As2S3 Glasses Research Articles

Impacts of hydroxyl and bond energy on laser‐induced damage in mid‐infrared chalcogenide glass

AbstractMid‐infrared chalcogenide glasses often suffer from a low laser damage threshold due to their weak bond energy and the presence of impurities, particularly at the specific wavelength of 2.94 µm, which is widely used in medical applications. In this paper, we first investigated the effect of the hydroxyl (OH⁻) peak absorption coefficient on the laser damage properties of As2S3 glasses. The surface temperature distribution of chalcogenide glasses under laser irradiation was also analyzed using the finite element method (FEM) and in‐situ heat monitoring. The results showed that the surface temperature of the glass increases exponentially with the rise in the absorption coefficient at the OH− peak position. Subsequently, Raman spectra analysis and average bond energy (ABE) theory were employed to compare five typical chalcogenide glasses without hydroxyl absorption, revealing the relationship between the laser damage threshold and the bond energies of the glass networks. Finally, an optimized glass composition of Ge25As10S65 was identified, possessing the highest laser damage threshold of 340.98 J/cm2, more than twice that of traditional As2S3. These findings provide essential glass host and data references for the future development of mid‐ and far‐infrared optical fibers and waveguide devices.

Defects in Se, As2S3, and GeS2 glasses: Ab initio analyses of related clusters

Dangling bonds in Se, As2S3, and GeS2 glasses and wrong bonds in the compounds have been comparatively studied using an ab initio molecular-orbital software. Defect energies and the densities in the chalcogenide glasses are estimated from the total energy Et of small clusters such as H-nSe-H, As3S4H, and Ge4S4H. Properties of corner- and edge-shared connections are also explored for the As-S and Ge-S systems. The three kinds of clusters show for a meta-stable energy ΔEt, relative to the total energy Et of normal bonding structures, a magnitude order of ΔEt(IVAP) < ΔEt(2D0) < ΔEt(D+/D−). Based on this result, we discuss why only GeS2 exhibits unpaired electron spins. The analysis also manifests that ΔEts of clusters containing wrong bonds (As-As, Ge-Ge, and S-S) are comparable with those of ΔEt(IVAP). Regarding electronic levels, the three glasses seem to possess marked gap states having different origins.

Uniform all-solid chalcogenide Bragg fiber with wide photonic bandgap via extrusion

As the Bragg fiber can guide light by tuning the structure parameters of claddings, it is possible to improve the ability of laser-power transmission in the mid-infrared with effective omnidirectional reflection, but it usually suffers from the disturbance of the air core and functional bandgap. Here, the structural parameters of three pairs of periodic cladding layers were optimized by the plane wave expansion method, and the thickness of each layer is 3.36 µm, consisting of Ge20As20Se15Te45 and As2S3 glasses with a refractive index contrast of Δn = 0.8. The simulation results showed that a wide bandgap of 1.2 µm can be realized in the fiber after structural optimization. Then, a fiber preform was prepared via an improved stacked extrusion based on seven thickness-compensated glass plates. The experimental results show that the all-solid Bragg fiber has three pairs of uniform periodic cladding and an extra-large core. The superior optical fiber structure can also be well maintained in the whole fiber length, and the average ratio of each cladding thickness to the fiber diameter is kept nearly at 3:100. Finally, the fiber loss at 1.55 µm and 2.94 µm is 12 dB/m and 18 dB/m, respectively. In all, such a well-structured all-solid chalcogenide Bragg fiber would pave a new way to develop high-quality laser transmission or optical sensors in mid-infrared.

High luminescence efficiency in Er3+-doped chalcogenide fiber with square inner-cladding

High-purity chalcogenide glasses and optimal fiber structure design are essential to enhance fluorescence lifetime and pump absorption efficiency in a chalcogenide-based fiber laser. Here, Er3+-doped As2S3 glasses, with a low –OH concentration of only 0.023 cm−1 (0.01 ppm), were prepared by the novel purification method, and the 4I11/2 level lifetime of purified glasses was increased successfully from 2.3 ms in unpurified glass to 4.8 ms in the purified glass. Furthermore, a special chalcogenide preform with square inner double cladding (S-DCF) was designed and fabricated via a novel extrusion-stacking method for the first time. Compared with circle inner double cladding fiber and single cladding fiber, the pump absorption efficiency is increased by 2–5 times, which fits well with the simulation result by the three-dimensional ray tracing method. All the results mentioned above demonstrated that the elimination of –OH and the optimized structure of S-DCF can improve the luminescence efficiency apparently and promote the development of mid-infrared fiber laser based on Er3+-doped chalcogenide glass.

Photoelastic coefficient measurement method of optical glasses based on Mach–Zehnder interferometer

A method based on Mach–Zehnder interferometer and stress optical coefficients theory was proposed for measuring the photoelastic coefficients of optical glasses. The corresponding apparatus is built to measure the photoelastic coefficients of fused silica and As2S3 glasses, with p12 = 0.27 and 0.26 at 632.8 nm, respectively. The validity and accuracy of the present technique were tested on the samples of fused silica and As2S3 glass, with the relative error not exceeding 10% compared to that in previous studies and the causes of errors were analyzed. The photoelastic coefficients of tellurite glasses with component 75TeO2-20ZnO-5Na2O were measured, with p11 = 0.23 and p12 = 0.22. The acousto-optic (AO) figure of merit M2 of the three types of glass was calculated and the role of photoelastic coefficient in the equation was discussed, providing an effective technique for investigating the AO interaction in a glass.

Chemically-invariant percolation in silver thioarsenate glasses and two ion-transport regimes over 5 orders of magnitude in Ag content

Ionic conductivity σi measurements of AgY−As2S3 (Y = Br, I) glasses, covering 13 orders of magnitude in σi(x) over 5 orders of magnitude in silver content x, confirm two drastically different ion transport regimes in silver halide thioarsenate glasses. As expected, the ionic conductivity in the critical percolation domain, 20 ppm < x ≤ 2 at.% Ag, follows a power-law dependence, σi(x,T)∝xT0/T, where the critical temperature T0 is related to the connectivity of the glassy host. Moreover, we show that σi(x,T) is chemically invariant in the critical percolation domain. Three silver thioarsenate glass families, AgY- and Ag2S-As2S3, reveal identical ionic conductivity within experimental uncertainty over three orders of magnitude in silver contentx. The ionic conductivity diverges in the modifier-controlled region, x > 7-10 at.% Ag, and the difference in σi(x) between AgI- and Ag2S-As2S3 glasses approaches 4 orders of magnitude. Random distribution of silver in the critical percolation domain, shown by DFT modeling of neutron and high-energy x-ray diffraction data, is a key of the observed conductivity invariance. When silver cation leaves the residence site and travels throughout the glass network, characterized by the average Ag-Ag separation distance of 12 Å or more, the memory of its original chemical form (sulfide or halide) vanishes rapidly with increasing the mean square displacement. A non-random silver distribution in the modifier controlled region implying formation of preferential conduction pathways via direct contacts of edge- and corner-sharing silver chalcogenide or chalcohalide polyhedra rules out this possibility. Chemically-invariant ionic conductivity seems to be a common feature of any disordered system with random distribution of mobile ions having similar size of charge carriers.

Lead thioarsenate system PbS–As2S3: Glass formation, macroscopic, and electric properties

AbstractLead thioarsenate glasses are promising materials for a number of potential applications in far infrared optics, chemical sensing, nonlinear photonics, etc. Electronic properties of the PbS–As2S3 glasses were studied in the past, however, the relationship between the glass and crystal characteristics have not been established. Here we compare the glass‐forming domain in the pseudo‐binary system obtained by usual melt–quenching and mechanical milling. Macroscopic and electrical glass properties are analyzed in comparison with their crystalline counterparts: PbAs2S4, Pb5As9S18, and Pb2As2S5, and the annealed glasses yielding glassy/crystalline alloys. Although the primary crystallization phases in glasses are consistent with the phase diagram, the lead local environment seems to be different in glasses and crystals, reflected by their properties and preliminary high‐energy X‐ray diffraction results.

Ablation of binary As2S3, As2Se3, GeS2, GeSe2 and GeSe3 bulk glasses and thin films with a deep ultraviolet nanosecond laser

Binary (As2S3, As2Se3, GeS2 GeSe2 and GeSe3) bulk glasses and corresponding thin films were prepared and illuminated with deep ultraviolet nanosecond (DUV ns) pulsed laser operating at 213 nm. The illumination of samples led to the reproducible crater's formation. Subsequently, the influence of the pulses number and laser fluence on their creation was studied. The ablation rate and laser-induced ablation threshold (LIAT) were determined based on these experiments. The craters with the help of digital holographic microscopy (DHM), atomic force microscopy (AFM), phase shift imaging mode of AFM, Raman scattering, scanning electron microscopy and energy-dispersive X-ray spectroscopy were characterized. As an application possibility, the formation of the diffraction gratings by laser direct writing is presented and their functionality is demonstrated.

The effect of Er on optical and mechanical properties of As2S3 glasses quenched in different media

Er3+-doped As2S3 glasses were synthesized using As, S and Er2S3 as raw materials. In order to produce glasses with high mechanical properties along with high solubility of rare earth ions in these glasses, different media such as water, hydraulics and heat-resistant oil were selected for quenching specimens. Heat-resistant oil was selected as optimized medium. The effects of Er content (0.5–2 wt%) on transmission, mechanical and structural properties of the glasses were investigated. By increasing Er content in the base glass, some clusters were introduced to glass field which causes reduction in transmission in infrared (from 70 to 25%) and visible ranges (from 70 to 60%). Density and microhardness of samples were increased from 2.78 to 3.26 g/cm3 and 81.5 to 91.75 Mpa, respectively, by increasing Er content.

The density, nanohardness and some optical properties of As-S and As-Se chalcogenide bulk glasses and thin films.

Amorphous As2S3, As2Se3 and As1Se99 bulk glasses and thin films were prepared by the melt quenching technique and vacuum thermal evaporation, respectively, on different substrates. The density (ρ) – determined by the simple and cheap method of precise weighting, refractive index (n), structural arrangement – inferred from Raman spectroscopy, and nanohardness (Hind) were determined for all the studied materials in both bulk and thin film states. It is found that regardless of the chemical composition, the bulk glass density, refractive index and nanohardness are higher in comparison with those of the corresponding virgin and by annealing relaxed thin films, and the observed differences are discussed. The almost negligible influence of the substrate on the thin films density, structural arrangement and nanohardness, was observed.

Femto- and nano-second laser-induced damages in chalcogenide glasses

We have studied damaging behaviors in bulk As2Se3, Se and As2S3 glasses using fs and ns laser pulses. Threshold fluence of laser damages markedly varies with excitations and materials. Under sub-gap fs pulses with photon-energy of ħω = 1.6 eV, the threshold in As2S3 is roughly twice that of the other two glasses, and photo-crystallization appears in Se. For ns pulses, all the glasses under bandgap (ħω = 2.3 eV) illumination possess higher thresholds than those under mid-gap (ħω = 1.2 eV) illumination. These observations are discussed, taking electronic and thermal effects into account.

Study of glass transition kinetics of As2S3 and As2Se3 by ultrafast differential scanning calorimetry**Project supported by the National Natural Science Foundation of China (Grant Nos. 61775111, 61775109, and 51771216), the Natural Science Foundation of Zhejiang Province, China (Grant No. LR18E010002), the International Cooperation Project of Ningbo City (Grant No. 2017D10009), the One Hundred Talents Program of Chinese Academy of Sciences,

Ultrafast differential scanning calorimetry (DSC) was employed to investigate the glass transition kinetics of As2S3 and As2Se3. By using the Arrhenius method, a fragility index of ∼22 can be estimated in both As2S3 and As2Se3. However, when the scanning rate is more than , non-Arrhenius behavior can be observed in such “strong” liquids where the Vogel–Fulcher method is more accurate to describe the glass transition kinetics. The fragilities of As2S3 and As2Se3 glasses are thus extrapolated as 28.3 ± 1.94 and 23.7 ± 1.80, respectively. This indicates that, As2Se3 glass has a better structural stability and it is a better candidate for device applications.

Optical activity induced by rare-earth ions in As2S3 glasses and KCl crystals

Optical transmission spectra of As2S3 glass-like plates and nanolayers, undoped and doped with Sm and Pr ions have been investigated. The spectral dependences of the refractive index and glass transmission spectra, registered in the configuration of crossed polarizers, were studied. The concentration of rare-earth ions in the matrix influences on the magnitude of refractive indices (n−, n+) of polarized light. The emission spectra of As2S3 glasses, doped with rare-earth ions (Sm and Pr) and KCl crystals doped by Sm ions have been investigated for different temperatures in the range 300–10 K. A broad luminescence band associated with recombination transitions of charge carriers from 5D0 levels to 7F0-6 levels or from 4G5/2 levels to 6H5/2…15/2 levels of samarium ions (Sm2+ and Sm3+, respectively) was registered. A number of narrow absorption bands were registered on this broad photoluminescence band, which can be attributed to self-absorption process, determined by electronic transitions between the levels (7F0-6 ⟶ 5D0 or 6H5/2…15/2 ⟶ 4G5/2) of samarium ions.

In-Situ and Ex-Situ Characterization of Femtosecond Laser-Induced Ablation on As₂S₃ Chalcogenide Glasses and Advanced Grating Structures Fabrication.

Femtosecond laser pulse of 800 nm wavelength and 150 fs temporal width ablation of As2S3 chalcogenide glasses is investigated by pump-probing technology. At lower laser fluence (8.26 mJ/cm2), the surface temperature dropping to the melting point is fast (about 43 ps), which results in a clean hole on the surface. As the laser fluence increases, it takes a longer time for lattice temperature to cool to the melting point at high fluence (about 200 ps for 18.58 mJ/cm2, about 400 ps for 30.98 mJ/cm2). The longer time of the surface heating temperature induces the melting pool in the center, and accelerates material diffusing and gathering surrounding the crater, resulting in the peripheral rim structure and droplet-like structure around the rim. In addition, the fabricated long periodic As2S3 glasses diffraction gratings can preserve with high diffraction efficiency by laser direct writing technology.

Sub-Tg enthalpy relaxation in milled and quenched As2S3 glasses

We investigate the sub-Tg relaxation in both the mechanically milled and the quenched As2S3 glasses by a differential scanning calorimeter (DSC). The results show that the sub-Tg enthalpy relaxation pattern of the milled As2S3 glass is similar to that of the quenched glass, but the fictive temperature (Tf) of the former is higher than that of the latter. By performing sub-Tg annealing, we find that the quenched As2S3 glass exhibits the Johari-Goldstein (JG) relaxation, whereas the milled glass shows the relaxation behavior with the activation energy of ~32RTg that deviates from the average value of 24RTg for the JG relaxation. An endotherm occurs prior to the sub-Tg relaxation peak when the milled glass undergoes sufficient sub-Tg annealing (temperature and time). The occurrence of the endothermic pre-peak and the higher activation energy of the milled glass imply its higher structural heterogeneity compared to the quenched glass. The Raman and X-ray photoelectron spectra indicate the existence of the As4S4 clusters and -S-S- chains in both the milled and the quenched glasses, confirming their structural heterogeneity.

Femtosecond-laser-induced submicron grating periodic structures on As2S3 and As35Se65 glasses

Submicron periodic structures produced by femtosecond Ti:sapphire laser irradiation (1 kHz, 150 fs, 3–5 μm) on As2S3 and As35Se65 glasses at edges of damage holes are observed. Effects of changes in laser wavelength (λ), pulse number, power, and irradiation time on grating periodicity were studied. Regular groove-like ripples and distinct parallel submicron periodic gratings were seen in damaged areas. The damage grating period (Λ) is approximately λ/2n. The period increases with wavelength but is hardly influenced by irradiation time and pulse number. Samples with high refractive index and low bandgap are more prone to melting, and edge stripes are not obvious.

Mid-infrared femtosecond laser-induced damages in As2S3 and As2Se3 chalcogenide glasses

In this paper, we report the first measurements of mid-infrared (MIR) femtosecond laser-induced damage in two typical chalcogenide glasses, As2S3 and As2Se3. Damage mechanism is studied via optical microscopy, scanning electron microscopy and elemental analysis. By irradiating at 3, 4 and 5 μm with 150 fs ultrashort pulses, the evolution of crater features is presented with increasing laser fluence. The dependence of laser damage on the bandgap and wavelength is investigated and finally the laser-induced damage thresholds (LIDTs) of As2S3 and As2Se3 at 3 and 4 μm are calculated from the experimental data. The results may be a useful for chalcogenide glasses (ChGs) applied in large laser instruments to prevent optical damage.

Mid-infrared nonlinear absorption in As2S3 chalcogenide glass.

We report mid-infrared (MIR) nonlinear absorption in As2S3 glasses which results from two-photon excitation of valence electron to the Urbach extension followed by strong linear absorption of excited states. The measured MIR nonlinear absorption can be 3 to 4 orders of magnitude stronger than the two-photon absorption in the near-infrared for similar laser intensities and does not result from contaminants, but it is intrinsic to As2S3 glasses. As2S3 fibers are widely used to generate supercontinuum by pumping them with high peak power laser pulses. For a 100 kilowatt peak power MIR soliton propagating in single mode As2S3 fiber, the nonlinear absorption can be of similar magnitude than the fiber background loss. Finally, for laser peak power around 1 MW, the MIR nonlinear absorption can be ~2 orders of magnitude larger than the fiber background loss in single mode As2S3 fiber.

Fluorescence whispering gallery modes in Tm3+-doped Ge-Ga-S chalcogenide glasses microsphere-silica fiber taper coupling system

Microsphere resonators based on chalcogenide glasses combine the superior optical properties of microsphere resonators (such as high Q-factors and small mode volumes) and excellent material properties of chalcogenide glasses in the infrared spectrum (such as good transmissivities, high refractive indices, and low phonon energies), and thus have promising applications in the fields of low-threshold infrared lasers, nonlinear Raman amplifiers/lasers, and narrow bandwidth infrared filters.In this work, the infrared microsphere resonators are built by using a novel chalcogenide glass composition of 75 GeS2-15 Ga2S3-10 CsI (Ge-Ga-S), doped with 1.3 wt% Tm. Compared with previously reported chalcogenide microsphere resonators fabricated with As2S3 and gallium lanthanum sulfide (Ga-La-S) glasses, the proposed Ge-Ga-S glass does not contain the toxic element of As nor the expensive rare earth element of La, and thus is more environmentally friendly and cost-effective for fabricators and users. We first fabricate bulk Ge-Ga-S glasses by using the facility in our laboratory. After measuring the absorption and fluorescence spectra of bulk glasses, they are crushed into powders and the powders are blown downwards through an inert-gas-filled vertical furnace (temperature set at 1000 ℃). Molten glass powders are transformed into high-quality microspheres in the furnace due to surface tension. Thousands of microspheres with diameters ranging from 50 to 200 m can be made in one fabrication process. By using optical microscopy and scanning electron microscopy, a microsphere with high surface quality is selected for further optical characterization. The selected microsphere has a diameter of 72.84 m, an eccentricity less than 1% (about 80 nm), and a Q-factor of 1.296104. A silica fiber taper with a waist-diameter of 1.93 m is fabricated as the coupling mechanism for the microsphere resonator. The coupling between the microsphere and the micro fiber taper is realized with the aid of nano-positioning stages. An 808 nm laser diode is used as a pump light source, which is sent into one end of the fiber taper and is evanescently coupled into the microsphere. Spontaneous emissions of fluorescent light are then generated in the microsphere, whose spectral characteristics are measured by using an optical spectrum analyzer. It can be clearly noted from the measurement results that the typical fluorescence spectrum of the Tm3+-doped Ge-Ga-S glass is modified by whispering gallery mode (WGM) patterns as periodic intensity peaks/valleys are apparently present in the measured spectral curves. The locations of those experimentally measured spectral peaks/valleys are in good agreement with WGM mode calculated results through using the Mie scattering theory, which verifies that the proposed Ge-Ga-S glass can be used to build high-quality infrared microsphere resonators. The largest deviation between the experimentally measured spectral peaks/valleys and theoretically calculated WGM modes is about 0.047%. Minor deviation is present because the experimentally fabricated microsphere has a small difference from an ideal sphere (with an eccentricity of about 1% in this work). Longer processing time of glass powders in the vertical furnace or a post-thermal treatment could help improve the sphericity of microspheres.

Role of iodine in the solubility of Tm^3+ ions in As_2S_3 glasses

The effect of iodine (I2) on the photoluminescence properties of Tm3+ ions in the As2S3 matrix was investigated. Results showed three strong emission bands at 1.22 µm (3H5→3H6), 1.46 µm (3H4→3F4) and 1.82 µm (3F4→3H6) under the excitation wavelength of 800 nm, indicating that I2 enables the solubility of Tm3+ ions in As2S3 glasses. The concentration ratio of I2 and Tm3+ were optimized and it revealed that the increasing of the concentration of I2 of 4 times in the glass increases the solubility of Tm ions three times. The effects of the I2 on the fundamental glass properties, including optical, thermal and structural characteristics, were explored as well.