One-dimensional, diluted magnetic semiconductor nanofibers have attracted increasing attention for their unique magnetic properties, large specific surface area, and high porosity. These qualities lead to excellent performance in magneto-optical devices, magnetic resonance imaging, ferrofluids and magnetic separation. The purpose of this study is to fabricate P-type one dimensional CuAlO2-based diluted magnetic semiconductor nanofibers. First, we fabricated CuAl0.95Co0.05O2 nanofibers with an average diameter of 1 μm with the electrospinning method. The annealed nanofibers were thermally treated at a temperature of 1 100℃ and then shrunk to a diameter of about 650 nm. We used X-ray diffraction measurements and Raman spectra to confirm that the CUAl0.95CO0.05O2 nanofihers had a single impurity free delafossite phase. The X-ray photoelectron spectroscopy analysis indicates that Co was present in the ＋2 oxidation state, resulting in an room temperature ferromagnetism in the CHAl0.95Co0.05O2 fiber. This contrststs with nonmagnetism in pristine CuAlO2 fiber. The coercivity （Hc） value of 65.26 Oe and approximate saturation magnetization （Ms） of 0.012 emu/g demonstrate good evidence of ferromagnetism at room temperature for CuAl0.95Co0.05O2 nanofibers.
Structure and design are proposed for a kind of novel polymer Mach-Zehnder electro-optic(EO)switch using side-coupled M series-cascaded EO microrings.Formulations are proposed to analyze its switching characteristics.The dependences of the device’s performances on M are thoroughly analyzed and concluded.As the increase of M from 2 to 10,the switching voltages for the 9 devices are as low as 0.84 V,0.82 V,0.52 V,0.5 V,0.37 V,0.36 V,0.29 V,0.28 V and 0.24 V,respectively;whereas the crosstalks under bar state are within-20.79--6.53 d B and those under cross state are within-20.36--5.29 d B.The analysis results indicate that a smaller M is preferred for dropping the insertion loss and crosstalk,and a larger M should be selected to increase the optical bandwidth and minimize the switching energy.Generally,due to low switching voltage,the proposed device shows potential applications in optical networks-on-chip.
Based on wide-band infrared(IR) light source and dual-channel pyroelectric detector with detection channel of 4.66 μm and reference channel of 3.95 μm,a differential mid-infrared(MIR) carbon monoxide(CO) detector is designed and implemented.In order to reduce the detection limit and improve the detection sensitivity,an open spherical mirror chamber is designed and fabricated according to the divergence angle of the light source.The CO detection system is established using the welded and debugged detection circuits,a series of CO gases with different concentrations are prepared,and gas concentration calibration experiment is carried out.Experimental results indicate that after the amplifying circuit,the signal-to-noise ratios(SNRs) of the two channels are 17.58 dB and 18.46 dB,respectively,and the detection error of this system is less than 9% in 0%-4% measuring range.The detection sensitivity in the low concentration range is approximately 0.05%.6 h measurement on the 0 ppm sample gas shows that the fluctuation range is about ±0.02%,and the measurement standard deviation is about 0.89%.
Ternary In-rich AlxIn1-x N films were successfully grown on Si （111） and （0001） sapphire substrates by radio-frequency magnetron sputtering on a relatively Al-rich AlxIn1-x N layer after AlN buffer. X-ray diffraction （XRD） patterns of the films indicate highly c axis-oriented wurtzite structure and the indium content of about 0.76 has been evaluated according to the Vegard＇s law. An Al-rich AlxIn1-xN transition layer was formed between the ultimate In-rich AlxIn1-x N film and the AlN buffer, which served as a further buffer to alleviate mismatch. X-ray photoelectron spectroscopy （XPS） depth profiling analyses confirm the alternative of indium and aluminum composition and the unavoidable oxygen impurities from surface to bulk. Owing to high indium content, obvious E2u and InN-like Al （LO） phonon model accompanying with slight A1N-like A1 （LO） phonon model are observed. Hall effect measurements demonstrate n-type electrical conductivity in these alloys with carrier concentrations n=1019 cm-3. The strain in In-rich AlxIn1-x N films can be significantly reduced by introducing an Al-rich interlayer, facilitating the improvement of film quality for diverse device applications.
By using poled-polymer/silicon slot waveguides in the active region and the Pockels effect of the poled-polymer,we propose a kind of Mach-Zehnder interferometer(MZI) electro-optic(EO) switch operated at 1 550 nm.Structural parameters are optimized for realizing normal switching function.Dependencies of switching characteristics on the slot waveguide parameters are investigated.For the silicon strip with dimension of 170 nm×300 nm,as the slot width varies from 50 nm to 100 nm,the switching voltage can be as low as 1.0 V with active region length of only 0.17–0.35 mm,and the length of the whole device is only about 770–950 μm.The voltage-length product of this switching structure is only 0.17–0.35 V·mm,and it is at least 19–40 times smaller than that of the traditional polymer MZI EO switch,which is 6.69 V·mm.Compared with our previously reported MZI EO switches,this switch exhibits some superior characteristics,including low switching voltage,compact device size and small wavelength dependency.
