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Plant roots integrate environmental signals with development using exquisite spatiotemporal control. This is apparent in the deposition of suberin, an apoplastic diffusion barrier, which regulates flow of water, solutes and gases, and is environmentally plastic. Suberin is considered a hallmark of endodermal differentiation but is absent in the tomato endodermis. Instead, suberin is present in the exodermis, a cell type that is absent in the model organism Arabidopsis thaliana. Here we demonstrate that the suberin regulatory network has the same parts driving suberin production in the tomato exodermis and the Arabidopsis endodermis. Despite this co-option of network components, the network has undergone rewiring to drive distinct spatial expression and with distinct contributions of specific genes. Functional genetic analyses of the tomato MYB92 transcription factor and ASFT enzyme demonstrate the importance of exodermal suberin for a plant water-deficit response and that the exodermal barrier serves an equivalent function to that of the endodermis and can act in its place.

We present a comparative study of two Lu-based oxide ceramics doped with Yb3+ ions, namely Yb:Lu3Al5O12 (garnet) and Yb:Lu2O3 (sesquioxide), promising for thin-disk lasers. The ceramics are fabricated using nanopowders of 3.6 at.% Yb:Lu2O3 and Al2O3 produced by laser ablation: Yb:Lu3Al5O12 – by vacuum sintering at 1800 °C for 5 h with the addition of 1 wt% TEOS as a sintering aid, and Yb:Lu2O3 – by vacuum pre-sintering at 1250 °C for 2 h followed by Hot Isostatic Pressing at 1400 °C for 2 h under Ar gas pressure of 207 MPa. The comparison includes the structure, Raman spectra, transmission, optical spectroscopy and laser operation. The crystal-field splitting of Yb3+ multiplets is revealed for Lu3Al5O12. A continuous-wave (CW) Yb:Lu3Al5O12 ceramic microchip laser generates 5.65 W at 1031.1 nm with a slope efficiency of 67.2%. In the quasi-CW regime, the peak power is scaled up to 8.83 W. The power scaling for the Yb:Lu2O3 ceramic laser is limited by losses originating from residual coloration and inferior thermal behavior. © 2020 Elsevier Ltd and Techna Group S.r.l.

© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement. We report on a mode-locked Tm,Ho:CLNGG laser emitting in the 2 µm spectral range using single-walled carbon nanotubes (SWCNTs) as a saturable absorber (SA). Pulses with duration of 98 fs are generated at 99.28 MHz repetition rate with an average output power of 123 mW, yielding a pulse energy of 1.24 nJ. Using a 0.5% output coupling, pulses as short as 67 fs, i.e., 10 optical cycles, are produced after extracavity compression with a 3-mm-thick ZnS plate.

© 2018 Optical Society of America. We report on the crystal growth, structure, Raman and optical spectroscopy of novel mixed tetragonal vanadates, Yb:Lu 1-x-y Y x La y VO 4 . Optical absorption, stimulatedemission, and gain cross-section spectra of Yb 3+ are determined for p and s polarizations. For a Yb:Lu 0.74 Y 0.23 La 0.01 VO 4 crystal, the absorption bandwidth is > 10 nm, the ? SE is 1.1 × 10 -20 cm 2 at 1013 nm, the gain bandwidth is > 40 nm (for p-polarization), and the radiative lifetime of the 2 F 5/2 state is ~305 ?s. The Stark splitting of the Yb 3+ multiplets is determined using low-temperature (6 K) spectroscopy. A diode-pumped a-cut 2 at.% Yb:Lu 0.74 Y 0.23 La 0.01 VO 4 laser generated 5.0 W at 1044 nm with a slope efficiency of 43%. The developed materials are promising for sub-100 fs mode-locked lasers at ~1 ?m.

We report on inkjet-printing of graphene saturable absorbers (SAs) suitable for passive Qswitching of ~2-μm bulk and waveguide lasers. Using graphene-SA in a microchip Tm:KLu(WO4)2 laser, 1.2 μJ/136 ns pulses are generated at 1917 nm., QC 20171030

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© 2017 Optical Society of America. Monoclinic thulium-doped magnesium monotungstate, Tm 3+ :MgWO 4 , is promising for efficient power-scalable continuous-wave (CW) and passively Q-switched lasers at > 2 ?m. Under diode pumping at 802 nm, a compact CW laser based on Z-cut Tm:MgWO 4 generated 3.09 W at 2022-2034 nm with a slope efficiency of 50% which represents the highest output power ever achieved with this type of laser host. Stable passive Q-switching of the Tm:MgWO 4 laser is demonstrated for the first time, to the best of our knowledge, using single-walled carbon nanotubes, graphene, and Cr 2+ :ZnS saturable absorbers. Using the latter, the best performance is achieved with 16.1 ?J/13.6 ns pulses at 2017.8 nm with a maximum average output power of 0.87 W and a peak power of 1.18 kW.

© 2017 Optical Society of America. Multi-watt continuous-wave (CW) operation of tetragonal rare-earth calcium aluminate Yb:CaLnAlO 4 Ln Gd;Y) crystals in plano–plano microchip lasers was demonstrated with an almost quantum-defect-limited slope efficiency. Pumped at 978 nm by an InGaAs laser diode, a 3.4 mm long 8 at. % Yb:CaGdAlO 4 laser generated 7.79 W at 1057–1065 nm with a slope efficiency of ? 84% (with respect to the absorbed pump power). An even higher ? 91% was achieved with a 2.5 mm long 3 at. % Yb:CaYAlO 4 laser, from which 5.06 W were extracted at 1048–1056 nm. Both lasers produced linearly polarized output (?-polarization) with an almost circular diffraction-limited beam (M 2 x,y < 1.1). The output performance of the developed lasers was modeled, yielding an internal loss coefficient as low as 0.004?0.007 cm ?1 . In addition, their spectroscopic properties were revisited.

We study cryogenic laser operation of an Yb-doped KLu(WO4)2 crystal pumped with a volume Bragg grating (VBG) stabilized diode laser at 981 nm. In the continuous wave laser regime, a maximum output power of 4.31 W is achieved at 80 K with a slope efficiency of 44.0% with respect to the incident pump power. Using a 85% initial transmission Cr:YAG crystal for passive Q-switching, an average output power of 2.11 W is achieved at 100 K for a repetition rate of 19 kHz. The pulse energy, pulse duration and peak power amount to 111 ¿J, 231 ns and 0.48 kW, respectively.

Open Access

We report on a model of diode-pumped Thulium lasers passively Q-switched by a graphene saturable absorber applicable also for any other "fast" saturable absorber. It reasonably predicts the dependence of the pulse duration, pulse energy and pulse repetition frequency on the absorbed power. The model is applied in the present work for a Tm: KLuW microchip laser passively Q-switched with a multi-layer graphene saturable absorber. The laser generates similar to 1 W at 1926 nm with a slope efficiency of 39%. Stable 190 ns /4.1 mu J pulses are achieved at a pulse repetition frequency of 260 kHz. The potential of graphene for the generation of few-ns pulses at similar to 2 mu m is discussed.

We report on the growth, spectroscopic and laser characterization of a novel monoclinic laser crystal, Yb,In:KLu(WO4)(2) (Yb,In:KLuW). The absorption, stimulated-emission and gain cross-section spectra of 3.5 at% Yb, 5.5 at% In-doped KLuW are determined at room temperature with polarized light and compared with those for Yb,In:KYW, as well as singly Yb-doped KLuW and KYW crystals. It is found that the introduction of In results in a decrease of the transition cross-sections and in a spectral broadening of the absorption and emission bands. Such a broadening is more pronounced for light polarization E parallel to N-p. For Yb,In:KLuW, the maximum sigma(abs) is 9.9 x 10(-20) cm(2) at 980.9 nm for E parallel to N-m and the corresponding bandwidth of the absorption peak is 3.7 nm. The radiative lifetime for Yb3+ ions is 237 +/- 5 mu s. The stimulated emission cross-sections are sigma(SE)(m)= 2.4 x 10(-20) cm(2) at 1022.4 nm and sigma(SE)(p) = 1.3 x 10(-20) cm(2) at 1039.1 nm corresponding to an emission bandwidth of > 30 nm and > 35 nm, respectively. The diode pumped N-g-cut Yb,In:KLuW microchip laser generated 4.11 W at 1042-1048 nm with a slope efficiency of 78%. The Yb,In:KLuW crystal is very promising for the generation of sub-100 fs pulses in mode-locked lasers due to its broadband emission characteristics. (C) 2016 Elsevier B.V. All rights reserved.