Gain Cross Section Research Articles

∼2 μm broadband luminescence in Tm3+/Ho3+/Er3+-doped tellurite glass

Improving the broadband luminescent properties in ∼2 μm band has always been a serious challenge. This paper proposed a Tm3+, Ho3+ and Er3+ doped combination in tellurite glass, which was synthesized through melt-quenching and characterized by a series of physical and spectral tests. Firstly, tellurite glass of Tm3+–Ho3+ co-doping produced a ∼2 μm broadband luminescence ranging from 1570 to 2200 nm with FWHM (full width at half maximum) of 379 nm under 808 nm pumping. This broadband luminescence originated from 3F4 to 3H6 level transition of Tm3+ and 5I7 to 5I8 level transition of Ho3+. Furthermore, after adding an appropriate amount of Er3+, the luminescent intensity was improved by 116 %, mainly attributed to the direct or indirect energy transfers from Er3+ to Tm3+ and Ho3+ ions. Calculations of Judd-Ofelt spectroscopic parameters and gain cross-sections supported the results obtained from Tm3+/Ho3+/Er3+ doped tellurite glass in ∼2 μm band. In addition, DSC (differential scanning calorimetry) curves exhibited excellent thermal stability, XRD (X-ray diffraction) patterns and Raman spectra disclosed the non-crystalline and network structural units of the synthesized tellurite glasses. The findings in this work demonstrate that tellurite glass with Tm3+, Ho3+ and Er3+ combination is an efficient strategy which can be applied in ∼2 μm band ultra-short pulse lasers and broadband amplifiers.

Explication of the luminescent and optically active RE3+ triply-doped silica phosphate glass films for photonic applications

The multi-component silicate glass films triply-doped with Er3+/Yb3+/Nd3+ were fabricated by spin coating technique. X-ray diffraction revealed a cristobalite phase in the glasses doped above 0.6 mol% of Nd3+. The transparency of the films increases with the addition of the co-dopant, due to the increase in optical band gap by the Burstein-Moss shift. The high value of the correlated color temperature of the blue emission indicates enhanced visual perception, suggestive of cool blue film lasers. The red emission from upconversion exhibits potentiality for flat display panels. The gain cross-section of the glass with 0.6 mol% of Nd3+ was 13.54 ×10−20 cm2 which makes it ideal for NIR film lasers in the S-band region. The Inokuti-Hirayama model predicts luminescence quenching due to dipole-dipole interactions in the glasses co-doped beyond 0.6 mol% of Nd3+. The 4F9/2→4I13/2 transition observed in the films, suggests their suitability for O + E + S band NIR film lasers in telecommunication sectors.

Growth, structure and spectroscopic properties investigation on a novel Tm3+-doped disordered Ca(GdxY1-x)Al3O7 hybrid melilite crystal

A disordered Tm3+-doped Ca(GdxY1-x)Al3O7 hybrid melilite crystal (Tm:CGYAM) was successfully grown by using the optical floating zone method, and its structure and spectroscopic properties were studied thoroughly. Structure analysis shows that the Tm:CGYAM crystallizes in tetragonal system. The maximum phonon energy of Tm:CGYAM crystal is estimated to be 765.8 cm−1. Absorption spectrum shows that the absorption cross-section of the Tm:CGYAM crystal is 0.44 ×10−20 cm2 at 788.5 nm, with a FWHM of 34.5 nm. The radiative lifetime of Tm3+:3F4→3H6 transition in Tm:CGYAM crystal is calculated to be 5.35 ms by J-O analysis. The emission cross-sections are 0.321×10−20 cm2 at 1785 nm and 0.324×10−20 cm2 at 1945 nm. The FWHM of Tm3+:3F4→3H6 transition emission band reaches 280 nm. By fitting the fluorescence decay curve, the fluorescence lifetime of Tm3+:3F4 level is estimated as 4.55 ms. The gain cross-section of Tm:CGYAM crystal achieves positive in the range of 1771–2200 nm once the population inversion level reaches 10 %. All the experimental results support the Tm:CGYAM crystal can be a promising candidate material for solid state tunable or ultrashort pulse laser application.

Er3+/ Yb3+ co-doped multi-functional silica phosphate glass films for integrated photonic applications

The multi-component silicate glasses co-doped with Er3+/Yb3+ were fabricated as thin films by the spin coating technique, which was analyzed for their optoelectronic response. Their monolith counterparts synthesized by the sol-gel route were used for the electrical studies. The films evidenced nanocristobalite phases at low levels of doping. The film micrographs explicated gas-trapped circular dimensions on the surface, due to the spreading of the sol on the substrate during the spin coating process. The glasses show a decrease in the number of polarizable non-bridging oxygen units with doping, reducing the polarizability and optical basicity. The films exhibit prominent green lasing in the downshifting process. The energy transfer from the Yb3+ ions endows the glasses with significant red lasing, suppressing the green emissions by the upconversion mechanism, which is also validated by the colorimetric chromaticity analysis. The gain cross-section of the glass doped with 1.5 mol% of Yb3+ is 23.3 × 10−20 cm2 in the S-band telecommunication domain. The glass film evidences its potential for NIR lasers, beyond a population inversion of 40 %, and a decreasing metastable lifetime of 6.6 μs. Beyond 1.5 mol% of the co-dopant Yb3+, energy transfer dominates, due to the dipole-quadrupole interactions, which has been corroborated by the Inokuti-Hirayama model. The conductivity in the glasses shows a decreasing trend with doping. The Randle's equivalent circuitry of the Nyquist impedance plots, predicts Warburg diffusion impedance that deters the space charge polarization. The consequential decrease in the dielectric constant and capacitance makes the glasses suggestive of multi-layer dielectric substrates in the integrated microelectronic technology for soldering of the printed circuit boards (PCB) that demand low signal losses.

Spectroscopic characteristics and gain cross-section profiles of erbium-doped boro-tellurite glasses for optical amplifier applications

A series of glass compositions (60-x) B2O3–10TeO2–15BaCO3–15MgF2–xEr2O3 with diverse quantities of erbium ions (Er3+) was synthesized using the melt quenching method and the samples were subjected to thorough characterization to explore their optical and structural properties. In order to ascertain the amorphous nature of the glass and acquire a deeper understanding of its chemical bonding, conventional methods of characterization, such as X-ray diffraction and Fourier transform infrared spectroscopy, were utilized. The Judd-Ofelt intensity parameters were computed using the absorption spectra of glasses doped with Er3+, providing vital information about the local environment and coordination of Er3+ ions in the glass matrix. The glasses underwent the collection of near -infrared (NIR) emission spectra. Following this, an analysis was carried out to look into and understand the spectral properties, emission cross-section, and gain coefficient parameters of the glasses. The spectra obtained discernible characteristics, notably a significant near-infrared (NIR) band associated with the transition between the 4I13/2 and 4I15/2 states. This band was seen to have a central wavelength of 1530 nm. This emission band spanned the wavelengths commonly used in optical communication systems (S + C) -bands, making these glasses suitable candidates for applications such as wavelength division multiplexing (WDM). These results suggest that the boro-tellurite glass may have potential use in photonic devices designed for near-infrared applications, including optical communication systems.

Growth and Characterization of Yb: CALYGLO Crystal for Ultrashort Pulse Laser Applications

Yb:CALYGLO crystals with a dopant concentration of 5 at.% were successfully grown using the Czochralski method. The crystal samples were extensively studied to analyze their structure, room temperature and low temperature spectra, and laser properties. The highest absorption cross-section at 977 nm was calculated to be 1.83 × 10−20 cm2 for σ polarization and 5.32 × 10−20 cm2 for π polarization. Similarly, the emission cross-section was determined to be 1.38 × 10−20 cm2 at 980 nm for σ polarization and 2.28 × 10−20 cm2 at 981 nm for π polarization, with a full width at half maximum (FWHM) of 50.3 nm and 89.5 nm, respectively. The fluorescence lifetime of the 5 at.% Yb:CALYGLO crystal at 2F5/2 was measured to be 1.10 ms. Additionally, gain cross-sections were calculated for different β values. In the continuous laser experiment, the crystal demonstrated a laser output of 20.15 W at 1057 nm, with a slope efficiency of 53.3%. These experimental findings indicate that the lattice of Y3+ in the crystal is partially replaced by Lu3+ and Gd3+, resulting in a broader spectrum. Consequently, this crystal shows promising potential as a gain medium for ultrashort pulse laser crystals.

Growth, spectroscopy and SESAM mode-locking of a "mixed" Yb:Ca(Gd,Y)AlO4 disordered crystal.

We present the growth, spectroscopy, continuous-wave (CW) and passively mode-locked (ML) operation of a novel "mixed" tetragonal calcium rare-earth aluminate crystal, Yb3+:Ca(Gd,Y)AlO4. The absorption, stimulated-emission, and gain cross-sections are derived for π and σ polarizations. The laser performance of a c-cut Yb:Ca(Gd,Y)AlO4 crystal is studied using a spatially single-mode, 976-nm fiber-coupled laser diode as a pump source. A maximum output power of 347 mW is obtained in the CW regime with a slope efficiency of 48.9%. The emission wavelength is continuously tunable across 90 nm (1010 - 1100 nm) using a quartz-based Lyot filter. With a commercial SEmiconductor Saturable Absorber Mirror to initiate and maintain ML operation, soliton pulses as short as 35 fs are generated at 1059.8 nm with an average output power of 51 mW at ∼65.95 MHz. The average output power can be scaled to 105 mW for slightly longer pulses of 42 fs at 1063.5 nm.

Spectroscopy of thulium ions in solid-solution sesquioxide laser ceramics: Inhomogeneous spectral line broadening, crystal-field engineering and C3i sites

We present a detailed spectroscopic study of Tm3+ ions in stoichiometric and “mixed” (solid-solution) cubic (C-type, sp. gr. Ia3‾) sesquioxides R2O3 (RY, Lu, Sc or their mixture), with the goal of developing broadband-emitting gain media for ultrafast lasers at ∼2 μm. Evidence of a linear variation (increase) of the crystal-field strength when decreasing the ionic radius of the host-forming cation R3+ in the isostructrural R2O3 series is presented. The crystal-field splitting of Tm3+ multiplets is determined for C2 sites and justified using a barycenter plot, and the first evidence of C3i Tm3+ species is presented. A remarkable inhomogeneous spectral broadening for compositionally “mixed” sesquioxides (in particular with Sc3+) with respect to the parent compounds is revealed at low temperatures. It is proven that binary and ternary “mixed” R2O3 compounds form substitutional solid-solutions with a mixing of the host-forming cations at the atomic level. The stimulated-emission and gain cross-sections for the 3F4 → 3H6 Tm3+ transition are determined. Guidelines for material engineering of Tm3+-doped gain media for mode-locked 2-μm lasers are also provided.

Downconversion luminescence studies in Er3+ activated P2O5 + Gd2O3 + NaF + AlF3 glasses for 1.54 μm NIR laser applications

A series of PGNAEr:(60-x)P2O5 + 7Gd2O3 + 25NaF + 8AlF3 + xEr2O3 (here, x = 0.1, 0.5, 1.0, 2.0 and 4.0 mol%) glasses have been successfully fabricated using the melt quenching technique. X-ray diffractometer has been used to study the amorphous-like structure of the PGNAEr glasses. Spectral measurements of optical absorption and excitation of PGNAEr glasses are studied in both visible and near-infrared wavelength range. The density (2.87–3.16 (g/cm3)) and refractive index (1.535–1.544) are found to increase with Er2O3 concentration, and the absorption spectrum of PGNAEr20 glass plays a vital role in evaluating Ωλ (λ = 2, 4, 6) and laser parameters. The down conversion emission process of PGNAEr glasses is examined in the near-infrared (1400–1700 nm) range upon the radiations at 522 nm (visible) and 980 nm (near-infrared) wavelengths. The emission at 1.54 μm (1545 nm) is observed to be enhanced by a factor of 7 when excited at 522 nm compared to the 980 nm laser source. The observed near-infrared emission from the PGNAEr glass system covers the C + L (1530–1600 nm) bands and third telecommunication window (1440–1530 nm). Using the McCumber’s theory, the emission cross-section is calculated to be around 4.20 × 10−20 cm2 from the absorption cross-section of 2.70 × 10−20 cm2 for the PGNAEr glass system. The calculated gain bandwidth (636 × 10−28 cm3) and gain cross-section (6.93 × 10−21 cm2) indicate that PGNAEr glasses are a promising candidate for optical gain media in the 1.54 μm wavelength region.

Precise determination of energy transfer upconversion coefficient for the erbium and ytterbium codoped laser crystals.

Energy transfer upconversion (ETU) coefficient plays a crucial role in investigating complex laser systems as it greatly influences both the laser output behavior and heat generation. For some quasi-three-energy-level lasers based on Er3+ doped, Ho3+ doped and codoped gain media, the available theoretical studies relied on some unreasonable approximations due to the lack of spectroscopic data, notably the ETU coefficient. We put forward what we believe is a novel approach to overcome the difficulties caused by wavelength jump occurred in aforementioned laser systems. Based on net gain cross-section analysis and rate equations modelling, the functional relationship between the ETU coefficient, the laser power and pump power at the jumping wavelength are established. ETU coefficients and their temperature dependences of Er,Yb:YAB crystals with different crystal doped concentrations are experimentally determined for the first time. The results reveal that the ETU process in Er,Yb:YAB laser system is 5∼35 times stronger than that in Er3+ and Yb3+ codoped phosphate glass. The determination of these spectroscopic data paves the way for precise modelling of laser system based on Er,Yb:YAB or similar gain media.

Energy transfer and laser gain cross-section analysis in Nd-Yb-Gd doped CaF2 crystals

A detailed spectroscopic characterization of CaF2 co-doped with neodymium and ytterbium ions is presented. The higher Nd3+ absorption cross-section around 791 nm than Yb3+ around 980 nm enables an efficient excitation of Yb3+ ions by pumping Nd3+ with a subsequent energy transfer (ET) from Nd3+ to Yb3+ ions. By combining Nd3+ and Yb3+, along with Gd3+ buffer ions Nd3+,Yb3+,Gd3+:CaF2 crystals exhibit very large emission bands extending the usual Yb3+ emission spectrum by adding the Nd3+ emission contribution at longer wavelengths. The Nd3+ ⟶ Yb3+ energy transfer efficiency is estimated using two different approaches based on luminescence intensity measurements and lifetimes, giving consistent results. An energy transfer efficiency of 80 % is achieved in CaF2:0.5%Nd,3%Yb,2%Gd illustrating the ET strength within Nd3+-Yb3+ clusters. Finally, a detailed study of the gain cross-sections and laser emission spectra, and their dependence with Yb3+ doping concentration and population inversion is carried out, providing a detailed model of the laser spectral dynamics in such crystals. The gain cross-section is either dominated by one of the Nd3+ peaks at 1065 nm or 1048 nm or exhibits a flat profile covering the 1045–1067 nm range, in which case the laser oscillates randomly over this spectral range. The results highlight the specifics of the Nd3+ four level laser coupled by energy transfer to the Yb3+ quasi three level laser. Among others, this study shows how a large Nd3+ inversion ratio initiates the depletion of the Yb3+2F7/2 ground state through the ET. This depletion then has two effects as it saturates the energy transfer since the number of Yb3+ acceptors diminishes and it also shifts the laser wavelength towards shorter wavelength as the Yb3+ laser reabsorption is weakened.

Spectroscopic properties of Pr:PbF2 crystal with different doping concentration

Three Pr:PbF2 single crystals with different doping concentrations (0.1, 0.5 and 1.0 at.%) have been detailed investigated to figure out the effect of doping concentration on spectroscopic properties for the first time. The XRD study shows the crystals belong to the cubic system and the lattice parameter of 1.0 at.% Pr:PbF2 crystal is 5.9336 Å. The maximum phonon energy of three crystals was speculated as low as 259 cm−1 through Raman spectra. The absorption and fluorescence spectra of the Pr:PbF2 crystals with different doping levels were recorded and analyzed with the J-O theory. The maximum absorption cross-section at 443 nm and maximum emission cross-section at 482 nm can be obtained as 1.00 × 10−20 cm2 and 1.08 × 10−20 cm2 in 1.0 at.% Pr:PbF2 crystal, respectively. The gain cross-sections of the Pr:PbF2 crystals become positive in a range of 482–497 nm once the population inversion level reaches 30 %. The maximum fluorescence lifetime of 3P0 energy level was found as 33 μs in 0.1 at.% Pr:PbF2 crystal. On the whole, the spectroscopic performance of Pr: PbF2 crystal would be improved by increasing the Pr3+ doping level appropriately.

The influence of Pr3+ ions on the emission characteristics of Er3+-doped YSGG single crystal fibers in the 1–3 μm wavelength range

A series of 20 mol% Er3+, x mol% Pr3+: Y2.4-3xSc2Ga3O12 (Er3+, Pr3+: YSGG) single-crystal fibers (SCFs) were successfully grown by micro-pulling-down (μ-PD) method. Er3+, Pr3+: YSGG SCFs with varying concentrations of Pr3+ dopant exhibit consistent retention of the identical cubic structural space group. Under 980 nm laser diode (LD) pumping, Er3+, Pr3+: YSGG exhibits two emission bands centered at 1.6 and 2.7 μm, respectively. The incorporation of Pr3+ ions in Er3+, Pr3+: YSGG SCF materials has a negative impact on the emission peak intensity at 1.6 μm within a specific range of doping concentration, while it can relatively enhance the emission peak intensity at 2.7 μm. The lifetime of Er3+ ions at 4I13/2 is showing a significant decrease trend with increasing Pr3+ ions doping concentration. The results presented above indicate that the incorporation of Pr3+ ions increase the likelihood of particle number inversion, improving laser operation and demonstrating the desensitizing influence of Pr3+ ions. Quantitative analysis of the gain cross-section reveals a particle number inversion rate of 52.73% at approximately 2.7 μm. These findings provide valuable insights for developing applications aiming to achieve efficient and precise emission at 2.7 μm using Erbium–Praseodymium co-doped yttrium scandium gallium garnet single crystal fibers.

Spectroscopic investigations of Tm3+ doped CdF2 single crystals and infrared laser potentialities

By use of standard Bridgman technique, CdF2 single crystals doped with Tm3+ have been obtained with good optical quality. XRD analysis has been performed confirming the cubic structure. An ordered sequence of spectroscopic measurements (including absorption, excitation, emission and fluorescence dynamics) was carried out at room temperature. By exploiting both UV–Visible and near-infrared absorption spectra, the JO phenomenological parameters are determined by taking into account the complete refractive index dispersion, which allowed us to compute the probabilities of all transitions. Under 355 nm wavelength excitation, the Stokes emission spectrum exhibits mainly an intense blue emission line around 450 nm which is associated to 1D2→3F4 excited state transition. Whereas, the anti-Stokes blue emission around 480 nm associated to 1G4→3H6 transition is obtained under infrared excitation according to a two photon absorption mechanism. For both blue emissions, the CIE chromaticity coordinates of CdF2:Tm3+ are located in the blue region.As trivalent Tm3+ ions are known for their emissions in the near- and mid-infrared spectral ranges suitable for efficient laser operation, we have systematically studied the fluorescence behavior of the eye safe emission (pointed at ∼1.8 μm) and associated to the 3F4 → 3H6 transition. Such transition exhibit a relatively high emission cross-section (σem = 0.22 × 10−20 cm2) and a positive gain cross-section at low pumping threshold with a metastable fluorescence lifetime decay.

Revisiting the luminescence properties of Er3+, Tm3+ and Ho3+ doped Bi4Ge3O12 rod-type crystal fibers for the laser application

BGO single crystals doped with Er3+, Tm3+ and Ho3+ rare-earth ions were prepared in the form of rod-type crystal fibers via the micro-pulling down technique to perform an extensive investigation of their visible, near- and mid-infrared luminescence properties and to really decide on their interest as solid-state laser media in the various spectral domains. Revisiting and completing the absorption spectra already available in the literature led to the derivation of more reliable “effective” radiative lifetimes and branching ratios. Registration of the fluorescence decays of the most important emitting levels versus dopant concentrations led for the first time to an unambiguous determination of “intrinsic” emission lifetimes – corresponding to negligible contributions from inter-ionic energy-transfers - and non-radiative multiphonon relaxation rates. Such data also allowed for the determination of the dominant phonon energy which comes into play in the electron-phonon coupling responsible for these multiphonon relaxation processes and for its lattice vibration origin, i.e. a high phonon energy of the order of 820 cm−1 corresponding to the coupling between bending vibrations of (GeO4)4- tetrahedra and vibrations corresponding to motions of these (GeO4)4- tetrahedra against the Bi3+ ions for which the rare-earth dopant ions substitute. Using the above data and different methods for the calibration of the registered emission spectra in cross section unit and for the derivation of gain cross section curves finally show that mid-infrared emissions of Er:BGO, Tm:BGO and Ho:BGO around 1.55 μm, 1.9 μm and 2 μm, respectively, occur with comparable gain cross sections as in the most important reference mid-infrared laser materials, although over slightly shifted thus complementary spectral domains. It is shown that potentialities also exist with Tm:BGO in the blue, deep-red and near-infrared spectral domains around 470 nm, 800 nm and 1.45 μm, by pumping the crystals with conventional pump sources and using some suitable co-dopants to avoid detrimental self-terminating processes.

Effect of Ca2+ ions on structure and spectroscopic properties of Er3+: KBaY(MoO4)3 crystals

This study successfully grew KBaY(MoO4)3 crystals doped with single Er3+ ions and co-doped with Ca2+/Er3+ ions using the top-seeded solution growth method. Thermal analysis of the KBaY(MoO4)3 crystals was performed by differential scanning calorimetry, and their phase and structure were characterized using X-ray diffraction and Fourier transform infrared spectroscopy. The luminescent properties of the crystals in the visible and near-infrared wavelength ranges under different concentrations of Er3+ ions were analyzed through emission spectroscopy, and the concentration quenching mechanism was investigated in depth. The results showed that the strongest emission intensity was obtained at an Er3+ ion concentration of 5 mol%. Additionally, by substituting Ba2+ ions with Ca2+ ions, the emission intensity was significantly enhanced, especially when the Ca2+ ion doping concentration reached 6 mol%, resulting in the maximum emission intensity. Furthermore, we investigated the effects of matrix structure and lattice distortion on the spectral properties by employing Judd-Ofelt (J-O) theory and studying energy transfer mechanisms. The mechanisms of Ca2+-induced fluorescence quenching and factors influencing the fluorescence decay time were analyzed. Through the analysis of the absorption cross-section, emission cross-section, and gain cross-section of crystals with different Ca2+ ion concentrations, it was found that Ca2+, Er3+: KBYM crystals exhibited a low laser pump threshold. The results demonstrate that the 6 mol% Ca2+, 5 mol% Er3+: KBYM crystals possess excellent performance and are a promising laser gain medium.

Nonlinear gain models in a quantum cascade laser.

Density matrix analysis of a three-state model of quantum cascade laser (QCL) reveals that in this device, the optical gain is composed of the linear part (proportional to population inversion Δn) and the remaining nonlinear part. The nonlinear component non-negligibly contributes even to the small-signal response of the medium. In many attempts to modeling QCLs, the common practice to account for nonlinear gain components is to complement the equation for the gain, g = gcΔn, gc is the gain cross-section, by a compression factor f. In this paper, improved (but still simple) models of the optical gain in QCL are proposed, which preserve the two-component gain structure. With these models, there is no need to solve the Hamiltonian with time-dependent potentials, so that extraordinary numerical loads can be avoided, but simultaneously the essential physics of the phenomena is kept. The improved gain models defined by Eqs.(12), (15) and (16) enable accounting for its nonlinear components while preserving the load-saving, scattering-like approach to light-matter interaction. It is also shown that as long as the populations and dc coherences are determined such that they account for the interaction with the optical field, the small-signal formulation of the gain gives its realistic estimate also for a large optical signal. This conjecture validates the use of non-equilibrium Green's function-based approaches, in which the interaction with the optical field is included through electron-photon selfenergies. The small-signal formulation of the gain can be used in this approach to monitor the saturation process, estimate the clamping flux and the light-current characteristic.

The growth and spectroscopic properties of Yb:KNGM crystal: A promising ultrashort pulse laser material

Yb3+-doped mixed laser crystals are widely recognized as materials capable of generating ultrashort pulses and have garnered significant attention in recent times. In this study, we thoroughly examined the structure and spectroscopic properties of a novel mixed molybdate crystal, Yb:KNGM. Notably, we made detailed observations of an exceptionally broad absorption band with a full width at half maximum (FWHM) of 78 nm. The broad absorption band indicates that the commercially available InGaAs laser diode (LD) can be effectively utilized for high pumping efficiency purpose. The absorption and emission cross-section at 967 and 1014 nm were calculated to be 1.56 × 10−20 cm2 and 2.05 × 10−20 cm2, respectively. The FWHM of the emission band reaches a substantial range of 62 nm, making it highly conducive to the production of ultrashort pulse lasers. The bandgap (Eg) was fitted as 3.26 eV by Tauc formula. Positive gain cross-section can be achieved while the β is only higher than 0.2 and a large FWHM of 41 nm was discovered when β is 0.5. The aforementioned merits provide compelling evidence that Yb:KNGM crystal holds great promise as a laser crystal for the application of wild tunable and ultrashort pulse lasers pumped by LD.

Study of radiation shielding and luminescence properties of 1.5 µm emission from Er3+ doped zinc yttrium borate glasses

Every year, a new material composition composed of various oxides glasses emerges, and researchers investigate fascinating properties because of which they contribute more scientific evidence to tailor their properties to enhance its technological importance in solid-state device applications. In purview of such contribution the present work provide a new material composed of (50-x)B2O3 + 45ZnO+ 5Y2O3 + xEr2O3 where (x = 0.0, 0.1, 0.25, 0.5, 1.0) glasses which were prepared with and without yttrium (x = 0.0, 0.1, 0.25, 0.5, 1.0) content. To determine their suitability, various physical, optical, and radiation shielding tests were performed on the synthesized glasses. In this perspective, we highlight some aspects of the prepared glasses, density of the glasses increases with increasing concentration of high ‘z′ oxides, interestingly non-bridging oxygen’s increases and bandgap decreases when erbium content introduced in the matrix. The oscillator strength was evaluated for the observed eight transitions for the present glasses and found to be within the limits as per the root mean square fitting. The Judd-Ofelt theory was used to estimate the Er3+ ions' spectral transition, and the trend (Ω6 > Ω2 > Ω4) for the current glasses indicates that the ligands and Er3+ ions have weak bonds with one another. The lifetime τexp of 4I13/2 transition shows an increase in its value from 112 μs to 238 μs for 0.5 mol% and 1.0 mol% Er2O3 concentration respectively. At 1.5 µm, the 4I13/2 → 4I15/2 transition-related photoemission band is notable because it is useful for IR laser applications. The optical gain co-efficient of the prepared glasses was investigated using the absorption gain cross-section, emission cross-section, and optical gain cross-section. The near-infrared absorption and emission reveal their role in IR device applications. Radiation shielding properties like the mass attenuation coefficient ((µm), effective electron density (Neff), and effective atomic numbers (Zeff) are critical system of measurements for evaluating transparent material shielding performance.

Synthesis and optical behavior of neodymium ion doped borophosphate glass for laser applications

Nd3+ ion doped lithium aluminum gadolinium borophosphate glasses were synthesized by melt quenching technique. The hypersensitive transitions were identified in the absorption spectra for ultraviolet (UV), visible (Vis) and near infrared (NIR) region, which the highest intensity is recorded at the transitions 4I9/2→4D5/2, 4I9/2→4G5/2 and 4I9/2→4F5/2 with wavelengths of 352, 582 and 804 nm, respectively. The spectroscopic properties of emission spectra in Nd3+ doped present glasses were investigated under 808 nm laser excitation and shows the strongest intensity at 1063 nm, which corresponding the transition 4F3/2→4I11/2. Furthermore, JO parameters (Ω2, Ω4 and Ω6) are produced, which are then utilized to examine the radiative characteristics of Nd3+ doped glasses for example radiative transition probability (AR), radiative lifetimes (τrad), branching ratios (β), gain bandwidth (Δλeff×σe), optical gain (σe×τrad) and emission cross-section (σe). The results demonstrated that the LBPNd0.5 glass might be used in laser applications around 1.058 µm region, which represent highest stimulated emission cross-section (53.49 ×10–21 cm2), higher branching ratio (>0.5), highest quantum efficiency (84.58%), lower non-radiative decay rates (720 s−1) compared with other glasses.