•A simple and quasi-tunable optical frequency comb generator is demonstrated.•A 10-dB bandwidth covers 16 nm optical frequency comb of 81, 58 and 30 tones.•Phase noise of the comb lines is less than −102 dBc/Hz at an offset of 1 kHz.•RF linewidth of the comb lines is less than 300 Hz.A simple and quasi-tunable optical frequency comb (OFC) generator is proposed and experimentally demonstrated using a C-band passively Fabry-Pérot quantum dot mode-locked laser and a dual-driven LiNbO3 Mach–Zehnder modulator. A 16-nm bandwidth OFC with 81, 58 and 30 comb lines at frequency interval of 23.3 GHz, 35 GHz and 70 GHz respectively is obtained experimentally. Measured average optical signal to noise ratio of 10-dB bandwidth OFCs is 36.3 dB, 38.5 dB and 40.8 dB at frequency interval of 23.3 GHz, 35 GHz and 70 GHz, respectively. Besides, single-sideband phase noise of the 23.3 GHz and 35 GHz frequency comb is −110 dBc/Hz and −102 dBc/Hz at an offset of 1 kHz, respectively. RF linewidth of the 23.3 GHz and 35 GHz OFC is about from 275 Hz to 289 Hz. This is considered a very simple OFC generator with a broadband and seamless spectrum.

ZnxSb100−x films with low Zn content are crystallized in a single-step process with Sb, while the film (Zn/Sb ratio is about 1:1) exhibits a two-step crystallization process with ZnSb metastable and stable phases. Importantly, ZnSb films have higher crystallization temperature (~257 °C), larger crystalline activation energy (~5.63 eV), better 10 year-data-retention (~201 °C) and lower melting temperature (~500 °C).

We deposited Ge28Sb12Se60 chalcogenide films using either thermal evaporation or radio-frequency magnetron sputtering techniques, and then measured their structural and optical properties using various diagnosis tools. The refractive indices of the films were obtained from the transmission spectra based on Swanepoel method, and the optical band gaps were derived from optical absorption spectra using the Tauc plot. Raman and X-ray photoelectron spectra (XPS) were measured and decomposed into several peaks that correspond to the different structural units, and then the evolution of the relative concentrations of the structural units was investigated in order to build up the correlation between the structure and optical properties of the films. It was found that, the films generally possess a large number of Ge2Se6/2, Sb2Se4/2 units and Se–Se bonds, and therefore are relatively higher defective compared with their bulk counterpart. This together with the modification of the chemical compositions results in a higher refractive index as well as a smaller optical band gap in the films. Thermal annealing of the deposited films could convert the optical and structure properties of the films close to those of bulk glass.Highlights► High quality Ge–Sb–Se films were fabricated by two deposition methods. ► Films are presenting good morphology and optical property for optical application. ► The films possess relatively higher defective compared with their bulk counterpart. ► Annealing can be used to convert film into a more mechanically optimized structure.

Surface plasmon resonance (SPR) of noble metal nanoparticles (NPs) fostered a new area of nanophotonics, especially in the selective photon absorption and scattering. The precipitation of Ag NPs in glass would enhance the emission efficiency. Here, we studied the effects of annealing temperature (resulted in the increased Ag NPs’ concentration) or AgCl concentration on the luminescence properties of Er3+/Yb3+ codoped bismuth-germanate glasses which were synthesized by a single-step melting–quenching technique. The SPR peak of Ag NPs appears around 600 nm, and the size of precipitated Ag NPs (spherical, hexagonal) ranges from 5 to 15 nm. With the precipitation of the Ag NPs, more intense green (527 nm, 548 nm) and red (661 nm) upconversion (UC) emission bands are observed up to 7.7, 10.1, and 6.5 folds in the glass containing 1 wt % AgCl annealed at 480 °C for 24 h, respectively. The Ag NPs embedded glasses showed significantly local field change that allowed for more bright UC emission by SPR.