Volume 4,Issue 5,2008 Table of Contents
2008, 4(5).
Abstract:
Through using both Cr4 :YAG and GaAs saturable absorbers, a diode-pumped double passively Q-switched Nd:GdVO4 laser is realized and compared with a single passively Q-switched laser. This laser can generate symmetric pulse temporal profiles and shorter pulses. A laser pulse width of 17 ns has been achieved with the incident pump power of 8.5 W.
Through using both Cr4 :YAG and GaAs saturable absorbers, a diode-pumped double passively Q-switched Nd:GdVO4 laser is realized and compared with a single passively Q-switched laser. This laser can generate symmetric pulse temporal profiles and shorter pulses. A laser pulse width of 17 ns has been achieved with the incident pump power of 8.5 W.
2008, 4(5).
Abstract:
A wavelength demultiplexer based on two dimensional photonic crystal waveguides is proposed. By using the finite difference time domain (FDTD) method and plane wave extension (PWE) method, the transmission spectra and the distributions of mode field are obtained, and the wavelength demultiplexer has been synthesized. The characteristics of the device are obtained.
A wavelength demultiplexer based on two dimensional photonic crystal waveguides is proposed. By using the finite difference time domain (FDTD) method and plane wave extension (PWE) method, the transmission spectra and the distributions of mode field are obtained, and the wavelength demultiplexer has been synthesized. The characteristics of the device are obtained.
2008, 4(5).
Abstract:
2008, 4(5):317-320.
Abstract:
Based on conventional double layer device, triple layer organic light-emitting diodes (OLEDs) with two heterostructures of indium-tin oxide (ITO)/N,N'-diphenyl-N,N'-his(1-naphthyl)(1,1'-biphenyl)-4,4'-diamine(NPB)/2,9 -dimethyl-4,7 -diphenyl-1,10-phenanthroline (BCP)/8-Hydroxyquinoline aluminum (Alq3)/Mg:Ag using vacuum deposition method have been fabricated. The influence of different film thickness of BCP layer on the performance of OLEDs has been investigated. The results showed that when the thickness of the BCP layer film gradually varied from 0.1 nm to 4.0 nm, the electrolumines-cence (EL) spectra of the OLEDs shifted from green to greenish-blue to blue, and the BCP layer acted as the recombination region of charge carriers related to EL spectrum, enhancing the brightness and power efficiency. The power efficiency of OLEDs reached as high as 7.3 lm/W.
Based on conventional double layer device, triple layer organic light-emitting diodes (OLEDs) with two heterostructures of indium-tin oxide (ITO)/N,N'-diphenyl-N,N'-his(1-naphthyl)(1,1'-biphenyl)-4,4'-diamine(NPB)/2,9 -dimethyl-4,7 -diphenyl-1,10-phenanthroline (BCP)/8-Hydroxyquinoline aluminum (Alq3)/Mg:Ag using vacuum deposition method have been fabricated. The influence of different film thickness of BCP layer on the performance of OLEDs has been investigated. The results showed that when the thickness of the BCP layer film gradually varied from 0.1 nm to 4.0 nm, the electrolumines-cence (EL) spectra of the OLEDs shifted from green to greenish-blue to blue, and the BCP layer acted as the recombination region of charge carriers related to EL spectrum, enhancing the brightness and power efficiency. The power efficiency of OLEDs reached as high as 7.3 lm/W.
2008, 4(5):321-323.
Abstract:
An efficient organic photovoltaic (OPV) cell with an indium-tin-oxide/CuPc/C60/Ag structure has been investigated by changing the film thickness of organic layers. A high open-circuit voltage (Voc) of 0.5 V, a short-circuit current density (JSC) of 5.81 mA/cm2, and a high power conversion efficiency (ηp) of 1.2% were achieved at an optimum film thickness. The results demonstrate that material thickness is an important factor to cell optimization, especially for maximizing the absorption rate as well as reducing the cell resistance. Experimental results also indicate that the power conversion efficiency increases from 1.2% to 1.54% as a BCP exciton blocking layer of 10 nm is introduced.
An efficient organic photovoltaic (OPV) cell with an indium-tin-oxide/CuPc/C60/Ag structure has been investigated by changing the film thickness of organic layers. A high open-circuit voltage (Voc) of 0.5 V, a short-circuit current density (JSC) of 5.81 mA/cm2, and a high power conversion efficiency (ηp) of 1.2% were achieved at an optimum film thickness. The results demonstrate that material thickness is an important factor to cell optimization, especially for maximizing the absorption rate as well as reducing the cell resistance. Experimental results also indicate that the power conversion efficiency increases from 1.2% to 1.54% as a BCP exciton blocking layer of 10 nm is introduced.
2008, 4(5):324-327.
Abstract:
A top contact n-type organic field-effect transistor with low operating voltage was fabricated by employing Ta2O5/PMMA as the double insulators and PTCDI-Cl2 as the semiconductor active layer. The Ta2O5 layer was prepared by using simple economical anodization technique and the PMMA layer was prepared by using the spin-coating method. Compared with the OFET with single Ta2O5 insulator, the device with double insulators shows obviously better electrical performance. It has a field effect electron mobility of 0.063 cm2/Vs, an on/offratio of 1.7×104 and a threshold voltage of 2.3 V.
A top contact n-type organic field-effect transistor with low operating voltage was fabricated by employing Ta2O5/PMMA as the double insulators and PTCDI-Cl2 as the semiconductor active layer. The Ta2O5 layer was prepared by using simple economical anodization technique and the PMMA layer was prepared by using the spin-coating method. Compared with the OFET with single Ta2O5 insulator, the device with double insulators shows obviously better electrical performance. It has a field effect electron mobility of 0.063 cm2/Vs, an on/offratio of 1.7×104 and a threshold voltage of 2.3 V.
2008, 4(5):328-330.
Abstract:
Porous silicon is functionalized using thermal oxidation and silanization. The HYSA antibodies are immobilized to the porous surface in this paper. The changes in the reflection spectrum and photoluminescence spectrum are investigated when BSA are attached to the PS surface. The result shows that the luminescence peak of PS disappears. After the antigen-antibody reaction, the higher light emission is observed and the reflection spectrum also red shifts. Therefore, this research lays a foundation for the development of sensitive label-free optical immunosensor.
Porous silicon is functionalized using thermal oxidation and silanization. The HYSA antibodies are immobilized to the porous surface in this paper. The changes in the reflection spectrum and photoluminescence spectrum are investigated when BSA are attached to the PS surface. The result shows that the luminescence peak of PS disappears. After the antigen-antibody reaction, the higher light emission is observed and the reflection spectrum also red shifts. Therefore, this research lays a foundation for the development of sensitive label-free optical immunosensor.
2008, 4(5):331-334.
Abstract:
Through using both Cr4+:YAG and GaAs saturable absorbers, a diode-pumped double passively Q-switched Nd:GdVO4 laser is realized and compared with a single passively Q-switched laser. This laser can generate symmetric pulse temporal profiles and shorter pulses. A laser pulse width of 17 ns has been achieved with the incident pump power of 8.5 W. This work has been supported by Natural Science Foundation of Shandong Province(Y2007G01).
Through using both Cr4+:YAG and GaAs saturable absorbers, a diode-pumped double passively Q-switched Nd:GdVO4 laser is realized and compared with a single passively Q-switched laser. This laser can generate symmetric pulse temporal profiles and shorter pulses. A laser pulse width of 17 ns has been achieved with the incident pump power of 8.5 W. This work has been supported by Natural Science Foundation of Shandong Province(Y2007G01).
2008, 4(5):335-338.
Abstract:
A frequency-stabilized 1.53 μm FBG external-cavity semiconductor laser by using acetylene absorption is presented and its basic principles are introduced. Graded refractive index fiber and pigtailed fiber are used in the absorption air chamber to enhance the coupling stability. The impact of the background power is eliminated by using the third-harmonic modelocking technique. A lock-in amplifier is utilized to ensure that the output laser wavelength is locked at the C2H2 absorption line of 1530.37 nm. The frequency stability reaches 10-8 within 24 h.
A frequency-stabilized 1.53 μm FBG external-cavity semiconductor laser by using acetylene absorption is presented and its basic principles are introduced. Graded refractive index fiber and pigtailed fiber are used in the absorption air chamber to enhance the coupling stability. The impact of the background power is eliminated by using the third-harmonic modelocking technique. A lock-in amplifier is utilized to ensure that the output laser wavelength is locked at the C2H2 absorption line of 1530.37 nm. The frequency stability reaches 10-8 within 24 h.
2008, 4(5):339-341.
Abstract:
A wavelength demultiplexer based on two dimensional photonic crystal waveguides is proposed. By using the finite difference time domain (FDTD) method and plane wave extension (PWE) method, the transmission spectra and the distributions of mode field are obtained, and the wavelength demultiplexer has been synthesized. The characteristics of the device are obtained.
A wavelength demultiplexer based on two dimensional photonic crystal waveguides is proposed. By using the finite difference time domain (FDTD) method and plane wave extension (PWE) method, the transmission spectra and the distributions of mode field are obtained, and the wavelength demultiplexer has been synthesized. The characteristics of the device are obtained.
2008, 4(5):342-346.
Abstract:
A generic numerical model of a long-wavelength Avalanche Photodiode (APD) based on narrow bandgap semiconductor InAsSb on lnAs substrate is reported for the first time. This model has been applied for theoretical characterization of a proposed N InAS/P-InAsSb avalanche photodiode structure for possible application in 2-5 μm wavelength region. The parameters such as gain, excess noise factor and their trade-offwith variation of doping concentration and bias voltage have been estimated for the APD taking into account history-dependent theory of avalanche multiplication process. The LWIR APD is expected to find application in optical gas sensor and in future generation of optical communication system.
A generic numerical model of a long-wavelength Avalanche Photodiode (APD) based on narrow bandgap semiconductor InAsSb on lnAs substrate is reported for the first time. This model has been applied for theoretical characterization of a proposed N InAS/P-InAsSb avalanche photodiode structure for possible application in 2-5 μm wavelength region. The parameters such as gain, excess noise factor and their trade-offwith variation of doping concentration and bias voltage have been estimated for the APD taking into account history-dependent theory of avalanche multiplication process. The LWIR APD is expected to find application in optical gas sensor and in future generation of optical communication system.
2008, 4(5):347-350.
Abstract:
Photodiode's reflectance plays an important role regarding the relation between responsivity and the incident flux. In this work we analyze how the spectral reflectance changes among photodiodes from the same manufacturer and batch and how the reflectance of three standard photodiodes has drifted during six years. The results show that the reflectance changes from diode to diode within the same batch and also show th.at the reflectance ofphotodiodes changes on time. This ageing is spectrally dependent.
Photodiode's reflectance plays an important role regarding the relation between responsivity and the incident flux. In this work we analyze how the spectral reflectance changes among photodiodes from the same manufacturer and batch and how the reflectance of three standard photodiodes has drifted during six years. The results show that the reflectance changes from diode to diode within the same batch and also show th.at the reflectance ofphotodiodes changes on time. This ageing is spectrally dependent.
2008, 4(5):351-353.
Abstract:
For cooled 320×240 detector with stating focal plane array, a novel middle infi'arod athermal optical system is presented. The system is composed of 5 spherical lenses. The materials of lenses are silicon and germanium. The optical parameters and modulation transfer function (MTF) are investigated. The system has the diffraction limited image quality and stable image plane from -30℃ to 70 ℃. The characteristic parameters of the system are as follows:flnumber of 4, cold shield efficiency of 100%, spectrum region of 3.7-4.8 μm and transmissivity of 80%. The system has the merits of simple structure, low price, and it is easy to machining.
For cooled 320×240 detector with stating focal plane array, a novel middle infi'arod athermal optical system is presented. The system is composed of 5 spherical lenses. The materials of lenses are silicon and germanium. The optical parameters and modulation transfer function (MTF) are investigated. The system has the diffraction limited image quality and stable image plane from -30℃ to 70 ℃. The characteristic parameters of the system are as follows:flnumber of 4, cold shield efficiency of 100%, spectrum region of 3.7-4.8 μm and transmissivity of 80%. The system has the merits of simple structure, low price, and it is easy to machining.
14 Laser lift-off technique and the re-utilization of GaN-based LED films grown on sapphire substrate
2008, 4(5):354-357.
Abstract:
A thin GaN LED film, grown on 2-inch-diameter sapphire substrates, is separated by laser lift-off. Atom force microscopy (AFM) and the double-crystal X-ray diffraction (XRD) have been employed to characterize the performance of GaN before and after the lift-off process. It is demonstrated that the separation and transfer processes do not alter the crystal quality of the GaN films obviously. InGaN/GaN multi-quantum-wells (MQW's) structure is grown on the separated sapphire substrate later and is compared with that grown on the conventional substrate under the same condition by using PL and XRD spectrum.
A thin GaN LED film, grown on 2-inch-diameter sapphire substrates, is separated by laser lift-off. Atom force microscopy (AFM) and the double-crystal X-ray diffraction (XRD) have been employed to characterize the performance of GaN before and after the lift-off process. It is demonstrated that the separation and transfer processes do not alter the crystal quality of the GaN films obviously. InGaN/GaN multi-quantum-wells (MQW's) structure is grown on the separated sapphire substrate later and is compared with that grown on the conventional substrate under the same condition by using PL and XRD spectrum.
2008, 4(5):358-360.
Abstract:
Based on the plane-wave method, the optical properties of complete forbidden bands of woodpile structure photonic crystal with an entire lattice rotation of 45°in the x-y plane were theoretically studied in terms ofheight-to-pitch ratios, filling factors, and rotation angles. The calculated results show that the gap to mid-gap ratio changes slightly with a filling fraction ranging from 0.25 to 0.30. The optimum height-to-pitch ratio is about 1.3. The gap to mid-gap ratio reaches more than 0.18 when the rotation angle increases from 40°to 50°and the maximum gap to mid-gap ratio of 0.2 remains unchanged for the rotation angle from 42°to 48°with a constant height-to-pitch ratio of 1.3. The gap to mid-gap ratio reaches the maximum value of 0.2 when the height-to-pitch ratio is 1.3. This woodpile-type photonic crystal can provide large band gaps within a wider parameter range, which makes it convenient to manufacture three-dimensional photonic crystals in the laboratory.
Based on the plane-wave method, the optical properties of complete forbidden bands of woodpile structure photonic crystal with an entire lattice rotation of 45°in the x-y plane were theoretically studied in terms ofheight-to-pitch ratios, filling factors, and rotation angles. The calculated results show that the gap to mid-gap ratio changes slightly with a filling fraction ranging from 0.25 to 0.30. The optimum height-to-pitch ratio is about 1.3. The gap to mid-gap ratio reaches more than 0.18 when the rotation angle increases from 40°to 50°and the maximum gap to mid-gap ratio of 0.2 remains unchanged for the rotation angle from 42°to 48°with a constant height-to-pitch ratio of 1.3. The gap to mid-gap ratio reaches the maximum value of 0.2 when the height-to-pitch ratio is 1.3. This woodpile-type photonic crystal can provide large band gaps within a wider parameter range, which makes it convenient to manufacture three-dimensional photonic crystals in the laboratory.
2008, 4(5):361-364.
Abstract:
The data packet buffering can be implemented in dual loop optical buffer (DLOB) through cross-phase modulation (XPM) between the control signal and the data packets. However, the output equality of dual wavelength signals will degrade due to the unbalanced gain and phase shift. This problem can be resolved by power equalization using the saturation characteristics of SOA. The data packets with 2.5 Gb/s can be buffered in DLOB for 16 cycles corresponding to 16.5 μs.The extinction ratio of the output packet is 8 dB while the S/N is 8.1 dB.
The data packet buffering can be implemented in dual loop optical buffer (DLOB) through cross-phase modulation (XPM) between the control signal and the data packets. However, the output equality of dual wavelength signals will degrade due to the unbalanced gain and phase shift. This problem can be resolved by power equalization using the saturation characteristics of SOA. The data packets with 2.5 Gb/s can be buffered in DLOB for 16 cycles corresponding to 16.5 μs.The extinction ratio of the output packet is 8 dB while the S/N is 8.1 dB.
2008, 4(5):365-368.
Abstract:
We propose a new method to perform an ultra high speed all optical remote controlled X-NOR logic operation at a very long distance by exploiting the interaction of hypersecant optical soliton pulses (HOSP). To implement such logic operation, three HOSPs maintaining a particular condition are introduced into an 6ptical fiber where they interact with each other. Two of them carry the input of the logic operation with the constant triggering of other HOSP.
We propose a new method to perform an ultra high speed all optical remote controlled X-NOR logic operation at a very long distance by exploiting the interaction of hypersecant optical soliton pulses (HOSP). To implement such logic operation, three HOSPs maintaining a particular condition are introduced into an 6ptical fiber where they interact with each other. Two of them carry the input of the logic operation with the constant triggering of other HOSP.
Xian-yun Liu
,
Wei-jun Zhang
,
Zhen-ya Wang
,
Li-qing Hao
,
Ming-qiang Huang
,
Wen-wu Zhao
,
Bo Long
,
Wei Zhao
2008, 4(5):369-370.
Abstract:
We develop a system to measure the elemental composition of unprepared samples using laser-induced breakdown spectroscopy (LIBS) in our laboratory, which can be used for the determination of elements in solids, liquids and aerosols. A description of the instrumentation, including laser, sample chamber and detection, is followed by a brief discussion. The time-resolved LIBS of aluminum at atmospheric pressure is presented. At the end, the possibilities and later uses of this technique are briefly discussed.
We develop a system to measure the elemental composition of unprepared samples using laser-induced breakdown spectroscopy (LIBS) in our laboratory, which can be used for the determination of elements in solids, liquids and aerosols. A description of the instrumentation, including laser, sample chamber and detection, is followed by a brief discussion. The time-resolved LIBS of aluminum at atmospheric pressure is presented. At the end, the possibilities and later uses of this technique are briefly discussed.
2008, 4(5):371-374.
Abstract:
A paper information anti-fake and tamper-proofing method based on human visual characteristics and morphology screen coding technology is proposed. Through controlling the distribution of mathematical morphology of screen dot-matrix, warning mark and information are hidden in the background texture. Because of the differences between human vision and the duplicate characteristics of copy machine, warning mark which can not be discriminated by human eyes will emerge after copy. Tampered or fake certificates can be verified by comparing embedded information which is extracted from scanned image of certificate with plain text printed on the certificate. This method is applied in many bills and certificates. Experimental results show that the identification accuracy is above 98%
A paper information anti-fake and tamper-proofing method based on human visual characteristics and morphology screen coding technology is proposed. Through controlling the distribution of mathematical morphology of screen dot-matrix, warning mark and information are hidden in the background texture. Because of the differences between human vision and the duplicate characteristics of copy machine, warning mark which can not be discriminated by human eyes will emerge after copy. Tampered or fake certificates can be verified by comparing embedded information which is extracted from scanned image of certificate with plain text printed on the certificate. This method is applied in many bills and certificates. Experimental results show that the identification accuracy is above 98%
2008, 4(5):375-378.
Abstract:
A typical Markov network for modeling the interaction among targets can handle the error merge problem, but it suffers from the labeling problem due to the blind competition among collaborative trackers. In this paper, we propose a motion constraint Markov network model for multi-target tracking. By augmenting the typical Markov network with an ad hoc Markov chain which carries motion constraint prior, this proposed model can overcome the blind competition and direct the label to the corresponding target even in the case of severe occlusion. In addition, the motion constraint prior is formu- lated as a local potential function and can be easily incorporated in the joint distribution representation of the novel model. Experimental results demonstrate that our model is superior to other methods in solving the error merge and labeling problems simultaneously and efficiently.
A typical Markov network for modeling the interaction among targets can handle the error merge problem, but it suffers from the labeling problem due to the blind competition among collaborative trackers. In this paper, we propose a motion constraint Markov network model for multi-target tracking. By augmenting the typical Markov network with an ad hoc Markov chain which carries motion constraint prior, this proposed model can overcome the blind competition and direct the label to the corresponding target even in the case of severe occlusion. In addition, the motion constraint prior is formu- lated as a local potential function and can be easily incorporated in the joint distribution representation of the novel model. Experimental results demonstrate that our model is superior to other methods in solving the error merge and labeling problems simultaneously and efficiently.
2008, 4(5):379-383.
Abstract:
A novel algorithm for a rotation invariant template matching is proposed when the fluctuating scope of the rotation angle is limited within the region of [-20°,20°]. The matching candidates are selected using a computationally low cost improved correlation algorithm. "AND" operation is adopted to reduce the computational cost. Therefore the algorithm improves the matching speed consumedly. The simulation results verify the efficiency of the proposed method. Moreover, when the size of reference image is fixed, the advantage of this time-saving algorithm is more obvious as the increase of the size of the real time image. The matching speed of the proposed method is over 20 times faster than the speed of the two-level pyramid decomposing accelerating method.
A novel algorithm for a rotation invariant template matching is proposed when the fluctuating scope of the rotation angle is limited within the region of [-20°,20°]. The matching candidates are selected using a computationally low cost improved correlation algorithm. "AND" operation is adopted to reduce the computational cost. Therefore the algorithm improves the matching speed consumedly. The simulation results verify the efficiency of the proposed method. Moreover, when the size of reference image is fixed, the advantage of this time-saving algorithm is more obvious as the increase of the size of the real time image. The matching speed of the proposed method is over 20 times faster than the speed of the two-level pyramid decomposing accelerating method.
2008, 4(5):384-386.
Abstract:
This paper proposes a novel wavelet-based face recognition method using thermal infrared (1R) and visible-light face images. The method applies the combination of Gabor and the Fisherfaces method to the reconstructed IR and visible images derived from wavelet frequency subbands. Our objective is to search for the subbands that are insensitive to the variation in expression and in illumination. The classification performance is improved by combining the multispectal information coming from the subbands that attain individually low equal error rate. Experimental results on Notre Dame face database show that the proposed wavelet-based algorithm outperforms previous multispectral images fusion method as well as monospectral method.
This paper proposes a novel wavelet-based face recognition method using thermal infrared (1R) and visible-light face images. The method applies the combination of Gabor and the Fisherfaces method to the reconstructed IR and visible images derived from wavelet frequency subbands. Our objective is to search for the subbands that are insensitive to the variation in expression and in illumination. The classification performance is improved by combining the multispectal information coming from the subbands that attain individually low equal error rate. Experimental results on Notre Dame face database show that the proposed wavelet-based algorithm outperforms previous multispectral images fusion method as well as monospectral method.
2008, 4(5):387-390.
Abstract:
In this report we illustrate our application of soft lithography-based microfabrication, surface modification, and our unique laser cell-patterning system toward the creation of neuron biochips. We deposited individual forebrain neurons from Day 7 embryonic chicks into two rows of eight in a silicon microstructure aligned over a microelectrode array (MEA). The polydimethylsiloxane (PDMS) membrane with microstructures to confine cells and guide network connectivity was aligned to the electrodes ofa MEA. Both the MEA and the PDMS membrane were treated with O2 plasma, Poly-L-Lysine, and Laminin to aid in cell attachment and survival. The primary advantage of our process is that it is quicker and simpler than previous cell-placement methods and may make highly defined neuronal network biochips more practical
In this report we illustrate our application of soft lithography-based microfabrication, surface modification, and our unique laser cell-patterning system toward the creation of neuron biochips. We deposited individual forebrain neurons from Day 7 embryonic chicks into two rows of eight in a silicon microstructure aligned over a microelectrode array (MEA). The polydimethylsiloxane (PDMS) membrane with microstructures to confine cells and guide network connectivity was aligned to the electrodes ofa MEA. Both the MEA and the PDMS membrane were treated with O2 plasma, Poly-L-Lysine, and Laminin to aid in cell attachment and survival. The primary advantage of our process is that it is quicker and simpler than previous cell-placement methods and may make highly defined neuronal network biochips more practical
2008, 4(5):391-394.
Abstract:
We give the characteristic equation of a W-type fiber by solving Maxwell's equations along with boundary conditions at the interfaces. The cutoff condition of the fundamental mode is examined, and a novel W-type fiber working in S-band is designed.
We give the characteristic equation of a W-type fiber by solving Maxwell's equations along with boundary conditions at the interfaces. The cutoff condition of the fundamental mode is examined, and a novel W-type fiber working in S-band is designed.
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