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Infrared gradient refractive index (GRIN) lenses have great application value and potential in multispectral imaging systems. This study reports various chalcogenide axial GRIN glasses prepared using the hot‐pressing diffusion method. It is worth noting that the S4–S60 GRIN sample has a difference in refractive index (RI) Δn of greater than 0.3 and a diffusion depth of about 5 mm, which is the deepest diffusion depth reported in chalcogenide glass to date. In addition, the linear portion in the profile of the GRIN sample has a RI difference of 0.15 and a thickness of 1.2 mm. The effects of the temperature, concentration difference, and diffusion time on the sample diffusion process are discussed. The dispersion properties of the GRIN samples were further calculated, providing a new option for correcting chromatic aberrations in optical systems. In addition, a method for the indirect nondestructive characterization of sample RI using the Raman intensity ratio is proposed, and the reliability of the method is verified by practical experiments, which is convenient for the subsequent measurement of the GRIN profile. [ABSTRACT FROM AUTHOR]

The fabrication and characterization of IR chalcogenide polarization-maintaining (PM) step-index optical fibers with elliptical-core and 1-in-line-core have been reported for the first time. An improved isolated co-extrusion method was used to fabricate these core-shaped PM fibers. The elliptical core had a horizontal radius of a = 3.66 μm, vertical radius of b = 1.83 μm and the 1-in-line core of a = 4.83 μm, b = 1.42 μm, respectively. Single-mode PM beam spots were observed for the elliptical-core and 1-in-line-core fibers in the near-field energy distributions. The highest values of birefringence of the elliptical-core and 1-in-line-core fibers are 2.09 × 10 −4 at 2.7 μm and 3.272 × 10 −4 at 2.8 μm, respectively. The extinction ratios of −3.7 dB and −2 dB were achieved in fibers of 0.5 m long with elliptical-core and 1-in-line-core, respectively. [ABSTRACT FROM AUTHOR]

Abstract: GeS2–In2S3–KI/AgI chalcohalide glasses were prepared by traditional melt-quenching method and the glass-forming region was determined. The dependence of glass properties on composition as formula of (100− x)(0.75GeS2–0.25In2S3)− x(In2S3–KI/AgI) was investigated. The allowed indirect transition of samples was calculated according to the classical Tauc equation. The results show that 50mol% AgI can be introduced in the glassy matrix while only 40mol% of KI can be incorporated in the GeS2–In2S3–KI glass system. GeS2–In2S3–AgI glass system has larger density, higher refractive index and better thermal stability, while GeS2–In2S3–KI glass system has shorter visible cut-off wavelength and higher optical band gap. [ABSTRACT FROM AUTHOR]

We have investigated the optimization parameters for polishing end-surface of chalcogenide glass fiber connector in the paper. Six SiC abrasive particles of different sizes were used to polish the fiber in order of size from large to small. We analyzed the effects of polishing parameters such as particle sizes, grinding speeds and polishing durations on the quality of the fiber end surface and determined the optimized polishing parameters. We found that, high-quality fiber end surface can be achieved using only three different SiC abrasives. The surface roughness of the final ChG fiber end surface is about 48 nm without any scratches, spots and cracks. Such polishing processes could reduce the average insertion loss of the connector to about 3.4 dB. [ABSTRACT FROM AUTHOR]

Chalcogenide suspended core fibers are considered as an excellent candidates for several applications in near-and-mid IR applications because of their characteristics of higher linearity and nonlinearity. In this paper, the influence of the fiber structure and host glass on dispersion and nonlinear properties, including the core size and the width of the bridge, especially the shape of the fiber core were analyzed with the finite element method in detail. And then, the optimized structure of SCFs made of As 2 S 3 , Ge 20 Sb 5 Se 75 , As 2 Se 3 , Ge 15 As 15 Se 17 Te 5 , which stand for the typical samples of S-based, Se-based and Te-based chalcogenide glasses, have been adopted to get suitable dispersion properties and highest nonlinear optical properties in all kinds of glasses. [ABSTRACT FROM AUTHOR]

• The mechanism of impurity absorption and heterophase inclusion in Ge-As-S glass was investigated. • Heterophase inclusions in Ge-As-S glass can be effectively suppressed by dynamic distillation and melting at the optimized melting temperature. • The average loss of purified fiber and unpurified one is 1.86 dB/m and 2.87 dB/m, respectively. About 1 dB/m decrease in the loss is due to the absence of the visible heterophase inclusion particles in the glass. Strong absorption from the impurities and background scattering induced by heterophase inclusions are major issue in the applications of Ge-As-S glass in mid-infrared (MIR). Here, we report that, the absorption of impurities sourced from raw materials can be removed effectively by oxygen getters and hydrogen getters under static vacuum distillation, leading to almost disappearance of the absorption at 3.11 μm due to S H, <4.08 ppm at 4.01 μm due to S H and < 11.03 ppm at 7.5 μm due to As-O, respectively, in Ge 10 As 28 S 62. The impurities of H 2 O and CO 2 can be further eliminated to near zero by dynamic distillation. On the other hand, the heterophase inclusions, originating from raw materials of sulfur, arsenic and germanium, the silica-container and deoxidizer of Mg, can be eliminated thoroughly by dynamic distillation and optimized melting temperature. We draw the fibers using unpurified and purified glasses and found that, comparing with the fiber loss of 2.87 dB/m at unpurified glass, the optical loss can be decreased to about 1.86 dB/m in purified glass without any visible particles or heterophase inclusions. All the results pave the way of developing low loss Ge-As-S glass fiber for high power laser delivery. [ABSTRACT FROM AUTHOR]

A number of Ge 17 Ga 4 Sb 10 S 69− x Se x ( x = 0, 15, 30, 45, 60, and 69) chalcogenide glasses have been synthesized by a melt-quenching method to investigate the effect of the Se content on thermo-mechanical and optical properties of these glasses. While it was found that the glass transition temperature ( T g ) decreases from 261 to 174 °C with increasing Se contents, crystallization temperature ( T c ) peak only be observed in glasses with Se content of x = 45. It was evident from the measurements of structural and physical properties that changes of the glass network bring an apparent impact on the glass properties. Also, the substitution of Se for S in Ge–Ga–Sb glasses can significantly improve the thermal stability against crystallization and broaden the infrared transmission region. [ABSTRACT FROM AUTHOR]

We conducted a numerical study of mid-infrared (MIR) supercontinuum (SC) generation with femtosecond pulses in Ge 23 Sb 12 S 65 chalcogenide photonic crystal fiber (PCF). This PCF has multilayer air holes in the cladding region, which renders its flexibility for controlling the dispersion and confinement loss of the fiber. The broad and flat dispersion profiles and the low confinement loss of the designed PCF combined with the wide MIR transparent window of Ge 23 Sb 12 S 65 chalcogenide glass largely contributed to the broadband MIR SC generation. Owing to the ultra-high nonlinearity of the designed Ge 23 Sb 12 S 65 PCF, an ultra-broadband SC ranging from 1.9 μm to 9.3 μm was obtained in a 15 cm fiber by applying a very low pump power of 165 W at 3.3 μm wavelength. [ABSTRACT FROM AUTHOR]

This study theoretically investigated a feasible modal phase-matching second-harmonic generation (SHG) in chalcogenide photonic crystal fiber. SHG is a technique that enables the acquisition of the mid-infrared resource at 5.3 µm with the use of a 10.6 µm commercial laser. The phase-matching condition between two low-order modes can be realized simply by modifying the air hole size and lattice pitch in the designed photonic crystal fiber. Numerical results showed that the confinement loss of the second-harmonic wave was 4.15×10 −4 dB/m at 5.3 µm, and the effective phase-matched fiber length reached as long as 6.382 m. [ABSTRACT FROM AUTHOR]

Abstract: Phase locking and mode shaping in multicore Ge20Sb15S65 chalcogenide photonic crystal fibers are proposed and demonstrated. By manipulating the geometrical structure of the fibers, a large mode area of 1962µm2 resulting from in-phase supermodes and equal amplitudes was obtained, which can significantly reduce the nonlinear damage in chalcogenide fibers in the infrared spectrum. With the coherent beam combining technology of multicore photonic crystal fibers, the far-field combining beam exhibits high brightness and high beam quality. Calculations show that with good phase locking and mode shaping, a seven-core photonic crystal fiber can achieve 49 times enhanced intensity compared with single-core fibers. [Copyright &y& Elsevier]

Abstract: Serials of chalcogenide glasses based on composition of 72GeS2–18Ga2S3–10CsI (in mol%) and doped with high Tm3+ content (up to 10,000ppm) were prepared, and their luminescence properties were investigated under excitation with 800nm laser. The influences of doping concentration on Judd–Ofelt intensity parameter Ω i , spontaneous transition probability A, fluorescence branching ratio β, and radiative lifetime τ rad of Tm3+ in the samples were studied. Four infrared emission bands observed were centered at 1.48, 1.8, 2.3, and 3.8μm, corresponding to optical transitions 3H4 → 3F4, 3F4 → 3H6, 3 H 4 → 3 H 5 and 3H5 → 3F4, respectively. For 1.0wt.% Tm3+: doped sample, no concentration quenching was observed and its emission cross-sections at 2.3 and 3.8μm calculated by using Füchtbauer–Ladenburg equation were 6.85×10− 21 and 7.66×10− 21 cm− 2, respectively. [Copyright &y& Elsevier]

Abstract: Dy3+ doped 40GeSe2–25Ga2Se3–35CsI (GGC) glass was synthesized, and optical spectrum, such as infrared transmission and Vis-Nir absorption was measured. Base on the Judd–Ofelt theory, the three Judd–Ofelt parameters Ω t (t =2, 4, 6) were calculated and the results were compared with other chalcogenide glasses. The small Ω 2 in GGC glass is ascribed to the weak covalency of Se–Dy bond. The theory of crystallization kinetics under non-isothermal condition was developed, and was applied to analyze this Dy3+ doped GGC glass. From the heating-rate dependence of crystallization temperature, the activation energy for crystallization E =148kJ/mol is obtained, and this value is much smaller than that of the undoped glass host, indicating the introduction of Dy3+ ions into the GGC glass will get the host crystallized easily. [Copyright &y& Elsevier]

• Two kinds of fibers based on S-rich and S-poor have been fabricated successfully. • As-S-Se system has a transmission varied range between full S-based and full Se-based. • S-rich fiber shows a lower loss, the of S-poor fiber shows a better SC results. Two kinds of single-mode (SMF) step-index(SIF) chalcogenide fibers based on S-rich and S-poor As-S-Se glass have been fabricated successfully by an isolated extrusion method. We experimentally explored the effects of S and Se weights on the IR light transmission in the infrared area of the waveguide medium. By exploring the infrared transmission. It is found that the As-S-Se system has a transmission varied range between full S-based (As 2 S 3) and full Se-based (As 2 Se 3) glasses. The results show that with the addition of selenium, the red-shift is observed in both the short-wavelength absorption edge and long-wave cut-off wavelength. This phenomenon can be sourced from the varying of optical band gaps and phonon energies. Simultaneously, single-mode fibers was employed to evaluate the attenuation and supercontinuum(SC). We found that S-rich fiber shows a lower optical loss of 0.67–1.5 dB/m in 4.1–5.9 μm region, with a minimum value of 0.67 dB/m at 4.6 μm than that of S-poor fiber does. Yet, the SC results of S-poor fiber shows a flatter and broader spectrum region than that of S-rich fiber does. [ABSTRACT FROM AUTHOR]