 MHz, and with an energy of 3.2 nJ. The mode-locked spectrum was centred at 1,029.1 nm and featured a FWHM bandwidth of 85 pm, which was effectively determined by the VBG. Combination of a large cascaded Kerr nonlinearity with spectral limiting by a VBG represents so far the best opportunity for stable mode-locking of a broadband laser to produce near-transform-limited picosecond pulses.

  • 29. Peltz, M.
    et al.
    Bader, U.
    Borsutzky, A.
    Wallenstein, R.
    Hellstrom, J.
    Karlsson, H.
    Pasiskevicius, Valdas
    KTH, Superseded Departments, Physics.
    Laurell, Fredrik
    KTH, Superseded Departments, Physics.
    Optical parametric oscillators for high pulse energy and high average power operation based on large aperture periodically poled KTP and RTA2001In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 73, no 7, p. 663-670Article in journal (Refereed)
    Abstract [en]

    We report on optical parametric oscillators (OPOs) based on large aperture periodically poled KTiOPO4 (PPKTP) and RbTiOAsO4 (PPRTA) pumped with high pulse energy and high average power Q-switched solid-state lasers. The OPOs were pumped with 1064-nm pulses of a diode-pumped Nd:YVO4 laser at 20 kHz repetition rate. The emitted signal wavelengths were 1.72 mum and 1.58 mum and the idler wavelengths were 2.79 mum and 3.26 mum, respectively. Pumping the PPKTP OPO with 7.2 W and the PPRTA OPO with 8 W average power, 2 W and 1.3 W total OPO output powers were generated. Two-dimensional measurements of the total OPO output power, the signal wavelength and the signal bandwidth in dependence on the crystal location indicated a good uniformity of the quasi phase matching structure over the entire 3-mm-thick crystals. This allowed pumping with larger pump beams and therefore with pulse energies of tens of millijoules. Pumping with different flash-lamp-pumped lasers, good OPO performance and high output pulse energies could be achieved for all pump lasers. Maximum input pulse energies of 56 mJ gave output pulse energies of as much as 18 mJ. The temperature tuning behaviors of both OPOs were measured, showing excellent agreement with calculated temperature tuning curves. New equations for temperature dispersion in RTA are presented. These results show that large-aperture PPKTP and PPRTA crystals are well suited for tunable nanosecond OPO operation with multi-watt average pump power and several tens of millijoules pump pulse energies.

  • 30.
    Seger, Kai
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Meiser, Niels
    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, passively Q-switched single-longitudinal-mode Nd:YVO4 laser using a chirped volume Bragg grating2012In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 109, no 1, p. 99-103Article in journal (Refereed)
    Abstract [en]

    A Nd:YVO4 laser was locked with a chirped volume Bragg grating to achieve single-longitudinal-mode output. Tuning was performed from 1,063 to 1,065 nm by translating the grating and a maximum output power of 4 W was obtained. With a Cr 4+:YAG saturable absorber, Q-switched pulses with 4 ns and a pulse energy of 5.7 lJ were achieved which could be frequency doubled in PPKTP with a conversion efficiency exceeding 50 %.

  • 31.
    Seger, Kai
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Meiser, Niels
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Tjörnhammar, Staffan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Zukauskas, Andrius
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canilias, 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.
    Intra-cavity frequency-doubled Yb: KYW laser using periodically poled Rb-doped KTP with a volume Bragg grating input coupler2014In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 115, no 2, p. 161-166Article in journal (Refereed)
    Abstract [en]

    An Yb:KYW laser intra-cavity frequency doubled to the green at 514.7 nm using a periodically poled Rb:KTP crystal with an output power exceeding 1 W is presented. Spectral narrowing and locking at the fundamental wavelength has been achieved by using a volume Bragg grating as the input coupler.

  • 32.
    Spiekermann, Stefan
    et al.
    KTH, Superseded Departments, Physics.
    Laurell, Fredrik
    KTH, Superseded Departments, Physics.
    Pasiskevicius, Valdas
    KTH, Superseded Departments, Physics.
    Karlsson, H.
    Freitag, I.
    Optimizing non-resonant frequency conversion in periodically poled media2004In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 79, no 2, p. 211-219Article in journal (Refereed)
    Abstract [en]

    Non-resonant frequency conversion into the blue, green, orange, and red spectral regions is reported. Fundamental light sources were continuous-wave non-planar monolithic single-mode ring Nd: YAG lasers as well as a standing-wave multi-mode Nd: YAG laser. Periodically poled KTiOPO4 was employed as the nonlinear medium, but the considerations could also be applied to other periodically poled materials. A multi-pass scheme resulted in a normalized conversion efficiency as high as 27.2 % W-1 for frequency doubling in the small-signal regime at 1064 nm.

  • 33. Sugiharto, A. B.
    et al.
    Johnson, Claes Magnus
    De Aguiar, H. B.
    Alloatti, L.
    Roke, S.
    Generation and application of high power femtosecond pulses in the vibrational fingerprint region2008In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 91, no 2, p. 315-318Article in journal (Refereed)
    Abstract [en]

    We present a novel high power femtosecond infrared laser source, based on a three-stage chirped-pulse amplification scheme. Owing to the high power output of the Ti:sapphire amplifiers, it becomes routinely possible to produce femtosecond infrared laser pulses in the wavelength region of 2.6-20 mu m with minimum pulse energies of 15 mu J, to our knowledge roughly an improvement of an order of magnitude. With such pulses we have performed femtosecond second-order nonlinear optical surface spectroscopy in the fingerprint region. We have probed the skeletal modes of the first few monolayers of a polymer/air interface in a femtosecond vibrational sum frequency generation experiment. This development opens up new possibilities to investigate surface structures and dynamics of, e.g., organo-metallic compounds, proteins, and peptides.

  • 34.
    Thilmann, Nicky
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Jacobsson, Björn
    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.
    A narrowband optical parametric oscillator tunable over 6.8 THz through degeneracy with a transversely-chirped volume Bragg grating2011In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 105, no 2, p. 239-244Article in journal (Refereed)
    Abstract [en]

    An efficient nanosecond optical parametric oscillator (OPO) with output energies of 0.75 mJ using a periodically poled KTiOPO(4) crystal pumped at 532 nm and generating narrowband output continuously tunable over the range of 6.8 THz, between 1053 nm and 1075 nm, is demonstrated by employing a transversely-chirped volume Bragg grating. The tunable reflectivity spectrum of the chirped volume Bragg grating allowed a smooth transition between singly-resonant and doubly-resonant operation of the OPO without cavity rearrangement. This gave a unique possibility to experimentally verify theoretical predictions regarding the efficiency of type-I and type-0 phase matched degenerate OPOs pumped by multimode Q-switched lasers.

  • 35.
    Thilmann, Nicky
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Strömqvist, Gustav
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Pujol, M. C.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Petrov, V.
    Diaz, F.
    Nonlinear refractive indices in Yb3+-doped and undoped monoclinic double tungstates KRE(WO4)(2) where RE=Gd, Y, Yb, Lu2009In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 96, no 2-3, p. 385-392Article in journal (Refereed)
    Abstract [en]

    The linear absorption bandgap in the ultraviolet and the nonlinear index n (2) in near infrared were systematically measured in undoped and Yb3+-doped top-seeded solution-grown monoclinic double-tungstate KRE(WO4)(2) (RE=Gd, Y, Yb, Lu) crystals. Anisotropic n (2) nonlinear indices have been determined for EaEuro-N (m) and EaEuro-N (p) polarizations with the maximum nonlinear index n (2) observed for the light polarized EaEuro-N (m). Moreover, the value of the nonlinear response of particular crystals in this family is proportional to the ionic radius of the RE3+ ion.

  • 36.
    Tiihonen, Mikael
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Fragemann, Anna
    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.
    Ultrabroad Gain in an Optical Parametric Generator with periodically poled KTiOPO42006In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 85, no 1, p. 73-77Article in journal (Refereed)
    Abstract [en]

    An optical parametric gain bandwidth of 115 THz at full-width half maximum is generated from a picosecond Ti:sapphire pumped degenerate optical parametric generator. This ultrabroad bandwidth could be obtained by first identifying the wavelength where the nonlinear optical material has zero group-velocity dispersion (GVD). By pumping at half this wavelength the degenerate signal-idler pairs can accommodate ultrabroad bandwidths. The explanation for this is that the group velocities of the signal and the idlers are approximately matched and the GVD is small. However, in order to thoroughly investigate the degeneracy region around 1700 nm we fabricated several periodically poled KTiOPO4 (PPKTP) crystals with different periods, and also one periodically poled RbTiOPO4 (PPRTP). Both collinear and noncollinear configurations were employed for broadband parametric generation in this region. It was found that the optimum pump wavelength is in the region between 800 nm to 850 nm for PPKTP, and we could also conclude that a similar performance was found for PPRTP. This work will allow the design of optical parametric devices for generating few-cycle pulses in the spectral region between 1.1 mu m and 3.8 mu m.

  • 37.
    Tjörnhammar, Staffan
    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.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    A frequency-locked and frequency-doubled, hybrid Q-switched Yb:KYW laser at 515 nm with a widely adjustable repetition rate2015In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 120, no 3, p. 545-550Article in journal (Refereed)
    Abstract [en]

    We demonstrate a compact wavelength-stabilized, frequency-doubled Yb-doped double-tungstate laser with widely tunable repetition rate, spanning from 35 Hz to 3 kHz obtained by hybrid Q-switching. The Q-switching unit consisted of a combination of a passive Cr:YAG crystal and an opto-mechanical active intensity modulator. The fundamental wavelength was locked at 1029 nm with a volume Bragg grating, and the pulse length and energy were 42 ns and 250 A mu J, respectively. As the laser was stabilized with the VBG and the opto-mechanical modulator, the frequency instability was reduced six times from free running down to 0.29 %. Frequency doubling was done extra-cavity in PPKTP, and a repetition rate-independent conversion efficiency of 63 % was obtained. The controllable repetition rate together with stable temporal and spatial characteristics makes this laser a suitable candidate in many biology-related experiments, as a pump source for in vivo excitation of fluorophores, e.g., pumping of "living lasers" and matrix-assisted laser desorption/ionization mass spectroscopy.

  • 38.
    Vogt, Ulrich
    et al.
    RheinAhrCampus Remagen, Univ. of Applied Sciences Koblenz.
    Frueke, Rolf
    RheinAhrCampus Remagen, Univ. of Applied Sciences Koblenz.
    Wilhein, Thomas
    RheinAhrCampus Remagen, Univ. of Applied Sciences Koblenz.
    Stollberg, Heide
    KTH, Superseded Departments, Physics.
    Jansson, Per
    KTH, Superseded Departments, Physics.
    Hertz, Hans
    KTH, Superseded Departments, Physics.
    High-resolution spatial characterization of laser produced plasmas at soft x-ray wavelengths2004In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 78, no 1, p. 53-58Article in journal (Refereed)
    Abstract [en]

    In this article, we describe the setup and application of a system for the spatial characterization of laser-produced plasma x-ray sources. While pinhole cameras are normally used for this purpose, we employed a zone plate to act as the x-ray lens. Together with an x-ray CCD camera as the detector, a spatial resolution of up to 2 mum was achieved. Due to the wavelength-dependent focal length of a zone plate, the monochromaticity of the image was better than lambda/Deltalambda=150, and the large aperture of the zone plate allowed single-laser-shot images to be collected. Methanol and ethanol were used as liquid-jet target systems. Two different Nd:YAG lasers with pulse durations of 3 ns and 10 ns produced the plasmas. Our measurements concentrated on the line emission of carbon in the soft x-ray spectral range, namely, the hydrogen-like alpha-line at 3.37 nm and the helium-like alpha-line at 4.03 nm. We investigated the influence of different nozzle sizes, laser energies, and pulse durations on the source size of the plasma. Depending on the experimental conditions, plasma diameters of 17-60 mum were measured.

  • 39. Zhang, Y. G.
    et al.
    Somesfalean, Gabriel
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Guo, W.
    Wang, H. S.
    Wu, S. H.
    Qin, Y. K.
    Zhang, Z. G.
    An optical system for measuring nitric oxide using spectral separation techniques2012In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 107, no 2, p. 435-440Article in journal (Refereed)
    Abstract [en]

    An optical sensor based on differential absorption spectroscopy for real-time monitoring of industrial nitric oxide (NO) gas emission is described. The influence of gas absorption interference from sulfur dioxide (SO2) in the environment was considered and a spectral separation technique was developed in order to eliminate this interference effect. The absorption spectrum of SO2 around 226 nm was evaluated by the SO2 concentration obtained using the experimentally recorded absorption spectrum around 300 nm. The absorption spectrum of NO around 226 nm was obtained by subtracting the absorption of SO2 from the integral absorption spectrum of SO2 and NO. The concentration measurements were performed at atmospheric pressure. The technique was found to have a lower detection limit of 0.8 ppm for NO per meter path length (SNR=2) and be immune from the influence from SO2 on the NO measurement. The sensor based on this technique was successfully employed for in situ measurement of SO2 and NO concentrations in the flue gas emitted from an industrial coal-fired boiler.

  • 40. Zisis, G.
    et al.
    Manzo, Michele
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Gallo, Katia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Soergel, E.
    Mailis, S.
    UV laser-induced poling inhibition in proton exchanged LiNbO3 crystals2017In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 123, no 4, article id 158Article in journal (Refereed)
    Abstract [en]

    The applicability of the UV laser-induced poling inhibition method for ferroelectric domain engineering in proton exchanged lithium niobate planar waveguides is investigated. Our results indicate that intense UV irradiation of proton exchanged lithium niobate samples can, indeed, produce poling inhibited domains in this material under certain irradiation conditions. However, there is strong indication that the temperature gradient that is formed during UV irradiation modifies the local proton concentration leading to changes in the refractive index profile of the original planar waveguide.

1 - 40 of 40
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