Peak Emission Cross Section Research Articles

Fabrication and spectral properties of Dy:Y2O3 transparent ceramics

Dy3+-doped Y2O3 ceramics were fabricated by Spark Plasma Sintering method. The effect of sintering temperature on the microstructure and the optical transmittance of the ceramics was studied. The maximum in-line transmittance of Dy:Y2O3 ceramics with thickness of 1 mm was 74.5% at 574 nm when sintering temperature was 1550 ℃. The spectroscopic parameters were determined by Judd-Ofelt theory based on the room temperature absorption spectra. The peak emission cross section for the 4F9/2 → 6H13/2 transition was calculated to be 0.569 × 10−20 cm2. The fluorescence decay curve and quantum efficiency of the 4F9/2 multiplet were measured to be 269.2 μs and 37.1%, respectively.

Intensities and spectral features of the – potential laser transition of Er3+ centers in CaF2–CeF3 disordered crystal**Project supported by Shanghai Engineering Research Center for Sapphire Crystals, China (Grant No. 14DZ2252500), the Fund of Key Laboratory of Optoelectronic Materials Chemistry and Physics Chinese Academy of Sciences (Grant No. 2008DP17301), the Fundamental Research Funds for the Central Universities of China, the National

A CaF2–CeF3 disordered crystal containing 1.06% of Er3+ ions was grown by the temperature gradient technique. Optical absorption and emission spectra recorded at room temperature and at 10 K, luminescence decay curve recorded at room temperature, and extended x-ray-absorption fine structure spectra were analyzed with an intention to assess the laser potential related to the transition of Er3+. In addition, the thermal diffusivity of the crystal was measured at room temperature. The analysis of room-temperature spectra revealed that the emission is long-lived with a radiative lifetime value of 5.5 ms, peak emission cross section of , and large spectral width pointing at the tunability of the emission wavelength in the region stretching from approximately 1480 nm to 1630 nm. The energies of the crystal field components for the ground and excited multiplets determined from low-temperature absorption and emission spectra made it possible to predict successfully the spectral position and shape of the room-temperature emission band. Based on the correlation of the optical spectra and dynamics of the luminescence decay, it was concluded that in contrast to Yb3+ ions in heavily doped CaF2 erbium ions in the CaF2–CeF3 crystal reside in numerous sites with dissimilar relaxation rates.

Crystal growth and characterization of undoped and Dy-doped TlPb2Br5 for infrared lasers and nuclear radiation detection

We report results of the crystal growth and characterization of undoped and Dy-doped TlPb2Br5 for applications in infrared (IR) lasers and nuclear radiation detection. TlPb2Br5 (TPB) was synthesized from commercial starting materials of PbBr2 and TlBr and further purified through a combination of zone-refinement and directional solidification. For doping experiments, 2 wt% of DyBr3 was added to the purified TPB material. Crystal growth of TPB and Dy: TPB was carried out in a two-zone tube furnace by a vertical Bridgman method. Following optical excitation at ∼1.36μm, the Dy: TPB crystal exhibited efficient mid-IR emission bands centered at 2.87μm and 4.35μm with room-temperature lifetimes of 9.5ms and 5.2ms, respectively. The peak emission cross-sections were determined to be ∼0.8×10−20cm2 and ∼0.5×10−20cm2, respectively, which makes Dy: TPB a promising candidate for mid-IR laser applications. Besides its potential as a solid-state laser host, an undoped TPB crystal was also tested for gamma-ray detection. Using Cs-137 and Am-241 sources resulted in energy resolutions for gamma-rays as good as 1–2% (FWHM) at room-temperature under non-optimized conditions.

Spectroscopic properties of Er3+-doped fluorotellurite glasses containing various modifiers

We have investigated the optical and spectroscopic properties of new Er3+-doped fluorotellurite glasses with the basic molar composition 75%TeO2-10%P2O5-10%ZnO-5%PbF2, modified by replacing 5%TeO2 by four various metal oxides, namely MgO, PbO, SrO and CdO. The ellipsometric data have provided a Sellmeier-type dispersion relation of the refractive index of the investigated glasses. The optical absorption edge has been described within the Urbach approach, while the absorption and fluorescence spectra have been analyzed in terms of the standard Judd–Ofelt theory along with the photoluminescence decay of the 4I13/2 and 4S3/2 levels of the Er3+ ion. The absorption and emission spectra of the 4I15/2 ↔ 4I13/2 infrared transition have been analyzed within the McCumber theory to yield the peak emission cross-section and figure of merit (FOM) for the amplifier gain. It appears that the glass containing MgO as a modifier is characterized by the largest FOM suggesting that the fluorotellurite matrix with this oxide can be a good novel host for Er3+ ion doping. Finally, we propose a new simple method to calculate the mean transition energy of the McCumber approach as the arithmetic average of the barycenter wavenumbers of absorption and emission spectra.

Anisotropy in spectroscopic and laser properties of Yb:Sr_3La_2(BO_3)_4 disordered crystal

We report, for the first time to our knowledge, on the polarized absorption and emission spectra and efficient laser action of the Yb:Sr3La2(BO3)4 disordered crystal. The strongest absorption and emission occur at about 977 nm for polarization direction parallel to the crystallographic b axis, with the peak absorption and emission cross-sections amounting, respectively, to 1.95 × 10−20 and 2.45 × 10−20 cm2. Efficient continuous-wave laser action is demonstrated with a-, b-, and c-cut crystal samples longitudinally pumped by a 976-nm diode laser, producing an output power of up to 8.2 W with an optical-to-optical efficiency of 32% with respect to incident pump power. Depending on the output coupling utilized, the laser action could exhibit a transition from single-polarization oscillation to dual-orthogonal-polarization oscillation at a certain pump level.

Modulated photoluminescence parameters of neodymium in Sr_095Y_005F_205 laser crystal

The photoluminescence parameters of Nd3+-doped Sr0.95Y0.05F2.05 crystal, which are a function of Nd3+ concentrations, were investigated. Abnormally, the peak emission cross section increased linearly with the lifetime. The quantum efficiency, peak emission cross section and lifetime were significantly improved from 26%, 2.8 × 10−20cm2 and 190μs to 90%, 5.4 × 10−20cm2 and 370μs, respectively. The results suggest that Y3+ ions worked as local lattice structure regulators and barrier layers besides the well known buffer ions.

Spectroscopic Properties and Continuous Wave Laser Performances at 1064 nm of Nd3+: LuAG Transparent Ceramic

A transparent 2 at% Nd3+-doped Lu3Al5O12 (LuAG) ceramic was fabricated by using tape-casting method and solid-state sintering technology. Based on the room temperature absorption spectrum, the three J–O intensity parameters were calculated with Judd–Ofelt analysis, and then, the radiative transition rates and branching ratios of transitions from 4 F 3/2 manifold to the ${}^4{{\rm {\mathbf I}}_{ \mathbf{{J}^{\prime}}}}$ ( $\mathbf{{ J}^{\prime}} = 13/2,\;11/2,\;9/2$ ) lower lying multiple manifolds were determined. The quantum efficiency of 80.4% was evaluated from the measured fluorescence lifetime and the radiative lifetime of the ${}^4{{\mathbf F}_{3/2 }}$ manifold state. Also, the inter-Stark energy levels of the $4{{{\mathbf I}}_{\boldsymbol{J^{\prime}}}}$ manifolds were performed, and the peak emission cross sections of the ${}^4{\mathbf{F}_{3/2 }} \to {}^4{{{\mathbf {I}}}_{\mathbf{{ J}^{\prime}}}}$ intermanifold transitions were determined. The total emission cross section for ${}^4{\mathbf{F}_{3/2 }} \to $ ${}^4{\mathbf{I}_{9/2 }}$ , ${}^4{\mathbf{I}_{11/2 }}$ , and ${}^4{\mathbf{I}_{13/2 }}$ transitions was calculated to be $7.41 \times {10^{ - 20}} {{\rm c}}{{{\rm m}}^2}$ , $29.83 \times {10^{ - 20}} {{\rm c}}{{{\rm m}}^2}$ , and $10.53 \times {10^{ - 20}} {{\rm c}}{{{\rm m}}^2}$ , respectively. Finally, under an 808 nm diode laser pumping, the continuous wave laser performances of the Nd:LuAG transparent ceramic were investigated.

Spectroscopic properties of Sm3+-doped NaGd(MoO4)2 crystal for visible laser application

A NaGd(MoO4)2 crystal doped with 2at.% Sm3+ was grown by the Czochralski method. Polarized absorption and fluorescence spectra of the crystal were measured at room temperature. Spectroscopic parameters, including absorption and emission cross sections, Judd-Ofelt intensity parameters, radiative transition rates, fluorescence branching ratios, and fluorescence lifetime of the 4G5/2 multiplet, were obtained and compared with other Sm3+-doped crystals. The main fluorescence band around 646nm is related to the 4G5/2→6H9/2 transition, which has a branching ratio of 45.4% and peak emission cross sections of 1.73×10–21 and 3.13×10–21cm2 for π and σ polarizations, respectively. The results indicate that the Sm3+:NaGd(MoO4)2 crystal may be a potential gain medium of red visible laser pumped directly by commercially available 405nm laser diode.

Spectroscopic properties and energy transfer process in Tm3+-doped Silica-germanate glasses

A Tm3+-doped silica-germanate was successfully prepared by high-temperature melting method in this work and compared with traditional silicate and germanate glasses comprehensively. The DSC results indicated a better ability against thermal damage (higher Tg=636°C) compared with silicate glass together with better thermal stability (ΔT=106°C and S=3.17) than germanate (ΔT=99°C and S=2.64) glass. Intense 1.8μm emission in the silica-germanate glass was also obtained when pumping by an 808nm laser diode, which possessed larger peak absorption and emission cross section (3.15×10–21cm2 and 7.08 ×10–21cm2). Finally, the structure analysis suggested a low phonon energy and high rare earth ions solubility in silica-germanate glass through Raman spectra and X-ray photoelectron spectroscopy. All results indicate that the prepared silica-germanate glass is a promising candidate for 2 μm laser applications.

Crystal growth, spectral properties and continuous wave laser operation of new mixed Nd:GdYNbO4 laser crystal

A new mixed laser crystal Nd:Gd0.69Y0.3NbO4 (Nd:GYNO) with high quality was grown successfully by Czochralski method. Its structure parameters are obtained by the X-ray Rietveld refinement method. The effective segregation coefficient of Nd3+ ions is 0.61 in GYNO host. The maximum absorption cross section at 809 nm and peak emission cross section at 1065.6 nm of Nd:GYNO crystal are 11.6 × 10−20 and 20.5 × 10−20 cm2, respectively. The fluorescence lifetime of 4F3/2 manifold for Nd3+ in Nd:GYNO crystal is fitted to be 156 μs. Diode-pumped continuous-wave laser operations at 1.06 μm with Nd:GYNO crystals cut perpendicular to crystallographic a, b, and c axes (denoted as a-, b- c-cut, respectively) were demonstrated. A maximum output power of 0.98 W was obtained with c-cut crystal, corresponding to an optical-to-optical conversion efficiency of 31.3% and a slope efficiency of 30.4%. All these results imply that the Nd:GYNO crystal has great potential application in low and even moderate lasers.

Detailed luminescence properties and laser potential of Pr:FAP

Polarized absorption spectra are recorded from 400nm to 2400nm and analyzed within the framework of the Judd–Ofelt formalism. The best fit to the data is obtained by using the so-called “standard method” but by omitting the 3H4→3P2 hypersensitive absorption transition from the fitting procedure. Polarized and continuous-wave as well as time-resolved emission spectra are registered for the first time between 450nm and 1200nm. Fluorescence lifetime measurements are performed at different emission and for different excitation wavelengths. The analysis of the data confirms the low emission quantum efficiency of the (3P0,1,1I6) set of thermalized emitting levels and the predominance of the emissions coming from the 1D2 multiplet. It reveals the existence of an interesting near-infrared emission band coming from a 1D2→3F3,3F4 emission transition and extending from about 1000nm to 1150nm with a peak emission cross-section of 6.2×10−20cm2 at 1073nm.

Lasing of Nd3+ in sapphire

AbstractWe present a rare‐earth‐doped sapphire laser. Single‐crystalline α‐Al2O3 films doped with trivalent neodymium have been grown by pulsed laser deposition on undoped sapphire substrates. The Nd3+ doping concentrations of the films have been varied between 0.3 at.% and 2 at.%. Epitaxial growth was proven by structural and optical characterization of the films. The samples exhibit strongly polarization dependent emission transitions from the 4F3/2 manifold with a fluorescence lifetime of 108 μs and peak emission cross sections of 1.1 × 10−18 cm2 around 1100 nm. Lasing at 1096.5 nm was achieved under Ti:sapphire‐pumping in a planar waveguide configuration with a maximum cw output power of 137 mW and a slope efficiency of 7.5% with respect to the incident pump power. image

Ho³⁺/Yb³⁺ codoped silicate glasses for 2 μm emission performances.

This paper discuss a series of Ho³⁺/Yb³⁺ codoped silicate glasses prepared by the melting method. 2 μm emissions of the samples are observed under the pump of 980 nm LD. The Judd-Ofelt parameters (Ω(λ)) and radiative properties are calculated and analyzed; the spontaneous transition probability can reach 78.71 s⁻¹. From the fluorescence spectra, the peak absorption and emission cross section of Ho³⁺ are 2.36×10⁻²¹ and 5.05×10⁻²¹ cm², respectively. In addition, we analyze the energy transfer process of Yb³⁺: ²F(5/2) level to Ho³⁺: ⁵I₆ level. Considering the luminance properties and good thermal property, we indicate that Ho³⁺/Yb³⁺ codoped silicate glass is a potential laser glass for the efficient 2 μm laser.

Heavily Ho^3+-doped lead silicate glass fiber for ~2 μm fiber lasers

A heavily Ho3+-doped lead silicate glass with low content of hydroxyls was prepared in this paper. Luminescent properties of this glass were characterized. Peak emission cross section reached 3.07 × 10−21 cm2 around 2055 nm and lifetime of Ho3+: 5I7 was fitted to be 1.31 ms. A single-cald fiber was prepared using this glass as the core. An all-fiber configuration was constructed. Under in-band core-pump of a silica fiber laser, a single-mode maximum 60 mW was realized in a 6 cm-long fiber, which shows high potential for single-frequency fiber lasers applications.

Broadband mid-infrared 2.8 μm emission in Ho3+/Yb3+-codoped germanate glasses

This work reports the mid-infrared emission properties around 2.85μm in Ho3+/Yb3+ codoped germanate glasses. The glass not only possesses considerably low OH− absorption coefficient (0.24cm−1), but also exhibits low phonon energy (790cm−1). A large spontaneous transition probability (36.66s−1) corresponding to the Ho3+:5I6→5I7 transition has been calculated based on the Judd–Ofelt theory. Besides, a broad 2.85μm fluorescence has been successfully observed and a reasonably model has been proposed to unravel the origin of the broadening emission band. Moreover, the peak emission cross sections of the glass is as high as 9.2×10−21cm2, and the maximum gain per unit length at 2.85μm could be as high as 4.3dB/cm. Results indicate that the prepared germanate glass is a promising candidate for 2.85μm mid-infrared laser materials applications.

R2O3 (R = La, Y) modified erbium activated germanate glasses for mid-infrared 2.7 μm laser materials.

Er3+ activated germanate glasses modified by La2O3 and Y2O3 with good thermal stability were prepared. 2.7 μm fluorescence was observed and corresponding radiative properties were investigated. A detailed discussion of J–O parameters has been carried out based on absorption spectra and Judd–Ofelt theory. The peak emission cross sections of La2O3 and Y2O3 modified germanate glass are (14.3 ± 0.10) × 10−21 cm2 and (15.4 ± 0.10) × 10−21 cm2, respectively. Non-radiative relaxation rate constants and energy transfer coefficients of 4I11/2 and 4I13/2 levels have been obtained and discussed to understand the 2.7 μm fluorescence behavior. Moreover, the energy transfer processes of 4I11/2 and 4I13/2 level were quantitatively analyzed according to Dexter’s theory and Inokuti–Hirayama model. The theoretical calculations are in good agreement with the observed 2.7 μm fluorescence phenomena. Results demonstrate that the Y2O3 modified germanate glass, which possesses more excellent spectroscopic properties than La2O3 modified germanate glass, might be an attractive candidate for mid-infrared laser.

$\sim 2$ -$\mu \text{m}$ Single-Mode Laser Output in Tm3+-Doped Tellurium Germanate Double-Cladding Fiber

A single-mode laser output of 0.75 W near $2~\mu \text{m}$ was obtained with a slope efficiency of 28.7% with respect to the absorbed pump power when a self-developed double-cladding Tm3+-doped tellurium germanate glass fiber laser was pumped using a 793-nm diode laser. The core glass possesses an infrared cutoff edge reaching $\sim 5~\mu \text{m}$ . The calculated peak emission cross section of Tm3+ at $1.9~\mu \text{m}$ was $6.8 \times 10^{-21}$ cm $^{2}$ . The measured fluorescence lifetime of 3F4 energy level was 2.96 ms. A single-mode double-cladding tellurium germanate glass fiber was fabricated in house using the rod-in-tube drawing technique. The lasing threshold was 0.56 W and the lasing wavelength was centered at 1968 nm. Spatial beam quality of the fiber was measured and a value of $M^{2} =1.36$ was obtained.

Assessment of structure and spectral characteristics of new laser crystal Nd3+:KBaY(MoO4)3

An Nd3+:KBaY(MoO4)3 crystal with dimensions of 27 × 21 × 8 mm3 was grown by the TSSG method. KBaY(MoO4)3 crystal with disordered structure crystallizes in the monoclinic system with space group C2/c. The spectral properties of KBaY(MoO4)3 crystal have been investigated. It exhibits broad absorption and emission bands, which is caused by its disordered structure and distorted Y(Nd) O8 polyhedron. Nd3+:KBaY(MoO4)3 crystal has large values of peak absorption and emission cross-sections. The fluorescence quantum efficiency η is up to 97.3%. Therefore, the combination of all the optical parameters favorably distinguishes the Nd3+:KBaY(MoO4)3 crystal from other Nd-doped crystals and makes it as a promising laser material for DPSSL application.

Spontaneous and stimulated emission in Sm3+-doped YAl3(BO3)4 single crystal

Single crystals of YAl3(BO3)4 doped with trivalent samarium were grown by the top-seeded high temperature solution method and their absorption and emission spectra were investigated. Optical pumping into prominent absorption band around 405nm feeds the 4G5/2 metastable level giving rise to intense visible luminescence distributed in several spectral lines with the most intense line around 600nm characterized by a branching ratio of 0.42 and peak emission cross section of 0.25×10−20cm2. Optical amplification at 600nm with a gain coefficient of 2.9cm−1 was achieved during a pump-and-probe experiment.

Near-infrared absorption–emission cross-sections of PbSe quantum dots doped in UV gel

We measure near-infrared absorption spectra of PbSe quantum dots (QDs) with three sizes (4.5, 5.0, and 5.6nm) doped in UV gel with the concentration of 0.25–1.50mgmL−1 by using an absorption-spectrum method. An empirical formula is proposed to describe the correlation of the first–second absorption-peak wavelengths and QD size. The peak-absorption cross-section is measured as 2.76–3.69×10−16cm2 for 5.6-nm QD, and the absorption coefficient ranges in 0.19–0.59cm−1, both associated with the doping concentration and the QD size. Furthermore, the emission cross-sections are determined by measuring the photoluminescence spectra of QDs and using the McCumber relationship, which depend weakly on both the doping concentration and the QD size. For 5.6-nm QD, the measured peak-emission cross-section is 3.36–4.48×10−16cm2 within the range of experimental doping concentration.