We fabricate a series of periodic arrays of subwavelength square and rectangular air holes on gold films, and measure the transmission spectra of these metallic nanostructures. By changing some geometrical and physica...We fabricate a series of periodic arrays of subwavelength square and rectangular air holes on gold films, and measure the transmission spectra of these metallic nanostructures. By changing some geometrical and physical parameters, such as array period, air hole size and shape, and the incident light polarization, we verify that both global surface plasmon resonance and localized waveguide mode resonance are influential on enhancing the transmission of light through nanostructured metal films. These two resonances induce different behaviours of transmission peak shift. The transmission through the rectangular air-hole structures exhibits an obvious polarization effect dependent on the morphology. Numerical simulations are also made by a plane-wave transfer-matrix method and in good consistency with the experimental results.展开更多
We present a grating model of two-dimensional (2D) rigorous coupled wave analysis (RCWA) to study top diffraction gratings on light-emitting diodes (LEDs). We compare the integrated-transmission of the non-grati...We present a grating model of two-dimensional (2D) rigorous coupled wave analysis (RCWA) to study top diffraction gratings on light-emitting diodes (LEDs). We compare the integrated-transmission of the non-grating, rectangular-grating, and triangular-grating cases for the same grating period of 6 μm, and show that the triangular grating has the best performance. For the triangular grating with 6-μm period, the LED achieves the highest light transmission at 6-μm grating bottom width and 2.9-μm grating depth. Compared with the non-grating case, the optimized light transmission improvement is about 74.6%. The simulation agrees with the experimental data of the thin polymer grating encapsulated flip-chip (FC) GaN-based LEDs for the light extraction improvement.展开更多
In this paper, we proposed and experimentally demonstrated a route-asymmetrical light transmission scheme based on the thermal radiative effect, which means that forward and backward propagations of an optical device ...In this paper, we proposed and experimentally demonstrated a route-asymmetrical light transmission scheme based on the thermal radiative effect, which means that forward and backward propagations of an optical device have different transmittances provided they are not present simultaneously. Employing a fiber-chipfiber optomechanical system, our scheme has successfully achieved a broad operation bandwidth of at least 24 nm and an ultra-high route-asymmetrical transmission ratio (RATR) up to 63 dB. The route-asymmetrical device has been demonstrated effectively with not only the continuous-wave (CW) light but also 10 Gbit/s on-off-keying (OOK) digital signals. Above mentioned unique features can be mostly attributed to the significant characteristics of the thermal radiative effect, which could cause a fiber displacement up to tens of microns. The powerful and significant thermal radiative effect opens up a new opportunity and method for route-asymmetrical light transmission. Moreover, this research may have important applications in all-optical systems, such as the optical limiters and ultra-low loss switches.展开更多
Transmission of light through model human epidermal samples is investigated at four different wavelengths and at varying ambient humidity. Light from light emitting diodes (LEDs) is used for transmission measurements ...Transmission of light through model human epidermal samples is investigated at four different wavelengths and at varying ambient humidity. Light from light emitting diodes (LEDs) is used for transmission measurements through the samples at a UVA wavelength of 365 nm, and visible wavelengths of 460 nm, 500 nm, and 595 nm. Ambient air-humidity is varied between 20% and 100%. Results show that for high ambient humidity, near 100%, transmission of light through the epidermis is higher than at low ambient humidity, 60% or lower. These results are explained with a simple model of epidermis as a turbid medium and the effect of adsorbed water in reducing light-scattering by refractive-index-matching. Biological implications of increased light-transmission through epidermis at high ambient humidity are discussed.展开更多
Two kinds of subwavelength hole arrays in metallic films are designed to verify the import, ant role of the periodicity in enhanced transmission of light. The measured optical spectra show that the quasiperiodic hole ...Two kinds of subwavelength hole arrays in metallic films are designed to verify the import, ant role of the periodicity in enhanced transmission of light. The measured optical spectra show that the quasiperiodic hole arrays exhibit an enhanced transmission peak centred at 707nm with a transmission intensity of about 20%, while no plasmon resonance peak is found for the amorphous hole arrays. When the hole diameter decreases in the quasiperiodic structure, the position of the transmission peak shifts slightly, and the transmittance drops, These phenomena indicate the important role of the long-range structural order (particularly the periodicity) in assisting the coupling of incident light wave with the surface plasmon modes of the metallic structures.展开更多
Short basal internodes are important for lodging resistance of rice(Oryza sativa L.).Several canopy indices affect the elongation of basal internodes,but uncertainty as to the key factors determining elongation of bas...Short basal internodes are important for lodging resistance of rice(Oryza sativa L.).Several canopy indices affect the elongation of basal internodes,but uncertainty as to the key factors determining elongation of basal internodes persists.The objectives of this study were(1)to identify key factors affecting the elongation of basal internodes and(2)to establish a quantitative relationship between basal internode length and canopy indices.An inbred rice cultivar,Yinjingruanzhan,was grown in two split-plot field experiments with three N rates(0,75,and 150 kg N ha−1 in early season and 0,90,and 180 kg N ha−1 in late season)as main plots,three seedling densities(16.7,75.0,and 187.5 seedlings m−2)as subplots,and three replications in the 2015 early and late seasons in Guangzhou,China.Light intensity at base of canopy(Lb),light quality as determined from red/far-red light ratio(R/FR),light transmission ratio(LTR),leaf area index(LAI),leaf N concentration(NLV)and final length of second internode(counted from soil surface upward)(FIL)were recorded.Higher N rate and seedling density resulted in significantly longer FIL.FIL was negatively correlated with Lb,LTR,and R/FR(P<0.01)and positively correlated with LAI(P<0.01),but not correlated with NLV(P>0.05).Stepwise linear regression analysis showed that FIL was strongly associated with Lb and LAI(R2=0.82).Heavy N application to pot-grown rice at the beginning of first internode elongation did not change FIL.We conclude that FIL is determined mainly by Lb and LAI at jointing stage.NLV has no direct effect on the elongation of basal internodes.N application indirectly affects FIL by changing LAI and light conditions in the rice canopy.Reducing LAI and improving canopy light transmission at jointing stage can shorten the basal internodes and increase the lodging resistance of rice.展开更多
Realizing high-fidelity optical information transmission through a scattering medium is of vital importance in both science and applications,such as short-range fiber communication and optical encryption.Theoretically...Realizing high-fidelity optical information transmission through a scattering medium is of vital importance in both science and applications,such as short-range fiber communication and optical encryption.Theoretically,an input wavefront can be reconstructed by inverting the transmission matrix of the scattering medium.However,this deterministic method for retrieving light field information encoded in the wavefront has not yet been experimentally demonstrated.Herein,we demonstrate light field information transmission through different scattering media with near-unity fidelity.Multi-dimensional optical information can be delivered through either a multimode fiber or a ground glass without relying on any averaging or approximation,where their Pearson correlation coefficients can be up to 99%.展开更多
3-Ethynyl-4-(trimethylsilyl)thiophene (1a) and 3-ethynyl-4-bromothiophene (1b) selectively undergo acetylene polymerizations in the presence of the MoCl5- and WCl6-Ph3SiH catalysts to give soluble, high-molecular-weig...3-Ethynyl-4-(trimethylsilyl)thiophene (1a) and 3-ethynyl-4-bromothiophene (1b) selectively undergo acetylene polymerizations in the presence of the MoCl5- and WCl6-Ph3SiH catalysts to give soluble, high-molecular-weight poly(thienylacetylenes) (2) (M-w up to 602000) in high yields (up to 100%). Light transmission spectra of THF solutions of 2 continuously red-shift with increasing concentration. The concentratochromism shows a logarithmic concentration dependence; that is, the optical transitions of 2 are predictably tunable by simply changing their concentrations.展开更多
Nano-sized CeO_2 powders were synthesized by homogeneous precipitation method in alcohol-water solution with HMT as precipitator and the nano-particles were characterized by TEM and BET. The process parameters which i...Nano-sized CeO_2 powders were synthesized by homogeneous precipitation method in alcohol-water solution with HMT as precipitator and the nano-particles were characterized by TEM and BET. The process parameters which influenced the sizes and agglomeration of nanometer CeO_2 powders were studied and the influence mechanism was discussed. The results show that the average size of the particles prepared by the above method with the best process parameters is about 8 nm, and the particles are of smaller size and better dispersion than those obtained from the ordinary powders synthesized by homogeneous precipitation in water solution.展开更多
Light transmission spectra of THF solutions of poly (C-60-co-methyl methacrylate)s and poly(C-60-co-styrene)s continuously red-shift with increasing concentration. Formation of fullerene nanoclusters may be responsibl...Light transmission spectra of THF solutions of poly (C-60-co-methyl methacrylate)s and poly(C-60-co-styrene)s continuously red-shift with increasing concentration. Formation of fullerene nanoclusters may be responsible for the unusual spectral shift, with concentration. It has long been scientists' dream to ''tune'' material's properties by simple means, and the C-60-containing polymers represent such a group of novel materials whose optical properties are predictably and reversibly tunable by a simple change in concentration.展开更多
The existing research on shrinkage of the injection molded plastic part mainly focuses on various shrinkage ratios of the part dimensions,and the relevant experimental studies belong to mere dimension measurement afte...The existing research on shrinkage of the injection molded plastic part mainly focuses on various shrinkage ratios of the part dimensions,and the relevant experimental studies belong to mere dimension measurement after demoulding.Obviously,measuring after the plastic part is demoulded from the cavity can not offer shrinkage displacements of points on the plastic part.However,shrinkage displacements of points on an injection molded plastic part are essential for exposing the inner relation among shrinkage ratios of various dimensions of the part.So visualization of the in-mold plastic part which can indicate the location relationship between the part and the cavity is needed.In this paper,a visual injection mold was fabricated by adopting the half mold structure and light transmission manner.With the visual mold,in-mold shrinkage images of injection molded plastic parts were photographed after the plastic part stayed in the injection mold for 24 h.By means of digital image processing of the in-mold shrinkage images,the experimental data of shrinkage displacements of points on injection molded parts were researched.From the experimental data,it is found that shrinkage directions of points on an injection molded part are related with both positions of the gate and of the part centroid,and either the gate or the centroid will exert more influence on the shrinkage direction of some point which is closer.Furthermore,some point at the later filled area has more shrinkage distance than the point at the earlier filled area.Combination of shrinkage directions and shrinkage distances of points on an injection molded part determine shrinkage ratios for various dimensions of the part,and shrinkage directions are more influential to shrinkage ratios of dimensions.This experimental research of shrinkage displacements offers a unique approach to understand the shrinkage principles of injection molded parts.展开更多
We propose and numerically investigate an efficient transmission-mode metasurface that consists of quasicontinuous trapezoid-shaped crystalline silicon nanoantennas on a quartz substrate. This metasurface provides a l...We propose and numerically investigate an efficient transmission-mode metasurface that consists of quasicontinuous trapezoid-shaped crystalline silicon nanoantennas on a quartz substrate. This metasurface provides a linear phase gradient and realizes both full 2π phase shift and high transmission efficiency in the operating wavelength range from 740 to 780 nm. At the central wavelength around 751 nm, the total transmission efficiency is up to 88.0% and the section of the desired anomalous refraction is 80.4%. The anomalous refraction angle is 29.62°, and larger refraction angle can be achieved by changing the period of the super cell. We demonstrate a refraction angle as large as 38.59°, and the anomalous transmission efficiency reaches 76.6% at wavelength of 741 nm. It is worth mentioning that the structure is much simpler than conventional metasurfaces based on arrays of discrete nanoantennas. Our research may pave the way for designing efficient all-dielectric phase-gradient metasurfaces and applying them in integrated optical devices for wavefront control.展开更多
We present a high-speed visible light communication (VLC) link that uses a commercially available phos- phorescent white light-emitting diode (LED). Such devices have few megahertz bandwidth due to the slow respon...We present a high-speed visible light communication (VLC) link that uses a commercially available phos- phorescent white light-emitting diode (LED). Such devices have few megahertz bandwidth due to the slow response of phosphorescent component, which severely limit the transmission data rate of VLC system. We propose a simple pre-emphasis circuit. With blue-filtering and the pre-emphasis circuit, the bandwidth of VLC system can be enhanced from 3 to 77.6 MHz, which allows non-return-to-zero on-off-keying (NRZ- OOK) data transmission up to 200 Mb/s with the bit error ratio of 5.3 × 10-7 which is below 10-6. The VLC link operates at the room illumination level of -1000 lx at 1.1 m range using a single 1 W white LED.展开更多
Stable picosecond soliton transmission is demonstrated numerically by use of concatenated gain-distributed nonlinear amplifying fiber loop mirrors (NALMs). We show that, as compared with previous soliton transmissio...Stable picosecond soliton transmission is demonstrated numerically by use of concatenated gain-distributed nonlinear amplifying fiber loop mirrors (NALMs). We show that, as compared with previous soliton transmission schemes that use conventional NALMs or nonlinear optical loop mirror (NOLM) and amplifier combinations, the present scheme permits significant increase of loop-mirror (amplifier) spacing. The broad switching window of the present device and the high quality pulses switched from it provide a reasonable stability range for soliton transmission. Soliton-soliton interactions can be reduced efficiently by using lowly dispersive fibers.展开更多
We report experimental results on enhanced light transmission through double-layered (Ag/Au) metallic hole arrays within a skin-depth. Zero-order transmission spectrums are characterized as a function of Ag film's ...We report experimental results on enhanced light transmission through double-layered (Ag/Au) metallic hole arrays within a skin-depth. Zero-order transmission spectrums are characterized as a function of Ag film's thickness, which extends from 5/15, 5/6 to approximately 5, where 5 is a skin-depth. In contrast with other reported results (Refs. [11 - 13]) in single-layered metallic hole arrays, our experimental results show much more dramatic properties of transmission process dependent on sub-5 thickness. It is shown that there is no negligible transmission enhancement at 5/15. At 5/6, much higher transmission efficiency can be achieved. With film's thickness being close to 5, the transmission efficiency declines contrarily. Simultaneously, the corresponding resonant peak also slightly moves toward the shorter wavelength. It is proposed that the coupling of surface plasmon polaritons (SPPs) at Ag/Au interface within 5 is involved in the process.展开更多
A new shaping method for producing nanosecond pulses with specific shape is introduced. When a Gaussian laser pulse passes through an electro-optic deflector, it. has been scanned as a line on the focal plane accordin...A new shaping method for producing nanosecond pulses with specific shape is introduced. When a Gaussian laser pulse passes through an electro-optic deflector, it. has been scanned as a line on the focal plane according to time precedence. Through controlling the intensity of transmitted light on each pixol of the liquid crystal spatial light modulator (LCSLM), various complicated pulses can be easily produced. Using this method, various specific shaped pulses with pulse duration varying from 750 ps to 5 ns are achieved.展开更多
We demonstrate the theory of chromatic dispersion (CD)-induced constellation rotation (CR) in a radio-over-fiber (ROF) link and a method for compensation. We also propose a 60 GHz full-duplex ROF system with vec...We demonstrate the theory of chromatic dispersion (CD)-induced constellation rotation (CR) in a radio-over-fiber (ROF) link and a method for compensation. We also propose a 60 GHz full-duplex ROF system with vector signal transmission including no CD effect. The evaluation of 5 Gb/s 16 quadrature amplitude modulation signal transmission shows that the CD-induced CR can be entirely overcome due to the proposed method which is simply implemented through an optical phase shifter. The proposed ROF schedule is not only applicable for V-band (57-64 GHz) but also fits for W-band (75-110 GHz), or any other bandwidth.展开更多
The operation of an ultra-narrow bandwidth optical filter based on the 5P3/2→5D3/2 excited-state transition in rubidium vapor is reported. The 5D3/2 state is excited by a circularly polarized pump beam at 780 nm from...The operation of an ultra-narrow bandwidth optical filter based on the 5P3/2→5D3/2 excited-state transition in rubidium vapor is reported. The 5D3/2 state is excited by a circularly polarized pump beam at 780 nm from a diode laser. The filter displays a single 398-MHz bandwidth at a peak transmission of 9.0%, which is narrower than the Doppler bandwidth. The dependence of peak transmission on the pump intensity and cell temperature is also given.展开更多
A new method for error detection using mode information of macroblocks (MBs) is proposed. For decodable inter MBs, inter residues are calculated by adding up absolute values of received residual pixels and intra com...A new method for error detection using mode information of macroblocks (MBs) is proposed. For decodable inter MBs, inter residues are calculated by adding up absolute values of received residual pixels and intra complexities are estimated by that of motion compensated reference blocks. If inter residues are larger than intra complexities by a predefined quantity, MBs are considered to be erroneous. For decodable intra MBs, the connective smoothness of the current MB with correctly decoded neighboring MBs is tested to find erroneous MBs. Combined with error concealment, the new method improves the quality of reconstructed images by about 0.5-1 dB in peak signal-noise ratio (PSNR).展开更多
We present a novel method for providing broadcast signal transmission in a wavelength division multiplexing passive optical network (WDM-PON). An unmodulated optical carrier for downstream transmission and a pair of...We present a novel method for providing broadcast signal transmission in a wavelength division multiplexing passive optical network (WDM-PON). An unmodulated optical carrier for downstream transmission and a pair of unmodulated single-side band subcarriers are utilized for broadcast delivery and upstream transmission, respectively. System performance at 2.5-Gb/s down/upstream and 2.5-Gb/s broadcast transmission is also investigated.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10525419,60736041 and 10874238)the National Key Basic Research Special Foundation of China (Grant No. 2006CB302901)
文摘We fabricate a series of periodic arrays of subwavelength square and rectangular air holes on gold films, and measure the transmission spectra of these metallic nanostructures. By changing some geometrical and physical parameters, such as array period, air hole size and shape, and the incident light polarization, we verify that both global surface plasmon resonance and localized waveguide mode resonance are influential on enhancing the transmission of light through nanostructured metal films. These two resonances induce different behaviours of transmission peak shift. The transmission through the rectangular air-hole structures exhibits an obvious polarization effect dependent on the morphology. Numerical simulations are also made by a plane-wave transfer-matrix method and in good consistency with the experimental results.
基金the Department of the Navy,Office of Naval Research,under Award # N00014-07-1-1152,USAthe"Chunhui"Exchange Research Fellow 2008,Ministry of Education of China,the National"973"Program of China(No.2007CB307004)+1 种基金the National"863"Program of China(No.2006AA03A113)and the National Natural Science Foundation of China(No.60276032,60577030,and 60607003)
文摘We present a grating model of two-dimensional (2D) rigorous coupled wave analysis (RCWA) to study top diffraction gratings on light-emitting diodes (LEDs). We compare the integrated-transmission of the non-grating, rectangular-grating, and triangular-grating cases for the same grating period of 6 μm, and show that the triangular grating has the best performance. For the triangular grating with 6-μm period, the LED achieves the highest light transmission at 6-μm grating bottom width and 2.9-μm grating depth. Compared with the non-grating case, the optimized light transmission improvement is about 74.6%. The simulation agrees with the experimental data of the thin polymer grating encapsulated flip-chip (FC) GaN-based LEDs for the light extraction improvement.
基金Acknowledgements This work was partially supported by the National Basic Research Program of China (No. 2011CB301704), the Program for New Century Excellent Talents in Ministry of Education of China (No. NCET-11-0168), a Foundation for the Author of National Excellent Doctoral Dissertation of China (No. 201139), the National Natural Science Foundation of China (Grant Nos. 11174096 and 61475052), and the Opened Fund of the State Key Laboratory on Advanced Optical Communication System and Network (No. 2015GZKF03004).
文摘In this paper, we proposed and experimentally demonstrated a route-asymmetrical light transmission scheme based on the thermal radiative effect, which means that forward and backward propagations of an optical device have different transmittances provided they are not present simultaneously. Employing a fiber-chipfiber optomechanical system, our scheme has successfully achieved a broad operation bandwidth of at least 24 nm and an ultra-high route-asymmetrical transmission ratio (RATR) up to 63 dB. The route-asymmetrical device has been demonstrated effectively with not only the continuous-wave (CW) light but also 10 Gbit/s on-off-keying (OOK) digital signals. Above mentioned unique features can be mostly attributed to the significant characteristics of the thermal radiative effect, which could cause a fiber displacement up to tens of microns. The powerful and significant thermal radiative effect opens up a new opportunity and method for route-asymmetrical light transmission. Moreover, this research may have important applications in all-optical systems, such as the optical limiters and ultra-low loss switches.
文摘Transmission of light through model human epidermal samples is investigated at four different wavelengths and at varying ambient humidity. Light from light emitting diodes (LEDs) is used for transmission measurements through the samples at a UVA wavelength of 365 nm, and visible wavelengths of 460 nm, 500 nm, and 595 nm. Ambient air-humidity is varied between 20% and 100%. Results show that for high ambient humidity, near 100%, transmission of light through the epidermis is higher than at low ambient humidity, 60% or lower. These results are explained with a simple model of epidermis as a turbid medium and the effect of adsorbed water in reducing light-scattering by refractive-index-matching. Biological implications of increased light-transmission through epidermis at high ambient humidity are discussed.
文摘Two kinds of subwavelength hole arrays in metallic films are designed to verify the import, ant role of the periodicity in enhanced transmission of light. The measured optical spectra show that the quasiperiodic hole arrays exhibit an enhanced transmission peak centred at 707nm with a transmission intensity of about 20%, while no plasmon resonance peak is found for the amorphous hole arrays. When the hole diameter decreases in the quasiperiodic structure, the position of the transmission peak shifts slightly, and the transmittance drops, These phenomena indicate the important role of the long-range structural order (particularly the periodicity) in assisting the coupling of incident light wave with the surface plasmon modes of the metallic structures.
基金supported by the Natural Science Foundation of Guangdong Province,China(S2012020011043)the National High Technology Research and Development Program of China(2014AA10A605)+2 种基金the Special Fund for Agro-scientific Research in the Public Interest(201503106)Modern Agriculture Industry Technology System for Rice in Guangdong Province(2016LM1066,2017LM1066,2018LM1066)the Swiss Agency for Development and Cooperation through its funding of “Closing Rice Yield Gaps in Asia” Project(CORIGAP)
文摘Short basal internodes are important for lodging resistance of rice(Oryza sativa L.).Several canopy indices affect the elongation of basal internodes,but uncertainty as to the key factors determining elongation of basal internodes persists.The objectives of this study were(1)to identify key factors affecting the elongation of basal internodes and(2)to establish a quantitative relationship between basal internode length and canopy indices.An inbred rice cultivar,Yinjingruanzhan,was grown in two split-plot field experiments with three N rates(0,75,and 150 kg N ha−1 in early season and 0,90,and 180 kg N ha−1 in late season)as main plots,three seedling densities(16.7,75.0,and 187.5 seedlings m−2)as subplots,and three replications in the 2015 early and late seasons in Guangzhou,China.Light intensity at base of canopy(Lb),light quality as determined from red/far-red light ratio(R/FR),light transmission ratio(LTR),leaf area index(LAI),leaf N concentration(NLV)and final length of second internode(counted from soil surface upward)(FIL)were recorded.Higher N rate and seedling density resulted in significantly longer FIL.FIL was negatively correlated with Lb,LTR,and R/FR(P<0.01)and positively correlated with LAI(P<0.01),but not correlated with NLV(P>0.05).Stepwise linear regression analysis showed that FIL was strongly associated with Lb and LAI(R2=0.82).Heavy N application to pot-grown rice at the beginning of first internode elongation did not change FIL.We conclude that FIL is determined mainly by Lb and LAI at jointing stage.NLV has no direct effect on the elongation of basal internodes.N application indirectly affects FIL by changing LAI and light conditions in the rice canopy.Reducing LAI and improving canopy light transmission at jointing stage can shorten the basal internodes and increase the lodging resistance of rice.
基金supported by the National Key R&D Program of China(No.2018YFB1801001)the National Natural Science Foundation of China(No.62222505)the Guangdong Introducing Innovative Entrepreneurial Teams of the Pearl River Talent Recruitment Program(Nos.2019ZT08X340 and 2021ZT09X044).
文摘Realizing high-fidelity optical information transmission through a scattering medium is of vital importance in both science and applications,such as short-range fiber communication and optical encryption.Theoretically,an input wavefront can be reconstructed by inverting the transmission matrix of the scattering medium.However,this deterministic method for retrieving light field information encoded in the wavefront has not yet been experimentally demonstrated.Herein,we demonstrate light field information transmission through different scattering media with near-unity fidelity.Multi-dimensional optical information can be delivered through either a multimode fiber or a ground glass without relying on any averaging or approximation,where their Pearson correlation coefficients can be up to 99%.
基金This work was in part supported by the Earmarked Research Grants of the Hong Kong Research Grants Council (HKUST597/95P and CUHK77/931).
文摘3-Ethynyl-4-(trimethylsilyl)thiophene (1a) and 3-ethynyl-4-bromothiophene (1b) selectively undergo acetylene polymerizations in the presence of the MoCl5- and WCl6-Ph3SiH catalysts to give soluble, high-molecular-weight poly(thienylacetylenes) (2) (M-w up to 602000) in high yields (up to 100%). Light transmission spectra of THF solutions of 2 continuously red-shift with increasing concentration. The concentratochromism shows a logarithmic concentration dependence; that is, the optical transitions of 2 are predictably tunable by simply changing their concentrations.
文摘Nano-sized CeO_2 powders were synthesized by homogeneous precipitation method in alcohol-water solution with HMT as precipitator and the nano-particles were characterized by TEM and BET. The process parameters which influenced the sizes and agglomeration of nanometer CeO_2 powders were studied and the influence mechanism was discussed. The results show that the average size of the particles prepared by the above method with the best process parameters is about 8 nm, and the particles are of smaller size and better dispersion than those obtained from the ordinary powders synthesized by homogeneous precipitation in water solution.
基金This work was in part supported by a grant from the Hong Kong Government Research Grants Council(DAG96/97.SC11)
文摘Light transmission spectra of THF solutions of poly (C-60-co-methyl methacrylate)s and poly(C-60-co-styrene)s continuously red-shift with increasing concentration. Formation of fullerene nanoclusters may be responsible for the unusual spectral shift, with concentration. It has long been scientists' dream to ''tune'' material's properties by simple means, and the C-60-containing polymers represent such a group of novel materials whose optical properties are predictably and reversibly tunable by a simple change in concentration.
基金supported by National Key Technology R & D Program of China during the 11th Five-Year Plan Period (Grant No.2006BAF04B13)
文摘The existing research on shrinkage of the injection molded plastic part mainly focuses on various shrinkage ratios of the part dimensions,and the relevant experimental studies belong to mere dimension measurement after demoulding.Obviously,measuring after the plastic part is demoulded from the cavity can not offer shrinkage displacements of points on the plastic part.However,shrinkage displacements of points on an injection molded plastic part are essential for exposing the inner relation among shrinkage ratios of various dimensions of the part.So visualization of the in-mold plastic part which can indicate the location relationship between the part and the cavity is needed.In this paper,a visual injection mold was fabricated by adopting the half mold structure and light transmission manner.With the visual mold,in-mold shrinkage images of injection molded plastic parts were photographed after the plastic part stayed in the injection mold for 24 h.By means of digital image processing of the in-mold shrinkage images,the experimental data of shrinkage displacements of points on injection molded parts were researched.From the experimental data,it is found that shrinkage directions of points on an injection molded part are related with both positions of the gate and of the part centroid,and either the gate or the centroid will exert more influence on the shrinkage direction of some point which is closer.Furthermore,some point at the later filled area has more shrinkage distance than the point at the earlier filled area.Combination of shrinkage directions and shrinkage distances of points on an injection molded part determine shrinkage ratios for various dimensions of the part,and shrinkage directions are more influential to shrinkage ratios of dimensions.This experimental research of shrinkage displacements offers a unique approach to understand the shrinkage principles of injection molded parts.
基金National Key R&D Program of China(2016YFA0301300)National Natural Science Foundation of China(NSFC)(61275201,61372037)+2 种基金BUPT Excellent Ph.D.Students Foundation(CX2016204,CX2017401)Fundamental Research Funds for the Central Universities(2016RC24)Fund of State Key Laboratory of Information Photonics and Optical Communications(IPOC20172204)
文摘We propose and numerically investigate an efficient transmission-mode metasurface that consists of quasicontinuous trapezoid-shaped crystalline silicon nanoantennas on a quartz substrate. This metasurface provides a linear phase gradient and realizes both full 2π phase shift and high transmission efficiency in the operating wavelength range from 740 to 780 nm. At the central wavelength around 751 nm, the total transmission efficiency is up to 88.0% and the section of the desired anomalous refraction is 80.4%. The anomalous refraction angle is 29.62°, and larger refraction angle can be achieved by changing the period of the super cell. We demonstrate a refraction angle as large as 38.59°, and the anomalous transmission efficiency reaches 76.6% at wavelength of 741 nm. It is worth mentioning that the structure is much simpler than conventional metasurfaces based on arrays of discrete nanoantennas. Our research may pave the way for designing efficient all-dielectric phase-gradient metasurfaces and applying them in integrated optical devices for wavefront control.
基金supported by the National "973" Program of China(Nos.2013CB329205 and 2011CBA00608)the National "863" Program of China(Nos.2013AA013602,2013AA013603,2013AA03A104,and 2013AA031903)the National Natural Science Foundation of China(Nos.61036002 and 61178051)
文摘We present a high-speed visible light communication (VLC) link that uses a commercially available phos- phorescent white light-emitting diode (LED). Such devices have few megahertz bandwidth due to the slow response of phosphorescent component, which severely limit the transmission data rate of VLC system. We propose a simple pre-emphasis circuit. With blue-filtering and the pre-emphasis circuit, the bandwidth of VLC system can be enhanced from 3 to 77.6 MHz, which allows non-return-to-zero on-off-keying (NRZ- OOK) data transmission up to 200 Mb/s with the bit error ratio of 5.3 × 10-7 which is below 10-6. The VLC link operates at the room illumination level of -1000 lx at 1.1 m range using a single 1 W white LED.
基金This work was supported by the National NaturalScience Foundation of China (No. 60277016) and theGuangdong Natural Science Foundation of China (No.021357 and 04011761).
文摘Stable picosecond soliton transmission is demonstrated numerically by use of concatenated gain-distributed nonlinear amplifying fiber loop mirrors (NALMs). We show that, as compared with previous soliton transmission schemes that use conventional NALMs or nonlinear optical loop mirror (NOLM) and amplifier combinations, the present scheme permits significant increase of loop-mirror (amplifier) spacing. The broad switching window of the present device and the high quality pulses switched from it provide a reasonable stability range for soliton transmission. Soliton-soliton interactions can be reduced efficiently by using lowly dispersive fibers.
基金the National Natural Science Foundation of China(No.90607015)the Doctoral Fund of Ministry of Education of China(No.20070246099)
文摘We report experimental results on enhanced light transmission through double-layered (Ag/Au) metallic hole arrays within a skin-depth. Zero-order transmission spectrums are characterized as a function of Ag film's thickness, which extends from 5/15, 5/6 to approximately 5, where 5 is a skin-depth. In contrast with other reported results (Refs. [11 - 13]) in single-layered metallic hole arrays, our experimental results show much more dramatic properties of transmission process dependent on sub-5 thickness. It is shown that there is no negligible transmission enhancement at 5/15. At 5/6, much higher transmission efficiency can be achieved. With film's thickness being close to 5, the transmission efficiency declines contrarily. Simultaneously, the corresponding resonant peak also slightly moves toward the shorter wavelength. It is proposed that the coupling of surface plasmon polaritons (SPPs) at Ag/Au interface within 5 is involved in the process.
文摘A new shaping method for producing nanosecond pulses with specific shape is introduced. When a Gaussian laser pulse passes through an electro-optic deflector, it. has been scanned as a line on the focal plane according to time precedence. Through controlling the intensity of transmitted light on each pixol of the liquid crystal spatial light modulator (LCSLM), various complicated pulses can be easily produced. Using this method, various specific shaped pulses with pulse duration varying from 750 ps to 5 ns are achieved.
基金supported by the National "973" Project of China(Nos.2010CB328202,2010CB328204,and 2012CB315604)the National Natural Science Foundation of China(Nos.61271191 and 61001124)+3 种基金the National "863" Project of China(No.2012AA011302)the Program for New Century Excellent Talents in University(No.NCET-12-0793)the Beijing Nova Program(No.2011065)the Fundamental Research Funds for the Central Universities
文摘We demonstrate the theory of chromatic dispersion (CD)-induced constellation rotation (CR) in a radio-over-fiber (ROF) link and a method for compensation. We also propose a 60 GHz full-duplex ROF system with vector signal transmission including no CD effect. The evaluation of 5 Gb/s 16 quadrature amplitude modulation signal transmission shows that the CD-induced CR can be entirely overcome due to the proposed method which is simply implemented through an optical phase shifter. The proposed ROF schedule is not only applicable for V-band (57-64 GHz) but also fits for W-band (75-110 GHz), or any other bandwidth.
基金This work was supported by the National Natural Science Foundation of China (No. 60272075 and 60478014) partially supported by the Program of Excellent Team in Harbin Institute of Technology (HIT).
文摘The operation of an ultra-narrow bandwidth optical filter based on the 5P3/2→5D3/2 excited-state transition in rubidium vapor is reported. The 5D3/2 state is excited by a circularly polarized pump beam at 780 nm from a diode laser. The filter displays a single 398-MHz bandwidth at a peak transmission of 9.0%, which is narrower than the Doppler bandwidth. The dependence of peak transmission on the pump intensity and cell temperature is also given.
基金This work was supported by the National Natural Sci-ence Foundation of China (No. 60372043, 60272050).
文摘A new method for error detection using mode information of macroblocks (MBs) is proposed. For decodable inter MBs, inter residues are calculated by adding up absolute values of received residual pixels and intra complexities are estimated by that of motion compensated reference blocks. If inter residues are larger than intra complexities by a predefined quantity, MBs are considered to be erroneous. For decodable intra MBs, the connective smoothness of the current MB with correctly decoded neighboring MBs is tested to find erroneous MBs. Combined with error concealment, the new method improves the quality of reconstructed images by about 0.5-1 dB in peak signal-noise ratio (PSNR).
基金supported by the Shanghai Leading Academic Discipline Project and Science and Technology Commission of Shanghai Municipality (STCSM) under Grant Nos. S30108 and 08DZ2231100
文摘We present a novel method for providing broadcast signal transmission in a wavelength division multiplexing passive optical network (WDM-PON). An unmodulated optical carrier for downstream transmission and a pair of unmodulated single-side band subcarriers are utilized for broadcast delivery and upstream transmission, respectively. System performance at 2.5-Gb/s down/upstream and 2.5-Gb/s broadcast transmission is also investigated.