Μm Tm Research Articles

High power continuous-wave, Q-switched, and quasi-continuous-wave operation of a diode-pumped Tm,Ho:YAG laser oscillator at 2.09 μm

A high-power diode-pumped 2.09 μm Tm,Ho:YAG laser oscillator with multi-regime operation is demonstrated. In the continuous-wave (CW) regime, it delivers 44.68 W output power with M2 = 3.47, yielding a record-high brightness of 87.57 MW/cm2·sr. In the Q-switched mode, stable laser performance across pulse repetition frequencies (PRFs) from 1 kHz to 4 kHz is achieved. At a PRF of 1 kHz, single pulse energy reaches 22.85 mJ with a pulse width of 443.4 ns and M2 = 3.50. In the quasi-continuous-wave (QCW) operation, a pulse energy of 31.85 mJ is obtained at 200 Hz with a 370 μs pulse width and M2 = 4.49. These pulse energies are the highest reported to date for Tm-Ho co-doped laser oscillators at high PRF. This also marks the first demonstration of a versatile 2 μm laser that can operate at room temperature while delivering high-energy, high-repetition-rate pulses in both nanosecond and microsecond durations within a single device, making it highly appealing for scientific and industrial applications.

High-efficiency 2.3 μm Tm:YLF laser based on 0.79 μm and 1.05 μm dual-wavelength pumping scheme

High-efficiency 2.3 μm Tm:YLF laser based on 0.79 μm and 1.05 μm dual-wavelength pumping scheme

High-power 2.3 µm Tm:YLF laser with intracavity upconversion pumping by a Nd:ASL laser at 1051 nm.

A Tm:LiYF4 laser operating on the 3H4 → 3H5 transition is embedded in a high-power diode-pumped Nd:ASL laser for intracavity upconversion pumping at 1.05 µm. This leads to a record-high output power at 2.3 µm for any bulk thulium laser pumped by an upconversion process. The continuous-wave Tm:LiYF4 laser delivers 1.81 W at 2.3 µm for 32 W of laser-diode pump power, making this kind of pumping competitive with direct diode pumping. The intracavity pumping process allows for counteracting the low absorption inherent to upconversion pumping and to dispatch the thermal loads on two separate laser crystals. The proposed laser architecture also features a relatively weak heating of the Tm:LiYF4 crystal and an increased tolerance to Tm3+ absorption. This laser design opens a new paradigm that holds great promise for high-power 2.3-µm solid-state lasers based on thulium ions.

Study on the Generation of 1.9 μm Mode Superposition Conversion Laser by Double-End Off-Axis Pumping

In this paper, the Laguerre–Gaussian (LG) mode superposition is obtained by using the technology of double-end off-axis pumping Tm:YLF crystal, and the LG mode superposition is achieved by combining the extra-cavity conversion method. The impact of changing the off-axis distance on the order of Hermite–Gaussian (HG) mode and the topological charge of LG mode is studied. The results show that when the off-axis distance of the pump source at both ends is tuned, when the off-axis distance is in the range of 260 μm~845 μm, the single-ended 0~10 order HG mode can be obtained. Subsequently, the mode converter is placed to obtain the LG mode beam, and the double-end simultaneously pumps the crystal to obtain the superimposed LG mode. The tuning off-axis quantity changes the topological charge number. When P = 0, l1=l2, the superimposed LG mode is a single-ring spot, and the vortex beam center’s dark hollow area increases with the topological charge number. When P = 0, l1=−l2, the superimposed LG mode is a petal-like spot. The number of petals differs from the topological charges of two opposite numbers. Finally, in the case of changing the topological charge number of the double-ended LG mode, the output of the vortex array structured beams of the tuning mode order 1.9 μm Tm:YLF is completed in the case of conversion and superposition.

Passively Q-switched 2.3 μm Tm:YVO4 laser using a Cr:ZnS saturable absorber.

A diode-pumped wavelength switchable passively Q-switched 2.3 μm Tm:YVO4 laser was demonstrated in this work. A Cr:ZnS saturable absorber was introduced into the cavity for initiating passive Q-switching. With the increase of the absorbed pump power, the passively Q-switched laser could be switched from the single wavelength of 2366 nm to the dual wavelength of 2290 and 2360 nm. The pulse duration and pulse repetition frequency could be tuned in the ranges of 0.745-1.782 μs and 2.9-43.4 kHz, respectively. The pulse energy and peak power were estimated to be 7.5 μJ and 10 W, respectively, at an absorbed pump power of 12 W.

Diode-pumped Tm:YAP laser operating at 2.3 µm with enhanced performance through cascade lasing.

The laser diode (LD)-pumped Tm:YAP (a-cut, 3.5 at.%) laser generated a maximum ∼2.3 µm continuous wave (CW) laser output power of ∼3 W. The higher output power benefited from the positive effect of the cascade lasing (simultaneously operating on the 3H4 → 3H5 and 3F4 → 3H6 Tm3+ transition). It was the highest CW laser output power amongst the LD/Ti:Sapphire-CW-pumped ∼2.3 µm Tm3+-doped lasers reported so far. Under the cascade laser operation, the slope efficiency of the ∼2.3 µm laser emission versus the absorbed pump power increased from 13.0% to 21.4%.

Doubly Q-switched Tm:YAP laser based on the Cr2+:ZnS crystal and electro-optical modulator

A doubly Q-switched Tm3+:YAlO3 (Tm:YAP) laser based on the Cr2+:ZnS saturable absorber (SA) and electro-optical modulator (EOM) is presented. The pulse duration of the doubly Q-switched lasers is shorter as compared to single actively and passively Q-switched operations. The shortest pulse duration of 17.3 ns with a repetition rate of 100 Hz was measured at the pump power of 12 W in the doubly Q-switched laser. The corresponding pulse peak power of 184.8 kW and the pulse energy of 3.2 mJ was obtained. The center wavelength of the doubly Q-switched operation was 1.94 μm. The results demonstrate that Cr2+:ZnS is an excellent saturable absorber for 2 μm Tm:YAP laser, and the doubly Q-switched operation can greatly narrow the Q-switched pulse width.

Diode-pumped efficient high-power cascade Tm:GdVO4 laser simultaneously operating at ∼2 μm and ∼2.3 μm.

The laser diode (LD)-pumped efficient high-power cascade Tm:GdVO4 laser simultaneously operating on the 3F4 → 3H6 (at ∼2 μm) and 3H4 → 3H5 (at ∼2.3 μm) Tm3+ transition was first reported in this paper. The cascade Tm:GdVO4 laser generated a maximum total continuous-wave (CW) laser output power of 8.42 W with a slope efficiency of 40%, out of which the maximum ∼2.3 μm CW laser output power was 2.88 W with a slope efficiency of 14%. To our knowledge, 2.88 W is the highest CW laser output power amongst the LD-CW-pumped ∼2.3 μm Tm3+-doped lasers reported so far.

Sensitization of 5–6 μm Nd3+ luminescence in selenide glass by Tb3+ ions

This investigation proposes Tb3+ ions as efficient sensitizers of 5–6 μm Nd3+ emission in selenide glasses. Tb3+ ions can be pumped by 2.9 μm Er:YAG as well as by 1.9–2 μm Tm3+ lasers and laser diodes. It was shown, that at room temperature the radiationless energy transfer from Tb3+ to Nd3+ is combined with the reverse process. At liquid nitrogen temperature the energy transfer from Tb3+ to Nd3+ becomes irreversible. The proposed sensitization scheme should allow the development of neodymium chalcogenide glass lasers emitting at ∼6 μm.

Nickel–cobalt layered double hydroxide saturable absorber for a mid-infrared 2 µm Tm:YAG ceramic mode-locked laser

Nickel–cobalt layered double hydroxide saturable absorber for a mid-infrared 2 µm Tm:YAG ceramic mode-locked laser

Cascade lasing at ∼2 μm and ∼2.3 μm in a diode-pumped Tm:YVO4 laser.

We report on the cascade continuous-wave operation of a diode-pumped Tm:YVO4 laser on the 3F4 → 3H6 (at ∼2 μm) and 3H4 → 3H5 (at ∼2.3 μm) Tm3+ transitions. Pumped with a fiber-coupled spatially multimode 794 nm AlGaAs laser diode, the 1.5 at.% Tm:YVO4 laser yielded a maximum total output power of 6.09 W with a slope efficiency of 35.7% out of which the 3H4 → 3H5 laser emission corresponded to 1.15 W at 2291-2295 and 2362-2371 nm with a slope efficiency of 7.9% and a laser threshold of 6.25 W.

Spectroscopy and lasing of cryogenically cooled Tm3+,Lu3+:CaF2 crystal

The temperature dependence of the spectroscopic and laser properties of a new cryogenically cooled mixed fluoride Tm,Lu:CaF2 crystal was investigated. The influence of optically inactive Lu3+ ions codoping was studied. Efficient 1.9 μm Tm3+ ions lasing at room temperature under 763 nm laser diode pumping was realized. With a temperature decrease down to 78 K the slope efficiency almost doubled up to 66% with respect to 300 K. The wide laser tuning range of 250 nm (1785–2035 nm) was demonstrated.

Study on 1.9 [formula omitted]m structured lasers based on Ince–Gaussian modes superposition with multi-modulation by different directions off-axis dual-end-pump

The double IGp,pe modes multi-modulation superposition evolution structured lasers output is realized, based on the proposed different directions off-axis dual-end-pumping Tm:YLF laser method. Under the modes orthogonal superposition, the theoretical simulation and experimental measurement results have a high degree of agreement, and the orthogonal superposition of double IGp,pe modes within 5 orders is realized, which proves that different order modes and optical field intensity ratio have the capability to modulate the formation of vortex array structured beams. When the low-order IGp,pe modes of the same order are orthogonally superimposed, the phenomenon of superposition of different phase differences occurs, which proves the possibility of modulating the superposition of IGp,pe modes by the phase difference. At the same time, it is found that the regular pattern output of high-order IGp,m modes (odd mode m ≤ 3 or even mode m ≤ 2) can be realized at different angles, which proves the ability of rotation angle to modulate the superposition of double IGp,pe modes. Finally, the 1.9μm Tm:YLF structure laser output with double IGp,pe modes multi-factor composite modulation superposition evolution within 10 orders is realized. When the 10-order double IG10,10e modes are superimposed, the output power exceeds 5.7 W, and the conversion efficiency is higher than 17.5%.

Nickel-vanadium layered double hydroxide for a mid-infrared 2 µm Tm:YAG ceramic ultrafast laser.

In this study, a nickel-vanadium layered double hydroxide (NiV-LDH) nanosheet was prepared as a saturable absorber (SA) by liquid phase exfoliation and a drop-coating method. The microstructure and optical transmission properties of the obtained NiV-LDH nanosheet were then systematically studied. An "X"-type fold cavity was designed to evaluate the ultrafast laser modulation performance of the NiV-LDH nanosheet with a Tm:YAG ceramic gain medium. A stable passively Q-switched mode-locked (QML) pulse centered at 2011.6 nm has successfully been realized, with a repetition frequency of 145 MHz and a pulse duration of 320 ps. To the best of our knowledge, this is the first time that the LDH has been used as an SA in a mid-infrared range ultrafast laser.

Continuous Tb-doped fiber laser emitting at ∼5.25 µm

The paper describes a chalcogenide glass fiber laser operating at the wavelength inaccessible to oxide and fluoride rare-earth doped fibers. The lasing fiber had 19 μm diam. selenide core doped with 2 × 1019 cm−3 of Tb3+ ions and 270 μm diam. undoped sulfide cladding. The pump source was a CW 1.98 µm Tm3+ fiber laser. Up to 36 mW TEM00 output was obtained in the 5.20–5.28 µm spectral band.

Near-IR Luminescence of Rare-Earth Ions (Er3+, Pr3+, Ho3+, Tm3+) in Titanate-Germanate Glasses under Excitation of Yb3.

Inorganic glasses co-doped with rare-earth ions have a key potential application value in the field of optical communications. In this paper, we have fabricated and then characterized multicomponent TiO2-modified germanate glasses co-doped with Yb3+/Ln3+ (Ln = Pr, Er, Tm, Ho) with excellent spectroscopic properties. Glass systems were directly excited at 980 nm (the 2F7/2 → 2F5/2 transition of Yb3+). We demonstrated that the introduction of TiO2 is a promising option to significantly enhance the main near-infrared luminescence bands located at the optical telecommunication window at 1.3 μm (Pr3+: 1G4 → 3H5), 1.5 μm (Er3+: 4I13/2 → 4I15/2), 1.8 μm (Tm3+: 3F4 → 3H6) and 2.0 μm (Ho3+: 5I7 → 7I8). Based on the lifetime values, the energy transfer efficiencies (ηET) were estimated. The values of ηET are changed from 31% for Yb3+/Ho3+ glass to nearly 53% for Yb3+/Pr3+ glass. The investigations show that obtained titanate–germanate glass is an interesting type of special glasses integrating luminescence properties and spectroscopic parameters, which may be a promising candidate for application in laser sources emitting radiation and broadband tunable amplifiers operating in the near-infrared range.

Pr3+/Tm3+/Er3+ tri-doped tellurite glass with ultra-broadband luminescence in the optical communication band

Pr3+/Tm3+/Er3+ tri-doped tellurite glass was synthesised using a melt-quenching method, and the broadband luminescent properties were measured in the near-infrared band. With an optimal combination of the three ions, a broadband luminescence ranging from 1280 to 1630 nm, located within the optical communication window of silica transmission fibre, was acquired under 808 nm excitation. The broadband luminescence comprises three bands: 1.34 μm (Pr3+), 1.47 μm (Tm3+), and 1.53 μm (Er3+); and the full width at half-maximum was about 248 nm. This valuable result is of great significance for novel broadband fibre amplifiers and ultra-short pulsed lasers.

Consequences of thimerosal on human erythrocyte hemoglobin: Assessing functional and structural protein changes induced by an organic mercury compound

BackgroundThimerosal (TM) is an organic mercury compound used as a preservative in many pharmacological inputs. Mercury toxicity is related to structural and functional changes in macromolecules such as hemoglobin (Hb) in erythrocytes (Ery). MethodHuman Hb and Ery were used to evaluate O2 uptake based on the TM concentration, incubation time, and temperature. The influence of TM on the sulfhydryl content, production of reactive oxygen species (ROS), and membrane fragility was also evaluated. Raman spectra and atomic force microscopy (AFM) profiles for Ery in the presence and absence of TM were calculated, and docking studies were performed. ResultsAt 37 °C, with 2.50 μM TM (higher concentration) and after 5 min of incubation in Hb and Ery, we observed a reduction in O2 uptake of up to 50 %, while HgCl2, which was used as a positive control, showed a reduction of at least 62 %. Total thiol assays in the presence of NEM (thiol blocker) quantified the preservation of almost 60 % of free SH in Ery. Based on the Raman spectrum profile from Ery-TM, structural differences in the porphyrinic ring and the membrane lipid content were confirmed. Finally, studies using AFM showed changes in the morphology and biomechanical properties of Ery. Theoretical studies confirmed these experimental results and showed that the cysteine (Cys) residues present in Hb are involved in the binding of TM. ConclusionOur results show that TM binds to human Hb via free Cys residues, causing conformation changes and leading to harmful effects associated with O2 transport.

GSA and ESA Dual-Wavelength Pumped 2.3 μm Tm∶YAP Lasers

GSA and ESA Dual-Wavelength Pumped 2.3 μm Tm∶YAP Lasers

Influence of Yb3+ co-doping on visible luminescence in ZBLAN:Ho3+ under 2-µm laser excitation

In this work, we present the results of theoretical and experimental analysis the processes of interionic energy transfer occurring in ZBLAN: 1%Ho3+ / ZBLAN: 1% Ho3++ 3% Yb3+ glasses compositions, which are responsible for up-conversion luminescence in the visible spectral region with 1.94 μm Tm3+:YAP laser excitation. A theoretical model based on a system of balance equations taking into account non-resonant transitions has been compiled. This made it possible to determine the main mechanisms of population of the 5F4, 5S2, and 5F5 states, to simulate the dynamics of energy transfer processes in the Ho3+ – Yb3+ system, and to explain the phenomenon of changes in the donor and acceptor functions between these ions, confirming the predominance of the interionic mechanism of population of the 5S2 level.