Transmission spectra of triangular lattice photonic crystals milled in the top surface of an annealed proton- exchange waveguide are numerically simulated. The effects of the finite depth, conical shape, trapezoidal s...Transmission spectra of triangular lattice photonic crystals milled in the top surface of an annealed proton- exchange waveguide are numerically simulated. The effects of the finite depth, conical shape, trapezoidal shape and hybrid shape of holes are theoretically analyzed. Due to the difficulty of milling high aspect-ratio cylindrical holes in lithium niobate （LiNbO3 ）, a compromised solution is proposed to improve the overlap between shallow holes and the waveguide mode, and useful transmission spectra with strong contrast and sharp band edges are achieved.展开更多
We investigate the effect of disorder and mechanical deformation on a two-dimensional photonic crystal waveguide. The dispersion characteristics and transmittance of the waveguide are studied using the finite element ...We investigate the effect of disorder and mechanical deformation on a two-dimensional photonic crystal waveguide. The dispersion characteristics and transmittance of the waveguide are studied using the finite element method. Results show that the geometric change of the dielectric material perpendicular to the light propagation direction has a larger influence on the waveguide characteristics than that parallel to the light propagation direction. Mechanical deformation has an obvious influence on the performance of the waveguide. In particular, longitudinal deformed structure exhibits distinct optical characteristics from the ideal one. Studies on this work will provide useful guideline to the fabrication and practical applications based on photonic crystal waveguides.展开更多
A two-dimensional （2D） photonic crystal waveguide in the Г-K direction with triangular lattice on a silicon-on-insulator （SOI） substrate in the near-infrared band is fabricated by the combination of electron beam...A two-dimensional （2D） photonic crystal waveguide in the Г-K direction with triangular lattice on a silicon-on-insulator （SOI） substrate in the near-infrared band is fabricated by the combination of electron beam lithography and inductively coupled plasma etching. Its transmission characteristics are analysed from the stimulated band diagram by the effective index and the 2D plane wave expansion （PWE） methods. In the experiment, the transmission band edge in a longer wavelength of the photonic crystal waveguide is about 1590 nm, which is in good qualitative agreement with the simulated value. However, there is a disagreement between the experimental and the simulated results when the wavelength ranges from 1607 to 1630 nm, which can be considered as due to the unpolarized source used in the transmission measurement.展开更多
With the method of replacing the surface layer of photonic crystal with tubes, a novel photonic crystal composite structure used as a tunable surface mode waveguide is designed. The tubes support tunable surface state...With the method of replacing the surface layer of photonic crystal with tubes, a novel photonic crystal composite structure used as a tunable surface mode waveguide is designed. The tubes support tunable surface states. The tunable propagation capabilities of the structure are investigated by using the finite-difference time-domain. Simulation results show that the beam transmission distributions of the composite structure are sensitive to the frequency range of incident light and the surface morphology which can be modified by filling the tubes with different organic liquids. By adjusting the filler in tubes, the T-shaped, Y-shaped, and L-shaped propagations can be realized. The property can be applied to the tunable surface mode waveguide. Compared with a traditional single function photonic crystal waveguide, our designed structure not only has a small size, but also is a tunable device.展开更多
This paper reports that a two-dimensional single-defect photonic crystal waveguide in the Г-K direction with triangular lattice on a silicon-on-insulator substrate is fabricated by the combination of electron beam li...This paper reports that a two-dimensional single-defect photonic crystal waveguide in the Г-K direction with triangular lattice on a silicon-on-insulator substrate is fabricated by the combination of electron beam lithography and inductively coupled plasma etching. A ministop band （MSB） is observed by the measurement of transmission characteristics. It results from the coupling between the two modes with the same symmetry, which is analysed from the stimulated band diagram by the effective index and the two-dimensional plane wave expansion methods. The parameter working on the MSB is the ratio of the radius of air holes to the lattice constant, fla. It is obtained that the critical τ/a value determining the occurrence or disappearance of MSB is 0.36. When τ/a is larger than or equal to 0.36, the MSB occurs. However, when τ/a is smaller than 0.36, the MSB disappears.展开更多
In this Letter, the effects of material/structure parameters of photonic crystal（Ph C） parallel waveguides on the coupling length are investigated. The results show that, increasing the effective relative permittivi...In this Letter, the effects of material/structure parameters of photonic crystal（Ph C） parallel waveguides on the coupling length are investigated. The results show that, increasing the effective relative permittivity of the Ph C leads to a downward shift of the photonic bandgap and a variation of the coupling length. A compact Ph C 1.31/1.55 μm wavelength division multiplexer（WDM）/demultiplexer with simple structure is proposed,where the output power ratios are more than 24 d B. This WDM can multiplex/demultiplex other light waves efficiently.展开更多
We investigate in this paper the influence of slow light on the balance between the Kerr and two-photon absorption(TPA) processes in silicon slotted hybrid nonlinear waveguides. Three typical silicon photonic waveguid...We investigate in this paper the influence of slow light on the balance between the Kerr and two-photon absorption(TPA) processes in silicon slotted hybrid nonlinear waveguides. Three typical silicon photonic waveguide geometries are studied to estimate the influence of the light slow-down factor on the mode field overlap with the silicon region, as well as on the complex effective nonlinear susceptibility. It is found that slotted photonic crystal modes tend to focalize in their hollow core with increasing group index(n_G) values. Considering a hybrid integration of nonlinear polymers in such slotted waveguides, a relative decrease of the TPA process by more factor of 2 is predicted from n_G=10 to n_G=50. As a whole, this work shows that the relative influence of TPA decreases for slotted waveguides operating in the slow light regime, making them a suitable platform for third-order nonlinear optics.展开更多
A current-driven source of long-range surface plasmons(LRSPs)on a duplex metal nanolayer is reported.Electrical excitation of LRSPs was experimentally observed in a planar structure,where an organic light-emitting fil...A current-driven source of long-range surface plasmons(LRSPs)on a duplex metal nanolayer is reported.Electrical excitation of LRSPs was experimentally observed in a planar structure,where an organic light-emitting film was sandwiched between two metal nanolayers that served as electrodes.To achieve the LRSP propagation in these metal nanolayers at the interface with air,the light-emitting structure was bordered by a one-dimensional photonic crystal(PC)on the other side.The dispersion of the light emitted by such a hybrid PC/organic-light-emitting-diode structure(PC/OLED)comprising two thin metal electrodes was obtained,with a clearly identified LRSP resonance peak.展开更多
We investigate the influences of structure parameters and interface shapes on the bandwidth of the edge state of lithium niobate valley photonic crystals. By increasing the size difference of two air holes in the same...We investigate the influences of structure parameters and interface shapes on the bandwidth of the edge state of lithium niobate valley photonic crystals. By increasing the size difference of two air holes in the same unit cell, we find that the bandwidth of the lossless nontrivial edge state possesses a peak value of 0.0201(a/λ), which can be used to construct broadband valley photonic crystal waveguides. Mode field distributions verify that the waveguide is robust against sharp bends and exhibits chirality. When the unit cell is arranged in a bearded interface with the top and bottom components showing negative and positive valley Chern numbers, respectively, we find that the lithium niobate valley photonic crystal is more likely to exhibit a lossless edge state, which is difficult to be realized in valley waveguides with low refractive index materials. This work can provide guidance on the design of the high-performance topological waveguide.展开更多
This Letter introduces the design and simulation of a microstrip-line-based electro-optic （EO） polymer optical phase modulator （PM） that is further enhanced by the addition of photonic crystal （PhC） structures t...This Letter introduces the design and simulation of a microstrip-line-based electro-optic （EO） polymer optical phase modulator （PM） that is further enhanced by the addition of photonic crystal （PhC） structures that are in close proximity to the optical core. The slow-wave PhC structure is designed for two different material configurations and placed in the modulator as a superstrate to the optical core; simulation results are depicted for both 1D and 2D PhC structures. The PM characteristics are modeled using a combination of the finite element method and the optical beam propagation method in both the RF and optical domains, respectively. The phase-shift simulation results show a factor of 1.7 increase in an effective EO coefficient （120 pm/V） while maintaining a broadband bandwidth of 40 GHz.展开更多
This paper summarizes our research work on optoelectronic devices with nanostructures. It was indi- cated that by manipulating so called ＂general energybands＂ of fundamental particles or quasi-particles, such as pho...This paper summarizes our research work on optoelectronic devices with nanostructures. It was indi- cated that by manipulating so called ＂general energybands＂ of fundamental particles or quasi-particles, such as photon, phonon, and surface plasmon polariton （SPP）, novel optoelectronic characteristics can be obtained, which results in a series of new functional devices. A silicon based optical switch with an extremely broadband of 24 nm and an ultra-compact （8 μm -17.6μm） footprint was demonstrated with a photonic crystal slow light waveguides. By proposing a nanobeam based hereto optomechanical crystal, a high phonon frequency of 5.66 GHz was realized experimentally. Also, we observed and verified a novel effect of two-surface-plasmon-absorption （TSPA）, and realized diffraction-limit-overcoming photolithography with resolution of-1/11 of the exposure wavelength.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 50872089,61077039 and 61377060the Research Grants Council of the Hong Kong Special Administrative Region of China under Grant No 11211014+1 种基金the Key Program for Research on Fundamental to Application and Leading Technology of Tianjin Science and Technology Commission of China under Grant No 11JCZDJC15500the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No 20100032110052
文摘Transmission spectra of triangular lattice photonic crystals milled in the top surface of an annealed proton- exchange waveguide are numerically simulated. The effects of the finite depth, conical shape, trapezoidal shape and hybrid shape of holes are theoretically analyzed. Due to the difficulty of milling high aspect-ratio cylindrical holes in lithium niobate （LiNbO3 ）, a compromised solution is proposed to improve the overlap between shallow holes and the waveguide mode, and useful transmission spectra with strong contrast and sharp band edges are achieved.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60908028, 60971068, 10979065, and 61275201)the Fundamental Research Funds for the Central Universities of China (Grant Nos. 2011RC0402 and 2012RC0402)the Program for New Century Excellent Talents in University of China (Grant No. NCET-10-0261)
文摘We investigate the effect of disorder and mechanical deformation on a two-dimensional photonic crystal waveguide. The dispersion characteristics and transmittance of the waveguide are studied using the finite element method. Results show that the geometric change of the dielectric material perpendicular to the light propagation direction has a larger influence on the waveguide characteristics than that parallel to the light propagation direction. Mechanical deformation has an obvious influence on the performance of the waveguide. In particular, longitudinal deformed structure exhibits distinct optical characteristics from the ideal one. Studies on this work will provide useful guideline to the fabrication and practical applications based on photonic crystal waveguides.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 60336010 and 60537010）. Acknowledgments The authors would like to thank Dr Han Wei-Hua, Dr Fan Zhong-Chao, and Mr Xing-Bo of the Institute of Semiconductors, Chinese Academy of Sciences, for their useful discussions and great help in the experiment and optical measurements.
文摘A two-dimensional （2D） photonic crystal waveguide in the Г-K direction with triangular lattice on a silicon-on-insulator （SOI） substrate in the near-infrared band is fabricated by the combination of electron beam lithography and inductively coupled plasma etching. Its transmission characteristics are analysed from the stimulated band diagram by the effective index and the 2D plane wave expansion （PWE） methods. In the experiment, the transmission band edge in a longer wavelength of the photonic crystal waveguide is about 1590 nm, which is in good qualitative agreement with the simulated value. However, there is a disagreement between the experimental and the simulated results when the wavelength ranges from 1607 to 1630 nm, which can be considered as due to the unpolarized source used in the transmission measurement.
基金supported by the National Natural Science Foundation of China(Grant No.31401136)the School Youth Fund of Henan University of Science and Technology,China(Grant No.2014QN045)
文摘With the method of replacing the surface layer of photonic crystal with tubes, a novel photonic crystal composite structure used as a tunable surface mode waveguide is designed. The tubes support tunable surface states. The tunable propagation capabilities of the structure are investigated by using the finite-difference time-domain. Simulation results show that the beam transmission distributions of the composite structure are sensitive to the frequency range of incident light and the surface morphology which can be modified by filling the tubes with different organic liquids. By adjusting the filler in tubes, the T-shaped, Y-shaped, and L-shaped propagations can be realized. The property can be applied to the tunable surface mode waveguide. Compared with a traditional single function photonic crystal waveguide, our designed structure not only has a small size, but also is a tunable device.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 60336010 and 60537010)
文摘This paper reports that a two-dimensional single-defect photonic crystal waveguide in the Г-K direction with triangular lattice on a silicon-on-insulator substrate is fabricated by the combination of electron beam lithography and inductively coupled plasma etching. A ministop band （MSB） is observed by the measurement of transmission characteristics. It results from the coupling between the two modes with the same symmetry, which is analysed from the stimulated band diagram by the effective index and the two-dimensional plane wave expansion methods. The parameter working on the MSB is the ratio of the radius of air holes to the lattice constant, fla. It is obtained that the critical τ/a value determining the occurrence or disappearance of MSB is 0.36. When τ/a is larger than or equal to 0.36, the MSB occurs. However, when τ/a is smaller than 0.36, the MSB disappears.
基金supported by the National Natural Science Foundation of China(No.61405058)the Hunan Provincial Natural Science Foundation of China(No.2017JJ2048)the Fundamental Research Funds for the Central Universities(No.531107050979)
文摘In this Letter, the effects of material/structure parameters of photonic crystal（Ph C） parallel waveguides on the coupling length are investigated. The results show that, increasing the effective relative permittivity of the Ph C leads to a downward shift of the photonic bandgap and a variation of the coupling length. A compact Ph C 1.31/1.55 μm wavelength division multiplexer（WDM）/demultiplexer with simple structure is proposed,where the output power ratios are more than 24 d B. This WDM can multiplex/demultiplex other light waves efficiently.
文摘We investigate in this paper the influence of slow light on the balance between the Kerr and two-photon absorption(TPA) processes in silicon slotted hybrid nonlinear waveguides. Three typical silicon photonic waveguide geometries are studied to estimate the influence of the light slow-down factor on the mode field overlap with the silicon region, as well as on the complex effective nonlinear susceptibility. It is found that slotted photonic crystal modes tend to focalize in their hollow core with increasing group index(n_G) values. Considering a hybrid integration of nonlinear polymers in such slotted waveguides, a relative decrease of the TPA process by more factor of 2 is predicted from n_G=10 to n_G=50. As a whole, this work shows that the relative influence of TPA decreases for slotted waveguides operating in the slow light regime, making them a suitable platform for third-order nonlinear optics.
基金supported by the Swiss National Science Foundation (Grant 200021_162767)
文摘A current-driven source of long-range surface plasmons(LRSPs)on a duplex metal nanolayer is reported.Electrical excitation of LRSPs was experimentally observed in a planar structure,where an organic light-emitting film was sandwiched between two metal nanolayers that served as electrodes.To achieve the LRSP propagation in these metal nanolayers at the interface with air,the light-emitting structure was bordered by a one-dimensional photonic crystal(PC)on the other side.The dispersion of the light emitted by such a hybrid PC/organic-light-emitting-diode structure(PC/OLED)comprising two thin metal electrodes was obtained,with a clearly identified LRSP resonance peak.
基金supported by the National Natural Science Foundation of China(No.91950107)the National Key R&D Program of China(Nos.2019YFB2203501 and 2017YFA0303701)。
文摘We investigate the influences of structure parameters and interface shapes on the bandwidth of the edge state of lithium niobate valley photonic crystals. By increasing the size difference of two air holes in the same unit cell, we find that the bandwidth of the lossless nontrivial edge state possesses a peak value of 0.0201(a/λ), which can be used to construct broadband valley photonic crystal waveguides. Mode field distributions verify that the waveguide is robust against sharp bends and exhibits chirality. When the unit cell is arranged in a bearded interface with the top and bottom components showing negative and positive valley Chern numbers, respectively, we find that the lithium niobate valley photonic crystal is more likely to exhibit a lossless edge state, which is difficult to be realized in valley waveguides with low refractive index materials. This work can provide guidance on the design of the high-performance topological waveguide.
文摘This Letter introduces the design and simulation of a microstrip-line-based electro-optic （EO） polymer optical phase modulator （PM） that is further enhanced by the addition of photonic crystal （PhC） structures that are in close proximity to the optical core. The slow-wave PhC structure is designed for two different material configurations and placed in the modulator as a superstrate to the optical core; simulation results are depicted for both 1D and 2D PhC structures. The PM characteristics are modeled using a combination of the finite element method and the optical beam propagation method in both the RF and optical domains, respectively. The phase-shift simulation results show a factor of 1.7 increase in an effective EO coefficient （120 pm/V） while maintaining a broadband bandwidth of 40 GHz.
基金This work was supported by the National Basic Research Program of China （No. 2013CB328704 and 2013CBA01704）, the National Natural Science Foundation of China （Grant No. 61307068）.
文摘This paper summarizes our research work on optoelectronic devices with nanostructures. It was indi- cated that by manipulating so called ＂general energybands＂ of fundamental particles or quasi-particles, such as photon, phonon, and surface plasmon polariton （SPP）, novel optoelectronic characteristics can be obtained, which results in a series of new functional devices. A silicon based optical switch with an extremely broadband of 24 nm and an ultra-compact （8 μm -17.6μm） footprint was demonstrated with a photonic crystal slow light waveguides. By proposing a nanobeam based hereto optomechanical crystal, a high phonon frequency of 5.66 GHz was realized experimentally. Also, we observed and verified a novel effect of two-surface-plasmon-absorption （TSPA）, and realized diffraction-limit-overcoming photolithography with resolution of-1/11 of the exposure wavelength.
