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Chalcogenide glass has achieved great success in manufacturing axial-type infrared gradient refractive index (IR-GRIN) lenses. However, studies on radial-type IR-GRIN lenses, which are more ideal for optical design, remain rare. The present study introduces what we believe to be a new method for preparing radial IR-GRIN lens by creating high refractive index ( n ) In 2 S 3 nanocrystals within a 65GeS 2 -25In 2 S 3 -10CsCl (GIC, in molar percentage) glass matrix. Upon introduction of multi-temperature field manipulation, we have successfully achieved central crystallization and simultaneous gradient attenuation spreading toward the edge within GIC glass, providing a radial GRIN profile with Δ n over 0.1 while maintaining excellent IR transparency. In addition, the optical and structural properties of the GIC GRIN samples were characterized. The relationship between Raman intensity and the n of glass ceramics at different heat treatment temperatures was investigated, thereby enabling the indirect confirmation of the presence of radial gradient crystallization within the prepared GIC GRIN samples through Raman intensity. Multiple experimental results have shown that this approach has excellent reproducibility and potential for large-scale productions.

Rare-earth doped chalcogenide films are major components in flexible and integrated photonic and optoelectronic devices for modern communication systems, metrology, and optical sensing. However, it is still challenging to develop a high concentration of rare-earth doping chalcogenide film with a smooth surface to realize efficient photoluminescence (PL). Here, we demonstrate that Er 3+ -doped GeS 2 films are prepared by spin-coating based on a two-step dissolution process. Such a two-step process provides the high solubility of Er 3+ in GeS 2 films and exhibits efficient emission at ∼1.5 µm crossing the telecommunication C-band. The highest PL emission intensity is obtained in GeS 2 films doped with 1.4 mol% of Er 3+ , and this PL in GeS 2 films is reported for the first time. We propose adjustments of annealing parameters for improving the PL characteristics in such materials. Through the control precision of the heating rate and annealing temperature, the smooth surface of GeS 2 films enables efficient photo-luminescence. This two-step dissolution-based strategy would pave a new path to design luminescent chalcogenide films for application in flexible and integrated optoelectronics and photonics.

A dual-peak long period fiber grating (DP-LPFG) sensor functionalized by polypyrrole-chitosan composite was proposed for sensitive detection of Cu 2+ ions in aqueous solution. The nitrogen atom on the polypyrrole ring and the amino group on the chitosan chain in the complex matrix can chelate the Cu 2+ ions. Thus, the refractive index of the overlay changed and further modulated the transmission spectrum of DP-LPFG. After special design, the double peaks can move in opposite directions with the increase of Cu 2+ ion concentration, thereby greatly improving detection sensitivity. The linear sensitivity of the fabricated sensor was measured to be 9.12 and 2.14 nm/ppm (0.61 and 0.14 nm/µM) for concentrations of 0.1-0.5 (1.5 µM-7.5 µM) and 0.5-2 ppm (7.5 µM-30 µM), respectively. In addition, the Langmuir isothermal model was used to evaluate the overall response of the sensor to Cu 2+ ions quantitatively, and the detection limit was determined to be 0.05 ppb (0.75 nM). This ingenious sensor offers a new solution for sensitive detection of heavy metal ions in environmental water.

The nonlinear optical properties of emerging metal halide perovskites (MHP) materials are sufficiently intriguing that this topic has become the hotspots in the realm of material science. Hence, we investigate the third-order nonlinear optical properties of CsPbBrx/I 3-x (x = 1, 2, 3) MHP nano-crystals (NCs) embedded chalcogenide glass (ChG) within a GeS 2 -Sb 2 S 3 pseudo-binary system, by monitoring the composition, excitation wavelength and intensity dependencies via femtosecond Z-scan technique. We have found that the intrinsic large optical nonlinearity of ChG can be further enhanced because of the incorporation of MHP NCs, and that the optical nonlinearity of MHP-ChG containing pristine Br NCs is more pronounced compared to its counterparts with mixed Br/I NCs, due to a combination of multiple factors.

The well-known Swanepoel method was often used to obtain the refractive index (RI) of thin films at the wavenumber values corresponding to the extremes of the transmission interference fringes. But it is difficult to accurately obtain the RI of chalcogenide thin films, especially at an arbitrary wavenumber. So a regional approach method (RAM) was presented here to extend the Swanepoel method to an arbitrary wavenumber. In the RAM the RI at the arbitrary wavenumber was determined through dynamic matching. The calculated values were used to match the experimental transmittance. The accuracy of the RI is better than 0.5%. The RI of a well-known film was obtained by the RAM. And the results are in great agreement with the true values of the RI of the film which indicates the correctness and effectiveness of the RAM. Moreover, the transmission spectrum of Ge-Sb-Se film was measured in the ultra-broadband range of 2000-18000 cm -1 (555-5000 nm), and finally the RI of the film was obtained at the 22 wavenumbers of the spacer 600 cm -1 by the RAM.

A simple and seamless broadband optical frequency comb (OFC) generator is proposed and experimentally demonstrated using a Fabry-Perot quantum dot mode-locked laser combined with a dual-driven LiNbO 3 Mach-Zehnder modulator driven by a low-power radio frequency (RF) signal. It is experimentally demonstrated that the 10-dB seamless bandwidth of the OFC is 8.2 nm (1.02 THz), which has 62 and 40 comb lines for frequency intervals of 16.56 GHz and 24.84 GHz, respectively. The single-sideband phase noise is as low as -112 and -108  dBc/Hz at an offset of 10 kHz, respectively, for the photodetector-converted 16.56 and 24.84 GHz frequency carriers. Correspondingly, the RF linewidths of the 16.56 GHz and 24.84 GHz carriers are about 251 Hz-263 Hz, respectively. Using a QD laser, an ultra-low phase noise and quasi-tunable broadband OFC generator is obtained easily.

Optical nonlinearities of chalcogenide glasses in the Ge-Sb-Se ternary system are investigated at mid-infrared wavelengths (2000 and 2500 nm) with femtosecond Z-scan technique. Strong nonlinear refraction in the chalcogenide glasses is observed at 2000 nm, due to three-photon absorption resonance. In addition, the variation in the nonlinear refraction (γ) of the Ge-Sb-Se glasses shows two jumpoints as mean co-ordination number (MCN) approaches 2.4 or 2.7, consistent with the theoretical predication.