A theory of the far spatial coherent-suppressed single-peak field distribution of a rectangular wave-guide CO2 laser is presented. The theoretical analysis shows that a rectangular wave-guide laser can have an output ...A theory of the far spatial coherent-suppressed single-peak field distribution of a rectangular wave-guide CO2 laser is presented. The theoretical analysis shows that a rectangular wave-guide laser can have an output intensity distribution in far field similar to that produced from a wave-guide array laser, which is in agreement with the experimental result. A single-peak mode output is obtained within 5 metres. The experimental far-field spread angle in the bigger-Fresnel number direction is 0.63 mrad, compared to the calculated one, 0.6 mrad, and when the length of the laser resonator is changed, a double-peak or multi-peak in far-field distribution of the laser is obtained.展开更多
Inner flange and side wrinkling often occur in rotary-draw bending process of rectangular aluminum alloy wave-guide tubes, and the distribution and magnitude of wrinkling is related to geometrical parameters of the tu...Inner flange and side wrinkling often occur in rotary-draw bending process of rectangular aluminum alloy wave-guide tubes, and the distribution and magnitude of wrinkling is related to geometrical parameters of the tubes. In order to study the effects of geometrical parameters on wrinkling of rectangular wave-guide tubes, a 3D-FE model for rotary-draw bending processes of thin-walled rectangular aluminum alloy wave-guide tubes was built based on the platform of ABA-QUS/Explicit, and its reliability was validated by experiments. Simulation and analysis of the influence laws of geometrical parameters on the wave heights of inner flange and side wrinkling were then carried out. The results show that inner flange wrinkling is the main wrinkling way to rectan- gular wave-guide tubes in rotary-draw bending processes, but side wrinkling cannot be neglected because side wrinkling is 2/3 of inner flange wrinkling when b and h are smaller. Inner flange and side wrinkling increase with increasing b and h; the influence of b on side wrinkling is larger than that of h, while both b and h affect inner flange wrinkling greatly. Inner flange and side wrinkling decrease with increasing R/h; the influence of h on inner flange and side wrinkling is larger than that of R.展开更多
The formation of the spatial solitons in the quadratic nonlinearity x(2) media by cascading second harmonic generation (SHG) in quasi-phase-matched (QPM) sample is studied on the basis of nonlinear Schrodinger equatio...The formation of the spatial solitons in the quadratic nonlinearity x(2) media by cascading second harmonic generation (SHG) in quasi-phase-matched (QPM) sample is studied on the basis of nonlinear Schrodinger equation (NLSE). When the solitary wave propagates in the QPM media, it formed optical wave-guides through cascading x(2) effect called self-induced soliton wave-guide. Transverse refractive index distribution of the self-induced soliton wave-guide of fundamental and SHG wave is obtained by cascading process. Analysis of guided-mode of such self-induced soliton wave-guide is first proposed to our knowledge. Because the power needed for forming the spatial solitons in cascading process is much lower than that in Kerr media, this kind of self-induced soliton wave-guide shows potential applications in all-optical signal process.展开更多
We investigate the unidirectional transmission behaviour of an asymmetrically confined photonic crystal （PC） defect with Kerr nonlinearity. Basically, the unidirectional transmission originates from the strong depen...We investigate the unidirectional transmission behaviour of an asymmetrically confined photonic crystal （PC） defect with Kerr nonlinearity. Basically, the unidirectional transmission originates from the strong dependence of the threshold input power for the sharp increase of transmission on the launch direction of the input wave. This can be well explained in the framework of the coupled mode theory. Our theoretical analysis reveals the existence of an upper limit for the transmission contrast when such a single PC defect is employed. This is supported by the simulation results based on the nonlinear finite-difference time-domain technique.展开更多
Using fully incoherent white light emitted from an incandescent lamp and amplitude mask, we experimentally investigate the influence of several factors on the fabrication of the lattice in photovoltaic self-defocusing...Using fully incoherent white light emitted from an incandescent lamp and amplitude mask, we experimentally investigate the influence of several factors on the fabrication of the lattice in photovoltaic self-defocusing LiNbO3：Fe crystal, the factors include the orientation of the crystalline c axis relative to the principal axis of the photonic lattice and the filament, the diameter of input dark spot and the separation of the adjacent input dark spots. Experimental results reveal that the best fabricating condition of photonic lattices is that the principal axis of lattice is tilted for 45^o relative to the crystalline c axis which is parallel to the filament of the lamp. In addition, it is necessary that the diameter of the input dark spot is larger than the half of their separation.展开更多
A novel woodpile lattice structure is proposed. Based on plane wave expansion （PWE） method, the complete photonic band gaps （PBGs） of the novel woodpile three^dimensional （3D） terahertz （THz） photonic crystal ...A novel woodpile lattice structure is proposed. Based on plane wave expansion （PWE） method, the complete photonic band gaps （PBGs） of the novel woodpile three^dimensional （3D） terahertz （THz） photonic crystal （PC） with a decreasing symmetry relative to a face-centred-tetragonal （fct） symmetry are optimized by varying some structural parameters and the highest band gap ratio can reach 27.61%. Compared to the traditional woodpile lattice, the novel woodpile lattice has a wider range of the filling ratios to gain high quality PBGs, which provides greater convenience for the manufacturing process. The novel woodpile 3D PC will be very promising for materials of THz Junctional components.展开更多
Work is devoted to the analysis of errors meeting in literature in treatment of a spatial part of a phase of running sound waves. In some cases, it is not taken into consideration that this part of a phase is formed b...Work is devoted to the analysis of errors meeting in literature in treatment of a spatial part of a phase of running sound waves. In some cases, it is not taken into consideration that this part of a phase is formed by scalar product of vectors which does not depend on a choice of system of co-ordinates. Taking into account the necessary corrections in record of a phase of plane waves, it is shown that the decision of the homogeneous wave equation in the form of “belated” potentials is simultaneously and the decision of the equations of movement of a liquid, and “outstripped” potentials does not satisfy them. The analysis of coefficients of reflection and passage of running waves in non-uniform space is carried out. It is shown that on boundary of spaces with different sound speeds, a turning point of a sound wave is the point of full internal reflection. The way of calculation of coefficients of reflection and passage is offered by consideration of all three waves on boundary of spaces as vectors with the set directions and amplitude of a falling wave. Calculation of coefficients of reflection and passage of a sound wave in a wave-guide of canonical type along the chosen trajectory by two methods—under traditional formulas and a vector method is carried out. Results of calculation practically coincide.展开更多
Near-field scanning optical microscopy is used to investigate the waveguiding properties of optical micro/nanofibres （MNFs） by means of detecting optical power carried by evanescent waves. Taper drawn silica and tel...Near-field scanning optical microscopy is used to investigate the waveguiding properties of optical micro/nanofibres （MNFs） by means of detecting optical power carried by evanescent waves. Taper drawn silica and tellurite MNFs, supported on low-index substrates, are used to guide a 532-nm-wavelength light beam for the test. Modification of the single-mode condition of the MNF in the presence of a substrate is observed. Spatial modulation of the longitudinal field intensity （with a 195-nm period） near the output end of a 760-nm-diameter silica MNF is well resolved. Energy exchange through evanescent coupling between two parallel MNFs is also investigated.展开更多
An erbium-doped phosphate glass fibre has been drawn by the rod-in-tube technique in our laboratory. The gain for the Er^3＋-doped phosphate glass fibre with different pump powers and with different input signal wavel...An erbium-doped phosphate glass fibre has been drawn by the rod-in-tube technique in our laboratory. The gain for the Er^3＋-doped phosphate glass fibre with different pump powers and with different input signal wavelengths is investigated. The 2.2-cm-long fibre, pumped by a single-mode 980-nm fibre-pigtailed laser diode, can provide a net gain per unit length greater than 1.SdB/cm. The pump threshold is about 50mW at the wavelength of 1534nm, and below 70roW at 1550nm. The gain linewidth of the Er^3＋-doped phosphate glass fibre is greater than 34 nm and can cover the C band in optical communication networks.展开更多
We experimentally study a novel fibre with high gain per unit length based on the homemade erbium-ytterbium codoped phosphate glass. The gain and noise characterizations with different pump powers at different wavelen...We experimentally study a novel fibre with high gain per unit length based on the homemade erbium-ytterbium codoped phosphate glass. The gain and noise characterizations with different pump powers at different wavelengths are investigated. The 1.8-cm-long fibre, dual-pumped by two single mode 980-nm fibre-pigtailed laser diodes, provides a gain per unit length greater than 3.0dB/cm and a noise figure less than 6.SdB. The gain saturation behaviour at 1535nm is obtained and the saturation output power （3 dB compression） is greater than 5 dBm.展开更多
Thermal stress-induced birefringence in borate glass which has been irradiated by 800-nm femtosecond laser pulses is observed under cross-polarized light. Due to the high temperature and pressure formed in the focal v...Thermal stress-induced birefringence in borate glass which has been irradiated by 800-nm femtosecond laser pulses is observed under cross-polarized light. Due to the high temperature and pressure formed in the focal volume, the material at the edge of the micro-modified region is compressed between the expanding region and the unheated one, then stress emerges. Raman spectroscopy is used to investigate the stress distribution in the micro-modified region and indicates the redistributions of density and refractive index by Raman peak shift. We suggest that this technique can develop waveguide polarizers and Fresnel zone plates in integrated optics.展开更多
An edge emitting laser based on two-dimensional photonic crystal slabs is proposed. The device consists of a square lattice microcavity, which is composed of two structures with the same period but different radius of...An edge emitting laser based on two-dimensional photonic crystal slabs is proposed. The device consists of a square lattice microcavity, which is composed of two structures with the same period but different radius of air-holes, and a waveguide. In the cavity, laser resonance in the inner structure benefits from not only the anomalous dispersion characteristic of the first band-edge at the M point in the first Brillouin-zone but also zero photon states in the outer structure. A line defect waveguide is introduced in the outer structure for extracting photons from the inner cavity. Three-dimensional finite-difference time-domain simulations apparently show the in-plane laser output from the waveguide. The microcavity has an effective mode volume of about 3.2（λ/nslab）^3 for oscillation mode and the quality factor of the device including line defect waveguide is estimated to be as high as 1300.展开更多
Hybrid ZnO/ormosils films are prepared by the sol-gel method. A FT-IR spectrometer, 900 UV/VIS/NIR spectrophotometer, atomic force microscope, and ellipsometer are employed to investigate microstructure and optical pr...Hybrid ZnO/ormosils films are prepared by the sol-gel method. A FT-IR spectrometer, 900 UV/VIS/NIR spectrophotometer, atomic force microscope, and ellipsometer are employed to investigate microstructure and optical properties of the films fired at different temperatures. The results show that the films with high transmittance and low surface roughness could be obtained at the heat-treatment temperature of 150℃, the refractive index and thickness of the film are 1.413, 2.11μm, respectively. Higher temperatures （350℃, 550℃） change the film microstructure severely, and then decrease the transmittance of the films,展开更多
Two-dimensional vector vortex solitons in harmonic optical lattices are investigated. The stability properties of such solitons are closely connected to the lattice depth V0. For small V0, vector vortex solitons with ...Two-dimensional vector vortex solitons in harmonic optical lattices are investigated. The stability properties of such solitons are closely connected to the lattice depth V0. For small V0, vector vortex solitons with the total zero-angular momentum are more stable than those with the total nonzero-angular momentum, while for large V0, this case is inversed. If V0 is large enough, both the types of such solitons are stable.展开更多
The structural and luminescence properties of nanocrystalline ZrO2 ：Er^3＋ films are reported. Transparent nano-ZrO2 crystalline films doped with Er^3＋ have been prepared using a wet chemistry process. An intense ro...The structural and luminescence properties of nanocrystalline ZrO2 ：Er^3＋ films are reported. Transparent nano-ZrO2 crystalline films doped with Er^3＋ have been prepared using a wet chemistry process. An intense roomtemperature emission at 1527nm with a full width at half-maximum of 46 nm has been observed, which is assigned to the ^4Ⅰ13/2 → ^4Ⅰ15/2 intra-4f^n electric transition of Er^3＋. Correlations between the luminescence properties and structures of the nanocrystalline ZrO2 ：Er^3＋ films have been investigated. Infrared-to-visible upconversion occurs simultaneously upon excitation of a commercially available 980-nm laser diode and the involved mechanisms have also been explained. The results indicate that the nanocrystalline ZrO2：Er^3＋ films might be suggested as promising materials for achieving broadband Er^3＋-doped waveguide amplifiers and upconversion waveguide lasers.展开更多
A long-range surface plasmon polariton （LRSPP） waveguide consisting of a 15nm thick gold stripe embedded in a homogeneous polymer BCB is reported. LRSPPs are excited by TM-mode input light successfully using an end-...A long-range surface plasmon polariton （LRSPP） waveguide consisting of a 15nm thick gold stripe embedded in a homogeneous polymer BCB is reported. LRSPPs are excited by TM-mode input light successfully using an end-fire method. By scanning the output coupling fibre, the near field of the LRSPP is measured. The propagation loss of as low as 2.34 dB/mm is demonstrated.展开更多
Modulation arms with different widths are introduced to Mach-Zehnder interferometers （MZIs） to obtain improved performance. Theoretical analysis and numerical simulation have shown that when tile widths of tile two ...Modulation arms with different widths are introduced to Mach-Zehnder interferometers （MZIs） to obtain improved performance. Theoretical analysis and numerical simulation have shown that when tile widths of tile two arms are properly designed to achieve an inherent mπ/2 （m is an odd integer） optical phase difference between the arms, the asymmetric MZI presents higher modulation speed. Furthermore, the carrier-absorption induced divergence of insertion losses in silicon-on-insulator （SOI） based MZI optical switches can be obviously improved.展开更多
Phase effect on the guided resonances in photonic crystal slabs is analysed. We present an analysis in the case of a mirror symmetric system and an asymmetric system irradiated from both sides, as well as the more rea...Phase effect on the guided resonances in photonic crystal slabs is analysed. We present an analysis in the case of a mirror symmetric system and an asymmetric system irradiated from both sides, as well as the more realistic and interesting case of a system bounded from one side by a perfect mirror. Gain is incorporated in the system, mainly to exemplify the results. Finally we find that phase effects persist in the asymmetric system resulting in a periodic response for the reflectivity versus the distance from the mirror, which is the main parameter controlling the phase relationship between the two incident waves.展开更多
It is consider that, from the standpoint of the law of conservation of energy, the process of converting sound wave falls on the boundary between two spaces in two, leaving the boundary, reflected and passage. It is a...It is consider that, from the standpoint of the law of conservation of energy, the process of converting sound wave falls on the boundary between two spaces in two, leaving the boundary, reflected and passage. It is assumed that the simultaneous presence of three waves is impossible, and that the process of converting one wave in two waves occurs instantaneously. Based on this concept, enter the following boundary conditions for the calculation of amplitudes (coefficients) of the reflected and passage waves. The initial phases of the reflected and passage waves coincide with the phase of the falling wave. The energy of the falling wave is equal to the sum of the energies of the reflected and passage waves. The normal component velocity amplitude of the particle of the liquid under the influence of the falling wave is equal to the sum of the normal component of particle velocity amplitudes of the reflected and passage waves. It was found that the character of dependence of the reflection coefficient on the angle of departure of the initial wave is the same as in the traditional formulas, but the coefficient of passage does not exceed unity. Calculations of reflection and passage coefficients for different values of the refractive coefficient at the boundary between two homogeneous spaces as well as the canonical form of the waveguide, wherein the speed of sound which is minimum at predetermined depth is carried out.展开更多
We propose a fluid sensor based on transmission dip caused by mini stop-band in photonic crystal slabs. Simulation results show that this novel type of sensors has large detective range （more than 1.5） and relative ...We propose a fluid sensor based on transmission dip caused by mini stop-band in photonic crystal slabs. Simulation results show that this novel type of sensors has large detective range （more than 1.5） and relative high sensitivity （4.3×10^-5 in certain conditions）. The central frequency and bandwidth of the mini stop-bands depend on the structure parameters of PC waveguides, which makes it possible to optimize the detective range and detective sensitivity.展开更多
文摘A theory of the far spatial coherent-suppressed single-peak field distribution of a rectangular wave-guide CO2 laser is presented. The theoretical analysis shows that a rectangular wave-guide laser can have an output intensity distribution in far field similar to that produced from a wave-guide array laser, which is in agreement with the experimental result. A single-peak mode output is obtained within 5 metres. The experimental far-field spread angle in the bigger-Fresnel number direction is 0.63 mrad, compared to the calculated one, 0.6 mrad, and when the length of the laser resonator is changed, a double-peak or multi-peak in far-field distribution of the laser is obtained.
基金financial support of the National Natural Science Foundation of China (No. 50975235 and 50575184)the 111 Project(B08040)
文摘Inner flange and side wrinkling often occur in rotary-draw bending process of rectangular aluminum alloy wave-guide tubes, and the distribution and magnitude of wrinkling is related to geometrical parameters of the tubes. In order to study the effects of geometrical parameters on wrinkling of rectangular wave-guide tubes, a 3D-FE model for rotary-draw bending processes of thin-walled rectangular aluminum alloy wave-guide tubes was built based on the platform of ABA-QUS/Explicit, and its reliability was validated by experiments. Simulation and analysis of the influence laws of geometrical parameters on the wave heights of inner flange and side wrinkling were then carried out. The results show that inner flange wrinkling is the main wrinkling way to rectan- gular wave-guide tubes in rotary-draw bending processes, but side wrinkling cannot be neglected because side wrinkling is 2/3 of inner flange wrinkling when b and h are smaller. Inner flange and side wrinkling increase with increasing b and h; the influence of b on side wrinkling is larger than that of h, while both b and h affect inner flange wrinkling greatly. Inner flange and side wrinkling decrease with increasing R/h; the influence of h on inner flange and side wrinkling is larger than that of R.
文摘The formation of the spatial solitons in the quadratic nonlinearity x(2) media by cascading second harmonic generation (SHG) in quasi-phase-matched (QPM) sample is studied on the basis of nonlinear Schrodinger equation (NLSE). When the solitary wave propagates in the QPM media, it formed optical wave-guides through cascading x(2) effect called self-induced soliton wave-guide. Transverse refractive index distribution of the self-induced soliton wave-guide of fundamental and SHG wave is obtained by cascading process. Analysis of guided-mode of such self-induced soliton wave-guide is first proposed to our knowledge. Because the power needed for forming the spatial solitons in cascading process is much lower than that in Kerr media, this kind of self-induced soliton wave-guide shows potential applications in all-optical signal process.
基金Supported by the National Natural Science Foundation of China under Grant No 10374065, the Natural Science Foundation of Guangdong Province under Grant No 32050, the Ministry of Education of China under Grant No 204107, and the Department of Education of Guangdong Province under Grant No Z03033.
文摘We investigate the unidirectional transmission behaviour of an asymmetrically confined photonic crystal （PC） defect with Kerr nonlinearity. Basically, the unidirectional transmission originates from the strong dependence of the threshold input power for the sharp increase of transmission on the launch direction of the input wave. This can be well explained in the framework of the coupled mode theory. Our theoretical analysis reveals the existence of an upper limit for the transmission contrast when such a single PC defect is employed. This is supported by the simulation results based on the nonlinear finite-difference time-domain technique.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60378013, 10474047, and 60278006.
文摘Using fully incoherent white light emitted from an incandescent lamp and amplitude mask, we experimentally investigate the influence of several factors on the fabrication of the lattice in photovoltaic self-defocusing LiNbO3：Fe crystal, the factors include the orientation of the crystalline c axis relative to the principal axis of the photonic lattice and the filament, the diameter of input dark spot and the separation of the adjacent input dark spots. Experimental results reveal that the best fabricating condition of photonic lattices is that the principal axis of lattice is tilted for 45^o relative to the crystalline c axis which is parallel to the filament of the lamp. In addition, it is necessary that the diameter of the input dark spot is larger than the half of their separation.
基金Supported by the National Natural Science Foundation of China under Grant No 10474071 and the Specialized Research Fund for the Doctoral Programme of Higher Education of China under Grant No 20040056010.
文摘A novel woodpile lattice structure is proposed. Based on plane wave expansion （PWE） method, the complete photonic band gaps （PBGs） of the novel woodpile three^dimensional （3D） terahertz （THz） photonic crystal （PC） with a decreasing symmetry relative to a face-centred-tetragonal （fct） symmetry are optimized by varying some structural parameters and the highest band gap ratio can reach 27.61%. Compared to the traditional woodpile lattice, the novel woodpile lattice has a wider range of the filling ratios to gain high quality PBGs, which provides greater convenience for the manufacturing process. The novel woodpile 3D PC will be very promising for materials of THz Junctional components.
文摘Work is devoted to the analysis of errors meeting in literature in treatment of a spatial part of a phase of running sound waves. In some cases, it is not taken into consideration that this part of a phase is formed by scalar product of vectors which does not depend on a choice of system of co-ordinates. Taking into account the necessary corrections in record of a phase of plane waves, it is shown that the decision of the homogeneous wave equation in the form of “belated” potentials is simultaneously and the decision of the equations of movement of a liquid, and “outstripped” potentials does not satisfy them. The analysis of coefficients of reflection and passage of running waves in non-uniform space is carried out. It is shown that on boundary of spaces with different sound speeds, a turning point of a sound wave is the point of full internal reflection. The way of calculation of coefficients of reflection and passage is offered by consideration of all three waves on boundary of spaces as vectors with the set directions and amplitude of a falling wave. Calculation of coefficients of reflection and passage of a sound wave in a wave-guide of canonical type along the chosen trajectory by two methods—under traditional formulas and a vector method is carried out. Results of calculation practically coincide.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60425517 and 60378036.
文摘Near-field scanning optical microscopy is used to investigate the waveguiding properties of optical micro/nanofibres （MNFs） by means of detecting optical power carried by evanescent waves. Taper drawn silica and tellurite MNFs, supported on low-index substrates, are used to guide a 532-nm-wavelength light beam for the test. Modification of the single-mode condition of the MNF in the presence of a substrate is observed. Spatial modulation of the longitudinal field intensity （with a 195-nm period） near the output end of a 760-nm-diameter silica MNF is well resolved. Energy exchange through evanescent coupling between two parallel MNFs is also investigated.
文摘An erbium-doped phosphate glass fibre has been drawn by the rod-in-tube technique in our laboratory. The gain for the Er^3＋-doped phosphate glass fibre with different pump powers and with different input signal wavelengths is investigated. The 2.2-cm-long fibre, pumped by a single-mode 980-nm fibre-pigtailed laser diode, can provide a net gain per unit length greater than 1.SdB/cm. The pump threshold is about 50mW at the wavelength of 1534nm, and below 70roW at 1550nm. The gain linewidth of the Er^3＋-doped phosphate glass fibre is greater than 34 nm and can cover the C band in optical communication networks.
基金Supported by the National Natural Foundation of China under Grant Nos 60307004 and 50472053, the Science and Technology Project of Guangdong Province （2005A10602001）, PSTG of Guangzhou （2006Z2-D0161）, the Program for New Century Excellent Talents in University under Grant Nos NCET-04-0821 and NCET-04-0823, Key Laboratory of Specially Functional Materials, SCUT, Ministry of Education （No 200500E）, and the Young Nature Science Foundation of South China University of Technology （No B09E5060570）.
文摘We experimentally study a novel fibre with high gain per unit length based on the homemade erbium-ytterbium codoped phosphate glass. The gain and noise characterizations with different pump powers at different wavelengths are investigated. The 1.8-cm-long fibre, dual-pumped by two single mode 980-nm fibre-pigtailed laser diodes, provides a gain per unit length greater than 3.0dB/cm and a noise figure less than 6.SdB. The gain saturation behaviour at 1535nm is obtained and the saturation output power （3 dB compression） is greater than 5 dBm.
基金Supported by the National Natural Science Foundation of China under Grant Nos 50125208 and 60377017, and the Shanghai Leading Academic Discipline Program.
文摘Thermal stress-induced birefringence in borate glass which has been irradiated by 800-nm femtosecond laser pulses is observed under cross-polarized light. Due to the high temperature and pressure formed in the focal volume, the material at the edge of the micro-modified region is compressed between the expanding region and the unheated one, then stress emerges. Raman spectroscopy is used to investigate the stress distribution in the micro-modified region and indicates the redistributions of density and refractive index by Raman peak shift. We suggest that this technique can develop waveguide polarizers and Fresnel zone plates in integrated optics.
文摘An edge emitting laser based on two-dimensional photonic crystal slabs is proposed. The device consists of a square lattice microcavity, which is composed of two structures with the same period but different radius of air-holes, and a waveguide. In the cavity, laser resonance in the inner structure benefits from not only the anomalous dispersion characteristic of the first band-edge at the M point in the first Brillouin-zone but also zero photon states in the outer structure. A line defect waveguide is introduced in the outer structure for extracting photons from the inner cavity. Three-dimensional finite-difference time-domain simulations apparently show the in-plane laser output from the waveguide. The microcavity has an effective mode volume of about 3.2（λ/nslab）^3 for oscillation mode and the quality factor of the device including line defect waveguide is estimated to be as high as 1300.
文摘Hybrid ZnO/ormosils films are prepared by the sol-gel method. A FT-IR spectrometer, 900 UV/VIS/NIR spectrophotometer, atomic force microscope, and ellipsometer are employed to investigate microstructure and optical properties of the films fired at different temperatures. The results show that the films with high transmittance and low surface roughness could be obtained at the heat-treatment temperature of 150℃, the refractive index and thickness of the film are 1.413, 2.11μm, respectively. Higher temperatures （350℃, 550℃） change the film microstructure severely, and then decrease the transmittance of the films,
基金Supported by the National Natural Science Foundation of China under Grant No 10274078.
文摘Two-dimensional vector vortex solitons in harmonic optical lattices are investigated. The stability properties of such solitons are closely connected to the lattice depth V0. For small V0, vector vortex solitons with the total zero-angular momentum are more stable than those with the total nonzero-angular momentum, while for large V0, this case is inversed. If V0 is large enough, both the types of such solitons are stable.
基金Supported by the National Natural Science Foundation of China under Grant No 50472053, NCET （NCET04-0823） and DSTG （04020036 and 2004A10602002）.
文摘The structural and luminescence properties of nanocrystalline ZrO2 ：Er^3＋ films are reported. Transparent nano-ZrO2 crystalline films doped with Er^3＋ have been prepared using a wet chemistry process. An intense roomtemperature emission at 1527nm with a full width at half-maximum of 46 nm has been observed, which is assigned to the ^4Ⅰ13/2 → ^4Ⅰ15/2 intra-4f^n electric transition of Er^3＋. Correlations between the luminescence properties and structures of the nanocrystalline ZrO2 ：Er^3＋ films have been investigated. Infrared-to-visible upconversion occurs simultaneously upon excitation of a commercially available 980-nm laser diode and the involved mechanisms have also been explained. The results indicate that the nanocrystalline ZrO2：Er^3＋ films might be suggested as promising materials for achieving broadband Er^3＋-doped waveguide amplifiers and upconversion waveguide lasers.
文摘A long-range surface plasmon polariton （LRSPP） waveguide consisting of a 15nm thick gold stripe embedded in a homogeneous polymer BCB is reported. LRSPPs are excited by TM-mode input light successfully using an end-fire method. By scanning the output coupling fibre, the near field of the LRSPP is measured. The propagation loss of as low as 2.34 dB/mm is demonstrated.
基金Supported by the National Natural Science Foundation of China under Grant No 60336010, and the Special Funds for Major State Basic Research Project of China under Grant No G20000366.
文摘Modulation arms with different widths are introduced to Mach-Zehnder interferometers （MZIs） to obtain improved performance. Theoretical analysis and numerical simulation have shown that when tile widths of tile two arms are properly designed to achieve an inherent mπ/2 （m is an odd integer） optical phase difference between the arms, the asymmetric MZI presents higher modulation speed. Furthermore, the carrier-absorption induced divergence of insertion losses in silicon-on-insulator （SOI） based MZI optical switches can be obviously improved.
文摘Phase effect on the guided resonances in photonic crystal slabs is analysed. We present an analysis in the case of a mirror symmetric system and an asymmetric system irradiated from both sides, as well as the more realistic and interesting case of a system bounded from one side by a perfect mirror. Gain is incorporated in the system, mainly to exemplify the results. Finally we find that phase effects persist in the asymmetric system resulting in a periodic response for the reflectivity versus the distance from the mirror, which is the main parameter controlling the phase relationship between the two incident waves.
文摘It is consider that, from the standpoint of the law of conservation of energy, the process of converting sound wave falls on the boundary between two spaces in two, leaving the boundary, reflected and passage. It is assumed that the simultaneous presence of three waves is impossible, and that the process of converting one wave in two waves occurs instantaneously. Based on this concept, enter the following boundary conditions for the calculation of amplitudes (coefficients) of the reflected and passage waves. The initial phases of the reflected and passage waves coincide with the phase of the falling wave. The energy of the falling wave is equal to the sum of the energies of the reflected and passage waves. The normal component velocity amplitude of the particle of the liquid under the influence of the falling wave is equal to the sum of the normal component of particle velocity amplitudes of the reflected and passage waves. It was found that the character of dependence of the reflection coefficient on the angle of departure of the initial wave is the same as in the traditional formulas, but the coefficient of passage does not exceed unity. Calculations of reflection and passage coefficients for different values of the refractive coefficient at the boundary between two homogeneous spaces as well as the canonical form of the waveguide, wherein the speed of sound which is minimum at predetermined depth is carried out.
基金Supported by the National Natural Science Foundation of China under Grant No 60537010, and the National Basic Research Programme of China under Grant Nos 2006CB302804 and 2007CB307004.
文摘We propose a fluid sensor based on transmission dip caused by mini stop-band in photonic crystal slabs. Simulation results show that this novel type of sensors has large detective range （more than 1.5） and relative high sensitivity （4.3×10^-5 in certain conditions）. The central frequency and bandwidth of the mini stop-bands depend on the structure parameters of PC waveguides, which makes it possible to optimize the detective range and detective sensitivity.
