Femtosecond-laser-written hexagonal cladding waveguide in Tm:KLu(WO_4)_2: µ-Raman study and laser operation

Kifle, Esrom; Loiko, Pavel; Mateos, Xavier; Aldana, Javier R. Vázquez de; Ródenas, Airán; Griebner, Uwe; Petrov, Valentín; Aguiló, Magdalena; Díaz, Francesc

doi:10.1364/ome.7.004258

Cited by 23 publications

(15 citation statements)

References 35 publications

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“…The achieved CW output power and the slope efficiency exceed the values reported previously for the hexagonalcladding fs-DLW buried Tm:KLuW WG [19].…”

Section: A Cw Operationsupporting

confidence: 40%

“…The least-square fit of the experimental data yields η 0 43 2%, δ 4.34L∕t 0.7 0.3 dB∕cm for the 60 μm WG and η 0 36 2%, δ 0.9 0.3 dB∕cm for the 50 μm one. These values of the WG propagation loss are lower than those reported for an fs-DLW Tm:KLuW WG with a hexagonal cladding (1.2 dB/cm) [19] and for an fs-DLW Yb:KGdWO 4 2 WG based on a pair of damage tracks (1.9 dB/cm) [49] and indicate the good potential of the designed structures for further PQS experiments.…”

Section: A Cw Operationmentioning

confidence: 55%

“…Power scaling of such lasers was shown in Ref. [19] using a hexagonal lattice-like cladding WG. The output power reached 136 mW at 1.844 μm with η 34.2%, and the WG propagation loss was estimated to be 1.2 dB/cm.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2018

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Surface channel waveguides (WGs) were fabricated in a monoclinic Tm 3 :KLuWO 4 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 μ-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 η 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 Q-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 η 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.

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“…The achieved CW output power and the slope efficiency exceed the values reported previously for the hexagonalcladding fs-DLW buried Tm:KLuW WG [19].…”

Section: A Cw Operationsupporting

confidence: 40%

Section: A Cw Operationmentioning

confidence: 55%

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

et al. 2018

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“…The separation between adjacent tracks was 2 μm. The estimated variation of the refractive index in the cladding was ~6 × 10 −4 [27]. To characterize the WG, we employed confocal laser microscopy (LSM 710, Carl Zeiss).…”

Section: Femtosecond-laser-written Waveguidementioning

confidence: 99%

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

et al. 2019

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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 MoS 2 . 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 MoS 2 . Graphene and MoS 2 are therefore promising for high repetition rate nanosecond Q-switched infrared waveguide lasers. IntroductionWaveguide (WG) lasers emitting in the spectral range of ~2 μm are of interest for spectroscopy, telecom and environmental sensing applications [1]. This is because their emission is eye-safe and matches the absorption lines of various atmospheric and biomolecules. The laser operation at ~2 μm is achieved using such trivalent rare-earth ions as Thulium (Tm 3+ ) or Holmium (Ho 3+ ). In the former case, the transition of interest is 3 F 4 → 3 H 6 . Due to the large Stark splitting of the Tm 3+ ground-state, its emission is wavelength-tunable. The Tm 3+ ions feature strong absorption at ~0.8 μm ( 3 H 6 → 3 H 4 transition) allowing for their efficient pumping by AlGaAs laser diodes and Ti:Sapphire lasers. Moreover, the crossrelaxation for adjacent Tm 3+ ions, 3 H 4 + 3 H 6 → 3 F 4 + 3 F 4 , can potentially raise the pump quantum efficiency up to 2.Efficient continuous-wave (CW) thulium WG lasers are known [2,3]. Several methods have been used to fabricate WGs based on Tm 3+ -doped materials, e.g., liquid phase epitaxy (LPE) in combination with ion beam etching [2], optical bonding [4], ion diffusion [5], reactive co-sputtering [6] and femtosecond direct laser writing (fs-DLW) also referred as ultrafast laser inscription (ULI) [7]. In the latter approach, the output of an ultrafast (fs) An overview of PQS thulium WG lasers reported to date is presented in Table 1. Regarding planar WG lasers produced by LPE, a "slow" SA (Cr 2+ :ZnS) was employed in a Tm:KY(WO 4 ) 2 laser yielding 1.2 μs / 0.12 μJ (duration / energy) pulses at a low repetition rate of 10 kHz [24]. The use of a "fast" SWCNT-based SA in a similar laser lead to much shorter pulses of 83 ns / 33 nJ at 1.39 MHz [25]. However, both these lasers generated spatially multimode output.

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“…Recently, we used the pump with fiber-coupled diode laser to achieve watt-level emission in continuous-wave (cw) operation from buried depressed-cladding waveguides that were inscribed by an fs-laser beam in Nd:YAG and Nd:YVO 4 [ 10 , 11 ]. Among the many recent results we can mention the laser emission in the 2.0 μm range in waveguides written in Ho:YAG [ 12 ], the interest for emission into the visible spectrum from depressed-cladding waveguides inscribed in the Pr:YLF crystal [ 13 ], or the realization of a hexagonal optical-lattice-like cladding structure in the Tm:KLu(WO 4 ) 2 crystal with efficient laser emission around 1.8 μm [ 14 ].…”

Section: Introductionmentioning

confidence: 99%

Passive Q-Switching by Cr4+:YAG Saturable Absorber of Buried Depressed-Cladding Waveguides Obtained in Nd-Doped Media by Femtosecond Laser Beam Writing

Gabriela

Pavel

2018

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We report on laser performances obtained in Q-switch mode operation from buried depressed-cladding waveguides of circular shape (100 μm diameter) that were inscribed in Nd:YAG and Nd:YVO4 media by direct writing with a femtosecond laser beam. The Q-switch operation was realized with a Cr4+:YAG saturable absorber, aiming to obtain laser pulses of moderate (few μJ) energy at high (tens to hundreds kHz) repetition rate. An average power of 0.52 W at 1.06 μm consisting of a train of pulses of 7.79 μJ energy at 67 kHz repetition rate, was obtained from a waveguide realized in a 4.8 mm long, 1.1-at % Nd:YAG ceramics; the pulse peak power reached 1.95 kW. A similar waveguide that was inscribed in a 3.4 mm long, 1.0-at % Nd:YVO4 crystal yielded laser pulses with 9.4 μJ energy at 83 kHz repetition rate (at 0.77 W average power) and 1.36 kW peak power. The laser performances obtained in continuous-wave operation were discussed for each waveguide used in the experiments. Thus, a continuous-wave output power of 1.45 W was obtained from the circular buried depressed-cladding waveguide inscribed in the 1.1-at %, 4.8 mm long Nd:YAG; the overall optical-to-optical efficiency, with respect to the absorbed pump power, was 0.21. The waveguide inscribed in the 1.0-at %, 3.4 mm long Nd:YVO4 crystal yielded 1.85 W power at 0.26 overall optical efficiency. This work shows the possibility to build compact laser systems with average-to-high peak power pulses based on waveguides realized by a femtosecond (fs) laser beam direct writing technique and that are pumped by a fiber-coupled diode laser.

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Femtosecond-laser-written hexagonal cladding waveguide in Tm:KLu(WO_4)_2: µ-Raman study and laser operation

Cited by 23 publications

References 35 publications

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

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

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

Passive Q-Switching by Cr4+:YAG Saturable Absorber of Buried Depressed-Cladding Waveguides Obtained in Nd-Doped Media by Femtosecond Laser Beam Writing

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Femtosecond-laser-written hexagonal cladding waveguide in Tm:KLu(WO_4)_2: µ-Raman study and laser operation

Cited by 23 publications

References 35 publications

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

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

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

Passive Q-Switching by Cr4+:YAG Saturable Absorber of Buried Depressed-Cladding Waveguides Obtained in Nd-Doped Media by Femtosecond Laser Beam Writing

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