Undoped ZnS nanocrystals (NCs) with different precursor molar ratios of [S²⁻]/[Zn²⁺] are prepared by the chemical precipitation method. The structural and optical properties of the samples are characterized by the X-ray diffraction (XRD) spectra, photoluminescence (PL) spectra and PL decay spectra. The XRD analysis shows that the crystal quality of ZnS NCs becomes better and the grain size is larger at higher [S²⁻]/[Zn²⁺] ratios. The PL peaked at 430 nm decreases with the [S²⁻]/[Zn²⁺] ratio increasing, which is ascribed to the structure defects of NCs. A multi-exponential decay time curve with hundreds of picoseconds, several nanoseconds and tens of nanoseconds is obtained, which also shows a distinct and regular change with [S²⁻]/[Zn²⁺] ratio. It is indicated that the PL and emission decay properties of ZnS NCs mainly depend on the change of the defects number from different particle sizes.

The influence of the polarized state of blue light on light scattering in InGaN blue chip nano-crystal luminescent glass for solid state lighting is investigated. Based on Rayleigh-Debye approximation theory, theoretical relationships between the light scattering turbidity and wavelength of the incident light, radius and refractive index of the nano-crystals are established to simulate the situations in yttrium aluminate garnet (YAG), silicate and oxynitride based luminescence glass. It is revealed that the scattering turbidity in luminescent glass turns to be the smallest as the effective refractive index of nanocrystals is equal to that of parent glass, and the scattering turbidity for the vertically polarized incident light is greater than that for the un-polarized incident light, while that for the horizontally polarized incident light is smaller than that for the unpolarized incident light under the same conditions.

The noise characteristics of dual-pumped fiber optical parametric amplifiers (FOPAs) induced by gain and loss in photonic crystal fibers (PCFs) are analyzed. A special photonic crystal fiber is designed. Its noise figure (NF) changes with structure parameters, and it decreases as the hole diameter decreases. Three factors including input-signal power, signal wavelength and pump separation which impact on the final noise figure are discussed with the designed PCF.

The propagation of picosecond pulses in the normal dispersion photonic crystal fiber (PCF) with a flattened dispersion profile is numerically investigated. The characteristics of the amplitude and phase noise in the supercontinuum generation (SCG) are also analyzed through the coherent sliced supercontinuum (SC). The effects of self-phase modulation (SPM) and four-wave mixing (FWM) on broadening of the pulse spectrum are presented, and the best amplitude and phase noise performance with a specific fiber length is obtained. The SCG in the wavelength range of 1475 to 1625 nm has only fluctuation between ±1.5 dB, and both the amplitude and phase noise caused by the intensity noise of the input power is below 2.5% in the range of 1500 to 1600 nm.

The effect of a new interfacial buffer layer material, rhenium oxide (ReO₃), on the performance of polymer solar cells based on regioregular poly (3-hexylthiophene) (P3HT) and methanofullerene [6,6]-phenyl C₆₁-butyric acid methyl ester (PCBM) blend is investigated. The effect of the thickness of the oxide layer on electrical characteristics of the device is also studied. Compared with traditional devices, by inserting a 10 nm-thick ReO₃ as the anode buffer layer, a power conversion efficiency (PCE) of 2.8 % (a 37% improvement compared with the control devices) can be obtained with J_sc of 13.6 mA/cm², V_oc of 0.45 V, and a fill factor (FF) of 53.6% under the simulated AM1.5 G 100 mW/cm² illumination in air. It is indicated that ReO₃ can be used as an effective buffer layer to enhance the polymer bulk heterojunction (BHJ) photovoltaic cell efficiency.

A coherent mid-infrared laser source, which can be tuned from 7.2 μm to 12.2 μm based on the type-II phase-matched difference frequency generation (DFG) in an uncoated ZnGeP₂ (ZGP) crystal, is reported. The two pump waves are from a type-II phase-matched dual-wavelength KTP optical parametric oscillator (OPO) of which the signal and idler waves are tuned during 1.85–1.96 μm (extraordinary wave) and 2.5–2.33 μm (ordinary wave), respectively. The maximum energy of the generated mid-infrared laser is 10 μJ at 9.22 μm, corresponding to the peak power of 2.2 kW.

The theory of mutual injection phase-locking applied in two or three fiber lasers is extended in this paper. Four fiber lasers injected mutually by any two lasers are firstly modeled. And the four fiber lasers with the same frequency and coupling coefficient are numerically simulated. Simulation results show that with changing the initial phase difference between lasers, coupling coefficient and the initial amplitude, the locking phase difference between lasers would not maintain the same value. Therefore, an array with more than or equal to four fiber lasers injected mutually by any two lasers is not suitable for self-organized coherent combination of fiber lasers.

The one dimension photonic crystal (1D-PC) polarization filters with four channels and nine channels are presented based on different angular responses of the 1D-PC band gap. By using the optical transfer matrix method (TMM), the filtering characteristics are studied numerically, and the results show that both of the filters have the even signal channel spacing, for each channel the polarization separation degree is more than 0.96, the quality factor is about 10⁴ magnitude, and the band width is almost even. So the 1D-PC polarization filter is a promising candidate for multi-channel polarization filters.

The transient photoresponse of a backside-illuminated InP/InGaAs uni-traveling carrier photodetector (UTC-PD) is simulated by a 2D drift-diffusion approach utilizing a commercial numerical device simulator (ATLAS). The effects of the epitaxial layer structure and device biasing are taken into account. The simulation results indicate that the absorption region has a critical effect on the photoresponse pulse, and an optimized epitaxial layer structure is given to achieve a fast response while maintaining a reasonable response. Here, the optimized material parameters of the absorption region are 180 nm and 5×10¹⁶cm⁻³, respectively.

Pentacene-based metal-base organic transistors (MBOTs) are fabricated. The influence of the charge carrier injection efficiency at the emitter electrode/emitter interface on the device performance is investigated. It is found that the current modulation and the on/off ratio increase with the injection efficiency. By inserting poly(3,4-ethylenedioxythiophene) (PEDOT): PSS/m-MTDATA layers at the emitter electrode/emitter interface, the current modulation and the on/off ratio reach 6.7 mAcm⁻² and 23, respectively. Meanwhile, the current gain is 95–96 in our experiment, which is almost independent on the injection efficiency.

The interface (IF) phonons of the wurtzite quantum cascade lasers (QCL) are investigated using the transfer-matrix method (TMM). The IF modes are presented in the longitudinal optical-phonon frequency for the Al_0.2Ga_0.8N/GaN and Al_0.15Ga_0.85N/GaN QCLs, and two IF modes can be changed into other modes if their wave numbers are less than the special values. Owing to the more dispersive properties of IF phonons with the increasing Al composition, the scattering rates in both QCLs increase with the Al composition.

A new photonic crystal ring resonator (PCRR) configuration is provided based on two-dimensional (2D) square lattice photonic crystal (PC) silicon rods. The ring is formed by removing the line defect along M direction instead of conventional ΓX direction. Its spectral information including transmission intensity, dropped efficiency and quality factor affected by different physical parameters and the cascaded engineering including parallel and serial configurations are numerically analyzed with 2D finite-difference time-domain (FDTD) technique. The spectral quality factor of more than 830 and dropped efficiency of 90% at 1550 nm channel can be obtained with a less than 2.2 μm ring radius.

The electromagnetic properties of one-dimensional photonic crystals with two kinds of single negative (SNG) materials are investigated by the transfer matrix method. The results show that the photonic crystals have zero-effective phase (zero-Φ_eff) gap and angular gap, which are both non-Bragg gap. The zero-Φ_eff gap is invariant with the incident angle and lattice scaling for different polarizations. The gap can be adjusted by varying the ratio between the two single negative materials’ thickness. The angular gap is highly dependent on the incident angle and polarization, but it is insensitive to the ratio between the two single negative materials’ thickness and lattice scale length. It is also found that the electric field gets extremely enhanced at the lower edge of the angular gap for transverse magnetic (TM) wave. The characteristics will have potential applications in nonlinear optical apparatus.

The influence of the periodicity of subwavelength hole arrays and hole shape on transmission frequency and intensity has been studied. The subwavelength hole array sample is prepared on the 220 nm Au film. The transmission characteristics are measured and analyzed. The transmission spectra show that the different transmission peaks depend on the periodicity of hole arrays and the shape of the holes. With the shorter hole array period, the transmission peak shows blue shift, and the ohmic losses of surface plasmon on the metal film also play an important role in the transmission intensity.

An optical frequency shift keying (FSK) transmitter performed by the cross gain modulation (XGM) in a semiconductor optical amplifier (SOA) is used in an optical label switching (OLS) system with 622 Mbit/s FSK label and 10 Gbit/s amplitude shift keying (ASK) payload. The key parameters in this system are optimized to achieve the best performance of FSK/ASK signal, including the input power of LD, the extinction ratio (ER) of the control light and that of the ASK payload. Besides, the transmission performance of ASK payload and FSK label is also investigated after propagating in the 50 km single-mode fiber (SMF).

Based on the coupling between photonic crystals (PCs) waveguide and micro-cavity, a new method to design wavelength division multiplexing (WDM) is proposed. By changing the position of border dielectric rods of micro-cavity and adopting the output waveguide with a 60° bend, the property of micro-cavity is optimized. The new WDM is designed based on the model. And by modulating the border dielectric rods, different wavelengths can be coupled into the micro-cavity, and then are output from the load waveguide selectively. Only by adding a reflective layer in the bus waveguide, the transmission efficiency of output wavelengths is greatly improved.

A new pattern of mask for probing the azimuthal and radial indexes of Laguerre-Gaussian (LG) beams is presented. The analysis formula describing the intensity distribution of Laguerre-Gaussian beams after passing through the mask is derived. Based on this formula, the intensity patterns for different azimuthal and radial indexes are obtained via numerical simulations. It’s indicated that for each pair of azimuthal and radial indexes, there is a defined intensity pattern in the observed plane, according to which the azimuthal and radial indexes can be measured. Using this method, the communication systems with large capacity can be achieved, which are encoded by the azimuthal and radial indexes of Laguerre-Gaussian beams simultaneously.

An experimental investigation on the nonlinear refractive index of nanoporous silicon at wavelengths of 532 nm and 1064 nm is reported by the reflection z-scan (RZ-scan) method with picosecond pulses. The porous silicon (PS) does not need to be peeled from silicon substrate. The method uses a p-polarized beam with oblique incidence. The modification of the reflected beam intensity gives the information of the surface nonlinear refractive index. The index of porous silicon at 1064 nm is at the same order of magnitude as that obtained by the conventional transmission z-scan technique, and the measured absolute value of nonlinear refractive index n₂ at 532 nm is two orders of magnitude higher than that at 1064 nm.

An artificial fish-swarm based coverage-enhancing algorithm (AFCEA) for visible light sensor networks is proposed. In AFCEA, the improved optimization algorithm is used into the solution for coverage-enhancing in directional visible light sensor networks with the rotational direction model. Compared with other classic directional sensor networks coverage-enhancing algorithms, AFCEA can achieve a higher directional sensor networks coverage with less iterative computing times.

Pump encoding is an effective approach to enhance the weak signal detection in distributed Brillouin fiber sensors. In this paper, a new encoding matrix that can improve the detection performance is proposed. Furthermore, a distributed fiber sensor for both single and encoding pump operations is numerically analyzed by using Brillouin-scattering coupled amplitudes equations. The results demonstrate that the matrix can reduce the transmission times for pumping light and simplify the coding process. The power of the scattering signal and the coding gain can be improved with the increasing code length. The detected scattering optical power is almost three orders of magnitude higher than that of the single pulse pump, as the coding length is 31, corresponding to 14.4 % improvement for the coding gain compared with the S matrix encoding method. At the same time, the temperature uncertainty can also be decreased.

In order to shorten the operation time of the Monte-Carlo simulation of photon transmission in the thicker high-scatterance matter, the fiber is chosen as the receiving device. At the same time, the light source and the receiving surface are aligned. According to the distinction of the anisotropic factor (g), increasing the restricted conditions could improve the simulation speed greatly. And the approximate restricted conditions could cut down the waste time of operations. Simulation results indicate that compared with the Monte-Carlo simulation, the optimized one could save 67% time, and ensure the precision higher than 0.7% in the thicker matter.