Xunsi Wang

Investigations of Ge–Te–AgI chalcogenide glass for far-infrared application

A serious of tellurium based chalcogenide glass were prepared and investigated. As it being transparent nearly up to 25 μm and strong anti-hydrability, it becomes an optimized material for far-infrared application. Here, AgI was incorporated into the glasses acting as a glass modifier. With the help of AgI, a highest glass transition temperature, T(g) (151 °C) can be obtained. Detailed physics and chemic properties of the glasses were analyzed with DTA and XRD. The infrared optical transmission spectra were studied with the help of FTIR and Raman test. A purifying process was adopted to eliminate the affections of impurities in the tellurium glass. These serious of glasses are all high transparent in the 8-20 μm region, which fits for the applications of far-infrared optic imaging and sensing.

Ultrabroad supercontinuum generated from a highly nonlinear Ge–Sb–Se fiber

We report the fabrication of a novel high nonlinear fiber made of Ge-Sb-Se chalcogenide glasses with high numerical aperture (∼1.0), where the core and the cladding glasses consist of Ge₁₅Sb₂₅Se₆₀ and Ge₁₅Sb₂₀Se₆₅ (mol. %), respectively. The nonlinear refractive index (n₂) of the core glass is 19×10^-18  m²/W at 1.55 μm, and its laser-induced damage threshold under irradiation of 3.0 μm fs laser is approximately 3674  GW/cm². By pumping a 20-cm-long fiber with a core diameter of 23 μm using 150 fs pulses at 6.0 μm, supercontinuum spanning from ∼1.8 to ∼14  μm was generated.

Robust multimaterial tellurium-based chalcogenide glass fibers for mid-wave and long-wave infrared transmission

We describe an approach for producing robust multimaterial chalcogenide glass fibers for mid-wave and long-wave mid-infrared transmission. By combining the traditional rod-in-tube process with multimaterial coextrusion, we prepare a hybrid glass-polymer preform that is drawn continuously into a robust step-index fiber with a built-in, thermally compatible polymer jacket. Using tellurium-based chalcogenides, the fibers have a transparency window covering the 3-12 μm spectral range, making them particularly attractive for delivering quantum cascade laser light and in space applications.

New far-infrared transmitting Te-based chalcogenide glasses

This study reports on the synthesis of tellurium-based glasses that have a wide transmission far beyond the second atmospheric window. Several far-infrared(IR) transmitting glass systems including Ge-In-Te, Ge-Ga-Te, as well as some compositions containing alkali halides (KI, CsI) or metal halides (PbI2, CuI, AgI, CdI2 or ZnI2) are reported. Their glass-forming ability, thermal stability, and IR transmitting property are investigated. The results show that the broad absorption peak in the 15–20 μm disappear in the Fourier-transform infrared (spectrometer) spectra when gallium is replaced by indium. Te-based chalcogenide glasses containing metal-halides show superior glass-forming ability and better thermal stability than those containing alkali halides. Among these glasses, the ΔT of glass composition 65GeTe4-17In2Te6-18AgI can be as great as 115 °C. In ternary system, the glass composition Ge16Te69(AgI)15 (ΔT = 120 °C) is stable enough toward crystallization in combination with broad transmission region ...

Fabrication and characterization of multimaterial chalcogenide glass fiber tapers with high numerical apertures

This paper reports on the fabrication and characterization of multimaterial chalcogenide fiber tapers that have high numerical apertures (NAs). We first fabricated multimaterial As(2)Se(3)-As(2)S(3) chalcogenide fiber preforms via a modified one-step coextrusion process. The preforms were drawn into multi- and single-mode fibers with high NAs (≈1.45), whose core/cladding diameters were 103/207 and 11/246 μm, respectively. The outer diameter of the fiber was tapered from a few hundred microns to approximately two microns through a self-developed automatic tapering process. Simulation results showed that the zero-dispersion wavelengths (ZDWs) of the tapers were shorter than 2 μm, indicating that the tapers can be conveniently pumped by commercial short wavelength infrared lasers. We also experimentally demonstrated the supercontinuum generation (SCG) in a 15-cm-long multimaterial As(2)Se(3)-As(2)S(3) chalcogenide taper with 1.9 μm core diameter and the ZDW was shifted to 3.3 μm. When pumping the taper with 100 fs short pulses at 3.4 µm, a 20 dB spectral of the generated supercontinuum spans from 1.5 μm to longer than 4.8 μm.

Redshifted surface plasma resonance-induced enhancement of third-order optical nonlinearities in silver nanoclusters embedded in Bi 2 O 3 -B 2 O 3 -TiO 2 pseudo-ternary glasses

A series of silver (Ag0) nanoclusters embedded in bismuthate glasses (Bi2O3-B2O3-TiO2) were synthesized by the thermochemical reduction method. When B2O3 was substituted with TiO2, the refractive index of the encapsulating medium increased, leading to redshifting of the surface plasmon resonance (SPR) absorption band of Ag0, which was initially located at 612 nm. Z-scan measurements with femtosecond laser pulses at 800 nm showed that third-order optical nonlinearities (TONs) were significantly enhanced in the SPR redshifted samples, and calculation of the figure of merit manifested excellent performances of present Ag0-bismuthate nanocomposites for TON-based all-optical switching.

Tm3+-doped tellurite glass with Yb3+ energy sensitized for broadband amplifier at 1400–1700 nm bands

A kind of novel experiment was disclosed as it possessed two bands of fluorescence emission at 1.4 and 1.6 μm, which were perfectly complimentary to the current C band of optic communication. The fluorescence was based on energy transfer and up-conversion processes between Tm3+ and Yb3+ under direct pumping of 975 nm LD. The spectra and lifetimes of Tm3+ fluorescence in the tellurite glass were described. The corresponding fluorescence characteristics and energy migration process were analyzed by the method of lifetime and intensity comparison. The mechanism of the up-conversion based IR fluorescence was presented upon analyzing the multi-photon pumping process. The potential advantages of Tm3+/Yb3+ co-doped tellurite glass as amplifier material were concluded.

Research on optical band gap of the novel GeSe2-In2Se3-KI chalcohalide glasses.

The glass-forming region of the GeSe(2)-In(2)Se(3)-KI system was reported firstly. The dependence of physical, thermal and optical properties on compositions as formula of (1-x)(0.8GeSe(2)-0.2In(2)Se(3))-xKI (x=0, 0.1, 0.2, 0.3) chalcohalide glasses was investigated. The allowed direct transition and indirect transition, and Urbach energy of samples were calculated according to the classical Tauc equation. The results show that the glass system has good thermal stability and that there is an obvious blue-shift at the visible absorbing cutting-off edge. When the dissolved amount of KI increased from 0 to 30mol%, the direct optical band gap and the indirect optical band gap were in the range from 1.617 to 1.893eV and 1.573 to 1.857eV. With the decrease of the molar refraction the refractive index decreases, optical band gap and metallization criterion increase. The relationship between energy band gap and metallization criterion was analyzed and the optical properties of chalcohalide glasses were summarized.

1.5-14 μm midinfrared supercontinuum generation in a low-loss Te-based chalcogenide step-index fiber.

We have experimentally demonstrated midinfrared (MIR) supercontinuum (SC) generation in a low-loss Te-based chalcogenide (ChG) step-index fiber. The fiber, fabricated by an isolated extrusion method, has an optical loss of 2-3 dB/m at 6.2-10.3 μm and 3.2 dB/m at 10.6 μm, the lowest value reported for any Te-based ChG step-index fiber. A MIR SC spectrum (∼1.5 to 14 μm) is generated from the 23-cm fiber pumped by a 4.5 μm laser (∼150  fs, 1 kHz). To the best of our knowledge, this is the first SC experimental demonstration in Te-based ChG fiber and the broadest MIR SC generation pumped in the normal dispersion regime in the optical fibers.

Investigation of 2.9 μm luminescence properties and energy transfer in Tm3+/Dy3+ co-doped chalcohalide glasses

Abstract A series of chalcohalide glasses based on the composition of 0.9(Ge 30 Ga 5 Se 65 )-0.1CsI with different Tm 3+ /Dy 3+ -codoped ions concentrations were synthesized by melt-quenching technique. The absorption spectra and 2.9μm mid-infrared fluorescence spectra of glass samples under 800 nm laser excitation were measured. The results showed that Tm 3+ was an efficient sensitizer, which could enhance the Dy 3+ :2.9 μm fluorescence intensity significantly. The effective energy transfer between the two rare-earth ions were mainly attributed to the resonance energy transfer from Tm 3+ : 3 F 4 to Dy 3+ : 6 H 11/2 level. Emission cross section of 2.9 μm mid-infrared luminescence was also investigated according to Judd-Ofelt theory, σ e =2.51×10 −20 cm 2 .