Tomi Leinonen

Tampere University of Technology, Tammerfors, Province of Western Finland, Finland

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Publications (81)79.01 Total impact

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    ABSTRACT: We demonstrate that a combination of ultrafast wafer bonded semiconductor disk laser and a bismuth-doped fiber amplifier provides an attractive design for high power 1.33 µm tandem hybrid systems. Over 0.5 W of average output power was achieved at a repetition rate of 827 MHz that corresponds to a pulse energy of 0.62 nJ.
    Optics Express 05/2014; 22(10):11446-11455. · 3.55 Impact Factor
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    ABSTRACT: We report on the development of a pulsed high-power frequency doubled vertical-external-cavity surface-emitting laser (VECSEL) with a peak output power of 14 W and emission spectrum near 588 nm. The semiconductor gain chip was grown by molecular beam epitaxy and comprised 10 GaInAs quantum wells. The gain structure was designed to be antiresonant at 1180 nm. The fundamental wavelength was frequency doubled to the yellow–orange spectral range using a 10-mm long critically phase matched lithium triborate nonlinear crystal, situated at the mode waist of the V-shaped laser cavity. The emission spectrum was narrowed down to FWHM of < 0.2 nm by employing a 1.5 mm birefringent filter and a 100-μm-thick etalon inside the cavity. By directly modulating the pump laser of the VECSEL, we were able to produce pulse widths down to 570 ns with average and peak output power of 81 mW and 14 W, respectively. The repetition rate was kept constant at 10 kHz throughout the measurements. The maximum peak power obtained was pump power limited. In comparison, at the same coolant temperature, a maximum of 8.5 W was achieved in continuous wave. The maximum optical-to-optical conversion efficiency (absorbed peak pump power to peak output power) was calculated to be 20–21 %.
    SPIE Photonics Europe; 05/2014
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    ABSTRACT: A high-efficiency optically pumped vertical-external-cavity surface-emitting laser emitting 20 W at a wavelength around 588 nm is demonstrated. The semiconductor gain chip emitted at a fundamental wavelength around 1170-1180 nm and the laser employed a V-shaped cavity. The yellow spectral range was achieved by intra-cavity frequency doubling using a LBO crystal. The laser could be tuned over a bandwidth of ~26 nm while exhibiting watt-level output powers. The maximum conversion efficiency from absorbed pump power to yellow output was 28% for continuous wave operation. The VECSEL's output could be modulated to generate optical pulses with duration down to 570 ns by directly modulating the pump laser. The high-power pulse operation is a key feature for astrophysics and medical applications while at the same time enables higher slope efficiency than continuous wave operation owing to decreased heating.
    Optics Express 03/2014; 22(6):6372-80. · 3.55 Impact Factor
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    ABSTRACT: We report on the development of a high-efficiency frequency doubled vertical-external-cavity surface-emitting laser with an output power of 20 W and emission spectrum centered at 588 nm. The MBE-grown gain chip incorporated 10 GaInAs quantum wells and emitted in the 1180 nm range. The frequency conversion was achieved using a lithium triborate nonlinear crystal in an intra-cavity configuration. In addition to the nonlinear crystal, the V-shaped cavity also included a birefringent filter and an etalon for linewidth narrowing and wavelength tuning. The maximum optical-to-optical conversion efficiency obtained was ~28 % for 16 W of output power and the VECSEL had a tuning bandwidth of ~26 nm ranging from about 576 to 602 nm. We were also able to generate yellow pulses down to 570 ns duration by directly modulating the VECSEL's pump laser.
    02/2014;
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    ABSTRACT: We report on the use of a Semiconductor Disk Laser (SDL) as a seed laser for an Ytterbium-Doped Photonic Bandgap Fiber (Yb-PBGF) amplifier in a Master-Oscillator Power-Amplifier (MOPA) configuration. The SDL comprised a GaInAs/GaAs/GaAsP gain chip, a 1-mm-thick etalon for mode selection, and a 3-mm-thick birefringent filter for wavelength tuning. The fiber amplifier consisted of an Yb-doped core surrounded by a structure of periodically arranged germanium rods with a pitch of 10.2 μm, and to maintain the polarization, the fiber comprised two boron rods. The output of the MOPA-configuration was 31 W and the linewidth of the amplifier output was 149±31 kHz.
    02/2014;
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    ABSTRACT: Room temperature lasing operation at 599 nm for a AlGaInP/AlInP/GaAs edge-emitting laser structure is reported. The structure was grown on GaAs substrate and pumped optically with a 532 nm q-switched laser. The lasing threshold for a 2 mm long and 25 $mu{rm m}$ wide ridge waveguide structure was 30 mW of average pump power. The orange output beam had an optical spectral width of 1.7 nm.
    IEEE Photonics Technology Letters 01/2014; 26(4):384-386. · 2.04 Impact Factor
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    ABSTRACT: A proof-of-principle study of a 1.97-µm Tm:Lu<sub>2</sub>O<sub>3</sub> ceramic disk laser, intracavity pumped by a 1.2-µm semiconductor disk laser, is presented. The demonstrated concept allows for improved pump absorption and takes advantage of the broad wavelength coverage provided by semiconductor disk laser technology. For thin disk lasers the small thickness of the gain element typically leads to inefficient pump light absorption. This problem is usually solved by using a complex multi-pass pump arrangement. In this study we address this challenge with a new laser concept of an intracavity pumped ceramic thin disk laser. The output power at 1.97 µm was limited to 250 mW due to heat spreader-less mounting scheme of the ceramic gain disk.
    Optics Express 10/2013; 21(20):23844-23850. · 3.55 Impact Factor
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    ABSTRACT: A proof-of-principle study of a 1.97-µm Tm:Lu2O3 ceramic disk laser, intracavity pumped by a 1.2-µm semiconductor disk laser, is presented. The demonstrated concept allows for improved pump absorption and takes advantage of the broad wavelength coverage provided by semiconductor disk laser technology. For thin disk lasers the small thickness of the gain element typically leads to inefficient pump light absorption. This problem is usually solved by using a complex multi-pass pump arrangement. In this study we address this challenge with a new laser concept of an intracavity pumped ceramic thin disk laser. The output power at 1.97 µm was limited to 250 mW due to heat spreader-less mounting scheme of the ceramic gain disk.
    Optics Express 10/2013; 21(20):23844-. · 3.55 Impact Factor
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    ABSTRACT: A picosecond GaInP/AlGaInP/GaAs vertical external-cavity surface-emitting laser (VECSEL) at 675 nm is reported. The laser is mode-locked with a GaInP/AlGaInP/GaAs saturable absorber mirror and emitted ∼5.1 ps pulses at a 973 MHz repetition rate and an average power of 45 mW. To our knowledge, this is the first demonstration of a passively mode-locked VECSEL emitting fundamental laser radiation at the visible part of the spectrum.
    Optics Letters 07/2013; 38(13):2289-91. · 3.39 Impact Factor
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    ABSTRACT: During the recent years, the wavelength coverage of optically-pumped vertical external-cavity surface-emitting lasers (VECSELs) has expanded significantly and currently reaches from the UV to mid-IR (although not without gaps). This progress has been fuelled by the ability to tailor the VECSELs emission wavelength via bandgap engineering and by the capability to deploy different kinds of semiconductor gain material systems, such as GaAs, InP, GaSb and PbTe, for example. The combination of wavelength flexibility and efficient intra-cavity second-harmonic generation makes these lasers excellent light sources for many applications for which conventional solid-state laser aren't available. In particular, the development of frequency-doubled VECSELs with blue, green and yellow-orange emission has experienced a surge of outstanding achievements.
    The European Conference on Lasers and Electro-Optics; 05/2013
  • The European Conference on Lasers and Electro-Optics; 05/2013
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    ABSTRACT: We report high power operation of a vertical external-cavity surface-emitting laser (VECSEL) operating around 1180 nm. The gain chip of the VECSEL comprises 10 strain-compensated GaInAs/GaAs quantum wells in a top-emitting configuration. A maximum output power of 23 W was achieved with a mount temperature of about 0 ‡C, and 20.5 W with the mount temperature of about 12 °C. By introducing a birefringent filter inside the laser cavity we demonstrate a tuning range of 67 nm. The gain chip was also used to construct a VECSEL for single-frequency operation. In this configuration, a maximum output power of about 11 W was recorded.
    Proc SPIE 02/2013;
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    ABSTRACT: The highest power result for an optically-pumped single-chip vertical external-cavity surface-emitting laser with emission near 1180 nm is reported. The gain mirror was grown by molecular beam epitaxy and incorporated a strain compensated GaInAs/GaAs/GaAsP active region. An intra-cavity diamond heat spreader was attached to the gain mirror for thermal management. In free-running operation, the laser emitted more than 20 W at a mount temperature of about 12 °C. The output spectrum was centred between 1165??1190 nm depending on the mount temperature and pump power. By using an intra-cavity birefringent filter, the full width at half-maximum linewidth could be narrowed to ⩾1 nm and at the same time achieved approximately 14 W of output power near 1178 nm. Moreover, the lasing wavelength could be tuned over more than 40 nm.
    Electronics Letters 01/2013; 49(1):59. · 1.04 Impact Factor
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    ABSTRACT: We report a high power single-frequency 1178 nm laser combining an optically-pumped semiconductor disk laser and an Yb-doped photonic bandgap fiber amplifier. An output power of 31 W with
    Lasers and Electro-Optics Pacific Rim (CLEO-PR), 2013 Conference on; 01/2013
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    ABSTRACT: Optically pumped semiconductor lasers in conjunction with intra-cavity frequency conversion and tuning elements offer high continuous-wave power, narrow linewidth, and broad tunability. As a result, they are well suited to precision spectroscopic applications. We describe the development and testing of optically pumped semiconductor lasers operating at fundamental wavelengths of 1119 and 1178 nm. The fourth and second harmonic wavelengths are resonant with transitions in Mg II and Na I, respectively. We demonstrate continuously tunable, single-frequency lasers with watt-level average power at 1119, 1178, and 589 nm.
    IEEE Journal of Quantum Electronics 01/2013; 49(8):719-727. · 2.11 Impact Factor
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    ABSTRACT: We review our results concerning the development of Semiconductor Disk Lasers with emission wavelength in the range of 1100-1200 nm. In particular, we highlight our recent demonstrations of SDLs with an output power of more than 20 W for emission around 1180 nm and corresponding frequency doubled power of more than 10 W at around 589 nm. The SDL gain chips utilize either dilute nitride (GaInNAs) or low-temperature GaInAs quantum wells.
    Lasers and Electro-Optics Pacific Rim (CLEO-PR), 2013 Conference on; 01/2013
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    ABSTRACT: We report on the development of an optically-pumped vertical external-cavity surface-emitting laser emitting near 1120 nm using strain compensated quantum wells. The development is motivated by the need to achieve narrow linewidth emission at ~280 nm via fourth harmonic generation, which is required to cool Mg+ ions. The gain mirror had a top-emitting geometry, was grown by molecular beam epitaxy and comprised GaInAs/GaAs quantum wells strain compensated by GaAsP layers; the strain compensation was instrumental for achieving a dislocation free epitaxial structure without dark lines. We demonstrate VECSEL operation at a fundamental wavelength close to 1118 nm with a linewidth of less than 300 kHz. Using a lithium triborate crystal we achieved frequency doubling to ~559 nm with an output power of 1.1W.
    Optical Materials Express 07/2012; 2(8):1011-1019. · 2.92 Impact Factor
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    ABSTRACT: Pulses of 118 nJ at the repetition rate of 170 kHz and central wavelength of 2097 nm have been produced by holmium fiber laser Q-switched by carbon nanotube saturable absorber. Efficient operation of holmium fiber with fairly high-doping level has been demonstrated by using refined preform fabrication, which allowed for short-length cavity laser. The results demonstrate the practical potential of holmium fibers for Q-switched lasers with high-repetition rate operating above 2 $\mu\hbox{m}$ wavelength.
    IEEE Photonics Journal 06/2012; 4(3):679-683. · 2.36 Impact Factor
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    ABSTRACT: We report on a 2085 nm holmium-doped silica fiber laser passively mode-locked by semiconductor saturable absorber mirror and carbon nanotube absorber. The laser, pumped by a 1.16 μm semiconductor disk laser, produces 890 femtosecond pulses with the average power of 46 mW and the repetition rate of 15.7 MHz.
    Optics Letters 05/2012; 37(9):1448-50. · 3.39 Impact Factor
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    ABSTRACT: This paper presents the development and narrow-linewidth characteristics of an optically-pumped vertical external-cavity surface-emitting laser emitting light near 1120 nm. The laser development is motivated by the need to achieve narrowlinewidth, frequency-stable laser emission near 280 nm for cooling of Mg+ ions. The laser is capable of emitting ~0.8 W at 1118.542 nm in a less than 300 kHz linewidth.
    Proc SPIE 05/2012;