Haihua Xu

Photosynthetic and yield responses of an old and a modern winter wheat cultivars to short-term ozone exposure

In order to study the responses of winter wheat cultivars released in different years to short-term high O3 exposure, an old cultivar (‘Nongda 311’, released in 1960s) and a modern one (‘Yannong 19’, released in 1990s) were treated with an O3 exposure (145 ± 12 mm3 m−3, 4 h d−1 for 3 d) shortly after anthesis stage (> 50 % main stems blossomed). During the O3 exposure, light-saturated photosynthetic rate (PN) and stomatal conductance (gs) of both cultivars decreased considerably. Elevated O3 did not decrease dark-adapted maximum photochemical efficiency, but induced significant reduction in actual photochemical efficiency and thereby considerably increase in non-photochemical quenching. PN, gs of the modern cultivar ‘Yannong 19’ decreased more than the older one ‘Nongda 311’, indicating the former exhibited higher sensitivity to O3 than the latter. After O3 exposure, PN, gs and chlorophyll (Chl) content in flag leaf decreased more quickly than control, indicating induction of faster premature leaf senescence. As a result, the short-term O3 exposure caused substantial yield loss, with larger reduction in ‘Yannong 19’ (−19.2 %) than in ‘Nongda 311’ (−8.4 %). Our results indicated that high O3 exposure at grain filling stage would have greater negative impacts on the high yielding modern cultivar relative to the old one with lower yield.

Photosynthetic characteristics of diploid honeysuckle ( Lonicera japonica Thunb.) and its autotetraploid cultivar subjected to elevated ozone exposure

In order to investigate the effect of chromosome doubling on ozone tolerance, we compared the physiological responses of a diploid honeysuckle (Lonicera japonica Thunb.) and its autotetraploid cultivar to elevated ozone (O3) exposure (70 ng g−1, 7 h d−1 for 31 d). Net photosynthetic rate (PN) of both cultivars were drastically (P<0.01) impaired by O3. Although there were significantly positive correlation between PN and stomatal conductance (gs) in both cultivars under each treatment, the decreased gs in O3 might be the result rather than the cause of decreased PN as indicated by stable or increasing the ratio of intercellular to ambient CO2 concentration(Ci/Ca). PN under saturating CO2 concentration (PNsat) and carboxylation efficiency (CE) significantly decreased under O3 fumigation, which indicated the Calvin cycle was impaired. O3 also inhibited the maximum efficiency of photosystem II (PSII) photochemistry in the dark-adapted state (Fv/Fm), actual quantum yield of PSII photochemistry (ΦPSII), electron transport rate (ETR), photochemical quenching coefficient (qP), non-photochemical quenching (NPQ), the maximum in vivo rate of Rubisco carboxylation (Vcmax) and the maximal photosynthetic electron transport rate (Jmax) which demonstrated that the decrease in PN of the honeysuckle exposed to elevated O3 was probably not only due to impairment of Calvin cycle but also with respect to the light-harvesting and electron transport processes. Compared to the diploid, the tetraploid had higher relative loss in transpiration rate (E), (gs), (PNsat), Vcmax and Jmax. This result indicated that the Calvin cycle and electron transport in tetraploid was damaged more seriously than in diploid. A barely nonsignificant (P=0.086) interaction between O3 and cultivar on PN suggested a higher photosynthetic sensitivity of the tetraploid cultivar.

Silicon optical modulator with integrated grating couplers based on 0.18-mu m complementary metal oxide semiconductor technology

national basic research program of china [2006cb302803]; national natural science foundation of china [60877036]; state key laboratory of advanced optical communication systems and networks, china [2008sh02]; institute of semiconductors, chinese academy of sciences [iscas2008t10]

A Compact and Highly Efficient Silicon-Based Asymmetric Mach-Zehnder Modulator with Broadband Spectral Operation

An asymmetric Mach?Zehnder electro-optic modulator is demonstrated by using a silicon-based p-i-n diode embedded in compact 200 ?m long phase shifters. The measured figure of merit V?L = 0.23 V ?mm shows highly efficient modulation by the device, and an open eye-diagram at 3.2 Gbit/s confirmed its fast electro-optic response. Integrated with the grating coupler, the device exhibits a broad operational wavelength range of 70 nm with a uniform 18 dB extinction ratio covering the C-band and part L-band of optical communication.

Sub-nanosecond silicon-on-insulator optical micro-ring switch with low crosstalk

We demonstrate a sub-nanosecond electro-optical switch with low crosstalk in a silicon-on-insulator (SOI) dual-coupled micro-ring embedded with p-i-n diodes. A crosstalk of -23 dB is obtained in the 20-mu m-radius micro-ring with the well-designing asymmetric dual-coupling structure. By optimizations of the doping profiles and the fabrication processes, the sub-nanosecond switch-on/off time of < 400 ps is finally realized under an electrical pre-emphasized driving signal. This compact and fast-response micro-ring switch, which can be fabricated by complementary metal oxide semiconductor (CMOS) compatible technologies, have enormous potential in optical interconnects of multicore networks-on-chip.

A Novel Blue Thin Film Electroluminescent Phosphor Gd3Ga5O12:Ag

A new blue thin film electroluminescence (TFEL) phosphor Gd3Ga5O12:Ag is prepared by electron beam evaporation. Photoluminescence and Electroluminescence of Gd3Ga5O12:Ag film were investigated. The luminance of TFEL device excited by an alternating-current sinusoidal voltage with frequency of 1000 Hz is about 2 cd/m2.

High-speed silicon-based microring modulators and electro-optical switches integrated with grating couplers

We demonstrate high-speed silicon-based microring modulators and electro-optical switches which are integrated with grating couplers. Wafer-level measurements are set up for the devices characterizations without wafer cleaving and facet polishing. 10 Gbit/s NRZ modulation is realized under pre-emphasis driving signals. Switch on / off time of 300 / 380ps are demonstrated in the asymmetrical 1×2 microring switch with an add-drop crosstalk of -23dB.

Design, fabrication and characterization of cascaded SOI rib waveguide microring resonators

We demonstrate a three-stage double channel cascaded microrings integrated with grating couplers based on SOI rib waveguide. The resonant frequencies were well matched at the drop-port and still splitting at the through-port which was considered to be due to fabrication variations. Flat-top and broadened bandwidth were achieved in the three-stage microring device.

Hybrid-integrated silicon photonic circuit with an InGaAs photodetetor

Flip-chip bonding and grating-assisted coupling techniques are proposed to integrate silicon photonic circuit with an InGaAs photodetector. Coupler-to-photodetector coupling efficiency of ∼ 4 dB and data transmission of 1 Gbps are demonstrated.

Research on SOI-based micro-resonator devices

SOI (silicon-on-insulator)-based micro-resonator is the key building block of silicon photonics, which is considered as a promising solution to alleviate the bandwidth bottleneck of on-chip interconnects. Silicon-based sub-micron waveguide, microring and microdisk devices are investigated in Institute of Semiconductors, Chinese Academy of Sciences. The main progress in recent years is presented in this talk, such as high Q factor single mode microdisk filters, compact thirdorder microring filters with the through/drop port extinctions to be ~ 30/40 dB, fast microring electro-optical switches with the switch time of < 400 ps and crosstalk < -23 dB, and > 10 Gbit/s high speed microring modulators.