Showing papers by "Uwe Griebner published in 2015"
TL;DR: The as-fabricated GG-SAM with ultra-broad bandwidth, ultrafast recovery time, low absorption, and low cost has great potential as a universal saturable absorber mirror for mode-locking of various bulk lasers with unprecedented spectral coverage.
Abstract: An ultra-broadband graphene-gold film saturable absorber mirror (GG-SAM) with a spectral coverage exceeding 1300 nm is experimentally demonstrated for mode-locking of bulk solid-state lasers. Owing to the p-type doping effect caused by graphene-gold film interaction, the graphene on gold-film substrate shows a remarkably lower light absorption relative to pristine graphene, which is very helpful to achieve continuous-wave mode-locking in low-gain bulk lasers. Using the GG-SAM sample, stable mode-locking is realized in a Yb:YCOB bulk laser near 1 μm, a Tm:CLNGG bulk laser near 2 μm and a Cr:ZnSe bulk laser near 2.4 μm. The saturable absorption is characterised at an intermediate wavelength of 1.56 μm by pump-probe measurements. The as-fabricated GG-SAM with ultra-broad bandwidth, ultrafast recovery time, low absorption, and low cost has great potential as a universal saturable absorber mirror for mode-locking of various bulk lasers with unprecedented spectral coverage.
67 citations
TL;DR: This work reports on the first Tm-doped double tungstate microchip laser Q-switched with graphene using a Tm:KLu(WO4)2 crystal cut along the Ng dielectric axis with maximum average output power of 310 mW with a slope efficiency of 13%.
Abstract: We report on the first Tm-doped double tungstate microchip laser Q-switched with graphene using a Tm:KLu(WO4)2 crystal cut along the Ng dielectric axis. This laser generates a maximum average output power of 310 mW with a slope efficiency of 13%. At a repetition rate of 190 kHz the shortest pulses with 285 ns duration and 1.6 µJ energy are achieved.
55 citations
TL;DR: Tunable and mode-locked laser operation near 2 µm based on different Tm-doped YAG ceramics, 4 at.% and 10 at.%, is demonstrated.
Abstract: Tunable and mode-locked laser operation near 2 µm based on different Tm-doped YAG ceramics, 4 at.% and 10 at.%, is demonstrated. Several designs of GaSb-based surface-quantum-well SESAMs are characterized and studied as saturable absorbers for mode-locking. Best mode-locking performance was achieved using an antireflection-coated near-surface quantum-well SESAM, resulting in a pulse duration of ~3 ps and ~150 mW average output power at 89 MHz. All mode-locked Tm:YAG ceramic lasers operated at 2012 nm, with over 133 nm demonstrated tuning for continuous-wave operation.
44 citations
TL;DR: A continuous-wave Ho:KLu(WO4)2 (KLuW) microchip laser with a record slope efficiency of 84%, the highest value among the holmium inband-pumped lasers, delivering 201 mW output power at 2105 nm is reported on.
Abstract: We report on a continuous-wave Ho:KLu(WO4)2 (KLuW) microchip laser with a record slope efficiency of 84%, the highest value among the holmium inband-pumped lasers, delivering 201 mW output power at 2105 nm. The Ho laser operating at room temperature on the I85→I57 transition is in-band-pumped by a diode-pumped Tm:KLuW microchip laser at 1946 nm. Ho:KLuW laser operation at 2061 and 2079 nm is also demonstrated with a maximum slope efficiency of 79%. The microchip laser generates an almost diffraction-limited output beam with a Gaussian profile and a M2<1.1. The laser performance of the Ng-cut Ho:KLuW crystal is very similar for pump light polarizations ‖Nm and Np. The positive thermal lens plays a key role in the laser mode stabilization and proper mode-matching. The latter, together with the low quantum defect under in-band-pumping (∼0.08), is responsible for the extraordinary high slope efficiency.
33 citations
TL;DR: In this article, the concept of Yb-doped double tungstate microchip lasers is verified and scaled to the multi-watt power level. And the mechanism of the thermal mode stabilization in the microchip cavity is confirmed.
Abstract: The concept of Yb-doped double tungstate microchip lasers is verified and scaled to the multi-watt power level. The active element is a 2.6 mm-thick Yb:KLuW crystal cut along the Ng optical indicatrix axis. Maximum continuous-wave output power of 4.4 W is extracted at 1049 nm with a slope efficiency of 65% and an optical-to-optical efficiency of 44% with respect to the absorbed pump power. The laser emission is linearly polarized and the intensity profile is characterized by a near-circular TEM00 mode with M2x,y < 1.1. Due to low intracavity losses of the microchip laser, laser operation at wavelengths as long as 1063 nm is achieved. The mechanism of the thermal mode stabilization in the microchip cavity is confirmed. At very low resonator losses polarization-switching between E || Nm and Np oscillating states is observed and explained on the basis of spectroscopic and thermal lens characteristics.
30 citations
TL;DR: Passive Q-switching of a compact Tm:KLu(WO(4))(2) microchip laser diode pumped at 805 nm is demonstrated with a polycrystalline Cr(2+):ZnS saturable absorber.
Abstract: Passive Q-switching of a compact Tm:KLu(WO(4))(2) microchip laser diode pumped at 805 nm is demonstrated with a polycrystalline Cr(2+):ZnS saturable absorber. This laser generates subnanosecond (780 ps) pulses with a pulse repetition frequency of 5.6 kHz at 1846.6 nm, the shortest pulse duration ever achieved by Q-switching of ~2 μm lasers. The maximum average output power is 146 mW with a slope efficiency of 21% with respect to the absorbed power. This corresponds to a pulse energy of 25.6 μJ and a peak power of 32.8 kW.
29 citations
TL;DR: A high-gain, cw-pumped regenerative amplifier which is based on Ho-doped crystals and seeded by a versatile broadband source emitting between 2050 and 2100 nm and chosen to operate in a tunable single-energy regime without instabilities is reported.
Abstract: We report a high-gain, cw-pumped regenerative amplifier which is based on Ho-doped crystals and seeded by a versatile broadband source emitting between 2050 and 2100 nm. The regenerative amplifier is implemented in a chirped-pulse amplification system operating at room temperature. Using Ho:YLF as gain medium, 1.1 mJ pulses with a 50 ps pulse duration and a 10 kHz repetition rate are generated at 2050 and 2060 nm, corresponding to an average power of 11 W. Using the same seed source, a 10 kHz Ho:YAG regenerative amplifier at 2090 nm is studied in the same configuration. In all cases the regenerative amplifier parameters are chosen to operate in a tunable single-energy regime without instabilities.
23 citations
TL;DR: In this article, a diode-pumped Yb:KYW planar waveguide laser, single-mode Q-switched by evanescent-field interaction with graphene, is demonstrated for the first time.
Abstract: A diode-pumped Yb:KYW planar waveguide laser, single-mode Q-switched by evanescent-field interaction with graphene, is demonstrated for the first time. Few-layer graphene grown by chemical vapor deposition is transferred onto the top of a guiding layer, which initiates stable Q-switched operation in a 2.4-cm-long waveguide laser operating near 1027 nm. Average output powers up to 34 mW and pulse durations as short as 349 ns are achieved. The measured output beam profile, clearly exhibiting a single mode, agrees well with the theoretically calculated mode intensity distribution inside the waveguide. As the pump power is increased, the repetition rate and pulse energy increase from 191 to 607 kHz and from 7.4 to 58.6 nJ, respectively, whereas the pulse duration decreases from 2.09 μs to 349 ns.
21 citations
TL;DR: Passive mode-locking of a Tm,Ho:KLu(WO(4))(2) laser operating at 2060 nm using different designs of InGaAsSb quantum-well based semiconductor saturable absorber mirrors (SESAMs) is demonstrated.
Abstract: Passive mode-locking of a Tm,Ho:KLu(WO(4))(2) laser operating at 2060 nm using different designs of InGaAsSb quantum-well based semiconductor saturable absorber mirrors (SESAMs) is demonstrated. The self-starting mode-locked laser delivers pulse durations between 4 and 8 ps at a repetition rate of 93 MHz with maximum average output power of 155 mW. Mode-locking performance of a Tm,Ho:KLu(WO(4))(2) laser is compared for usage of a SESAM to a single-walled carbon nanotube saturable absorber.
20 citations
TL;DR: The recorded complete RA bifurcation diagram agrees well with the numerical simulations and the main amplifier system is based on Ho:YLF and consists of a regenerative amplifier and a single-pass booster amplifier running at room temperature.
Abstract: A 2.051-µm laser source delivering picosecond pulses with energies as high as 34 mJ at a 1 kHz repetition rate is reported. The main amplifier system is based on Ho:YLF and consists of a regenerative amplifier (RA) and a single-pass booster amplifier running at room temperature. The continuous-wave pumped, high-gain RA produces pulse trains with up to 10-mJ energy when operating in a stable periodic doubling regime. The recorded complete RA bifurcation diagram agrees well with our numerical simulations. At the highest pulse energy after the booster amplifier the pulse-to-pulse fluctuations are as low as 0.9% rms. Pulse compression is performed up to the 10-mJ level resulting in a duration of 37 ps.
18 citations
TL;DR: In this article, the isotropic disordered crystal Yb:CLNGG under diode pumping using SESAM was used to generate short-length pulses at 1051.5nm.
Abstract: Pulses as short as 55 fs are generated at 1051.5 nm with the isotropic disordered crystal Yb:CLNGG under diode pumping using SESAM. The bandwidth of ~23 nm corresponds to almost transform-limited sech 2 -shape pulses. The average power in this case of 1% output coupling is 60 mW at a repetition rate of ~87 MHz. Maximum average output power of 194 mW is achieved with higher output coupling of 5% for which the pulse duration amounts to 115 fs.
TL;DR: In this article, a Yb:YAG laser Q-switched by a graphene-based saturable absorber and pumped by a laser diode at 932 or 969 nm was described.
Abstract: We describe a compact Yb:YAG laser Q-switched by a graphene-based saturable absorber and pumped by a laser diode at 932 or 969 nm. The compact laser generates a maximum average output power value of 185 mW at 1032 nm with a slope efficiency value of 12%. The shortest duration of the Q-switched pulse achieved is 228 ns at a repetition frequency of 285 kHz. The maximum pulse energy amounts to 0.65 $\mu\mathrm{J}$ .
TL;DR: In this article, a comparative study of anisotropy and dispersion of the optical path for monoclinic oxoborate YCOB and GdCOB host crystals is presented.
Abstract: We report on a comparative study of anisotropy and dispersion of thermo-optic coefficients, dn/dT, and thermal coefficients of the optical path for monoclinic oxoborate YCOB and GdCOB laser host crystals. Near 1 μm, all dn/dT coefficients are found to be negative: dnX/dT = –1.2, dnY/dT = –3.7 and dnZ/dT = –2.5 × 10−6 K−1 for YCOB, dnX/dT = –3.8, dnY/dT = –4.8 and dnZ/dT = –3.7 × 10−6 K−1 for GdCOB. Thermo-optic dispersion formulas are derived for these crystals in the spectral range of 0.4–2 μm. The existence of athermal directions is predicted for both YCOB and GdCOB.
TL;DR: In this article, a compact intracavity-pumped microchip Ho laser was realized using stacked Tm:KLuW/Ho: KLuW crystals pumped by a laser diode at 805-nm.
Abstract: A compact intracavity-pumped microchip Ho laser is realized using stacked Tm:KLuW/Ho:KLuW crystals pumped by a laser diode at 805 nm; both crystals are cut for light propagation along the N
g optical indicatrix axis and emit with polarization along the N
m axis. Maximum CW output power of 285 mW is achieved at a wavelength of 2080 nm for 5.6 W absorbed pump power in the Tm:KLuW crystal with a maximum slope efficiency of 8.3 %. Maximum total (Tm3+ and Ho3+ emission) output of 887 mW with a slope efficiency of 23 % is achieved. Laser operation is obtained in the 1867–1900 nm spectral range corresponding to the Tm emission, while Ho emits at 2078–2100 nm, depending on the output coupling. The microchip Ho laser generates a near-circular output beam with M
2 < 1.1. The compact laser setup with plane–plane cavity provides automatic mode-matching condition for the Tm and Ho laser modes.
TL;DR: In this article, a passively Q-switched laser operation based on active medium and saturable absorber was demonstrated, with the polarized emission centered at 1876 nm, with pulse parameters of 13 ns (duration), 467 $\mu\hbox{J} $ (energy), and 37 kW (peak power) at a repetition rate of 350 Hz.
Abstract: We demonstrate efficient passively Q-switched laser operation, based on $\hbox{Tm}^{3+}\hbox{:LiGdF}_{4}$ and $\hbox{Cr}^{2+} $
:ZnSe, as active medium and saturable absorber, respectively. The polarized emission was centered at 1876 nm, with pulse parameters of 13 ns (duration), 467 $\mu\hbox{J} $ (energy), and 37 kW (peak power) at a repetition rate of 350 Hz.
TL;DR: In this article, a diode-pumped passively Q-switched Tm-laser emitting near 2 μm using single-layer graphene as the saturable absorber was demonstrated.
Abstract: We demonstrate a diode-pumped passively Q-switched Tm-laser emitting near 2 μm using single-layer graphene as the saturable absorber. The commercially available graphene samples were characterized by Raman spectroscopy and pump–probe measurements indicating high quality layered graphene. The Q-switched Tm:KLuW laser generated maximum pulse energy of ~1 μJ with a slope efficiency of 11%. The maximum average output power was 34 mW at a repetition rate of 35 kHz.
04 Oct 2015
TL;DR: In this paper, a diode-pumped Yb:LuGG laser generated a maximum output power of 9.0 W at 1040 nm with 75% slope efficiency.
Abstract: Thermal lens and microchip laser operation were studied for Yb:YGG, Yb:LuGG, Yb:CNGG and Yb:CLNGG. A diode-pumped Yb:LuGG laser generated a maximum output power of 9.0 W at 1040 nm with 75% slope efficiency.
04 Oct 2015
TL;DR: Anisotropy and dispersion of thermo-optic coefficients, dn/dT, and thermal coefficients of the optical path (TCOP) were studied for monoclinic oxoborate YCOB and GdCOB laser host crystals.
Abstract: Anisotropy and dispersion of thermo-optic coefficients, dn/dT, and thermal coefficients of the optical path (TCOP) are studied for monoclinic oxoborate YCOB and GdCOB laser host crystals. Thermo-optic dispersion formulas are derived for these crystals.
04 Oct 2015
TL;DR: In this article, a Tm:KLuW laser is Q-switched with a saturable absorber based on aligned SWCNTs, generating a maximum average output power of 260 mW with a slope efficiency of 12%.
Abstract: A Tm:KLuW laser is Q-switched with a saturable absorber based on aligned SWCNTs, generating a maximum average output power of 260 mW with a slope efficiency of 12%. The shortest pulse duration is 97 ns.
04 Oct 2015
TL;DR: In this article, high gain, continuous-wave pumped Ho:YLF regenerative amplifiers are reported, delivering up to 8 mJ picosecond pulses at 2050 nm, with energy fluctuations of the 1 kHz pulse train as low as 2% rms.
Abstract: High-gain, continuous-wave pumped Ho:YLF regenerative amplifiers are reported, delivering up to 8 mJ picosecond pulses at 2050 nm, with energy fluctuations of the 1 kHz pulse train as low as 2% rms.
04 Oct 2015
TL;DR: A Tm:KLu(WO4)2 microchip laser Q-switched by a Cr2+:ZnS saturable absorber generates 780 ps / 26 μJ pulses at 1846.6 nm as discussed by the authors.
Abstract: A Tm:KLu(WO4)2 microchip laser Q-switched by a Cr2+:ZnS saturable absorber generates 780 ps / 26 μJ pulses at 1846.6 nm. The maximum output power is 146 mW with a slope efficiency of 21%.
01 Aug 2015
TL;DR: In this article, the authors studied the operation characteristics of a Gd3+ and Lu3+ co-doped Yb:KYW planar waveguide laser, Q-switched by carbon nanotube-based saturable absorbers in two direct interaction and one evanescent field interaction regimes.
Abstract: We studied operation characteristics of a Gd3+ and Lu3+ co-doped Yb:KYW planar waveguide laser, Q-switched by carbon nanotube-based saturable absorbers in two direct interaction and one evanescent-field interaction regimes.
10 May 2015
TL;DR: In this article, a diode-pumped Q-switched Tm:KLu(WO 4 ) 2 microchip laser generated a maximum average output power of 310 mW with M2 < 1.2 at 1947 nm.
Abstract: A diode-pumped Q-switched Tm:KLu(WO 4 ) 2 microchip laser generated a maximum average output power of 310 mW with M2 < 1.2 at 1947 nm. The shortest pulse duration was 285 ns at a pulse repetition rate of 190 kHz.
10 May 2015
TL;DR: In this paper, a passively Q-switched Ho:KLu(WO 4 ) 2 microchip laser inband-pumped by a Tm:kLu(wO 4 2 ) 2 Tm laser was used to achieve an average output power of 84 mW, slope efficiency of 42%, and pulse duration of 55 ns.
Abstract: Maximum average output power of 84 mW, slope efficiency of 42%, and pulse duration of 55 ns are achieved at 2.06 μm with a passively Q-switched Ho:KLu(WO 4 ) 2 microchip laser inband-pumped by a Tm:KLu(WO 4 ) 2 microchip laser.
04 Oct 2015
TL;DR: In this paper, a Z-cut crystal with a maximum output power of 8.35 W was achieved at 1040 nm with a slope efficiency of 70% using a Yb:YCOB crystal cut along the optical indicatrix axes.
Abstract: Microchip lasers are realized with Yb:YCOB crystals cut along the optical indicatrix axes. Using a Z-cut crystal, a maximum output power of 8.35 W is achieved at ~1040 nm with a slope efficiency of 70%.