Efficient 2.7-μm emission in Er3＋-doped bismuth germanate glass pumped by 980-nm laser diode

An Er 3+-doped lead-free bismuth germanate glass is synthesized. Its 2.7-μm emission property is analyzed, and the efficient 2.7-μm emission from the glass is observed under 980-nm laser diode excitation. The prepared glass possesses high spontaneous transition probability (64.8 s 1 ) and a large calculated emission cross section (6.61×10 21 cm 2 ) corresponding to the 4I11/2→4I13/2 transition. The multiphonon relaxation rate for the excited state 4I11/2 is only 236 s 1 . Therefore, the excellent spectroscopic properties and outstanding thermal stability suggest that this glass is a suitable host for developing solid-state lasers operating in the mid-infrared.     

Intense 2.7 μm and broadband 2.0 μm emission from diode-pumped Er3+/Tm3+/Ho(3+)-doped fluorophosphate glass

This Letter reports intense emission at 2.7 μm and broadband emission at 2.0 μm from Er(3+)/Tm(3+)/Ho(3+)-doped fluorophosphate glass. The fluorescence characteristics and energy transfer upon excitation of a conventional 980 nm laser diode are investigated. Based on the fluorescence spectra and lifetime measurement, the effect of Tm(3+) and Ho(3+) ions on intense 2.7 μm emission in fluorophosphate glass is demonstrated. It is also found that the effective bandwidth of 2.0 μm emission due to Tm(3+) and Ho(3+) ions can reach as high as 196 nm. These results indicate that the advantageous spectroscopic characteristics of Er(3+)/Tm(3+)/Ho(3+) triply doped fluorophosphate glass together with the outstanding thermal properties may become an attractive host for the mid-IR solid state lasers.     

A 1.54 μm Er glass laser pumped by a 1.064 μm Nd:YAG laser

Laser oscillation in Er-glass, co-doped with Yb sensitiser, has been achieved by pumping with the 1.064 μm output of a Nd:YAG laser.     

High-peak-power passively Q-switched 1.3 μm Nd:YAG/V~(3+):YAG laser pumped by a pulsed laser diode

We demonstrate a high-pulse-energy, short-pulse-width passively Q-switched(PQS) Nd:YAG∕V3t:YAG laser at 1.3 μm, which is end-pumped by a pulsed laser diode. During the PQS regime, a maximum total output pulse energy of 3.3 m J is obtained under an absorbed pump pulse energy of 21.9 m J. Up to 400 μJ single-pulse energy is realized with the shortest pulse width of 6.16 ns and a pulse repetition frequency of 34.1 k Hz,corresponding to a peak power of 64.9 k W. The high-energy laser pulse is operated in the dual wavelengths of 1319 and 1338 nm, which is a potential laser source for THz generation.     

Generation of 1.5 μm emission through an upconversion-mediated looping mechanism in Er3+/Sc3+-codoped LiNbO3 single crystal

Important for telecommunications, luminescence of trivalent erbium (Er) at 1.5 μm generally arises from a Stokes-shifted downconversion mechanism. We show that this luminescence following direct excitation of the 4I11/2 state is generated by upconversion-mediated looping process in Er3+/Sc3+-codoped LiNbO3 single crystal. Emissions at 1.0 and 1.5 μm from the 4I11/2 and 4I13/2 states display linear and quadratic dependences on the excitation density in two separated ranges with a threshold of 20 W/cm2. This observation correlates with two- and four-photon processes in green and red upconversion emissions. The mechanism described has implications in the improvement of the output of 1.5 μm luminescence.     

A single-longitudinal-mode continuous-wave Ho~(3+):YVO_4 laser at 2.05 μm pumped by a Tm-fibre laser

We present a single-longitudinal-mode continuous-wave Ho~(3+):YVO_4 laser at 2.05 μm pumped by a Tm-doped fibre laser. Use of a cavity etalon enables spectral selectivity for single-mode operation. The highest power achieved in the single longitudinal mode at 2052.5 nm is 282 mW at a slope efficiency of 6.9%, corresponding to an optical conversion efficiency of 3.0%. These features demonstrate that this single-longitudinal-mode Ho:YVO_4 laser is suitable for use as a seed laser in some Lidar systems(e.g., coherent Lidar or differential absorption Lidar). To the best of our knowledge, this is the first report on such a single-longitudinal-mode Ho:YVO_4 laser at 2.05 μm.     

Actively Q-switched 2.9 μm Ho(3+)Pr(3+)-doped fluoride fiber laser

We report an efficient Q-switched Ho(3+)Pr(3+)-doped fluoride fiber laser, producing a peak power of 77 W, with pulse width of 78 ns. A slope efficiency of 20% with respect to the launched pump power was achieved. A TeO(2) acousto-optic modulator allowed continuous tunability of the pulse repetition frequency from 40 to 300 kHz.     

Emission enhancement in Er^3＋/Pr^3＋-codoped germanate glasses and their use as a 2.7-μm laser material

Emission enhancement at 2.7 μm is observed in Er^3＋/Pr^3＋--codoped germanate glasses when pumped by a 980-nm laser diode. Significant reductions in 1.5-μm emission and upeonversion intensity indicate efficient energy transfer between Er^3＋ and Pr^3＋; the energy transfer efficiency is as high as 77.4%. The mechanisms of energy transfer are discussed in detail. The calculated emission cross-section of Er^3＋/Pr^3＋- codoped germanate glass is 8.44× 10 ^-21 cm^2, which suggests that Er^3＋/Pr^3＋-codoped germanate glass can be used to achieve efficient 2.7-μm emission.     

2 μm emission properties in Tm3+/Ho3+ codoped fluorophosphate glasses

New type of fluorophosphate glasses with different Tm³⁺/Ho³⁺ doping concentrations have been prepared. From the measured fluorescence spectra, strong emission near 2 μm is demonstrated in the samples. Based on the absorption spectra, the Judd–Ofelt parameters and radiative properties were calculated and compared with those of other glass hosts. Then for our prepared Tm³⁺/Ho³⁺ codoped fluorophosphate glass, the higher predicted spontaneous transition probability (76.54 s^?1) along with the larger calculated emission cross-section (6.15×10^?21 cm²) gives evidence of intense 2 μm fluorescence. Besides, it is found that the optimum doping concentration is 4 mol% Tm³⁺/1 mol% Ho³⁺ for the strongest 2 μm emission in our prepared samples.     

4-W single transverse mode Yb~(3+)-doped fiber laser pumped by 915-nm laser diode array

A cladding-pumped ytterbium-doped fiber laser is described in this letter. Using unusual pumping source with 915-nm wavelength, slope efficiency up to 75% with respect to absorbed input power and output power is obtained, a maximum output power of 4.006 W with fundamental mode is measured.     

Efficient high-power Ho:YAG laser directly in-band pumped by a GaSb-based laser diode stack at 1.9 μm

An efficient high-power Ho:YAG laser directly in-band pumped by a recently developed GaSb-based laser diode stack at 1.9 μm is demonstrated. At room temperature a maximum continuous wave output power of 55 W at 2.122 μm and a slope efficiency of 62% with respect to the incident pump power were achieved. For narrow linewidth laser operation a volume Bragg grating was used as output coupler. In wavelength stabilized operation a maximum output power of 18 W at 2.096 μm and a slope efficiency of 30% were obtained. In this case the linewidth is reduced from 1.2 nm to below 0.1 nm. Also spectroscopic properties of Ho:YAG crystals at room temperature are presented.     

Effect of PbCl2 addition on structure, OH− content, and upconversion luminescence in Yb3+/Er3+-codoped germanate glasses

Yb³⁺/Er³⁺-codoped oxychloride germanate glasses have been synthesized by a conventional melting and quenching method. Structural properties were obtained based on Raman-spectra investigation, indicating that PbCl₂ plays an important role in the formation of the glass network and has an important influence on the phonon density and the maximum phonon energy. The Judd–Ofelt intensity parameters and quantum efficiencies were calculated based on the Judd–Ofelt theory and lifetime measurements. The enhanced upconversion luminescence intensity of Er³⁺ with increasing PbCl₂ content could not be explained only by the maximum phonon-energy change of the host glasses. For the first time, the effect of PbCl₂ addition on phonon density, OH^– content, and upconversion luminescence in oxychloride glasses has been discussed and evaluated. The results show that the effect of phonon density and OH^– content on upconversion luminescence in oxychloride glasses is much stronger than that of the decrease of the maximum phonon energy. The possible upconversion luminescence mechanisms have also been estimated and are discussed.     

2-μm emission performance of Tm~(3+)-Ho~(3+) co-doped tellurite glasses

The emission properties of 2-μm region fluorescence of Tm~(3+)-Ho~(3+) co-doped tellurite glasses are investigated. Introducing F~- ions to the composition of tellurite glasses plays a positive effect on the 2-μm emission.A maximum intensity of 2-μm emission is achieved when 1.5-mol%Tm_2O_3 and l-mol% Ho_2_O3 concentration are doped in the glasses.The emission cross section and gain coefficient of the ~5I_8→~5I_7 transition of Ho~(3+) are calculated.The emission cross section has a maximum of 1.29×10~(-2...     

Enhanced mid-infrared emissions of Er3+ at 2.7 μm via Nd3+ sensitization in chalcohalide glass

Nd(3+) sensitized Er(3+):(4)I(13/2) mid-IR emissions around 2.7 μm were investigated in the transparent Ga(2)S(3)-GeS(2)-CsCl chalcohalide glasses for the first time. Remarkably, it is found that Nd(3+) greatly enhances Er(3+) 2.7 μm emission by a maximal 20 times, and depopulates the lower level of Er(3+):(4)I(13/2) for population inversion. Based on Judd-Ofelt theory, the 2.7 μm emission cross section is calculated (as high as 0.66×10(-20) cm(2)) and the gain property of the Er(3+):(4)I(11/2)→(4)I(13/2) transition is discussed. Hopefully, the materials studied here may find potential applications in the fields of fiber amplifiers and mid-IR lasers.     

Free-running and Q-switched operation of a diode pumped Er:YSGG laser at the 3 μm transition

A study is made of a diode pumped Er³⁺:YSGG laser crystal operating at 2.797 μm. Lasers were constructed in the bounce geometry, using a transversely cooled 50 at.% Er:YSGG slab and a face-cooled 38 at.% Er:YSGG slab. Results from these are compared with those from a 50 at.% Er³⁺:YAG laser, also in the bounce geometry. With quasi-continuous wave diode pumping, free-running pulse energies of up to ~55 mJ and a slope efficiency of 20.5% are obtained from 50 at.% Er:YSGG. Better thermal performance is obtained from the face-cooled 38 at.% Er:YSGG slab, allowing average power of ~2 W to be obtained at a repetition rate and pump pulse duration of 140 Hz and 500 μs, respectively. Both Er:YSGG systems perform better than Er:YAG. Numerical modelling of the free-running 50 at.% Er:YSGG and Er:YAG systems is undertaken with good qualitative agreement with experimental results. Electro-optic Q-switching of the 50 at.% Er:YSGG laser using a LiNbO₃ crystal yields ~0.5 mJ pulses with ~77 ns duration.     

Performance of a diode end-pumped Cr,Er:YSGG laser at 2.79 μm

We present a diode end-pumped Cr,Er:YSGG laser at 2.79 μm operated in the continuous-wave (CW) and pulsed modes. Er³⁺ ions are directly pumped into the upper laser state ⁴ I _11/2 using a 967-nm diode laser, which avoids various nonradiative losses. The laser produces 50.2 mW of power in the CW mode. An average power of 169 mW is obtained at a repetition rate of 100 Hz and a pulse duration of 2 ms. The maximum laser energy achieved is 1.95 mJ at a repetition rate of 50 Hz, corresponding to a peak power of 970 mW and a slope efficiency is 7.6%. The far-field divergence angle of the laser is measured to be 8 mrad.     

Er~(3+)/Yb~(3+) codoped phosphate glass laser end-pumped by laser diode

An Er3 /Yb3 phosphate laser glass was fabricated and characterized. According to McCumber theory, the stimulated emission cross-section of Er3 ions at 1533 nm calculated by absorption spectrum was 0.84×10-20 cm2, and the fluorescence lifetime of 4I13/2 level was 8.5 ms. Continuous wave (CW) laser operation of this Er3 /Yb3 phosphate glass pumped by laser diode (LD) was demonstrated at room temperature. The maximum output power of 80 mW and slope efficiency of 16.5% were obtained.     

Resonantly pumped 1.645 μm high repetition rate Er:YAG laser Q-switched by a graphene as a saturable absorber

A fiber laser resonantly pumped 1.645 μm passively Q-switched Er:YAG laser is reported. Graphene on a silicon carbide was used as the saturable absorber for the Q-switching. The pulse energy of the 1.645 μm Q-switched Er:YAG laser was 7.05 μJ, with a pulse repetition rate of 35.6 kHz and an average output power of 251 mW.     

Spectroscopic and radiation-resistant properties of Er,Pr:GYSGG laser crystal operated at 2.79 μm

We demonstrate the spectroscopic and laser performance before and after 100 Mrad gamma-ray irradiation on an Er,Pr:GYSGG crystal grown by the Czochralski method. The additional absorption of Er,Pr:GYSGG crystal is close to zero in the 968 nm pumping and 2.7-3 μm laser wavelength regions. The lifetimes of the upper and lower levels show faint decreases after gamma-ray irradiation. The maximum output powers of 542 and 526 mW with the slope efficiencies of 17.7% and 17.0% are obtained, respectively, on the GYSGG/Er,Pr:GYSGG composite crystal before and after the gammaray irradiation. These results suggest that Er,Pr:GYSGG crystal as a laser gain medium possesses a distinguished antiradiation ability for application in space and radiant environments.     

Thermal Lensing, Laser Performance at 1.06 μm and 0.53 μm of a NYAB Laser End pumped by a Diode laser array

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