Volume 3,Issue 4,2007 Table of Contents
2007, 3(4).
Abstract:
A rearrangeable nonblocking silicon-on-insulator-based thermo-optic 4×4 switch matrix with spot size converters (SSCs) and a new driving circuit are designed and fabricated. The introduction of a spot size converter (SSC) has decreased the insertion loss to less than 10dB and the new driving circuit has improved the response speed to less than 1μs.
A rearrangeable nonblocking silicon-on-insulator-based thermo-optic 4×4 switch matrix with spot size converters (SSCs) and a new driving circuit are designed and fabricated. The introduction of a spot size converter (SSC) has decreased the insertion loss to less than 10dB and the new driving circuit has improved the response speed to less than 1μs.
2007, 3(4).
Abstract:
M. Paturzo
,
C. Del Core
,
S. Grilli
,
S. De Nicola
,
P. Ferraro
,
P. De Natale
,
G. Coppola
,
M. Iodice
,
M. Gioffré
2007, 3(4):243-245.
Abstract:
Photolithography experiments are performed by means of an optical phase mask with electrooptically tunable phase step.The phase mask consists of a 2-dimensional hexagonal lattice of inverted ferroelectric domains fabricated on a z-cut lithium niobate substrate. The electro-optically tunable phase step, between inverted domain, is obtained by the application of an external electric field along the z axis of the crystal via transparent electrodes. The collimated beam of an argon laser passes through the phase mask and the near field intensity patterns, at different planes of the Talbot length and for different values of the applied voltage, are used for photolithographic experiments. Preliminary results are shown and further applications are discussed.
Photolithography experiments are performed by means of an optical phase mask with electrooptically tunable phase step.The phase mask consists of a 2-dimensional hexagonal lattice of inverted ferroelectric domains fabricated on a z-cut lithium niobate substrate. The electro-optically tunable phase step, between inverted domain, is obtained by the application of an external electric field along the z axis of the crystal via transparent electrodes. The collimated beam of an argon laser passes through the phase mask and the near field intensity patterns, at different planes of the Talbot length and for different values of the applied voltage, are used for photolithographic experiments. Preliminary results are shown and further applications are discussed.
2007, 3(4):246-247.
Abstract:
In order to solve excessive insertion loss and low on/off ratio in quantum well reflection-type waveguide optical switches,a novel InGaAs/InAlAs coupled quantum well structure is proposed. In the case of low applied electric field (F=19 kV/cm)and low absorption loss (α≈ 61.2 cm-1), a large negative field-induced refractive index change ( △ n=-0.0134) is obtained in the novel coupled quantum well structure at the operating wavelength ( λ =1550 nm). The value is larger by over one to two order of magnitude compared to that in a rectangular quantum well (RQW) on the above same work conditions.
In order to solve excessive insertion loss and low on/off ratio in quantum well reflection-type waveguide optical switches,a novel InGaAs/InAlAs coupled quantum well structure is proposed. In the case of low applied electric field (F=19 kV/cm)and low absorption loss (α≈ 61.2 cm-1), a large negative field-induced refractive index change ( △ n=-0.0134) is obtained in the novel coupled quantum well structure at the operating wavelength ( λ =1550 nm). The value is larger by over one to two order of magnitude compared to that in a rectangular quantum well (RQW) on the above same work conditions.
2007, 3(4):248-250.
Abstract:
Based on the self-imaging effect, multimode interference (MMI) optical switches with area modulation were proposed. The field transfer matrix was introduced to analyze the MMI switches. As an example, the phase modulation parameters of a 3 × 3 MMI switch for different switching cases were obtained by solving the field transfer equation. And the finite-difference beam propagation method (FD-BPM) was used to confirm the analytical results.
Based on the self-imaging effect, multimode interference (MMI) optical switches with area modulation were proposed. The field transfer matrix was introduced to analyze the MMI switches. As an example, the phase modulation parameters of a 3 × 3 MMI switch for different switching cases were obtained by solving the field transfer equation. And the finite-difference beam propagation method (FD-BPM) was used to confirm the analytical results.
2007, 3(4):251-253.
Abstract:
Design optimization of a novel integrated triplexer based on planar lightwave circuit (PLC) for fiber-to-the-home applications is described. The two-mode interference coupler and Mach-Zehnder interference are used to construct the filter chip.Simulation results of high isolation and low insertion loss are gotten for proposed design. Technique tolerance is improved for fabricating device.
Design optimization of a novel integrated triplexer based on planar lightwave circuit (PLC) for fiber-to-the-home applications is described. The two-mode interference coupler and Mach-Zehnder interference are used to construct the filter chip.Simulation results of high isolation and low insertion loss are gotten for proposed design. Technique tolerance is improved for fabricating device.
2007, 3(4):254-256.
Abstract:
Multimode interference (MMI) devices are widely used in planar lightwave circuit (PLC). The device length can be well reduced with tapered multimode region. Traditional design formula shows large error for MMI devices based on weaklyrestricted waveguide. Based on the analysis with mode width as a substitution of waveguide width, a design formula with better precision was presented. Comparison with software simulation verified its exactness.
Multimode interference (MMI) devices are widely used in planar lightwave circuit (PLC). The device length can be well reduced with tapered multimode region. Traditional design formula shows large error for MMI devices based on weaklyrestricted waveguide. Based on the analysis with mode width as a substitution of waveguide width, a design formula with better precision was presented. Comparison with software simulation verified its exactness.
2007, 3(4):257-259.
Abstract:
In the weakly guided case, the power propagation in the core and the cladding of a left-handed material fiber is obtained by solving Maxwell's equations. The wave-guide efficiency is analyzed at cutoff and far from cutoff. Far from cutoff, the wave-guide efficiency equals to 1. At cutoff, for m=0, 1, the wave-guide efficiency equals to zero; for m=2, the wave-guide efficiency approaches to infinite; for m＞2, the wave-guide efficiency is less than zero, but its absolute value is larger than 1. Those are novel characteristics of left-handed material fiber.
In the weakly guided case, the power propagation in the core and the cladding of a left-handed material fiber is obtained by solving Maxwell's equations. The wave-guide efficiency is analyzed at cutoff and far from cutoff. Far from cutoff, the wave-guide efficiency equals to 1. At cutoff, for m=0, 1, the wave-guide efficiency equals to zero; for m=2, the wave-guide efficiency approaches to infinite; for m＞2, the wave-guide efficiency is less than zero, but its absolute value is larger than 1. Those are novel characteristics of left-handed material fiber.
2007, 3(4):260-263.
Abstract:
This paper describes our research activity involved in the identification, development and test of a prototype SHM system constituted by optical sensing nodes to measure both temperature and strain on ultra high temperature ceramics (UHTC) materials up to 1000 ℃. Commercially available optic devices can operate up to 550 ℃. To raise temperature limit up to 1000 ℃, custom devices, mainly under development for scientific applications, have been identified. A prototype SHM system has been developed adopting a FBG sensor for temperature measurement and an EFPI sensor in sapphire fiber for strain measurement. The preliminary findings from thermo-mechanical tests indicate that former SHM system is capable of accurately measuring strain at elevated temperatures on UHTC materials.
This paper describes our research activity involved in the identification, development and test of a prototype SHM system constituted by optical sensing nodes to measure both temperature and strain on ultra high temperature ceramics (UHTC) materials up to 1000 ℃. Commercially available optic devices can operate up to 550 ℃. To raise temperature limit up to 1000 ℃, custom devices, mainly under development for scientific applications, have been identified. A prototype SHM system has been developed adopting a FBG sensor for temperature measurement and an EFPI sensor in sapphire fiber for strain measurement. The preliminary findings from thermo-mechanical tests indicate that former SHM system is capable of accurately measuring strain at elevated temperatures on UHTC materials.
2007, 3(4):264-266.
Abstract:
A new fiber optic hydrophone is described. based on a distributed feedback fiber laser (DFB-fiber laser) Experimental arrangement consists of DFB-FL, unbalanced Mach-Zehnder interferometer, piezoelectric (PZT) modulator, detection and feedback control circuit, and oscillograph. Experimental results show that the bare DFB-FL hydrophone is extremely sensitive to small perturbations in their environment and can acquire exact acoustic signals.
A new fiber optic hydrophone is described. based on a distributed feedback fiber laser (DFB-fiber laser) Experimental arrangement consists of DFB-FL, unbalanced Mach-Zehnder interferometer, piezoelectric (PZT) modulator, detection and feedback control circuit, and oscillograph. Experimental results show that the bare DFB-FL hydrophone is extremely sensitive to small perturbations in their environment and can acquire exact acoustic signals.
2007, 3(4):267-270.
Abstract:
The impact of XPM on the microwave photonic switching with NOLM is analyzed by the split-step Fourier method (SSFM) that can solve the coupled nonlinear Schr(o)dinger equation (CNLSE). The simulation results show that XPM induces the distortion of waveforms and the leak of side lobes. And the larger the modulation bandwidth is, the larger the leak of side lobes is. Furthermore, the power transmission function of NOLM Tm is distorted because of the XPM-induced nonreciprocity: Tm decreases when the splitting ratio of the couplerf ∈ (0,0.5) and increases when f ∈ (0.5,1.0).
The impact of XPM on the microwave photonic switching with NOLM is analyzed by the split-step Fourier method (SSFM) that can solve the coupled nonlinear Schr(o)dinger equation (CNLSE). The simulation results show that XPM induces the distortion of waveforms and the leak of side lobes. And the larger the modulation bandwidth is, the larger the leak of side lobes is. Furthermore, the power transmission function of NOLM Tm is distorted because of the XPM-induced nonreciprocity: Tm decreases when the splitting ratio of the couplerf ∈ (0,0.5) and increases when f ∈ (0.5,1.0).
12 Application of genetic algorithm in quasi-static fiber grating wavelength demodulation technology
2007, 3(4):271-274.
Abstract:
A modified genetic algorithm (GA) has been proposed, which was used to wavelength demodulation in quasi-static fiber grating sensing system. The modification method of GA has been introduced and the relevant mathematical model has been established. The objective function and individual fitness evaluation strategy interrelated with GA are also established. The influence of population size, chromosome size, generations, crossover probability and mutation probability on the GA has been analyzed, and the optimal parameters of modified GA have been obtained. The simulations and experiments, show that the modified GA can be applied to quasi-static fiber grating sensing system, and the wavelength demodulation precision is equal to or less than 3 pm.
A modified genetic algorithm (GA) has been proposed, which was used to wavelength demodulation in quasi-static fiber grating sensing system. The modification method of GA has been introduced and the relevant mathematical model has been established. The objective function and individual fitness evaluation strategy interrelated with GA are also established. The influence of population size, chromosome size, generations, crossover probability and mutation probability on the GA has been analyzed, and the optimal parameters of modified GA have been obtained. The simulations and experiments, show that the modified GA can be applied to quasi-static fiber grating sensing system, and the wavelength demodulation precision is equal to or less than 3 pm.
2007, 3(4):275-277.
Abstract:
Measuring amplitude of signal is the usual method in wavelength demodulation of fiber Bragg grating (FBG) sensors recently. This method is easy to be disturbed and has low precision. In this paper, a novel counting wavelength demodulation scheme of FBG sensors using a high birefringent fiber (HBF) loop mirror is reported. This demodulator has simple structure, high precision, cheap price and convenient use. The resolution of the loop mirror device with a HBF of 30 meters long is 0.067 nm. For a center wavelength of FBG of about 1550 nm and a 40 nm shift range of its reflection wavelength,the relative error of measurement is only ± 0.001. This wavelength demodulation device has significance for widespread application of FBG sensors.
Measuring amplitude of signal is the usual method in wavelength demodulation of fiber Bragg grating (FBG) sensors recently. This method is easy to be disturbed and has low precision. In this paper, a novel counting wavelength demodulation scheme of FBG sensors using a high birefringent fiber (HBF) loop mirror is reported. This demodulator has simple structure, high precision, cheap price and convenient use. The resolution of the loop mirror device with a HBF of 30 meters long is 0.067 nm. For a center wavelength of FBG of about 1550 nm and a 40 nm shift range of its reflection wavelength,the relative error of measurement is only ± 0.001. This wavelength demodulation device has significance for widespread application of FBG sensors.
2007, 3(4):278-281.
Abstract:
Diffraction efficiency of grating plays an important role in output power of incoherent fiber laser beam combination.Through theoretic analysis and numerical simulations it has been proved that the diffraction efficiency would increase with the decrease of grating frequency and wavelength bandwidth. On the condition that the width of a fiber array is fixed at W=10 cm, an optimum grating frequency were numerically simulated as f=230 mm-1. Also an unequal interval method was proposed to improve the system efficiency of diffraction into 0.4293, which is higher than 0.3824 under the equal interval condition.
Diffraction efficiency of grating plays an important role in output power of incoherent fiber laser beam combination.Through theoretic analysis and numerical simulations it has been proved that the diffraction efficiency would increase with the decrease of grating frequency and wavelength bandwidth. On the condition that the width of a fiber array is fixed at W=10 cm, an optimum grating frequency were numerically simulated as f=230 mm-1. Also an unequal interval method was proposed to improve the system efficiency of diffraction into 0.4293, which is higher than 0.3824 under the equal interval condition.
2007, 3(4):282-285.
Abstract:
The hole transporting layer (HTL) of organic light-emitting device (OLED) was processed by vacuum deposition and spin coating method, respectively, where N,N'-biphenyl-N, N'-bis(3-methylphenyl)-1, 1'-biphenyl-4,4' -diamine (TPD) and poly (vinylcarbazole) (PVK) acted as the hole-transport materials. Tris-(8-hydroxyquinoline)- aluminum (Alq3) was utilized as both the light-emitting layer and the electron transporting layer. The basic structure of the device cell was: indium-tin-oxide (ITO)/PVK: TPD/Alq3/Mg:Ag. The electroluminescent (EL) characteristics of devices were characterized. The results showed that the peak of EL spectra was located at 530 nm, which conformed to the characterizing spectrum of Alq3.Compared with using vacuum deposition method, the green emission with a maximum luminance up to 26135 cd/m2 could be achieved at a drive voltage of 15 V by selecting proper solvent using spin-coating technique, and its maximum luminance efficiency was 2.56 lm/W at a drive voltage of 5.5 V.
The hole transporting layer (HTL) of organic light-emitting device (OLED) was processed by vacuum deposition and spin coating method, respectively, where N,N'-biphenyl-N, N'-bis(3-methylphenyl)-1, 1'-biphenyl-4,4' -diamine (TPD) and poly (vinylcarbazole) (PVK) acted as the hole-transport materials. Tris-(8-hydroxyquinoline)- aluminum (Alq3) was utilized as both the light-emitting layer and the electron transporting layer. The basic structure of the device cell was: indium-tin-oxide (ITO)/PVK: TPD/Alq3/Mg:Ag. The electroluminescent (EL) characteristics of devices were characterized. The results showed that the peak of EL spectra was located at 530 nm, which conformed to the characterizing spectrum of Alq3.Compared with using vacuum deposition method, the green emission with a maximum luminance up to 26135 cd/m2 could be achieved at a drive voltage of 15 V by selecting proper solvent using spin-coating technique, and its maximum luminance efficiency was 2.56 lm/W at a drive voltage of 5.5 V.
2007, 3(4):286-288.
Abstract:
Aluminum nitride (AlN) films with h＜100＞ crystalline orientation are fabricated on p-Si (100) substrates at room temperature by pulsed laser deposition. The effects of laser energy density and annealing on the quality of the films are studied by x-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. The crystalline quality of AlN films is improved considerably by increasing the laser energy density while there is increased number of farraginous particles on the surface. The annealing treatment at 600℃ produces a recrystallization process in the film, characterized by the improvement of the original crystallinity, the appearance of new crystalline orientations, and the increase of the crystallites.The surface becomes rougher due to the increase of the grain size during annealing.
Aluminum nitride (AlN) films with h＜100＞ crystalline orientation are fabricated on p-Si (100) substrates at room temperature by pulsed laser deposition. The effects of laser energy density and annealing on the quality of the films are studied by x-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. The crystalline quality of AlN films is improved considerably by increasing the laser energy density while there is increased number of farraginous particles on the surface. The annealing treatment at 600℃ produces a recrystallization process in the film, characterized by the improvement of the original crystallinity, the appearance of new crystalline orientations, and the increase of the crystallites.The surface becomes rougher due to the increase of the grain size during annealing.
2007, 3(4):289-293.
Abstract:
A theoretical model is proposed in order to study the configuration resonance in s-SNOM. The electromagnetic coupling between the sample and the probe tip is described with the quasi-electrostatic field theory. This method permits us to analyze the configurational resonance evoked by the interaction between the probe tip and the sample in s-SNOM intuitively.The resonant conditions for a certain system are presented in an explicit form. On the condition of considering the actual size of the sample dipoles and the probe dipole, we discuss the possibility of realizing the configurational resonance for various material samples. The numerical results indicate that the polarizability of the dielectric probe tip is too small to arouse this resonance, whereas, with the surface plasmon resonance emerging on the metallic nanoparticles, the enhanced polarizability of the metallic probe tip ensures the requirements of fulfilling the resonance.
A theoretical model is proposed in order to study the configuration resonance in s-SNOM. The electromagnetic coupling between the sample and the probe tip is described with the quasi-electrostatic field theory. This method permits us to analyze the configurational resonance evoked by the interaction between the probe tip and the sample in s-SNOM intuitively.The resonant conditions for a certain system are presented in an explicit form. On the condition of considering the actual size of the sample dipoles and the probe dipole, we discuss the possibility of realizing the configurational resonance for various material samples. The numerical results indicate that the polarizability of the dielectric probe tip is too small to arouse this resonance, whereas, with the surface plasmon resonance emerging on the metallic nanoparticles, the enhanced polarizability of the metallic probe tip ensures the requirements of fulfilling the resonance.
2007, 3(4):294-298.
Abstract:
The dual-light displacement sensor is presented to obtain a higher accuracy compared with the single. The structure and principle of the system are also introduced, and the hardware and software are brought in too. The function of the system is feasible through the experiments and simulating the data process based on FPGA.
The dual-light displacement sensor is presented to obtain a higher accuracy compared with the single. The structure and principle of the system are also introduced, and the hardware and software are brought in too. The function of the system is feasible through the experiments and simulating the data process based on FPGA.
2007, 3(4):299-302.
Abstract:
The phase information of an enlarged source is reconstructed with an annular two-zone phase-only filter in a fluorescent confocal scanning optical microscope for resolution improvement. The dependences of its resolution on the source size and on the phase transmission of the outer annular zone of the filter are investigated theoretically by use of its three-dimensional optical transfer function (3D OTF ). The increased source size and the required phase value of the outer annular zone of the phase-only filter for an optimal 3D OTF of the optical system are presented.
The phase information of an enlarged source is reconstructed with an annular two-zone phase-only filter in a fluorescent confocal scanning optical microscope for resolution improvement. The dependences of its resolution on the source size and on the phase transmission of the outer annular zone of the filter are investigated theoretically by use of its three-dimensional optical transfer function (3D OTF ). The increased source size and the required phase value of the outer annular zone of the phase-only filter for an optimal 3D OTF of the optical system are presented.
2007, 3(4):303-307.
Abstract:
A global motion estimation method based on robust statistics is presented in this paper. By using tracked feature points instead of whole image pixels to estimate parameters the process speeds up. To further speed up the process and avoid numerical instability, an alterative description of the problem is given, and three types of solution to the problem are compared. By using a two step process, the robustness of the estimator is also improved. Automatic initial value selection is an advantage of this method. The proposed approach is illustrated by a set of examples, which shows good results with high speed.
A global motion estimation method based on robust statistics is presented in this paper. By using tracked feature points instead of whole image pixels to estimate parameters the process speeds up. To further speed up the process and avoid numerical instability, an alterative description of the problem is given, and three types of solution to the problem are compared. By using a two step process, the robustness of the estimator is also improved. Automatic initial value selection is an advantage of this method. The proposed approach is illustrated by a set of examples, which shows good results with high speed.
2007, 3(4):308-311.
Abstract:
An algorithm using fixed-lag smooth filtering to improve the precision of EIS algorithm is presented in this paper. Firstly,gray projection algorithm (GPA) is used to calculate the interframe global motion vectors. Secondly, the fixed-lag smooth filter is used to smoothen the motion track of the original video sequence, according to different motion models. At last, the original sequence is compensated by using the compensation vectors calculated from filtering. This algorithm has been proved superior in filtering precision by experiments of video sequences in different motion scenes. This algorithm also satisfies the real-time request.
An algorithm using fixed-lag smooth filtering to improve the precision of EIS algorithm is presented in this paper. Firstly,gray projection algorithm (GPA) is used to calculate the interframe global motion vectors. Secondly, the fixed-lag smooth filter is used to smoothen the motion track of the original video sequence, according to different motion models. At last, the original sequence is compensated by using the compensation vectors calculated from filtering. This algorithm has been proved superior in filtering precision by experiments of video sequences in different motion scenes. This algorithm also satisfies the real-time request.
2007, 3(4):312-314.
Abstract:
Features of human skin in HSV color space are widely applied in the area of image retrieval based on content. H is selected as the basic recognition parameter because its value has a narrow range for the skin color and can keep stable while the illumination intensity or the curvature of skin surface is changing. Rules of parameters with the change of illumination in HSV color space are studied. It is firstly found that the mean of saturation and value (S V)/2 can keep stable when the illumination intensity is changed or the skin surface is inflected, and (S V)/2 changes with skin color, but the tendency of change is contrary to that of H. Therefore, (S V)/H can be used as a new recognition parameter which can enhance HSV ability to recognize human skin.
Features of human skin in HSV color space are widely applied in the area of image retrieval based on content. H is selected as the basic recognition parameter because its value has a narrow range for the skin color and can keep stable while the illumination intensity or the curvature of skin surface is changing. Rules of parameters with the change of illumination in HSV color space are studied. It is firstly found that the mean of saturation and value (S V)/2 can keep stable when the illumination intensity is changed or the skin surface is inflected, and (S V)/2 changes with skin color, but the tendency of change is contrary to that of H. Therefore, (S V)/H can be used as a new recognition parameter which can enhance HSV ability to recognize human skin.
2007, 3(4):315-317.
Abstract:
Phase diverse speckle is a novel kind of imaging technique and can be used to overcome image degradation from unknown phase aberrations, such as atmospheric turbulence. The wave-front phase expanded on the Zernike polynomials is estimated from a pair of images (in the focal and out of focus planes). In this paper the principle of PDS is analyzed, and genetic algorithm is used as the iterative algorithm to simulate some characteristics, such as the influence of Zernike polynomials'mode, amplitude of turbulence on the phase estimation. Thus, a new method for recovery of images is explored.
Phase diverse speckle is a novel kind of imaging technique and can be used to overcome image degradation from unknown phase aberrations, such as atmospheric turbulence. The wave-front phase expanded on the Zernike polynomials is estimated from a pair of images (in the focal and out of focus planes). In this paper the principle of PDS is analyzed, and genetic algorithm is used as the iterative algorithm to simulate some characteristics, such as the influence of Zernike polynomials'mode, amplitude of turbulence on the phase estimation. Thus, a new method for recovery of images is explored.
2007, 3(4):318-320.
Abstract:
Two novel structures of fractal Cantor multilayer with defects are presented. The Optical transmission matrix method is used to calculate the transmittance and the reflectance. Compared with the general Cantor multilayer, these novel structures have wider stopbands and show super narrow bands in the middle of the wider stopbands, which can be used as super narrow bandpass filters. The pass band can be less than 0.6 nm near the infrared wavelength of 1530 nm when there is an embedded defect in the cantor multilayer. The optical transmission in the central wavelength is higher than 99 %, which means a very low insert loss. If there are three layers, three super narrow peaks can be found in the middle of the stopband.The central wavelengths are respectively 1232.4 nm, 1372.8 nm and 1538.3 nm. It is much better than other kinds of narrow band filters and it may be used in the optical communications.
Two novel structures of fractal Cantor multilayer with defects are presented. The Optical transmission matrix method is used to calculate the transmittance and the reflectance. Compared with the general Cantor multilayer, these novel structures have wider stopbands and show super narrow bands in the middle of the wider stopbands, which can be used as super narrow bandpass filters. The pass band can be less than 0.6 nm near the infrared wavelength of 1530 nm when there is an embedded defect in the cantor multilayer. The optical transmission in the central wavelength is higher than 99 %, which means a very low insert loss. If there are three layers, three super narrow peaks can be found in the middle of the stopband.The central wavelengths are respectively 1232.4 nm, 1372.8 nm and 1538.3 nm. It is much better than other kinds of narrow band filters and it may be used in the optical communications.
2007, 3(4):F0003-F0003.
Abstract:
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