Large Stimulated Emission Cross-section Research Articles

Fabrication and spectral properties of Nd3+-doped yttrium lanthanum oxide transparent ceramics

Transparent 1at% Nd3+:Y1.9La0.1O3 ceramics were fabricated with nanopowders prepared by carbonate coprecipitation method. The powder compacts were sintered in H2 atmosphere at 1550°C for 30h. The Nd3+:Y1.9La0.1O3 ceramics display uniform grains of about 50μm and high transparency. The highest transmittance of the ceramics reaches 67%. The strongest absorption peak is in the wavelength of 820nm with absorption cross section of 2.48×10−20cm2. The absorption is still high at LD wavelength 806nm with absorption cross section of 1.78×10−20cm2 and broad full width at half maximum (FWHM) of about 6.3nm. The strongest emission peak was centered at 1078nm with large stimulated emission cross section of 9.63×10−20cm2 and broad FWHM of about 7.8nm. The broad absorption and emission bandwidth of Nd3+:Y1.9La0.1O3 transparent ceramics are favorable to achieve the miniaturized LD pumping apparatus and ultrashort modelocked pulse laser output, respectively.

Spectroscopic Properties of Er3+/Yb3+-codoped PbO–Bi2O3–Ga2O3–GeO2 Glasses

We investigate the spectroscopic properties of the 1.5-microm emission from the (4)I(13/2)-->(4)I(15/2) transition of Er(3+) ions in PbO-Bi(2)O(3)-Ga(2)O(3)-GeO(2) glasses for applications in broadband fiber amplifiers. The measured emission peak locates at 1,532 nm with a full width at half-maximum of approximately 45 nm. The glasses exhibit a large stimulated emission cross-section of 0.89 x 10(-20) cm(2) and a large FWHM x sigma(e)(peak) product of 40.0. Infrared-to-green upconversion occurs simultaneously upon excitation of the 1.5-microm emission with a commercially available 980 nm laser diode. The green-upconversion intensity has a quadratic dependence on incident pump laser power, indicating a two-photon process. Energy transfer processes and nonradiative phonon-assisted decays could account for the population of the (2)H(11/2) of Er(3+). The results indicate the possibility towards the development of lead-bismuth-gallate-germanate based glasses as photonics devices.

Effect of Ga 2O 3 on the spectroscopic properties of erbium-doped boro-bismuth glasses

The spectroscopic properties and thermal stability of Er 3+-doped Bi 2O 3–B 2O 3–Ga 2O 3 glasses are investigated experimentally. The effect of Ga 2O 3 content on absorption spectra, the Judd-Ofelt parameters Ω t ( t = 2, 4, 6), fluorescence spectra and the lifetimes of Er 3+: 4I 13/2 level are also investigated, and the stimulated emission cross-section is calculated from McCumber theory. With the increasing of Ga 2O 3 content in the glass composition, the Ω t ( t = 2, 4, 6) parameters, fluorescence full width at half maximum (FWHM) and the 4I 13/2 lifetimes of Er 3+ first increase, reach its maximum at Ga 2O 3 = 8 mol.%, and then decrease. The results show that Er 3+-doped 50Bi 2O 3–42B 2O 3–8Ga 2O 3 glass has the broadest FWHM (81 nm) and large stimulated emission cross-section (1.03 × 10 −20 cm 2) in these glass samples. Compared with other glass hosts, the gain bandwidth properties of Er 3+-doped Bi 2O 3–B 2O 3–Ga 2O 3 glass is better than tellurite, silicate, phosphate and germante glasses. In addition, the lifetime of 4I 13/2 level of Er 3+ in bismuth-based glass, compared with those in other glasses, is relative low due to the high-phonon energy of the B–O bond, the large refractive index of the host and the existence of OH − in the glass. At the same time, the glass thermal stability is improved in which the substitution of Ga 2O 3 for B 2O 3 strengthens the network structure. The suitability of bismuth-based glass as a host for a Er 3+-doped broadband amplifier and its advantages over other glass hosts are also discussed.

Effects of Nb 2 O 5 on thermal stability and optical properties of Er 3+ -doped tellurite glasses

Er3+-doped tellurite glasses with molar compositions of xNb2O5−(14.7−x)Na2O–10ZnO–5K2O–10GeO2– 60TeO2–0.3Er2O3 (x = 0,3,5,7 and 9) have been investigated for developing 1.5 μm fibre and planar amplifiers. The effects of Nb2O5 on the thermal stability and optical properties of Er3+-doped tellurite glasses have been discussed. It is noted that the incorporation of Nb2O5 (x = 5) increases the thermal stability of tellurite glasses significantly. Er3+-doped niobium tellurite glasses exhibit a large stimulated emission cross-section (7.2×10−21−10.7×10−21 cm2) and the gain bandwidth, FWHM×σepeak (274×10−28−480×10−28 cm3), which are significantly higher than that of silicate and phosphate glasses. In addition, the intensity of upconversion luminescence of the Er3+-doped niobium tellurite glasses decreases rapidly with increasing Nb2O5 content. As a result, Er3+-doped niobium tellurite glasses might be a potential candidate for developing laser or optical amplifier devices.

High lasing oscillation efficiency of Eu(III) complexes having remarkably sharp emission band

Luminescent Eu(III) complexes with bis-phosphine oxide ligands were synthesized. Geometric structures of novel Eu(III) complexes were determined by single-crystal X-ray diffraction. One of the Eu(III) complexes showed remarkably sharp red emission and large stimulated emission cross-section (full width at half maximum (FWHM) = 2.1 nm, stimulated emission cross-section = 1.80 × 10 −20 cm 2). The sharpness of the emission bands of the Eu(III) complexes was discussed in terms of the symmetry of the geometrical structure.

Thermal stability, Judd–Ofelt theory analysis and spectroscopic properties of a new Er 3+/Yb 3+-codoped germano-tellurite glass

The Er 3+/Yb 3+-codoped 70TeO 2–5Li 2O–10B 2O 3–15GeO 2 glass was prepared. The thermal stability, absorption spectra, emission spectra and up-conversion spectra were measured and investigated. The Judd–Ofelt analysis based on absorption spectra was performed in order to determine the Judd–Ofelt intensity parameters Ω t ( t = 2, 4, 6), spontaneous emission probability, radiative lifetime and branching ratios of several Er 3+ transitions. It was found that this studied glass has good thermal stability, broad fluorescence full width at half maximum (FWHM), large stimulated emission cross-section and strong up-conversion emissions at about 532, 546 and 659 nm, corresponding to the 2H 11/2 → 4I 15/2, 4S 3/2 → 4I 15/2 and 4F 9/2 → 4I 15/2 transitions of Er 3+, respectively under the excitation at 970 nm. The results suggest that this Er 3+/Yb 3+-codoped germano-tellurite glass may be a potentially useful material for developing potential amplifiers and up-conversion optical devices.

Novel luminescent Eu(III) complex with remarkably narrow emission band

In order to fabricate a high-power laser medium using Eu(III) complex, strong-luminescent Eu(III) complexes with low vibrational ligands were synthesized. One of the Eu(III) complex showed remarkably sharp red emission and large stimulated emission cross-section. The value of stimulated emission cross-section was the same order as the values of Nd-glass laser for practical use.

Effect of Bi2O3 on spectroscopic properties of Er3+-doped lead oxyfluorosilicate glasses for broadband optical amplifiers

The spectroscopic properties of Er3+-doped lead oxyfluorosilicate glasses were analyzed with Judd–Ofelt and McCumber theories. The obtained data suggest that the fluorescence full width at half maximum (FWHM) is related to the Ω6 parameter, the larger the Ω6 parameter, and the broader the FWHM. The results showed that Er3+-doped 45SiO2–5Bi2O3–50PbF2 glass had the broadest FWHM (64nm) and large stimulated emission cross-section (0.73×10−20cm2) in these glass samples. Compared with other glass hosts, the gain bandwidth properties of Er3+-doped 45SiO2–5Bi2O3–50PbF2 glass is close to those of tellurite and bismuth glasses, and has advantage over those of silicate, phosphate and germante glasses. The results suggest that Er3+-doped 45SiO2–5Bi2O3–50PbF2 glass can be used as potential host material for developing broadband optical amplifiers in wavelength-division-multiplexing network system.

Spectral Properties of Erbium-Doped Oxyfluoride SilicateGlasses for Broadband Optical Amplifiers

The new oxyfluoride silicate glasses of Er3+-doped50SiO2-(50-x)PbO-xPbF2 were prepared. Withincreasing PbF2 content in the glass composition, the fluorescencefull width at half maximum and lifetimes of the 4I13/2level of Er3+ increase, while the refractive indices anddensities decrease. Er3+-doped 50SiO2-50PbF2 glassshowed broad fluorescence spectra of 1.55 mum with a large stimulatedemission cross-section and long lifetimes of 4I13/2 levelof Er3+. Compared with other glass hosts, the gain bandwidthproperties of Er3+-doped 50SiO2-50PbF2 glass areclose to those of tellurite and bismuth glasses, and have advantagesover those of silicate, phosphate and germante glasses. The broad andflat 4I13/2→4I15/2emission of Er3+ around 1.55 µm can be used as host materialfor potential broadband optical amplifier inwavelength-division-multiplexing network system.

Fluorescence quenching in Er3+ doped tellurite glass due to the introduction of BO3/2

Er3+ doped tellurite glass is considered as a promising material for broadband applications because of its large stimulated emission cross section and broad emission bandwidth at the third communication window (1.55 μm) in order to increase the transmission capacity of the wavelength division multiplexing (WDM) system. The relatively low phonon energy of tellurite glass decreases the nonradiative transition probability of I13/2 → I15/2 emission and thus increases the quantum efficiency of Er3+. On the other hand, however, the nonradiative energy transfer rate from I11/2 level to I13/2 level of Er3+ in tellurite glass is lower than those in silicate and phosphate glasses with high phonon energies, which provides a long population duration on I11/2 level, which results in several undesirable effects [1] and hence leads to the decrease of the 980 nm pumping efficiency. 980 nm pumping is preferable to the success of an Er3+ doped amplifier since 1480 nm pumping cannot contribute to sufficient population inversion and a good signal-to-noise ratio. Several efforts have been made on methods of decreasing upconversion emission of Er3+ in tellurite glass. Choi et al. [2] studied the addition of energy acceptor ions such as Ce3+, Eu3+, and Tb3+ to deplete the I11/2 level by nonradiative energy transfer, because their electronic transition energies are approximately resonant with the energy gap corresponding to the I11/2 → I13/2 transition of Er3+. Hee Cho et al. [3] reported the introduction of BO3/2, which has the largest phonon energy (1400−1), into tellurite glass to increase the maximum phonon energy of the glass host to improve the I11/2 → I13/2 transition rate. However, a strong fluorescence quenching of I13/2 level was observed in our study when BO3/2 content is more than 10 mol% in the glass. In this letter, the effect of BO3/2 on lifetime of I13/2 level of Er3+ in tellurite glass was investigated. The quenching mechanisms of lifetime results from the BO3/2 addition are discussed based on nonradiative transition probability and interactions between rare earth ions. The glasses were prepared using conventional melting and quenching method from reagent-grade powders of H3BO3, ZnO, La2O3, Er2O3, and high purity powders of TeO2 (99.999%). About 20 g batches of starting materials were fully mixed and then melted in a platinum crucible at about 800–900 ◦C. The melt was poured into a brass mold and cooled in air and subsequently annealed to room temperature gradually. The obtained glasses were cut and polished carefully in order to meet the requirements for optical measurements. The fluorescence lifetime for the I13/2 level of Er3+ was measured with a 970 nm LD and a HP546800B 100 MHz oscilloscope. In order to minimize the influence of reabsorption on emission, the excitation beam was focused immediately below the surface of the samples so that the emitted light traveled only a short distance inside the sample. The radiative lifetime of I13/2 level of Er3+ is calculated according to the well-known Judd-Ofelt theory described anywhere. The quantum efficiency for the I13/2 → I15/2 transition was evaluated using the equation: η = τmea/τrad, where τmea is the measured lifetime and τrad is the calculated radiative lifetime. Fig. 1 illustrates the compositional dependence of the lifetimes and the quantum efficiency of Er3+ on BO3/2 concentration in tellurite glasses. The radiative lifetime τrad increases monotonically owing to the decrease of the refractive index of the glass host. The measured lifetime τmea and the quantum efficiency η initially decrease slightly up to BO3/2 = 8 mol% and then decrease rapidly as BO3/2 content increases. The lifetime of I13/2 level is also an important factor to the success of Er3+-doped amplifiers, since a long lifetime permits to obtain the required high-population inversion under steady-state condition using modest pump power [4]. The measured lifetime is mainly influenced by the maximum phonon energy of the glass host. If we neglect the energy transfer process between excited ions, the measured lifetime τmea is written as:

UV-Visible Lasers Based on Rare-Earth Ions

An issue on novel applications of materials doped with rare-earth (RE) ions can scarcely fail to address lasers, but it need not address all RE-based lasers. Some Nd3+ -doped lasers, particularly Nd:YAG (Y3Al5O12, yttrium aluminum garnet), emitting light with a wavelength of 1064 nm, are very well-established commercial products—by no means novelties.1 Some other near-infrared (NIR) lasers, based on Er3+ or Tm3+, are also available commercially. That wavelength region is relatively easy for RE laser ions, involving energy spacings between initial and final energy levels small enough to give large stimulated emission cross sections for useful, long upper-state life-times, yet large enough to minimize thermal deexcitation mechanisms. On the other hand, RE-doped lasers for ultraviolet (UV) and visible wavelengths are quite novel, since efficient laser operation is more difficult to achieve in these spectral ranges. Intriguing progress on such devices has been made in recent years, driven by several important applications.In this article, we begin by noting some of the alternative ways to obtain laser light at these wavelengths, including their advantages and drawbacks. We then discuss basic properties of RE-doped laser materials and how these can be advantageous. We then review a few of the most important and recent RE-doped laser materials and techniques for obtaining UV and visible output.

Growth and fluorescence properties of Tm 3+ doped YVO 4 and Y 2O 3 single crystals

This work is focused on the growth and the analysis of the potentials of Tm 3+ doped YVO 4 and Y 2O 3 single crystals for diode-pumped laser emission around the 1.5 μm eye safe laser wavelenght. Both systems show broad-band absorptions around 800 nm and large stimulated emission cross sections around 1.5 μm.

Spectroscopy of argon fluoride and krypton fluoride exciplexes in rare gas matrices

The spectroscopy of argon fluoride and krypton fluoride exciplexes in rare gas matrices is investigated using synchrotron radiation over the range of 50 to 600 nm. The diatomic Ar+F− and Kr+F− species are observed in excitation and emission spectra. Extensive vibrational progressions are observed in the excitation spectra and are used to determine the spectroscopic parameters of the ArF B state (Te=50233 cm−1,ωe=415.5 cm−1, ωexe=3.1 cm−1) and D state (Te=51738 cm−1,ωe=476.7 cm−1,ωexe=3.8 cm−1) and of the KrF B state (Te=39024 cm−1,ωe=342.4 cm−1,ωexe=2.0 cm−1) and D state (Te=44479 cm−1,ωe=331.6 cm−1,ωexe=1.4 cm−1). Lifetimes of 4 to 8 ns are measured for the diatomic emissions. A perturbed KrF species is observed which is identified in analogy to a similarly perturbed XeF species. Excitation spectra of the triatomic exciplexes Kr+2F− and Ar+2F− in neon are presented and described in terms of previous ab initio calculations. Emission and excitation of argon fluoride and krypton fluoride species in other matrices are presented. Large stimulated emission cross sections on the order of 10−16 cm2 are determined for the diatomic D→X and B→X emissions, which, together with nonradiative relaxation processes within the B and D states of ArF that efficiently populate the B(v=0) regardless of initial excitation, make ArF in neon a viable solid-state laser candidate.

The fluorescence of Nd3+ in lead borate and bismuth borate glasses with large stimulated emission cross section

The stimulated emission cross section σp for the 1060 nm transition of Nd3+ in lead borate and bismuth borate glasses has been determined from fluorescence measurements. The compositional dependence of σp, which has been evaluated using radiative transition probability, refractive index of the host glass, effective fluorescence linewidth, and position of the band, with PbO/Bi2O3 content is investigated. The σp values of the 1060 nm band of Nd3+ for lead borate and bismuth borate glasses are found to be in the range 2.6–5.7×10−20 cm2 at 298 K and 3.0–6.3×10−20 cm2 at 4.2 K. The σp values are comparatively large suggesting the possible utilization of these materials in laser applications.

Pr3+-doped GeGaS glasses for 1.3 μm optical fiber amplifiers

The synthesis and optical properties of Pr-doped GeGaS glasses are reported. The radiative properties associated with the important 1G4 → 3H5 transition of Pr3+ at 1.3 μm have been determined by absorption and fluorescence measurements coupled with Judd-Ofelt analysis. As compared with ZBLAN glass, Pr-doped GeGaS glasses have a longer fluorescence lifetime and a larger stimulated emission cross-section, which are favorable for an efficient fiber amplifier. The concentration quenching of Pr3+ in these glasses has also been studied by fluorescence lifetime measurements.

Efficient 2.05 μm room temperature Y 2SiO 5:Tm 3+ cw laser

Efficient 2.05 μm room temperature cw laser operation of a Tm 3+ -doped Y 2SiO 5 single crystal has been demonstrated for the first time. This system is characterized by a large absorption cross section at about 800 nm and a large stimulated emission cross section around 2 μm with the possibility of a broad wavelength tunability. A slope efficiency of 18% has been obtained under non-optimized conditions.

Feedback-controlled mode-locking operation of a Nd:YLF laser at 1.047 μm

Feedback-controlled mode locking (FCM) of a Nd:YLF laser at 1.047 μm is demonstrated. The larger stimulated emission cross section of the π-polarized (λ=1.047 μm) transition compared to the cross section of the σ-polarized (λ=1.053 μm) transition leads to a lower pump energy threshold. Inserting an anti-resonantly tuned etalon in the cavity yields stable operation with short bandwidth-limited pulses of less than 3 ps at a repetition rate of 70 Hz.

LD-pumped Nd:YAG laser crystal.

A laser diode-pumped solid-state laser has merits of compactness, high efficiency, long life, and easy maintenance. Nd: YAG is an excellent crystal for its large stimulated emission cross section and good thermal properties. The crystal shows good spectral matching with high power laser diodes. When used as a pump source, the its crystal growth and properties are described.

Laser diode pumped Nd:YVO4 laser.

Having a larger stimulated emission cross section and stronger fluorescence emission, a laserdiode (LD) pumped Nd: YVO4 laser has higher efficiency and power than Nd: YAG laser.Spectral property and CW end-pumped lasing characteristics have been measured on thismaterial. Stimulated emission cross section of 2.5×10-18cm2 for π polarization, slope efficiencyof 48.6% and light to light conversion efficiency of upto 40% for laser rod along a-axiswere obtained.

Tailoring stimulated emission cross sections of Nd3+ laser glass: Observation of large cross sections for BiCl3 glasses

The stimulated emission cross sections of rare-earth transitions depend strongly on the host. The properties that influence the cross sections—line strength, linewidth, and refractive index—are reviewed, and rules for tailoring cross sections are discussed. To illustrate the application of these rules, the largest stimulated emission cross section for the 4F3/2→4I11/2 transition of Nd3+ observed for any oxide or halide glass was obtained for a new class of bismuth-chloride-based glasses. Spectroscopic and physical properties and laser parameters of these and other halide glasses are presented.