In this paper, we demonstrate the conversion of graphene oxide (GO) into boron carbon oxynitride (BCNO) hybrid nanosheets via a reaction with boric acid and urea, during which the boron and nitrogen atoms are incorporated into graphene nanosheets. The experimental results reveal that GO is important for the photoluminescence (PL) BCNO phosphor particles. More importantly, in this system, the prepared BCNO phosphors can be used to prepare the materials needed for red light emitting diodes (LEDs).

In this paper, a novel refractive index (RI) sensor is proposed based on the fused tapered special multi-mode fiber (SMMF). Firstly, a section of SMMF is spliced between two single-mode fibers (SMFs). Then, the SMMF is processed by a fused tapering machine, and a tapered fiber structure is fabricated. Finally, a fused tapered SMMF sensor is obtained for measuring external RI. The RI sensing mechanism of tapered SMMF sensor is analyzed in detail. For different fused tapering lengths, the experimental results show that the RI sensitivity can be up to 444.517 81 nm/RIU in the RI range of 1.334 9—1.347 0. The RI sensitivity is increased with the increase of fused tapering length. Moreover, it has many advantages, including high sensitivity, compact structure, fast response and wide application range. So it can be used to measure the solution concentration in the fields of biochemistry, health care and food processing.

This paper proposes a novel de-noising algorithm based on ensemble empirical mode decomposition (EEMD) and the variable step size least mean square (VS-LMS) adaptive filter. The noise of the high frequency part of spectrum will be removed through EEMD, and then the VS-LMS algorithm is utilized for overall de-noising. The EEMD combined with VS-LMS algorithm can not only preserve the detail and envelope of the effective signal, but also improve the system stability. When the method is used on pure R6G, the signal-to-noise ratio (SNR) of Raman spectrum is lower than 10 dB. The de-noising superiority of the proposed method in Raman spectrum can be verified by three evaluation standards of SNR, root mean square error (RMSE) and the correlation coefficient ρ.

According to the plasma dispersion effect of silicon (Si), a silicon-on-insulator (SOI) based variable optical attenuator (VOA) with p-i-n lateral diode structure is demonstrated in this paper. A wire rib waveguide with sub-micrometer cross section is adopted. The device is only about 2 mm long. The power consumption of the VOA is 76.3 mW (0.67 V, 113.9 mA), and due to the carrier absorption, the polarization dependent loss (PDL) is 0.1 dB at 20 dB attenuation. The raise time of the VOA is 34.5 ns, the fall time is 37 ns, and the response time is 71.5 ns.

A fiber optic sensor for the measurement of total cholesterol is designed and developed. The developed chitosan coated long period grating (LPG) sensor shows a sensitivity of 5.025×10⁶pm·mL/g in the measurement range of the sensor. The sensor also shows a linear response in the measured range of cholesterol levels, which is highly desirable for exploitation as a commercial cholesterol sensor.

For enhancing the response of light-addressable potentiometric sensor (LAPS) and further improving its signal- to-noise ratio (SNR), an optical focusing method is adopted. Experimental research and theoretical analysis reveal that the magnitude of responsive signal is increased by optical focusing, and the SNR is improved remarkably. These research results indicate that the optical focusing is an effective approach for improving SNR of LAPS.

Micro heat pipe (MHP) is applied to implement the efficient heat transfer of light emitting diode (LED) device. The fabrication of MHP is based on micro-electro-mechanical-system (MEMS) technique, 15 micro grooves were etched on one side of silicon (Si) substrate, which was then packaged with aluminum heat sink to form an MHP. On the other side of Si substrate, three LED chips were fixed by die bonding. Then experiments were performed to study the thermal performance of this LED device. The results show that the LED device with higher filling ratio is better when the input power is 1.0 W; with the increase of input power, the optimum filling ratio changes from 30% to 48%, and the time reaching stable state is reduced; when the input power is equal to 2.5 W, only the LED device with filling ratio of 48% can work normally. So integrating MHP into high-power LED device can implement the effective control of junction temperature.

Zinc oxide (ZnO) microrod arrays were synthesized on Si substrate by a vapor phase transport (VPT) method in a tube furnace. The obtained ZnO microrods are characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The photoluminescence (PL) measurement indicates that the ZnO microrods have a strong ultraviolet (UV) emission centered at ~391 nm and a defect-related emission centered at ~530 nm. After the microrods were coated with graphene oxide (GO), the PL intensity of the hybrid microstructure is quenched compared with that of the bare one at the same excitation condition, and the PL intensity changes with the concentration of the GO. The fluorescence quenching mechanism is also discussed in this work.

Indium oxide (In₂O₃) films were prepared on Al₂O₃(0001) substrates at 700 °C by metal-organic chemical vapor deposition (MOCVD). Then the samples were annealed at 800 °C, 900 °C and 1 000 °C, respectively. The X-ray diffraction (XRD) analysis reveals that the samples were polycrystalline films before and after annealing treatment. Triangle or quadrangle grains can be observed, and the corner angle of the grains becomes smooth after annealing. The highest Hall mobility is obtained for the sample annealed at 900 °C with the value about 24.74 cm²·V^-1·s^-1. The average transmittance for the films in the visible range is over 90%. The optical band gaps of the samples are about 3.73 eV, 3.71 eV, 3.70 eV and 3.69 eV corresponding to the In2O3 films deposited at 700 °C and annealed at 800 °C, 900 °C and 1 000 °C, respectively.

A kind of functional graphene thin film metamaterial on a metal-plane separated by a thick dielectric layer is designed for terahertz (THz) absorbers. We investigate the properties of the graphene metamaterial with different interlayers in the 0–3 THz range. The simulation results show that the absorption rate reaches up to 99.9% at the frequency of 1.917 THz. Changing the period to 80 μm×18 μm can get a narrow-band high quality factor (Q) absorber. We present a novel theoretical interpretation based on the standing wave field theory, which shows that the coherent superposition of incident and reflection rays produces standing waves, and the field energy is localized inside the thick spacers and dissipates through the metal-planes.

We experimentally demonstrate an efficient enhancement of luminescence from two-dimensional (2D) hexagonal photonic crystal (PC) airbridge double-heterostructure microcavity with Er-doped silicon (Si) as light emitters on siliconon- insulator (SOI) wafer at room temperature. A single sharp resonant peak at 1 529.6 nm dominates the photoluminescence (PL) spectrum with the pumping power of 12.5 mW. The obvious red shift and the degraded quality factor (Q-factor) of resonant peak appear with the pumping power increasing, and the maximum measured Q-factor of 4 905 is achieved at the pumping power of 1.5 mW. The resonant peak is observed to shift depending on the structural parameters of PC, which indicates a possible method to control the wavelength of enhanced luminescence for Si-based light emitters based on PC microcavity.

The photoluminescence (PL) properties of porous silicon microcavities (PSMs) in the visible range at room temperature are improved by doping the rare earth ytterbium (Yb) into PSMs prepared by the electrochemical etching method. It is observed that PSMs doped with the rare earth have an emission band around 630 nm. Compared with the single- layer porous silicon (PS) film, the PSMs doped with Yb have narrower and stronger PL spectrum.

The microstructure and magnetic properties of Mn-doped ZnO films with various Mn contents, synthesized by magnetron sputtering at room temperature, are investigated in detail. X-ray diffraction (XRD) measurement results suggest that the doped Mn ions occupy the Zn sites successfully and do not change the crystal structure of the ZnO films. However, the microstructure of the Mn-doped ZnO films apparently changes with increasing the Mn concentration. Arrays of well-aligned nanoscale rods are found in the Mn-doped ZnO films with moderate Mn concentrations. Magnetic measurement results indicate that the ZnO films doped with moderate Mn concentration are ferromagnetic at room temperature. The possible origin of the ferromagnetism in our samples is also explored in detail.

The Ho³⁺/Pr³⁺co-doped NaYF₄single crystals with various Pr³⁺concentrations and constant Ho³⁺molar percentage of ~1% were grown by an improved Bridgman method. Compared with the Ho³⁺single-doped NaYF₄crystal, an obviously enhanced emission band at 2.85 μm is observed under 640 nm excitation. The Judd-Ofelt strength parameters (Ω₂, Ω₄and Ω₆) are calculated, the radiative transition probabilities (A), the fluorescence branching ratios (β) and the radiative lifetime (τrad) are obtained in the meantime. The energy transfer from Pr³⁺to Ho³⁺and the optimum fluorescence emission of Ho³⁺ions around 2.85 μm are investigated. Moreover, the maximum emission cross section of above samples at 2.85 μm is calculated to be 0.72×10^-20cm²for the NaYF₄single crystal with Ho³⁺molar percentage of 1% and Pr³⁺molar percentage of 0.5% according to the measured absorption spectrum. All results suggest that the Ho³⁺/Pr³⁺co-doped NaYF₄single crystal may have potential applications in mid-infrared lasers.

According to the requirements of the increasing development for optical transmission systems, a novel construction method of quasi-cyclic low-density parity-check (QC-LDPC) codes based on the subgroup of the finite field multiplicative group is proposed. Furthermore, this construction method can effectively avoid the girth-4 phenomena and has the advantages such as simpler construction, easier implementation, lower encoding/decoding complexity, better girth properties and more flexible adjustment for the code length and code rate. The simulation results show that the error correction performance of the QC-LDPC(3 780,3 540) code with the code rate of 93.7% constructed by this proposed method is excellent, its net coding gain is respectively 0.3 dB, 0.55 dB, 1.4 dB and 1.98 dB higher than those of the QC-LDPC(5 334,4 962) code constructed by the method based on the inverse element characteristics in the finite field multiplicative group, the SCG-LDPC(3 969,3 720) code constructed by the systematically constructed Gallager (SCG) random construction method, the LDPC(32 640,30 592) code in ITU-T G.975.1 and the classic RS(255,239) code which is widely used in optical transmission systems in ITU-T G.975 at the bit error rate (BER) of 10-7. Therefore, the constructed QC-LDPC(3 780,3 540) code is more suitable for optical transmission systems.

An offset quadrature amplitude modulation orthogonal frequency-division multiplexing (OQAM-OFDM) passive optical network (PON) architecture with direct detection is brought up to increase the transmission range and improve the system performance. In optical line terminal (OLT), OQAM-OFDM signals at 40 Gbit/s are transmitted as downstream. At each optical network unit (ONU), the optical OQAM-OFDM signal is demodulated with direct detection. The results show that the transmission distance can exceed 20 km with negligible penalty under the experimental conditions.

A location-adaptive transmission scheme for indoor visible light communication (VLC) system is proposed in this paper. In this scheme, the symbol error rate (SER) of less than 10^-3should be guaranteed. And the scheme is realized by the variable multilevel pulse-position modulation (MPPM), where the transmitters adaptively adjust the number of time slots n in the MPPM symbol according to the position of the receiver. The purpose of our scheme is to achieve the best data rate in the indoor different locations. The results show that the location-adaptive transmission scheme based on the variable MPPM is superior in the indoor VLC system.

In this paper, we propose a roll angle measurement method with a large range based on the photoelectronic autocollimator. According to the corresponding relationship between the rotation position of the measured shaft and the spot position on the circular trajectory, the roll angle is calculated quickly and conveniently using a simple algorithm. Only a mirror, a coupler and a fine shaft are contained in the measurement system besides the photoelectronic autocollimator. Aiming at the terrible measurement error induced by the axis wobbly error, two measurement schemes are proposed, which are linking the fine precision shaft to the measured shaft for reducing the axis wobbly error and using the segment measurement to enlarge the radius of the circular trajectory. The experimental results show that the measurement error is decreased by ±0.38°. The roll angle error of the mechanism is ±0.14°, and the measurement precision is about ±2′. The proposed method can be widely used in the engineering fields.

A new depth resampling for multi-view coding is proposed in this paper. At first, the depth video is downsampled by median filtering before encoding. After decoding, the classified edges, including credible edge and probable edge from the aligned texture image and the depth image, are interpolated by the selected diagonal pair, whose intensity difference is the minimum among four diagonal pairs around edge pixel. According to different category of edge, the intensity difference is measured by either real depth or percentage depth without any parameter setting. Finally, the resampled depth video and the decoded full-resolution texture video are synthesized into virtual views for the performance evaluation. Experiments on the platform of multi-view high efficiency video coding (HEVC) demonstrate that the proposed method is superior to the contrastive methods in terms of visual quality and rate distortion (RD) performance.

Using two-step growth method and buffer layer annealing treatment, the double heterojunction structures of In_0.82Ga_0.18epilayer capped with InAs_0.6P_0.4layer were prepared on InP substrate by low pressure metal organic chemical vapor deposition (LP-MOCVD). Based on the high quality In_0.82Ga_0.18As structures, the In_0.82Ga_0.18PIN photodetector with cut-off wavelength of 2.56 μm at room temperature was fabricated by planar semiconductor technology, and the device performance was investigated in detail. The typical dark current at the reverse bias VR=10 mV and the resistance area product R₀A are 5.02 μA and 0.29 Ω·cm²at 296 K and 5.98 nA and 405.2 Ω·cm²at 116 K, respectively. The calculated peak detectivities of the In_0.82Ga_0.18As photodetector are 1.21×10¹⁰cm·Hz^1/2/W at 296 K and 4.39×10¹¹cm·Hz^1/2/W at 116 K respectively, where the quantum efficiency η=0.7 at peak wavelength is supposed. The results show that the detection performance of In_0.82Ga_0.18As prepared by two-step growth method can be improved greatly.