A multi-hole vertical-cavity surface-emitting laser （VCSEL） operating in stable single mode with a low threshold current was produced by introducing multi-leaf scallop holes on the top distributed Bragg-refleetor of...A multi-hole vertical-cavity surface-emitting laser （VCSEL） operating in stable single mode with a low threshold current was produced by introducing multi-leaf scallop holes on the top distributed Bragg-refleetor of an oxidation- confined 850 nm VCSEL. The single-mode output power of 2.6 mW, threshold current of 0.6 mA, full width of half maximum lasing spectrum of less than 0.1 nm, side mode suppression ratio of 28.4 dB, and far-field divergence angle of about 10% are obtained. The effects of different hole depths on the optical characteristics are simulated and analysed, including far-field divergence, spectrum and lateral cavity mode. The single-mode performance of this multi-hole device is attributed to the large radiation loss from the inter hole spacing and the scattering loss at the bottom of the holes, particularly for higher order modes.展开更多
We report on the room-temperature cascade laser （QCL） at λ -4.7μm. cw operation of a surface grating Both grating design and material distributed feedback （DFB） quantum optimization are used to decrease the thre...We report on the room-temperature cascade laser （QCL） at λ -4.7μm. cw operation of a surface grating Both grating design and material distributed feedback （DFB） quantum optimization are used to decrease the threshold current density and to increase the output power. For a high-reflectivity-coated 13-μm-wide and 4- mm-long laser, high wall-plug efficiency of 6% is obtained at 20℃ from a single facet producing over I W of ew output power. The threshold current density of DFB QCL is as low as 1.13kA/cm^2 at 10℃ and 1.34kA/cm2 at 30℃ in cw mode. Stable single-mode emission with a side-mode suppression ratio of about 30 dB is observed in tile working temperature range of 20-50℃.展开更多
Pulsed anodic oxidation technique, a new way of forming current blocking layers, was successfully used in ridge-waveguide QW laser fabrication. This method was applied in 980 nm VCSELs fabrication to form a high-quali...Pulsed anodic oxidation technique, a new way of forming current blocking layers, was successfully used in ridge-waveguide QW laser fabrication. This method was applied in 980 nm VCSELs fabrication to form a high-quality native oxide current blocking layer, which simplifies the device process. A significant reduction of threshold current and a distinguished device performance are achieved. The 500 μm diameter device has a current threshold as low as 0.48 W. The maximum CW operation output power at room temperature is 1.48 W. The lateral divergence angle θ‖ and vertical divergence angle θ⊥ are as low as 15.3° and 13.8° without side-lobes at a current of 6 A.展开更多
Visible light microlasers are essential building blocks for integrated photonics.However,achieving low-threshold(μw),continuous-wave(CW)visible light lasing at room temperature(RT)has been a challenge because of the ...Visible light microlasers are essential building blocks for integrated photonics.However,achieving low-threshold(μw),continuous-wave(CW)visible light lasing at room temperature(RT)has been a challenge because of the formidable requirement of population inversion at short wavelengths.Rare-earth(RE)-activated microcavities,featuring highquality factor(Q)and small mode volume of whispering gallery modes,offer a great opportunity for achieving infrared-to-visible upconversion(UC)lasing.Here,we report that batch-produced nano-glass composite(GC)microspheres incorporating RE-doped fluoride nanocrystals show efficient UC emissions.These multi-phase composite microspheres exhibit a high Q value(≥10^(5)),comparable to that of conventional multi-component glass microspheres.The UC lasing with pure red,green,and blue(RGB)emissions are demonstrated based on a highly efficient tapered fiber-microsphere system.More importantly,the GC microspheres manifest reduced(by 45%)lasing threshold and enhanced(more than four times)slope effciency.These characteristics,together with excellent long-term stability,suggest a promising solution to achieving highly robust,stand-alone,low-threshold,and versatile UC microlasers.展开更多
We herein report the effective performance enhancement of the pentacene-based organic thin film transistors with silicon di- oxide dielectric by inserting a thin metal phthalocyanines interlayer between Au source/drai...We herein report the effective performance enhancement of the pentacene-based organic thin film transistors with silicon di- oxide dielectric by inserting a thin metal phthalocyanines interlayer between Au source/drain electrodes and the pentacene active layer. The threshold voltage decreased remarkably from ca. -20 V to a few volts （below -7.6 V） while the mobility in- creased 1.5-3 times after the insertion of the interlayer of only ca. 2 nm, which could be attributed to the reduction of the car- tier injection barrier. The results suggest a simple and effective way to achieve low-threshold-voltage pentacene-based organic thin film transistors with high mobility on silicon dioxide dielectric.展开更多
To achieve low threshold current as well as high single mode output power, a graded index separate confinement heterostructure （GRIN-SCH） A1GaInAs/A1GaAs quantum well laser with an optimized ridge wave- guide was fa...To achieve low threshold current as well as high single mode output power, a graded index separate confinement heterostructure （GRIN-SCH） A1GaInAs/A1GaAs quantum well laser with an optimized ridge wave- guide was fabricated. The threshold current was reduced to 8 mA. An output power of 76 mW was achieved at 100 mA current at room temperature, with a slope efficiency of 0.83 W/A and a horizon divergent angle of 6.3°. The maximum single mode output power of the device reached as high as 450 mW.展开更多
A high efficiency,low threshold,high repetition rate H-βFraunhofer line light at 486.1 nm was demonstrated.A high-efficiency KTP optical parametric oscillator was achieved by double-pass pumping with a high-maturity ...A high efficiency,low threshold,high repetition rate H-βFraunhofer line light at 486.1 nm was demonstrated.A high-efficiency KTP optical parametric oscillator was achieved by double-pass pumping with a high-maturity 5 kHz 532 nm laser.Thanks to the efficient intracavity frequency doubling of the circulating signal wave by a BIBO crystal,the threshold pump power of the 486.1 nm output was 0.9 W,and the maximum output power of 1.6 W was achieved under the pump power of7.5 W.The optical–optical conversion efficiency was 21.3%,with the pulse duration of 45.2 ns,linewidth of~0.12 nm,and beam quality factor M~2 of 2.83.展开更多
Many studies have estimated approximately ranges of thresholds of low soil temperature in the growth and ecophysi-ological traits of trees, but difficultly determined the exact values. To resolve the problem, black sp...Many studies have estimated approximately ranges of thresholds of low soil temperature in the growth and ecophysi-ological traits of trees, but difficultly determined the exact values. To resolve the problem, black spruce （Picea mariana） and jack pine （Pinus banksiana） seedlings were exposed to 5, 10, 15, 20, 25, 30 and 35℃ soil temperature in greenhouses. After 90 days of the treatment, net photosynthetic rate （A）, stomatal conductance （gs）, transpiration rate （E）, water use efficiency （WUE） and specific leaf area （SLA） were measured. This study showed that all the traits had an asymmetrical peak relationship with changing soil temperature, the relationship was well simulated using a cubic curvilinear model, and the exact thresholds could be derived from the second derivative of the model. The results revealed that the thresholds varied among ecophysiological traits and between tree species. In black spruce, the thresholds were 14.1, 14.7, 10.7, 14.4 and 16.2℃ forA, gs, E, WUE and SLA; 15.4, 10.4, 14.7, 16.9 and 10.5℃ for the corresponding traits in jack pine. The lowest thresholds of E in black spruce and gs in jack pine were an indicator representing the minimum requirement of soil temperature for the regular processes of ecophysiology. The highest thresholds of SLA in black spruce and WUE in jack pine suggest they are the most sensitive to decreasing soil temperature and may play an important role in the acclimation. The averaged thresholds were at 14.0 and 13.6℃ for black spruce and jack pine, suggesting that the sensitivity of both species to low soil temperature was quite close.展开更多
We investigate the low-energy structure （LES） in the above-threshold ionization spectrum at a mid-infrared laser wavelength with a semiclassical model. Using a softened Coulomb potential （CP） and changing the soft...We investigate the low-energy structure （LES） in the above-threshold ionization spectrum at a mid-infrared laser wavelength with a semiclassical model. Using a softened Coulomb potential （CP） and changing the softening parameter, we show that though the very low-energy structure （VLES） and high low-energy structure （HLES） are both due to the interaction between the ionic CP and the electron, the two structures have different physical mechanisms： the VLES can be attributed to the electron-ion Coulomb interaction at a rather small distance and the HLES is more likely to be ascribed to the electron-ion Coulomb interaction at a large distance.展开更多
Based on 0.13μm complementary metal-oxide-semiconductor（CMOS） technology,a phase and frequency detector（PFD） is designed with a low supply voltage of 0.5V for frequency synthesizers used in wireless sensor netwo...Based on 0.13μm complementary metal-oxide-semiconductor（CMOS） technology,a phase and frequency detector（PFD） is designed with a low supply voltage of 0.5V for frequency synthesizers used in wireless sensor networks（WSNs）.The PFD can compare the frequency and phase differences of input signals and deliver a signal voltage proportional to the difference.Low threshold transistors are used in the circuits since a power supply of 0.5V is adopted.A pulse latched structure is also used in the circuits in order to increase both the detection range of phase errors and the maximum operation frequency.In experiments,a phase error with a range from-358° to 358° is measured when the input signal frequency is 2MHz.The PFD has a faster acquisition speed compared with conventional digital PFDs.When the input signals are at a frequency of 2MHz with zero phase error,the circuits have a power consumption of 1.8[KG＊8]μW,and the maximum operation frequency is 1.25GHz.展开更多
针对Leach(low energy adaptive clustering hierarchy)协议在大规模网络中存在着数据传输效率不高和网络生命周期短的问题,提出了一种LEACH-CM-NGO优化算法。该方法通过在簇头选取阶段优化簇头数在所有节点中占比,引进能量密度因子和...针对Leach(low energy adaptive clustering hierarchy)协议在大规模网络中存在着数据传输效率不高和网络生命周期短的问题,提出了一种LEACH-CM-NGO优化算法。该方法通过在簇头选取阶段优化簇头数在所有节点中占比,引进能量密度因子和能耗因子改进阈值公式优化簇头分布,并在数据传输阶段,由原本的单跳传输改为多跳方式传输数据,引入基于立方映射方法,自适应权重策略和柯西变异的北方苍鹰优化算法改进簇头间数据传输路径,以提高网络的能效和数据传输效率。仿真结果表明,所提出的方法在减少能耗的同时,显著延长了网络的生命周期并提高了数据传输的成功率。展开更多
基金Project supported by the National High Technology Research and Development Program of China (Grant No. 2008AA03Z402)the National Natural Science Foundation of China (Grant No. 61076044)the Natural Science Foundation of Beijing,China(Grant Nos. 4092007 and 4102003)
文摘A multi-hole vertical-cavity surface-emitting laser （VCSEL） operating in stable single mode with a low threshold current was produced by introducing multi-leaf scallop holes on the top distributed Bragg-refleetor of an oxidation- confined 850 nm VCSEL. The single-mode output power of 2.6 mW, threshold current of 0.6 mA, full width of half maximum lasing spectrum of less than 0.1 nm, side mode suppression ratio of 28.4 dB, and far-field divergence angle of about 10% are obtained. The effects of different hole depths on the optical characteristics are simulated and analysed, including far-field divergence, spectrum and lateral cavity mode. The single-mode performance of this multi-hole device is attributed to the large radiation loss from the inter hole spacing and the scattering loss at the bottom of the holes, particularly for higher order modes.
基金Supported by the National Basic Research Program of China under Grant Nos 2013CB632801 and 2013CB632803the National Natural Science Foundation of China under Grant Nos 61435014,61306058 and 61274094the Beijing Natural Science Foundation under Grant No 4144086
文摘We report on the room-temperature cascade laser （QCL） at λ -4.7μm. cw operation of a surface grating Both grating design and material distributed feedback （DFB） quantum optimization are used to decrease the threshold current density and to increase the output power. For a high-reflectivity-coated 13-μm-wide and 4- mm-long laser, high wall-plug efficiency of 6% is obtained at 20℃ from a single facet producing over I W of ew output power. The threshold current density of DFB QCL is as low as 1.13kA/cm^2 at 10℃ and 1.34kA/cm2 at 30℃ in cw mode. Stable single-mode emission with a side-mode suppression ratio of about 30 dB is observed in tile working temperature range of 20-50℃.
文摘Pulsed anodic oxidation technique, a new way of forming current blocking layers, was successfully used in ridge-waveguide QW laser fabrication. This method was applied in 980 nm VCSELs fabrication to form a high-quality native oxide current blocking layer, which simplifies the device process. A significant reduction of threshold current and a distinguished device performance are achieved. The 500 μm diameter device has a current threshold as low as 0.48 W. The maximum CW operation output power at room temperature is 1.48 W. The lateral divergence angle θ‖ and vertical divergence angle θ⊥ are as low as 15.3° and 13.8° without side-lobes at a current of 6 A.
基金supported by the National Natural Science Foundation of China(62305244,52372003,62374112,62105078)Shandong Province Natural ScienceFoundation(ZR2021QE060,ZR2021QF009)+2 种基金Natural Science Foundation of Heilongjiang Province of China(ZD2023E004)Young Elite Scientists Sponsorship Program by China Association for Science and Technology(2022QNRC001)Youth science and technology innovation team of Shandong Province institution of higher learning(2022KJ258).
文摘Visible light microlasers are essential building blocks for integrated photonics.However,achieving low-threshold(μw),continuous-wave(CW)visible light lasing at room temperature(RT)has been a challenge because of the formidable requirement of population inversion at short wavelengths.Rare-earth(RE)-activated microcavities,featuring highquality factor(Q)and small mode volume of whispering gallery modes,offer a great opportunity for achieving infrared-to-visible upconversion(UC)lasing.Here,we report that batch-produced nano-glass composite(GC)microspheres incorporating RE-doped fluoride nanocrystals show efficient UC emissions.These multi-phase composite microspheres exhibit a high Q value(≥10^(5)),comparable to that of conventional multi-component glass microspheres.The UC lasing with pure red,green,and blue(RGB)emissions are demonstrated based on a highly efficient tapered fiber-microsphere system.More importantly,the GC microspheres manifest reduced(by 45%)lasing threshold and enhanced(more than four times)slope effciency.These characteristics,together with excellent long-term stability,suggest a promising solution to achieving highly robust,stand-alone,low-threshold,and versatile UC microlasers.
基金financially supported by the National Basic Research Program of China (973 Program) (Grant No. 2007CB936302)the National Natural Science Foundation of China (Grant No. 20833002)
文摘We herein report the effective performance enhancement of the pentacene-based organic thin film transistors with silicon di- oxide dielectric by inserting a thin metal phthalocyanines interlayer between Au source/drain electrodes and the pentacene active layer. The threshold voltage decreased remarkably from ca. -20 V to a few volts （below -7.6 V） while the mobility in- creased 1.5-3 times after the insertion of the interlayer of only ca. 2 nm, which could be attributed to the reduction of the car- tier injection barrier. The results suggest a simple and effective way to achieve low-threshold-voltage pentacene-based organic thin film transistors with high mobility on silicon dioxide dielectric.
基金supported by the National Military Electronic Component Program of China(No.1107XG0700)
文摘To achieve low threshold current as well as high single mode output power, a graded index separate confinement heterostructure （GRIN-SCH） A1GaInAs/A1GaAs quantum well laser with an optimized ridge wave- guide was fabricated. The threshold current was reduced to 8 mA. An output power of 76 mW was achieved at 100 mA current at room temperature, with a slope efficiency of 0.83 W/A and a horizon divergent angle of 6.3°. The maximum single mode output power of the device reached as high as 450 mW.
基金supported by the National Natural Science Foundation of China(No.62175181)。
文摘A high efficiency,low threshold,high repetition rate H-βFraunhofer line light at 486.1 nm was demonstrated.A high-efficiency KTP optical parametric oscillator was achieved by double-pass pumping with a high-maturity 5 kHz 532 nm laser.Thanks to the efficient intracavity frequency doubling of the circulating signal wave by a BIBO crystal,the threshold pump power of the 486.1 nm output was 0.9 W,and the maximum output power of 1.6 W was achieved under the pump power of7.5 W.The optical–optical conversion efficiency was 21.3%,with the pulse duration of 45.2 ns,linewidth of~0.12 nm,and beam quality factor M~2 of 2.83.
基金supported by the Lakehead University Graduate Fellowship, Nature Science and Engineer Research Council Scholarship of Canada (NSERC) PGS A,the National Natural Science Foundation of China (Grant No. 30872000)K. C. Wong Education Foundation of Hong Kong (2008) and the funding initiative of Institute of Mountain Hazards and Environment, Chinese Academy of Sciences to the author and NSERC research grant to Qing-Lai Dang
文摘Many studies have estimated approximately ranges of thresholds of low soil temperature in the growth and ecophysi-ological traits of trees, but difficultly determined the exact values. To resolve the problem, black spruce （Picea mariana） and jack pine （Pinus banksiana） seedlings were exposed to 5, 10, 15, 20, 25, 30 and 35℃ soil temperature in greenhouses. After 90 days of the treatment, net photosynthetic rate （A）, stomatal conductance （gs）, transpiration rate （E）, water use efficiency （WUE） and specific leaf area （SLA） were measured. This study showed that all the traits had an asymmetrical peak relationship with changing soil temperature, the relationship was well simulated using a cubic curvilinear model, and the exact thresholds could be derived from the second derivative of the model. The results revealed that the thresholds varied among ecophysiological traits and between tree species. In black spruce, the thresholds were 14.1, 14.7, 10.7, 14.4 and 16.2℃ forA, gs, E, WUE and SLA; 15.4, 10.4, 14.7, 16.9 and 10.5℃ for the corresponding traits in jack pine. The lowest thresholds of E in black spruce and gs in jack pine were an indicator representing the minimum requirement of soil temperature for the regular processes of ecophysiology. The highest thresholds of SLA in black spruce and WUE in jack pine suggest they are the most sensitive to decreasing soil temperature and may play an important role in the acclimation. The averaged thresholds were at 14.0 and 13.6℃ for black spruce and jack pine, suggesting that the sensitivity of both species to low soil temperature was quite close.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.10925420,11074026,11174330,and 11274050)the National Basic Research Program of China (Grant Nos.2011CB808102 and 2013CB922201)
文摘We investigate the low-energy structure （LES） in the above-threshold ionization spectrum at a mid-infrared laser wavelength with a semiclassical model. Using a softened Coulomb potential （CP） and changing the softening parameter, we show that though the very low-energy structure （VLES） and high low-energy structure （HLES） are both due to the interaction between the ionic CP and the electron, the two structures have different physical mechanisms： the VLES can be attributed to the electron-ion Coulomb interaction at a rather small distance and the HLES is more likely to be ascribed to the electron-ion Coulomb interaction at a large distance.
基金The National High Technology Research and Development Program of China (863 Program) (No. 2007AA01Z2A7)Program for Special Talents in Six Fields of Jiangsu Province
文摘Based on 0.13μm complementary metal-oxide-semiconductor（CMOS） technology,a phase and frequency detector（PFD） is designed with a low supply voltage of 0.5V for frequency synthesizers used in wireless sensor networks（WSNs）.The PFD can compare the frequency and phase differences of input signals and deliver a signal voltage proportional to the difference.Low threshold transistors are used in the circuits since a power supply of 0.5V is adopted.A pulse latched structure is also used in the circuits in order to increase both the detection range of phase errors and the maximum operation frequency.In experiments,a phase error with a range from-358° to 358° is measured when the input signal frequency is 2MHz.The PFD has a faster acquisition speed compared with conventional digital PFDs.When the input signals are at a frequency of 2MHz with zero phase error,the circuits have a power consumption of 1.8[KG＊8]μW,and the maximum operation frequency is 1.25GHz.
文摘针对Leach(low energy adaptive clustering hierarchy)协议在大规模网络中存在着数据传输效率不高和网络生命周期短的问题,提出了一种LEACH-CM-NGO优化算法。该方法通过在簇头选取阶段优化簇头数在所有节点中占比,引进能量密度因子和能耗因子改进阈值公式优化簇头分布,并在数据传输阶段,由原本的单跳传输改为多跳方式传输数据,引入基于立方映射方法,自适应权重策略和柯西变异的北方苍鹰优化算法改进簇头间数据传输路径,以提高网络的能效和数据传输效率。仿真结果表明,所提出的方法在减少能耗的同时,显著延长了网络的生命周期并提高了数据传输的成功率。
