ZnO nanocrystals doped with trivalent europium ions (Eu³⁺) and dysprosium ions (Dy³⁺) were synthesized by the precipitation method. The structural and optical properties of the samples are investigated by the X-ray diffraction (XRD) and photoluminescence (PL). The results show that rare earth ions are incorporated into the lattice of ZnO, and the combination of blue, green and red emissions can be obtained. Specially, the emission can be obtained even under the nonresonant excitation of 320 nm, which is explained based on the energy transfer. The concentration quenching mechanism is also presented in this paper.

By adjusting pH values of reactant system, the mass ratio of stabilizer/water and aging temperature, size controllable spherical silver nanoparticles (NPs) were synthesized. The properties of silver NPs are characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and ultraviolet visible (UV-VIS) absorption spectra. Within the pH values of 7.0-11.0, the aging temperature of 80 °C is better to improve silver NPs in shape to nearly sphere, concentrate size distribution and reduce aggregation than the aging temperature of 25 °C. The shape and dispersibility of silver NPs are the best when the pH of the reactant system is within 7.0-8.0. With pH of 7.5, aging at 80 °C, and stabilizer/ water mass ratio of 1%, the spherical silver NPs with sizes of 50-70 nm were synthesized. The results are promising to be used to synthesize core/shell NPs when silver NPs are as core.

4H-SiC/SiO₂nanowires are synthesized and the temperature-dependent photoluminescence (PL) properties of the nanowires are studied. Their structure and chemical composition are studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectra. At room temperature, an ultraviolet PL peak and a green PL band are observed. From the PL spectrum measured in the temperature range from 80 K to 300 K, the free excition emission, donor bound excition emission and their multiple-phonon replicas have been observed in ultraviolet region, and their origins have been identified. Moreover, it has been found that the temperature dependence of the free exciton peak position can be described by standard expression, and the thermal activation energy values extracted from the temperature dependence of the free exciton and bound exciton peak integral intensity are about 40 meV and 181 meV, respectively.

A type of spatial modulating micro Fourier transform spectrometer (FTS) based on micro multi-step mirrors (MMSMs) is designed and manufactured in this paper. The interference system is based on Michelson interferometer, using two MMSMs instead of plane mirrors in two arms. The recovered spectrum is simulated with different distances between MMSMs and the detector, and the influence of diffraction on the recovered spectrum is analyzed. The edge-enlarging method for the MMSMs is proposed to eliminate edge noise, and the influence of surface roughness of MMSMs on the recovered spectrum is also analyzed. Moreover, the way of manufacturing the MMSMs is investigated.

A novel high sensitivity all-fiber micro-displacement sensor is proposed and experimentally demonstrated. This sensor consists of a long period fiber gating and a fiber tip, which is achieved only by a commercial arc discharge fusion splicer, and thus possesses a lower cost. The wavelength sensitivity of the proposed sensor could be up to 934 pm/μm, which is four times higher than that of the long period fiber grating (LPFG) with an air cavity structure. The intensity change sensitivity is -1.973 dB/μm.

A terahertz bandpass filter with the sandwich structure consisting of thermally tunable vanadium dioxide (VO₂) thin film, silica substrate and subwavelength rectangular Cu hole arrays is designed and theoretically analyzed. The results show that the transmittance of the filter can be actively tuned by controlling the temperature of VO₂, the narrow band terahertz (THz) waves with the transmittance from 85.2% to 10.5% can be well selected at the frequency of 1.25 THz when the temperature changes from 50 ℃ to 80 ℃, and the maximum modulation depth of this terahertz bandpass filter can achieve 74.7%.

?Tianjin University of Technology and Springer-Verlag Berlin Heidelberg 2014 A model of Er³⁺-doped chalcogenide glass (Ga₅Ge₂₀Sb₁₀S₆₅) microstructured optical fiber (MOF) amplifier under the excitation of 980 nm is presented to demonstrate the feasibility of it applied for 1.53 μm band optical communications. By solving the Er³⁺population rate equations and light power propagation equations, the amplifying performance of 1.53 μm band signals for Er³⁺-doped chalcogenide glass MOF amplifier is investigated theoretically. The results show that the Er³⁺-doped chalcogenide glass MOF exhibits a high signal gain and broad gain spectrum, and its maximum gain for small-signal input (-40 dBm) exceeds 22 dB on the 300 cm MOF under the excitation of 200 mW pump power. Moreover, the relations of 1.53 μm signal gain with fiber length, input signal power and pump power are analyzed. The results indicate that the Er^{3++-doped Ga₅Ge₂₀Sb₁₀S₆₅MOF is a promising gain medium which can be applied to broadband amplifiers operating in the third communication window.}

We propose a novel pressure sensor based on the combination of the ring resonator with two straight waveguides and a two-end fixed beam. The principle of this device is acquiring the system static pressure by monitoring the changes in the transmission wavelength shift of the ring resonator with double waveguides. The numerical results show that the sensitivity of the system is up to 49.3 pm/kPa while the pressure range is 0—300 kPa. The thickness of the fixed beam is an important factor which impacts the sensitivity of the system. This device can provide support for fabricating high sensitivity and low cost micro pressure sensors.

This letter reports an autostereoscopic three-dimensional (3D) flat panel display system employing a newly designed LCD-pixel-associated parallax barrier (LPB). The barrier’s parameters can be conveniently determined by the LCD pixels and can help to greatly simplify the conventional design. The optical system of the proposed 3D display is built and simulated to verify the design. For further experimental demonstration, a 508-mm autostereoscopic 3D display prototype is developed and it presents good stereoscopic images. Experimental results agree well with the simulation, which reveals a strong potential for 3D display applications.

We prepare a new type of multi-wavelength infrared laser diode with four chips, three wavelengths (865 nm, 905 nm and 1064 nm) and two working modes (pulse and single). The preparation technology of the diode includes two key processes: heat-sink and packaging processing technique to package four different chips on a same heat-sink. The experimental results show that four output peak-wavelengths of the prototype diode all possess favorable stability.

A tunable surface-emitting integrated lighting system is constructed using a combination of inorganic light-emitting diodes (LEDs) and transparent organic LEDs (OLEDs). An RB two-color LED is used to supply red and blue light emission, and a green organic LED is used to supply green light emission. Currents of the LED and OLED are tuned to produce a white color, showing different Commission Internationale d’Eclairage (CIE) chromaticity coordinates and correlated color temperatures with a wide adjustable range. Such an integration can compensate for the lack of the LED’s luminance uniformity and the transparent OLED’s luminance intensity.

Hydrogenated microcrystalline silicon-germanium (μc-SiGe:H) films are fabricated by radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD). The optical absorption coefficient and the photosensitivity of the μc-SiGe:H films increase dramatically by increasing the plasma power and deposition pressure simultaneously. Additionally, the microstructural properties of the μc-SiGe:H films are also studied. By combining Raman, Fourier transform infrared (FTIR) and X-ray fluoroscopy (XRF) measurements, it is shown that the Ge-bonding configuration and compactability of the μc-SiGe:H thin films play a crucial role in enhancing the optical absorption and optimizing the quality of the films via a significant reduction in the defect density.

ZnS:Na thin films with (111) preferred orientation were deposited on glass substrates by vacuum evaporation method. The as-prepared films were annealed in flowing argon at 400—500 °C to improve the film crystallinity and electrically activate the dopants. The structural, optical and electrical properties of ZnS:Na films are investigated by X-ray diffraction (XRD), photoluminescence (PL), optical transmittance measurements and the four-point probe method. Results show that the as-prepared ZnS:Na films are amorphous, and exhibit (111) preferred orientation after annealing at 400 —500 °C. The PL emissions at 414 nm and 439 nm are enhanced due to the increase of the intrinsic defects induced by the thermal annealing. However, all the samples exhibit high resistivity due to the heavy self-compensation.

Er³⁺-doped tellurite glass (TeO₂-ZnO-Na₂O) prepared using the conventional melt-quenching method is modified by introducing the SiO₂, and its effects on the thermal stability of glass host and the 1.53 μm band spectroscopic properties of Er³⁺are investigated by measuring the absorption spectra, 1.53 μm band fluorescence spectra, Raman spectra and differential scanning calorimeter (DSC) curves. It is found that for Er³⁺+-doped tellurite glass, besides improving its thermal stability, introducing SiO₂is helpful for the further improvement of the fluorescence full width at half maximum (FWHM) and bandwidth quality factor. The results indicate that the prepared Er³⁺-doped tellurite glass containing an appropriate amount of SiO₂has good prospect as a candidate of gain medium applied for 1.53 μm broadband amplifier.

The tensile strained Ge/SiGe multiple quantum wells (MQWs) grown on a silicon-on-insulator (SOI) substrate were fabricated successfully by ultra-high chemical vapor deposition. Room temperature direct band photoluminescence from Ge quantum wells on SOI substrate is strongly modulated by Fabry-Perot cavity formed between the surface of Ge and the interface of buried SiO2. The photoluminescence peak intensity at 1.58 μm is enhanced by about 21 times compared with that from the Ge/SiGe quantum wells on Si substrate, and the full width at half maximum (FWHM) is significantly reduced. It is suggested that tensile strained Ge/SiGe multiple quantum wells are one of the promising materials for Si-based microcavity light emitting devices.

The refractive indices of thin films based on Kramers-Kronig theory are corrected. And the correction theory is used to determine the optical indices of nano-ZnO thin films prepared by low temperature sol-gel method. The calculated results indicate that in the visible (Vis) range, the refractive indices of nano-ZnO thin films exhibit a slight abnormal dispersion, while in the ultraviolet (UV) region, the refractive indices increase with wavelengths increasing (normal dispersion). But the refractive indices show complex change near the absorption edge. The maximum refractive index (1.95) of nano-ZnO thin films within UV range at low temperature annealing is much lower than that of the films annealed at high temperature. The absorption and refractive indices are closely related to the defects in nano-ZnO thin films.

In this paper, a novel radio-over-fiber (ROF) scheme to simultaneously generate and transmit wideband code division multiple access (WCDMA) and millimeter-wave (MMW) signals by using a single dual-electrode Mach-Zehnder modulator (MZM) is proposed. There is no apparent nonlinearity induced by the ROF system. By employing this analog ROF signal transmission technique, the highly transparent fiber-wireless networks, which are ideal for multi-standard wireless system operation, can be realized.

We experimentally assess the bit error rate (BER) performance of an intensity modulation/direct detection (IM/DD) optical orthogonal frequency division multiplexing (OFDM) system based on discrete Hartley transform (DHT) precoding in single-mode fiber (SMF) link for 2.5 Gbit/s quadrature phase shift keying (QPSK) OFDM symbol rate. The experimental results show that for the optical OFDM system based on DHT-precoding, the receiver sensitivity at the BER of 10_-4after 100 km SMF transmission is about 1.5 dBm better than that of the original QPSK OFDM signal, and the DHT-precoded OFDM QPSK signal can achieve approximately 1.3 dB of peak-to-average power ratio (PAPR) reduction.

A tunable modulation format converter based on spectral line-by-line pulse shaper is proposed to realize different format conversions. The pulse shaper works as a format converter by setting its frequency response equivalent to the transform function between two formats. The working principles show that the format converter is suitable for different formats by adjusting its frequency response. Examples of format conversion from return to zero differential phase-shift keying (RZ-DPSK) to on-off keying (OOK) with different data packets and from return to zero (RZ) to non-return to zero (NRZ) are given. The results show that the format converter is not only suitable for different formats but also for random data packets.

A widely tunable high precision chaotic fiber laser is proposed and experimentally demonstrated. A tunable fiber Bragg grating (TFBG) filter is used as a tuning element to determine the turning range from 1533 nm to 1558 nm with a linewidth of 0.5 nm at any wavelength. The wide tuning range is capable of supporting 32 wavelength-division multiplexing (WDM) channels with 100 GHz channel spacing. All single wavelengths are found to be chaotic with 10 GHz bandwidth. The full width at half maximum (FWHM) of the chaotic correlation curve of the different wavelengths is on a picosecond time scale, thereby offering millimeter spatial resolution in WDM detection.

In order to classify the gears and achieve high precision measurement results, a non-contact gear measurement system based on the laser vision is developed in this paper. The laser vision precision measurement method (LVPMM) is proposed to ensure the accuracy. Experimental results indicate that the gear measuring uncertainty is 2.1 μm. The precision can satisfy the gear measurement requirements for two-grade or under two-grade standard gears in industry, and can classify the gears very well.