Spectroscopic Properties Of Tm3 Research Articles

Growth and spectroscopic properties of Tm3+ doped YPO4 crystal

Good quality single crystal of Tm3+ doped YPO4 crystal with an astounding emission cross-section was grown utilizing the flux method and the KF–P2O5 flux was employed for the first time to grow YPO4 crystal.

Pr3+ deactivation effect to Tm3+ at ∼1.5 μm emission in Bi4Ge3O12 crystals grown by the micro-pulling-down method

Tm3+, Pr3+ co-doped Bi4Ge3O12 (Tm,Pr:BGO) crystals with various Pr3+ doping concentration were successfully grown using the micro-pulling-down (μ-PD) method. The use of Pr3+ co-doping for deactivating the Tm3+ ions at 1.5 μm emission was investigated in the BGO single crystal for the first time. The effect of Pr3+ concentration on the spectroscopic properties of Tm,Pr:BGO crystals were demonstrated. In addition, the fluorescence lifetime of Tm3+:3F4 level of 0.5 at.% Pr, 2 at.% Tm:BGO crystal was quenched effectively (from 5.64 ms down to 0.36 ms) and the population inversions between Tm3+:3H4 and 3F4 levels are enhanced to achieve a four-level laser system at 1.5 μm.

Spectroscopic properties of Tm:Bi4Ge3O12 crystals grown by the micro-pulling-down method

Tm3+-doped bismuth germanate crystals (Tm:BGO) with various doping concentrations of 0.5, 0.75, 1.0, 1.5, and 2.0 at.% were grown by the micro-pulling-down method (μ-PD). The effect of thulium concentration on the growth, structure, absorption spectra, emission spectra and fluorescence lifetime of 3H4 and 3F4 state was studied. Under excitation of 792 nm, Tm:BGO crystals exhibit two fluorescence bands corresponding to the 3H4 → 3F4 and the 3F4 → 3H6 transitions. The fluorescence lifetime of 3H4 state decreased strongly as the thulium concentration increased, while the lifetime of 3F4 state was relatively constant for all thulium concentrations.

Growth and spectroscopic properties of Tm3+ and Tb3+ co-doped GdScO3 crystal

GdScO3 single crystal codoped with Tm3+ and Tb3+ ions was successfully grown by the Edge-defined Film-fed Growth Method (EFG) for the first time. Absorption, fluorescence spectrum and fluorescence lifetimes of the grown crystal at room temperature were measured. The absorption cross-section at 789 nm was calculated to be 8.20 × 10−21 cm2. The emission cross-section was 1.35 × 10−21 cm2 at 1504 nm with the FWHM of 95.3 nm. The fluorescence lifetimes of the 3H4 state and the 3F4 state were fitted to be 253 μs and 1460 μs, respectively. Compared with Tm3+ single doped GdScO3 crystal, the codoping of Tb3+ successfully depopulated the 3F4 energy level and enhanced the emission at 1.5 μm region. It indicated that Tm,Tb:GdScO3 could be favorable laser medium for 1.5 μm-laser operation.

Watt-level mid-infrared continuous-wave Tm:YAG laser operating on the 3H4 → 3H5 transition

We report on the first continuous-wave mid-infrared Tm:Y3Al5O12 laser operating on the 3H4 → 3H5 transition. The 3.2 at.% Tm:Y3Al5O12 laser generated a maximum output power of 1.07 W at ~2.19 & 2.32 μm with a high slope efficiency of 46.3% (vs. the absorbed pump power) exceeding the Stokes limit. Depending on the output coupling and the pump power, a set of discrete laser lines in the range of 2.164–2.346 μm was observed. The spectroscopic properties of Tm:Y3Al5O12 relevant for the mid-infrared laser operation are revised. The maximum stimulated-emission cross-section for the 3H4 → 3H5 transition is 0.35 × 10−20 cm2 at 2324 nm and the emission bandwidth is ~37 nm. The overlap of the 3F4 → 3H6 and the 3H4 → 3H5 transitions is quantified revealing the formulas for Stokes and anti-Stokes phonon sidebands of emission bands. Tm:Y3Al5O12 is promising for broadly tunable (2.1–2.5 μm) and mode-locked mid-infrared oscillators.

Efficient Tm:LiYF4 Lasers at ${\sim}2.3~\mu$ m: Effect of Energy-Transfer Upconversion

The 3H4 $ \to $ 3H5 transition of Thulium ions (Tm3+), which features laser emission at $\sim 2.3~\mu \text{m}$ is studied in details. We revise the conditions for efficient laser operation using a rate-equation model accounting for the ground-state bleaching, cross-relaxation and energy-transfer upconversion (ETU). We show that ETU has a crucial role in reaching more than unity pump quantum efficiency (QE) for $\sim 2.3~\mu \text{m}$ Tm lasers based on highly-doped crystals. A Ti:Sapphire pumped quasi-continuous-wave 3.5 at.% Tm:LiYF4 laser generated 0.73 W at 2306 nm with a record-high slope efficiency of 47.3% (versus the absorbed pump power, for double-pass pumping) featuring a QE of 1.27. Diode-pumping of this crystal yielded a peak output power of >2 W. The first $2.3~\mu \text{m}$ Tm waveguide laser is also reported based on Tm:LiYF4 epitaxial layers with even higher doping of 6.2 at.% generating 0.23 W with a slope efficiency of 19.8%. The spectroscopic properties of Tm:LiYF4 relevant for the $\sim 2.3~\mu \text{m}$ laser operation are revised as well.

Formation of Tm-Y centers in CaF2-YF3:Tm3+ solid-solution crystals

The spectroscopic properties of Tm3+ optical centers at the 3F4-3H6 two-micron transition in CaF2-YF3:Tm3+ solid-solution crystals are studied by the selective laser excitation technique. The low-temperature (14 K, 77 K) time-resolved fluorescence spectra and lifetimes of several observed optical centers of thulium ions are measured under selective excitation at the 3H6-3H5 transition. Four optical centers in the CaF2-YF3:Tm3+ crystal are identified, namely, a new long-lifetime (3F4 level lifetime longer than 100 ms) optical center similar to a center observed in CaF2:Tm3+ crystals and three spectrally different clustered centers, one of which has an analogue in the CaF2:Tm3+ crystal and two others are new complex Tm-Y clusters.

Spectroscopic and laser properties of Tm3+ ions in Ca3(VO4)2 crystal

The spectroscopic properties of Tm3+ ions in Ca3(VO4)2 crystal were investigated and diode pumped tunable lasing was demonstrated. The maximum absorption and emission cross-sections for E⊥c at 3F4-3H6 2 µm transition were calculated to be ~1 × 10–20 cm2 and ~1.3 × 10–20 cm2 respectively. Noticeable 3H4-3F43H6-3F4 cross-relaxation was observed resulting in a slope laser efficiency up to 15% at ~1960 nm under 792 nm laser diode pumping. Broadband tuning of the oscillation wavelength within the 1850–2070 nm spectral range was realized.

Laser potential of calcium aluminate glasses

Deeply dehydrated calcium aluminate glasses doped by rare-earth ions were synthesized and investigated. Spectroscopic properties of Tm3+ and Ho3+ doped glasses were found attractive for fiber lasers emitting in 2–2.5 μm spectral range. Cascade laser action (at 2300 and 2100 nm) in Tm doped bulk calcium aluminate glass was demonstrated for the first time.

High Average Power Thulium-Doped Silica Fiber Lasers: Review of Systems and Concepts

Thulium-doped fiber lasers (TDFLs) have had the second highest growth in average output power next to ytterbium-doped fiber lasers. This has been enabled by access to high power, high brightness ∼790-nm pump diodes in conjunction with the cross-relaxation process that improves laser efficiency. While numerous high power TDFLs have been recently demonstrated, a 1-kW result from 2010 remains the highest output power system reported to date. This paper reviews these systems and the concepts behind high power TDFLs. The spectroscopic properties of Tm3+ -doped silica are first detailed, revealing complex processes and large variations among published measurements. Notable multi-100 W TDFLs are then summarized, with outputs ranging from 1908 to 2130 nm. Another route for power scaling is to in-band pump with another TDFL to enable >90% efficiencies. Both 790- and 1900-nm pumped TDFL architectures are theoretically modeled based on currently available systems. Hindered by high background losses and available pump sources, achieving >4 kW like ytterbium-fiber systems will be a substantial challenge.

Spectroscopic properties of Tm3+ ions cubic (Oh) centers in low concentrated Ca-Sr-Ba fluorides under ground state selective excitation

Fluorescence and excitation spectra as well as 1G4 level fluorescence lifetime of Tm3+ ions cubic (Oh) optical centers in CaF2, SrF2 and BaF2 crystals were measured at low (77 K) temperature under direct 3H6-1G4 excitation.

Spectroscopy and microchip laser operation of Tm, Ho:KYW crystals with different Ho concentrations

The spectroscopic properties of Tm, Ho:KYW crystals with different Ho concentrations were investigated. The diode-pumped microchip laser operation of Tm (5 at.%), Ho (0.5 at.%):KYW and Tm (5 at.%), Ho (1 at.%):KYW was demonstrated. The highest, to our knowledge, output power of 480 mW with slope efficiency of 31% for CW Tm (5 at.%), Ho (0.5 at.%):KYW microchip laser was obtained.

Thulium doped LuAG ceramics for passively mode locked lasers.

Passive mode-locking of a thulium doped Lu3Al5O12 ceramic laser is demonstrated at 2022 nm. By applying different near surface GaSb-based saturable absorber mirrors, stable self-starting mode-locked operation with pulse durations between 2 and 4 picoseconds was achieved at a repetition rate of 92 MHz. The SESAM mode-locked Tm:LuAG ceramic laser exhibits an excellent stability with a fundamental beat note extinction ratio of 80 dB above the noise level. Furthermore, spectroscopic properties of Tm:LuAG ceramics at room temperature are presented.

Concentration quenching of blue upconversion luminescence in Tm 3+ /Yb 3+ co-doped Gd 2 (WO 4 ) 3 phosphors under 980 and 808 nm excitation

Abstract This paper reported on the upconversion (UC) spectroscopic properties of Tm 3+ /Yb 3+ codoped Gd 2 (WO 4 ) 3 phosphors synthesized by a traditional co-precipitation method upon excitation of 980 and 808 nm commercial available fiber lasers, respectively. X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were used to characterize the crystal structure and morphology of the samples. Intense blue emission ( 1 G 4 → 3 H 6 ) and near-infrared (NIR) emission ( 3 H 4 → 3 H 6 ) as well as weak red emission ( 1 G 4 → 3 F 4 ) of Tm 3+ were observed under 980 nm excitation. The concentration quenching processes for blue and NIR emissions were discussed. The blue emission intensity has a cubic dependence on the fiber laser working current, indicating a three-photon process involved in blue UC emission. The blue emission and its concentration quenching process for Tm 3+ /Yb 3+ codoped Gd 2 (WO 4 ) 3 phosphors were also investigated under 808 nm excitation. Weak blue emission ( 1 D 2 → 3 F 4 ) was detected in the UC spectra other than the weak red emissions ( 1 G 4 → 3 F 4 , 3 F 2,3 → 3 H 6 ). The dominant mechanism for blue emission under 808 nm excitation was attributed to the back energy transfer (BET) Tm 3+ → Yb 3+ and the energy transfer (ET) Yb 3+ → Tm 3+ processes. Upon 808 nm excitation, a two-photon process was deduced from the quadratic dependence of blue UC emission intensity on the fiber laser working current.

Disordered Tm:Ca_9La(VO_4)_7: a novel crystal with potential for broadband tunable lasing

We report on the crystal growth, structural and spectroscopic investigation of a novel trigonal calcium vanadate crystal, Tm3+:Ca9La(VO4)7. Polarized absorption, stimulated-emission and gain cross-section spectra are determined for this material. The maximum σSE corresponding to the 3F4 → 3H6 transition amounts to 1.28 × 10−20 cm2 at 1854 nm for σ-polarization. The measured lifetime of the Tm3+ ions in the 3F4 state is 1.19 ms. The Judd-Ofelt analysis performed yielded intensity parameters of Ω2 = 4.682, Ω4 = 0.659 and Ω6 = 0.475 [10−20 cm2]. The polarized Raman spectra indicate a strong and broad band centered at 867 cm−1. Owing to the disordered nature of Ca9La(VO4)7, the Tm3+ ions exhibit a broad and smooth gain profile at ~2 μm. The spectroscopic properties of Tm3+:Ca9La(VO4)7 are very promising for broadly tunable and ultrashort pulse lasers near 2 µm.

Influence of La/Al ratio on the structure and spectroscopy of Tm3+ doped Al2O3[sbnd]La2O3[sbnd]SiO2 glasses

Lanthanum aluminosilicate (LAS) glasses with compositions (Tm2O3)0.8-(Al2O3)12-x (La2O3)x-(SiO2)87.2 (x = 0, 1.2, 4.5 mol%; La/Al = 0, 1/9, 3/5) were prepared via a sol–gel method combined with high temperature sintering. The total amount of Al2O3 and La2O3 was 12 mol%. The effect of the La/Al ratio on the structure and spectroscopic properties of Tm3+ has been studied in detail. The structure of Tm3+ doped LAS glasses was studied via 27Al nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The spinning sideband patterns of the 27Al NMR spectra showed that the population of Tm3+ ions in the vicinity of Al3+ decreased with an increase in the La2O3 concentration. FTIR and Raman spectra suggest that glasses with high La/Al ratios have less interconnected glass networks. The spectroscopic properties of Tm3+ ions were investigated via the Judd–Ofelt method using the measurement of absorption and emission spectra. Both the 1.8 μm fluorescence intensity and the relative intensity of up-conversion emission of Tm3+ ions decrease with an increase in the La/Al ratio. This indicates reduced cross relaxation between Tm3+ ions in glass with a high La/Al ratio. We conclude that the spatial distribution homogeneity of Tm3+ ions in LAS glass improves when the La/Al ratio increases.

Spectroscopy of thulium and holmium co-doped silicate glasses

In this study, the spectroscopic properties of Tm3+/Ho3+ co-doped silicate glasses under an 808 nm diode laser excitation are reported to discover their potential laser performance. To confirm the best candidates for glass fiber drawing, the optimal ratio of Tm3+ and Ho3+ is 1: 0.3. We calculate and discuss the J-O parameters (Ωt), the transition probability (A) of the transition from 5I7 to 5I8 is 129.89s−1 and the calculated lifetime (τrad) is 7.70 ms, respectively. The maximum emission cross section of the transition from Ho: 5I7→5I8 is 7.59 × 10−21 cm2 at 2065 nm as well as the gain coefficient of the STH glasses is discussed. The energy transfer between Tm3+ and Ho3+ plays an important role in the luminescence process. The sample doped with 1 mol% Tm2O3 and 0.3 mol% Ho2O3 presents a broad band spectrum with a full width at half-maximum of 189 nm, the transfer efficiency from Tm3+ to Ho3+ is 0.6702. Energy transfer constant is 63.2 × 10−40 cm6 /s and the measured fluorescence lifetimes of the sample is 0.637 ms, and the ΔT is 167 °C.These values indicate that the Tm3+/Ho3+ co-doped silicate is a promising way to achieve 2 μm laser emissions.

Spectroscopic properties of Tm3+ long-lifetime optical centers at the 1G4–3H5 transition in CaF2 crystal

The spectroscopic properties of Tm3+ optical centers with a long fluorescence lifetime at the magnetic dipole that allowed 1G4–3H5 transition are investigated at low (77 K) temperature.

Erratum to: Spectroscopic properties of Tm,Ho: CaYAlO4 single crystal [Cryst. Res. Technol. 49, 446–451 (2014)

We correct fit description from a previous paper [Cryst. Res. Technol. 49, 446–451 (2014)].

Spectroscopic properties of Tm3+/Al3+ co-doped sol–gel silica glass

Tm3+/Al3+ co-doped silica glass was prepared by sol–gel method combined with high temperature sintering. Glasses with compositions of xTm2O3–15xAl2O3–(100−16x) SiO2 (in mol%, x=0.1, 0.3, 0.5, 0.8 and 1.0) were prepared. The high thulium doped silica glass was realized. Their spectroscopic parameters were calculated and analyzed by Judd–Ofelt theory. Large absorption cross section (4.65×10−21cm2 at 1668nm) and stimulated emission cross section (6.00×10−21cm2 at 1812nm), as well as low hydroxyl content (0.180cm−1), long fluorescence lifetime (834μs at 1800nm), large σem×τrad (30.05×10−21cm2ms) and large relative intensity ratio of the 1.8μm (3F4→3H6) to 1.46 (3H4→3F4) emissions (90.33) are achieved in this Tm3+/Al3+ co-doped silica glasses. According to emission characteristics, the optimum thulium doping concentration is around 0.8mol%. The cross relaxation (CR) between ground and excited states of Tm3+ ions was used to explain the optimum thulium doping concentration. These results suggest that the sol–gel method is an effective way to prepare Tm3+ doped silica glass with high Tm3+ doping and prospective spectroscopic properties.