SiO 2 colloidal spheres were synthesized by Stöber method. In order to enhance surface charge of the SiO 2 spheres, they were modified with succinic acid. Scanning electron microscope (SEM) shows that the average size of modified SiO 2 spheres is 473 nm, and its distribution standard deviation is less than 5%; Fourier-transform infrared spectra (FT-IR) and X-ray photoelectron spectrometer (XPS) results indicate that one end of succinic acid is chemically bonded to the SiO 2 spheres through esterification; Zeta potential of the modified SiO 2 spheres in water solution is improved from −53.72 to −67.46 mV, and surface charge density of the modified SiO 2 spheres is enhanced from 0.19 to 0.94 μC/cm 2 . SiO 2 colloidal crystal was fabricated from aqueous colloidal solution by the vertical deposition method at 40℃ and 60% relative humidity. SEM images show that the sample of SiO 2 colloidal crystal is face-centered cubic (fcc) structure with its (111) planes parallel to the substrate. Transmission measurement shows the existence of photonic band gap at 1047 nm.photonic crystals, colloidal crystals, vertical deposition method, SiO 2 colloidal spheres, surface charge density Since the pioneer works of Yablonovitch [1] and John [2] , photonic crystals have received a great deal of attention because of their technological application in zerothreshold lasers, high efficiency light emitting diodes, optical switch and integrated optical waveguides, etc. [3,4] .Currently, there are two main fabrication strategies, namely, "top-down" microfabrication and "bottom-up" self-assembly. Although the traditional microfabrication techniques offer a good control over structured defects and have application in making 3D structures which diffract light in microwave range [5,6] , they are very timeconsuming and have trouble in creating photonic crystals which diffract lights in visible or near-infrared region. By contrast, the self-assembly approach, namely, assembly of the colloidal crystals, affords 3D periodic structures in a controllable, simple, and inexpensive way. When the volume concentration of highly monodispersed colloids reaches a certain value, they would like to assemble into 3D ordered structures under the effect of electrostatic repulsive force. These structures include face-centered cubic (fcc), body-centered cubic (bcc), etc., whose crystal lattice constants are in submicron range. Thus, in the past few years, remarkable advances were seen in the self-assembly of colloidal crystals to create photonic crystals in visible or near-infrared region [7,8] .Up to now, the fabrication routes for creating colloidal crystals can be roughly divided into two techniques: gravity sedimentation and solvent evaporation. For the gravity sedimentation method, crystal formation can only occur at specific colloid volume fraction, as a result, the crystal thickness is not easily controlled [9] . For the solvent evaporation method, the thickness and quality can be controlled by either varying colloid concentrations or repeating layer-by-layer...
The lasing wavelength of a complex-coupled DFB laser is controlled by a sampled grating.The key concepts of the approach are to utilize the −1st order (negative first order) reflection of a sampled grating for laser single mode operation, and use conventional holographic exposure combined with the usual photolithography to fabricate the sampled grating. The typical threshold current of the sampled grating based DFB laser is 32 mA, and the optical output is about 10 mW at an injected current of 100 mA. The lasing wavelength of the device is 1.5356 μm, which is the −1st order wavelength of the sampled grating.
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