Volume 4,Issue 3,2008 Table of Contents
2008, 4(3).
Abstract:
Thin film transistors (TFTs) of microcrystalline silicon (μc-Si) can provide higher mobility and stability than that of a-Siand better uniformity than that of poly-Si TFTs,and it would be more suitable to be applied to larger-area AMOLEDs.By using 2ωYAG laser annealing,crystalline μc-Si thin film on plastic substrate has been investigated and the proper laser energy needed for crystallization has been indicated.It has been found that the dehydrogenation process at 300-450℃ for a few of hours could be omitted by decreasing the H content in the crystallization precursor,which is suitable for laser crystallization on plastic substrates.The crystalline volume fraction (Xc) and the grain size of the resulted μc-Si could be adjusted by controlling the laser energy.By this method,the μc-Si on plastic substrate with Xc and grain size is respectively 85% (at the maximum) and 50 nm.
Thin film transistors (TFTs) of microcrystalline silicon (μc-Si) can provide higher mobility and stability than that of a-Siand better uniformity than that of poly-Si TFTs,and it would be more suitable to be applied to larger-area AMOLEDs.By using 2ωYAG laser annealing,crystalline μc-Si thin film on plastic substrate has been investigated and the proper laser energy needed for crystallization has been indicated.It has been found that the dehydrogenation process at 300-450℃ for a few of hours could be omitted by decreasing the H content in the crystallization precursor,which is suitable for laser crystallization on plastic substrates.The crystalline volume fraction (Xc) and the grain size of the resulted μc-Si could be adjusted by controlling the laser energy.By this method,the μc-Si on plastic substrate with Xc and grain size is respectively 85% (at the maximum) and 50 nm.
2008, 4(3):161-164.
Abstract:
Large-scale synthesis of single-crystal CdSe nanoribbons is achieved by a modified thermal evaporation method,in which two-step-thermal-evaporation is used to control CdSe sources' evaporation.The synthesized CdSe nanoribbons are usually several micrometers in width,50 run in thickness,and tens to several hundred micrometers in length.Studies have shown that high-quality CdSe nanoribbons with regular shapes can be obtained by this method.Room-temperature photoluminescence indicates that the lasing emission at 710 nm has been observed under optical pumping (266 nm) at power densities of 25-153 kW/cm2.The full width half maximum (FWHM) of the lasing mode is 0.67 nm
Large-scale synthesis of single-crystal CdSe nanoribbons is achieved by a modified thermal evaporation method,in which two-step-thermal-evaporation is used to control CdSe sources' evaporation.The synthesized CdSe nanoribbons are usually several micrometers in width,50 run in thickness,and tens to several hundred micrometers in length.Studies have shown that high-quality CdSe nanoribbons with regular shapes can be obtained by this method.Room-temperature photoluminescence indicates that the lasing emission at 710 nm has been observed under optical pumping (266 nm) at power densities of 25-153 kW/cm2.The full width half maximum (FWHM) of the lasing mode is 0.67 nm
2008, 4(3):165-167.
Abstract:
In this paper,we discussed a slab wave-guide of five layers,The core is a left-handed material,but the claddings are righthanded materials.A dispersion equation of TE modes is obtained by using Maxwell's equations,and some new dispersion characteristics are obtained based on the equation.
In this paper,we discussed a slab wave-guide of five layers,The core is a left-handed material,but the claddings are righthanded materials.A dispersion equation of TE modes is obtained by using Maxwell's equations,and some new dispersion characteristics are obtained based on the equation.
2008, 4(3):168-171.
Abstract:
We calculate the Langevin noise sources of self-pulsation laser diodes,analyze the effects of active region noise and saturable-absorption region noise on the power fluctuation as well as period fluctuation,and propose a novel method to restrain the noise effects.A visible SIMULINK model is established to simulate the system,The results indicate that the effects of noise in absorption region can be ignored; that with the increase of DC injecting current,the noise effects enhance power jitter,and nevertheless,the period jitter is decreased; and that with external sinusoidal current modulating the selfpulsation laser diode,the noise-induced power jitter and period jitter can be suppressed greatly.This work is valuable for clock recovery in all-optical network.
We calculate the Langevin noise sources of self-pulsation laser diodes,analyze the effects of active region noise and saturable-absorption region noise on the power fluctuation as well as period fluctuation,and propose a novel method to restrain the noise effects.A visible SIMULINK model is established to simulate the system,The results indicate that the effects of noise in absorption region can be ignored; that with the increase of DC injecting current,the noise effects enhance power jitter,and nevertheless,the period jitter is decreased; and that with external sinusoidal current modulating the selfpulsation laser diode,the noise-induced power jitter and period jitter can be suppressed greatly.This work is valuable for clock recovery in all-optical network.
2008, 4(3):172-176.
Abstract:
In this letter,the authors propose a new concept of implementing all-optical logic gates by representing the logic states with polarization of an optical signal .As the state of polarization of the light signal is very much suitable for encoding and detecting the bits of data of a digital signal in communication,the scheme may extend some wide applications in alloptical parallel computation and information processing.
In this letter,the authors propose a new concept of implementing all-optical logic gates by representing the logic states with polarization of an optical signal .As the state of polarization of the light signal is very much suitable for encoding and detecting the bits of data of a digital signal in communication,the scheme may extend some wide applications in alloptical parallel computation and information processing.
2008, 4(3):177-179.
Abstract:
A novel technology to manufacture holographic ion beam etched diffraction gratings based on surface thermokinematics is presented.The surface roughness of photoresist gratings is solved by this technology.According to this technology,a holographic ion beam etched blazed grating of 1200 1/mm for use in the ultraviolet region is manufactured.The experimental results show that the grating has good surface quality,low stray light and high diffraction efficiency.In addition,the performance of thes gratings satisfies the operating requirements of ultraviolet spectrograph.
A novel technology to manufacture holographic ion beam etched diffraction gratings based on surface thermokinematics is presented.The surface roughness of photoresist gratings is solved by this technology.According to this technology,a holographic ion beam etched blazed grating of 1200 1/mm for use in the ultraviolet region is manufactured.The experimental results show that the grating has good surface quality,low stray light and high diffraction efficiency.In addition,the performance of thes gratings satisfies the operating requirements of ultraviolet spectrograph.
2008, 4(3):180-183.
Abstract:
Because it is complex and inconvenient to use the common temperature field calculating method and experiment method,for arialyzing heat transfer properties of laser diode module (LDM),an equivalent electrical network mathod is presented in this paper.Simulation results show that the temperature stability is closely related to ambient temperature,heat sink,LDM current and TEC current.Ambient temperature and TEC controller axe the dominant terms effecting on temperature control in practice.
Because it is complex and inconvenient to use the common temperature field calculating method and experiment method,for arialyzing heat transfer properties of laser diode module (LDM),an equivalent electrical network mathod is presented in this paper.Simulation results show that the temperature stability is closely related to ambient temperature,heat sink,LDM current and TEC current.Ambient temperature and TEC controller axe the dominant terms effecting on temperature control in practice.
2008, 4(3):184-187.
Abstract:
A type of combined optical fiber interferometric acoustic emission sensor is proposed.The sensor can be independent on the laser source and make light interference by matching the lengths of two arms,so it can be used to monitor the health of large structure.Theoretical analyses indicate that the system can be equivalent to the Michelson interferometer with two optical fiber loop reflectors,and its sensitivity has been remarkably increased because of the decrease of the losses of light energy.PZT is powered by DC regulator to control the operating point of the system,so the system can accurately detect feeble vibration which is generated by ultrasonic waves propagating on the surface of solid.The amplitude and the frequency of feeble vibration signal are obtained by detecting the output light intensity of intefferometer and using Fourier transform technique.The results indicate that the system can be used to detect the acoustic emission signals by the frequency characteristics.
A type of combined optical fiber interferometric acoustic emission sensor is proposed.The sensor can be independent on the laser source and make light interference by matching the lengths of two arms,so it can be used to monitor the health of large structure.Theoretical analyses indicate that the system can be equivalent to the Michelson interferometer with two optical fiber loop reflectors,and its sensitivity has been remarkably increased because of the decrease of the losses of light energy.PZT is powered by DC regulator to control the operating point of the system,so the system can accurately detect feeble vibration which is generated by ultrasonic waves propagating on the surface of solid.The amplitude and the frequency of feeble vibration signal are obtained by detecting the output light intensity of intefferometer and using Fourier transform technique.The results indicate that the system can be used to detect the acoustic emission signals by the frequency characteristics.
2008, 4(3):188-192.
Abstract:
We present a systematic scheme to achieve both high birefringence and low confinement loss in index-guiding photonic crystal fibers (PCFs),using a structurally-simple PCF with finite number of air holes in the cladding region.By increasing the size of the outermost-ring air holes in the cladding region,highly birefringent PCFs with low confinement loss can be successfully achieved.The design strategy is based on the fact that the modal birefringence of PCFs is dominated by the inner-ring air holes in PCF,which is verified by a full-vector finite element method with anisotropic perfectly matched layers.Numerical results show that modal birefringence in the order of 10.3 and confinement loss less than 0.1 dB/km can be easily realized in the proposed PCF with only four rings of air holes in the cladding region.We expect that such fibers will be much easier to be fabvicated than those with more air holes in the cladding region.
We present a systematic scheme to achieve both high birefringence and low confinement loss in index-guiding photonic crystal fibers (PCFs),using a structurally-simple PCF with finite number of air holes in the cladding region.By increasing the size of the outermost-ring air holes in the cladding region,highly birefringent PCFs with low confinement loss can be successfully achieved.The design strategy is based on the fact that the modal birefringence of PCFs is dominated by the inner-ring air holes in PCF,which is verified by a full-vector finite element method with anisotropic perfectly matched layers.Numerical results show that modal birefringence in the order of 10.3 and confinement loss less than 0.1 dB/km can be easily realized in the proposed PCF with only four rings of air holes in the cladding region.We expect that such fibers will be much easier to be fabvicated than those with more air holes in the cladding region.
2008, 4(3):193-195.
Abstract:
A kind of electric circuit is improved to optimize the linearity of edge filter demodulators in FBG .By using a logarithm amplifier and an extraction operation,the linear range of optimized edge filter demodulators has been broadened effectively,and the requirement of optical filter's linear range has been reduced.Theoretical analyses and the simulation results indicated that the linear range of optimized edge filter demodulator's covers the whole transition region of the edge filter,while a strict linearity of the optical filter is not necessary.
A kind of electric circuit is improved to optimize the linearity of edge filter demodulators in FBG .By using a logarithm amplifier and an extraction operation,the linear range of optimized edge filter demodulators has been broadened effectively,and the requirement of optical filter's linear range has been reduced.Theoretical analyses and the simulation results indicated that the linear range of optimized edge filter demodulator's covers the whole transition region of the edge filter,while a strict linearity of the optical filter is not necessary.
2008, 4(3):196-200.
Abstract:
For a 100 GHz DWDM angle-tuned filter with low polarization dependent loss,the insertion loss and the Gaussiantransformation tendency of the transmission spectrum will become more serious as the incident angle is increased.It is because of that the optical path and the transmission modes of the thin film filter will change when the incident angle is varied.According to the thin film matrix theory,the analysis model is established,the displacement change of the transmission field is simulated,and a dynamic compensation fitting is also designed and fabricated in the paper.The experimental results show that it can effectively reduce the insertion loss and the phenomenon of Gaussian process.Using the compensation fitting,the tunable range of the filter is at about 20 nm which coincides with the theoretical design.
For a 100 GHz DWDM angle-tuned filter with low polarization dependent loss,the insertion loss and the Gaussiantransformation tendency of the transmission spectrum will become more serious as the incident angle is increased.It is because of that the optical path and the transmission modes of the thin film filter will change when the incident angle is varied.According to the thin film matrix theory,the analysis model is established,the displacement change of the transmission field is simulated,and a dynamic compensation fitting is also designed and fabricated in the paper.The experimental results show that it can effectively reduce the insertion loss and the phenomenon of Gaussian process.Using the compensation fitting,the tunable range of the filter is at about 20 nm which coincides with the theoretical design.
2008, 4(3):201-204.
Abstract:
A doping system consisting of NPB and PVK is employed as a composite hole transporting layer (CHTL).By adjusting the component ratio of the doping system,a series of devices with different concentration proportion of PVK:NPB are constructed.The result shows that doping concentration of NPB enhances the competence of hole transporting ability,and modifies the recombination region of charge as well as affects the surface morphology of doped film.Optimum device with a maximum brightness of 7852 cd/m2 and a power efficiency of 1.75 1m/W has been obtained by choosing a concentration
A doping system consisting of NPB and PVK is employed as a composite hole transporting layer (CHTL).By adjusting the component ratio of the doping system,a series of devices with different concentration proportion of PVK:NPB are constructed.The result shows that doping concentration of NPB enhances the competence of hole transporting ability,and modifies the recombination region of charge as well as affects the surface morphology of doped film.Optimum device with a maximum brightness of 7852 cd/m2 and a power efficiency of 1.75 1m/W has been obtained by choosing a concentration
2008, 4(3):205-208.
Abstract:
We have fabricated the white organic light-emitting devices (WOLEDs) based on 4,4'-bis(2,2-diphenyl vinyl)-1,1'-biphenyl (DPVBi) and phosphorescence sensitized 5,6,11,12,-tetraphenylnaphthacene (rubrene).The device structure is ITO/2T-NATA (20 nm)/NPBX (20 nm)/CBP:x%Ir(ppy)3:0.5% rubrene (8 nm)/NPBX (5 nm)/DPVBi (30 nm)/Alq(30nm)/LiF(0.5 nm)/Al.In the devices,DPVBi acts as a blue light-emitting layer,the rubrene is sensitized by a phosphorescent material,fac tris (2-phenylpyridine) iridium [Ir(ppy)3],acts as a yellow light-emitting layer,and N,N'-bis-(1-naphthyl)-N,N'-dipheny1-1,1'-biphenyl-4,4'-diamine (NPBX) acts as a hole transporting and exciton blocker layer,respectively.When the concentration of Ir(PPY)3 is 6wt%,the maximum luminance is 24960 cd/m2 at an applied voltage of 15 V,and the maximum luminous efficiency is 5.17 cd/A at an applied voltage of 8 V.
We have fabricated the white organic light-emitting devices (WOLEDs) based on 4,4'-bis(2,2-diphenyl vinyl)-1,1'-biphenyl (DPVBi) and phosphorescence sensitized 5,6,11,12,-tetraphenylnaphthacene (rubrene).The device structure is ITO/2T-NATA (20 nm)/NPBX (20 nm)/CBP:x%Ir(ppy)3:0.5% rubrene (8 nm)/NPBX (5 nm)/DPVBi (30 nm)/Alq(30nm)/LiF(0.5 nm)/Al.In the devices,DPVBi acts as a blue light-emitting layer,the rubrene is sensitized by a phosphorescent material,fac tris (2-phenylpyridine) iridium [Ir(ppy)3],acts as a yellow light-emitting layer,and N,N'-bis-(1-naphthyl)-N,N'-dipheny1-1,1'-biphenyl-4,4'-diamine (NPBX) acts as a hole transporting and exciton blocker layer,respectively.When the concentration of Ir(PPY)3 is 6wt%,the maximum luminance is 24960 cd/m2 at an applied voltage of 15 V,and the maximum luminous efficiency is 5.17 cd/A at an applied voltage of 8 V.
2008, 4(3):209-212.
Abstract:
An insert layer structure organic electroluminescent device(OLED) based on a new luminescent material (Zn(salen)) is fabricated.The configuration of the device is ITO/CuPc/NPD/Zn(salen)/Liq/LiF/Al/CuPc/NPD/Zn(salen)/Liq/LiF/Al.Effective insert electrode layers comprising LiF(1nm)/Al(5 nm) are used as a single semitransparent mirror,and bilayer cathode LiF(1 nm)/Al(100 nm) is used as a reflecting mirror.The two mirrors form a Fabry-Perot microcavity and two emissive units.The maximum brightness and luminous efficiency reach 674 cd/m2 and 2.652 cd/A,respectively,which are 2.1 and 3.7 times higher than the conventional device,respectively.The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microeavity effect.
An insert layer structure organic electroluminescent device(OLED) based on a new luminescent material (Zn(salen)) is fabricated.The configuration of the device is ITO/CuPc/NPD/Zn(salen)/Liq/LiF/Al/CuPc/NPD/Zn(salen)/Liq/LiF/Al.Effective insert electrode layers comprising LiF(1nm)/Al(5 nm) are used as a single semitransparent mirror,and bilayer cathode LiF(1 nm)/Al(100 nm) is used as a reflecting mirror.The two mirrors form a Fabry-Perot microcavity and two emissive units.The maximum brightness and luminous efficiency reach 674 cd/m2 and 2.652 cd/A,respectively,which are 2.1 and 3.7 times higher than the conventional device,respectively.The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microeavity effect.
2008, 4(3):213-216.
Abstract:
Thin film transistors (TFTs) of microcrystalline silicon (μc-Si) can provide higher mobility and stability than that of a-Si and better uniformity than that of poly-Si TFTs, and it would be more suitable to be applied to larger-area AMOLEDs. By using 2ωYAG laser annealing, crystalline μc-Si thin film on plastic substrate has been investigated and the proper laser energy needed for crystallization has been indicated. It has been found that the dehydrogenation process at 300–450 °C for a few of hours could be omitted by decreasing the H content in the crystallization precursor, which is suitable for laser crystallization on plastic substrates. The crystalline volume fraction (Xc) and the grain size of the resulted μc-Si could be adjusted by controlling the laser energy. By this method, the μc-Si on plastic substrate with Xc and grain size is respectively 85% (at the maximum) and 50 nm. This work has been supported by “863” Project of National Ministry of Science and Technology (No. 2004AA33570), Key Project of NSFC (No. 60437030) and Tianjin Natural Science Foundation (No.05YFJMJC01400)
Thin film transistors (TFTs) of microcrystalline silicon (μc-Si) can provide higher mobility and stability than that of a-Si and better uniformity than that of poly-Si TFTs, and it would be more suitable to be applied to larger-area AMOLEDs. By using 2ωYAG laser annealing, crystalline μc-Si thin film on plastic substrate has been investigated and the proper laser energy needed for crystallization has been indicated. It has been found that the dehydrogenation process at 300–450 °C for a few of hours could be omitted by decreasing the H content in the crystallization precursor, which is suitable for laser crystallization on plastic substrates. The crystalline volume fraction (Xc) and the grain size of the resulted μc-Si could be adjusted by controlling the laser energy. By this method, the μc-Si on plastic substrate with Xc and grain size is respectively 85% (at the maximum) and 50 nm. This work has been supported by “863” Project of National Ministry of Science and Technology (No. 2004AA33570), Key Project of NSFC (No. 60437030) and Tianjin Natural Science Foundation (No.05YFJMJC01400)
2008, 4(3):217-222.
Abstract:
A displacement sensor based on transmission varied-line-space (VLS) phase gratings is proposed.The relationship between the properties of the sensor and the parameters of VLS is discussed.Compared with the displacement sensor manufactured by the reflective VLS grating,this type of sensor contains a grating with simpler structure and high diffraction efficiency.It also has good stability with the change of temperature.
A displacement sensor based on transmission varied-line-space (VLS) phase gratings is proposed.The relationship between the properties of the sensor and the parameters of VLS is discussed.Compared with the displacement sensor manufactured by the reflective VLS grating,this type of sensor contains a grating with simpler structure and high diffraction efficiency.It also has good stability with the change of temperature.
2008, 4(3):223-226.
Abstract:
A shape measurement based on ESPI by using carder is presented.When the tested object is tilted with a small angle,the carrier pattern containing altitude information is formed on the object surface.By using the carrier pattern captured by a CCD camera,the phase of the object can be derived by Fourier transform and the shape measurement is realized.The principle of the method is introduced and proved by an experiment.
A shape measurement based on ESPI by using carder is presented.When the tested object is tilted with a small angle,the carrier pattern containing altitude information is formed on the object surface.By using the carrier pattern captured by a CCD camera,the phase of the object can be derived by Fourier transform and the shape measurement is realized.The principle of the method is introduced and proved by an experiment.
2008, 4(3):227-230.
Abstract:
In this paper,a new optimal time-frequency atom search method based on a modified ant colony algorithm is proposed to improve the precision of the traditional methods.First,the discretization formula of finite length time-frequency atom is inferred at length.Second; a modified ant colony algorithm in continuous space is proposed.Finally,the optimal timefrequency atom search algorithm based on the modified ant colony algorithm is described in detail and the simulation experiment is carried on.The result indicates that the developed algorithm is valid and stable,and the precision of the method is higher than that of the traditional method.
In this paper,a new optimal time-frequency atom search method based on a modified ant colony algorithm is proposed to improve the precision of the traditional methods.First,the discretization formula of finite length time-frequency atom is inferred at length.Second; a modified ant colony algorithm in continuous space is proposed.Finally,the optimal timefrequency atom search algorithm based on the modified ant colony algorithm is described in detail and the simulation experiment is carried on.The result indicates that the developed algorithm is valid and stable,and the precision of the method is higher than that of the traditional method.
2008, 4(3):231-233.
Abstract:
Soliton amplitude squeezed state is obtained and dctected by using asymmetric Sagnac interferometer and balanced homodyne detecting system.An improved photo detector circuit for quantum state detection is introduced.The circuit has a bandwidth of 10MHz and the saturation power is about 19 mW.A maximum photocurrent noise reduction of 1.1 dB below the shot noise is achieved.Taking the detection efficiency into account,the squeezing will be about 1.5 dB.
Soliton amplitude squeezed state is obtained and dctected by using asymmetric Sagnac interferometer and balanced homodyne detecting system.An improved photo detector circuit for quantum state detection is introduced.The circuit has a bandwidth of 10MHz and the saturation power is about 19 mW.A maximum photocurrent noise reduction of 1.1 dB below the shot noise is achieved.Taking the detection efficiency into account,the squeezing will be about 1.5 dB.
2008, 4(3):234-238.
Abstract:
The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied.In collinear phase-matching,the optimum phase-matching wave bands of these two crystals are calculated.The optimum phase-matching wave bands in GaAs and InP are 0.95～1.38 μm and 0.7～0.96 μm respectively.The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed.The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed.It can serve for the following experiments as a theoretical evidence and a reference aswell.
The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied.In collinear phase-matching,the optimum phase-matching wave bands of these two crystals are calculated.The optimum phase-matching wave bands in GaAs and InP are 0.95～1.38 μm and 0.7～0.96 μm respectively.The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed.The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed.It can serve for the following experiments as a theoretical evidence and a reference aswell.
2008, 4(3):F0003.
Abstract:
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