Femtosecond-laser-written Ho:KGd(WO4)2 waveguide laser at 21 μm

We report on efficient laser operation of the first holmium monoclinic double tungstate waveguide laser fabricated by femtosecond direct laser writing. A depressed-index buried channel waveguide with a 60 μm diameter circular cladding was inscribed in 5 at.% Ho3+:KGd(WO4)2. It was characterized by confocal microscopy and μ-Raman and μ-luminescence spectroscopy, indicating well-preserved crystallinity of its core. Pumped by a thulium bulk laser, the holmium waveguide laser generated 212 mW at 2055 nm with a slope efficiency of 67.2%. The waveguide propagation losses were 0.94±0.2  dB/cm.Agència de Gestió d’Ajuts Universitaris i de Recerca (AGAUR) (2017SGR755); Horizon 2020 Framework Programme (H2020) (747055); Consejería de Educación, Junta de Castilla y León (SA046U16, UIC016); Ministerio de Economía y Competitividad (MINECO) [FIS2017-87970-R, MAT2016-75716-C2-1-R (AEI/FEDER, UE), TEC 2014-55948-R]; Generalitat de Catalunya (2016FI_B00844, 2017FI_B100158, 2018FI_B200123); ICREA academia (2010ICREA-02); Government of the Russian Federation (074-U01); European Community’s Horizon 2020 Research (654148); Laserlab- EUROPE (MBI MBI002365)

Passively Q-switched femtosecond-laser-written thulium waveguide laser based on evanescent field interaction with carbon nanotubes

Surface channel waveguides (WGs) were fabricated in a monoclinic Tm3+:KLu(WO4)2 crystal by femtosecond direct laser writing (fs-DLW). The WGs consisted of a half-ring cladding with diameters of 50 and 60 μm located just beneath the crystal surface. They were characterized by confocal laser microscopy and -Raman spectroscopy, indicating a reduced crystallinity and stress-induced birefringence of the WG cladding. In continuous-wave (CW) mode, under Ti:sapphire laser pumping at 802 nm, the maximum output power reached 171.1 mW at 1847.4 nm, corresponding to a slope efficiency of 37.8% for the 60 μm diameter WG. The WG propagation loss was 0.7±0.3 dB/cm. The top surface of the WGs was spin-coated by a polymethyl methacrylate film containing randomly oriented (spaghetti-like) arc-discharge single-walled carbon nanotubes serving as a saturable absorber based on evanescent field coupling. Stable passively -switched (PQS) operation was achieved. The PQS 60 μm diameter WG laser generated a record output power of 150 mW at 1846.8 nm with =34.6%. The conversion efficiency with respect to the CW mode was 87.6%. The best pulse characteristics (energy/duration) were 105.6 nJ/98 ns at a repetition rate of 1.42 MHz.Ministerio de Economía y Competitividad (MINECO) (FIS2013-44174-P, FIS2015-71933-REDT, MAT2016-75716-C2-1-R (AEI/FEDER,UE), TEC2014-55948-R); Agència de Gestió d’Ajuts Universitaris i de Recerca (AGAUR) (2017SGR755); Consejería de Educación, Junta de Castilla y León (SA046U16, UIC016); Generalitat de Catalunya (2016FI_B00844, 2017FI_B100158, 2018 FI_B2 00123)

Investigation of Nonlinear Optical Properties of Quantum Dots Deposited onto a Sample Glass Using Time-Resolved Inline Digital Holography

We report on the application of time-resolved inline digital holography in the study of the nonlinear optical properties of quantum dots deposited onto sample glass. The Fresnel diffraction patterns of the probe pulse due to noncollinear degenerate phase modulation induced by a femtosecond pump pulse were extracted from the set of inline digital holograms and analyzed. The absolute values of the nonlinear refractive index of both the sample glass substrate and the deposited layer of quantum dots were evaluated using the proposed technique. To characterize the inhomogeneous distribution of the samples’ nonlinear optical properties, we proposed plotting an optical nonlinearity map calculated as a local standard deviation of the diffraction pattern intensities induced by noncollinear degenerate phase modulation.publishedVersionPeer reviewe

Fs-laser-written thulium waveguide lasers Q-switched by graphene and MoS2

[EN]We report the generation of mid-infrared (~2 µm) high repetition rate (MHz) sub-100 ns pulses in buried thulium-doped monoclinic double tungstate crystalline waveguide lasers using two-dimensional saturable absorber materials, graphene and MoS2. The waveguide (propagation losses of ~1 dB/cm) was micro-fabricated by means of ultrafast femtosecond laser writing. In the continuous-wave regime, the waveguide laser generated 247 mW at 1849.6 nm with a slope efficiency of 48.7%. The laser operated at the fundamental transverse mode with a linearly polarized output. With graphene as a saturable absorber, the pulse characteristics were 88 ns / 18 nJ (duration / energy) at a repetition rate of 1.39 MHz. Even shorter pulses of 66 ns were achieved with MoS2. Graphene and MoS2 are therefore promising for high repetition rate nanosecond Q-switched infrared waveguide lasers

Fs-laser-written erbium-doped double tungstate waveguide laser

[EN]We report on the first erbium (Er3+) doped double tungstate waveguide laser. As a gain material, we studied a monoclinic Er3+:KLu(WO4)2 crystal. A depressed-index buried channel waveguide formed by a 60 μm-diameter circular cladding was fabricated by 3D femtosecond direct laser writing. The waveguide was characterized by confocal laser microscopy, μ-Raman and μ-luminescence mapping, confirming that the crystallinity of the core is preserved. The waveguide laser, diode pumped at 981 nm, generated 8.9 mW at 1533.6 nm with a slope efficiency of 20.9% in the continuous-wave regime. The laser polarization was linear (ENm). The laser threshold was at 93 mW of absorbed pump power

Nanostructured Luminescent Gratings for Sensorics

Two-dimensional holographic structures based on photopolymer compositions with luminescent nanoparticles, such as quantum dots, are promising candidates for multiresponsive luminescence sensors. However, their applicability may suffer from the incompatibility of the components, and hence aggregation of the nanoparticles. We showed that the replacement of an organic shell at the CdSe/ZnS quantum dots’ surface with monomer molecules of the photopolymerizable medium achieved full compatibility with the surrounding medium. The effect was demonstrated by luminescence spectroscopy, and steady-state and time-resolved luminescent laser scanning microscopy. We observed the complete spectral independence of local photoluminescence decay, thus proving the absence of even nanoscale aggregation, either in the liquid composition or in the nodes and antinodes of the grating. Therefore, nanostructured luminescent photopolymer gratings with monomer-covered quantum dots can act as hybrid diffractive–luminescent sensor elements

Liquid Phase Epitaxy growth, structure and spectroscopy of highly-doped 20 at.% Yb3+:LiYF4 thin films

International audienc

Ultrafast Laser Inscription and ∼2 μm Laser Operation of Y-Branch Splitters in Monoclinic Crystals

International audienc

Tm 3+ and Ho 3+ colasing in in-band pumped waveguides fabricated by femtosecond laser writing

International audienc

Low-loss fs-laser-written surface waveguide lasers at >2 µm in monoclinic Tm 3+ :MgWO 4

International audienc