Visible light curable photoresist consisting of epoxy resin Epon SU8 and iron arene photo initiator Irgacure 261 was used to fabricate three dimensional microstructure by means of three dimensional holographic lithogr...Visible light curable photoresist consisting of epoxy resin Epon SU8 and iron arene photo initiator Irgacure 261 was used to fabricate three dimensional microstructure by means of three dimensional holographic lithography technique. Argon ion laser with wavelength of 488 nm was used as light source in the experiments. Field emission microscope diagram showed the formation of three dimensional microstructure. It was found that the amount of photo initiator, the laser intensity and the exposure time are the key factors to obtain well defined three dimensional microstructure.展开更多
This paper demonstrates experimentally and numerically that a significant modification of spontaneous emission rate can be achieved near the surface of a three-dimensional photonic crystal. In experiments, semiconduct...This paper demonstrates experimentally and numerically that a significant modification of spontaneous emission rate can be achieved near the surface of a three-dimensional photonic crystal. In experiments, semiconductor coreshell quantum dots are intentionally confined in a thin polymer film on which a three-dimensional colloidal photonic crystal is fabricated. The spontaneous emission rate of quantum dots is characterised by conventional and time-resolved photoluminescence （PL） measurements. The modification of the spontaneous emission rate, which is reflected in the change of spectral shape and PL lifetime, is clearly observed. While an obvious increase in the PL lifetime is found at most wavelengths in the band gap, a significant reduction in the PL lifetime by one order of magnitude is observed at the short-wavelength band edge. Numerical simulation reveals a periodic modulation of spontaneous emission rate with decreasing modulation strength when an emitter is moved away from the surface of the photonic crystal. It is supported by the fact that the modification of spontaneous emission rate is not pronounced for quantum dots distributed in a thick polymer film where both enhancement and suppression are present simultaneously. This finding provides a simple and effective way for improving the performance of light emitting devices.展开更多
This paper has theoretically studied the characteristic frequencies of band structures in two-dimensional metallic- dielectric photonic crystals. It is demonstrated that a large filling fraction benefits the existence...This paper has theoretically studied the characteristic frequencies of band structures in two-dimensional metallic- dielectric photonic crystals. It is demonstrated that a large filling fraction benefits the existence of absolute photonic band gap, while a smaller filling fraction benefits an absolute negative refraction band. In addition, it also finds that the relation between the cut-off frequency of E-polarized wave and the filling fraction exceeding 10% is content with a linear increasing function, whose coefficients are exponential to the normalized lattice constant. These investigations have significant implications for tuning the operational frequencies to desired applications and manufacturing photonic crystals.展开更多
We analyse surface solitons at the interface between a one-dimensional photonic superlattice and a uniform medium with weak nonlocal nonlinearity. We demonstrate that in deep lattices there exist three kinds of surfac...We analyse surface solitons at the interface between a one-dimensional photonic superlattice and a uniform medium with weak nonlocal nonlinearity. We demonstrate that in deep lattices there exist three kinds of surface solitons when the propagation constant exceeds a critical value, including two on-site solitons and one off-site soliton. These three kinds of surface solitons have unique dynamical properties. If the relative depth of the superlattice is low, there is only one kind of off-site soliton; however, the solitons of this kind can propagate stably, unlike their deep superlattice counterparts. Dipole surface solitons are also investigated, and the stable domain is given.展开更多
The transient photoluminescence(PL)of DO-PPV(poly-(2,5-dioctyloxy-1,4-phenylene vinylene))solution in chloroform was investigated by picosecond time-resolved PL spectroscopy.An ultrafast rise of PL and the following s...The transient photoluminescence(PL)of DO-PPV(poly-(2,5-dioctyloxy-1,4-phenylene vinylene))solution in chloroform was investigated by picosecond time-resolved PL spectroscopy.An ultrafast rise of PL and the following single exponential decay with a time constant about 400ps were assigned to the formation of intrachain exciton and its decay process,respectively.The redshift of the PL emission spectrum with time was caused by the subsequent exciton migration among the different conjugated segments in the DO-PPV polymer.展开更多
The fluorescent decays and spectra of pump power density dependent emission demonstrated that the excitation power density was enhanced in Rh640 dye solution containing scattering nanoparticles.Lasing in disordered sc...The fluorescent decays and spectra of pump power density dependent emission demonstrated that the excitation power density was enhanced in Rh640 dye solution containing scattering nanoparticles.Lasing in disordered scattering medium with low threshold,narrow bandwidth,and short duration was observed.The mechanism of this enhancement,together with the lasing properties of low threshold and narrow bandwidth,was discussed.展开更多
We study the surface defect gap solitons in an interface between a defect of one-dimensional dual-frequency lattices and the uniform media. Some unique properties are revealed that such lattices can broaden the region...We study the surface defect gap solitons in an interface between a defect of one-dimensional dual-frequency lattices and the uniform media. Some unique properties are revealed that such lattices can broaden the region of semi-finite gap, and the semi-finite gap exists not only in the positive and zero defects but also in the negative defect; unlike in the regular lattices, the semi-finite gap exists in the positive and zero defects but does not exist in the negative defect. In particular, stable solitons exist almost in the whole semi-finite gap for the positive and zero defects. These properties are different from other lattices with defects. In addition, it is found that the existence of surface dual-frequency lattice solitons does not need a threshold power.展开更多
文摘Visible light curable photoresist consisting of epoxy resin Epon SU8 and iron arene photo initiator Irgacure 261 was used to fabricate three dimensional microstructure by means of three dimensional holographic lithography technique. Argon ion laser with wavelength of 488 nm was used as light source in the experiments. Field emission microscope diagram showed the formation of three dimensional microstructure. It was found that the amount of photo initiator, the laser intensity and the exposure time are the key factors to obtain well defined three dimensional microstructure.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10974060 and 10774050)the Program for Innovative Research Team of the Higher Education in Guangdong,China (Grant No. 06CXTD005)
文摘This paper demonstrates experimentally and numerically that a significant modification of spontaneous emission rate can be achieved near the surface of a three-dimensional photonic crystal. In experiments, semiconductor coreshell quantum dots are intentionally confined in a thin polymer film on which a three-dimensional colloidal photonic crystal is fabricated. The spontaneous emission rate of quantum dots is characterised by conventional and time-resolved photoluminescence （PL） measurements. The modification of the spontaneous emission rate, which is reflected in the change of spectral shape and PL lifetime, is clearly observed. While an obvious increase in the PL lifetime is found at most wavelengths in the band gap, a significant reduction in the PL lifetime by one order of magnitude is observed at the short-wavelength band edge. Numerical simulation reveals a periodic modulation of spontaneous emission rate with decreasing modulation strength when an emitter is moved away from the surface of the photonic crystal. It is supported by the fact that the modification of spontaneous emission rate is not pronounced for quantum dots distributed in a thick polymer film where both enhancement and suppression are present simultaneously. This finding provides a simple and effective way for improving the performance of light emitting devices.
基金Project supported by the National 973 （Grant No 2004CB719804） and the National Natural Science Foundation of China.
文摘This paper has theoretically studied the characteristic frequencies of band structures in two-dimensional metallic- dielectric photonic crystals. It is demonstrated that a large filling fraction benefits the existence of absolute photonic band gap, while a smaller filling fraction benefits an absolute negative refraction band. In addition, it also finds that the relation between the cut-off frequency of E-polarized wave and the filling fraction exceeding 10% is content with a linear increasing function, whose coefficients are exponential to the normalized lattice constant. These investigations have significant implications for tuning the operational frequencies to desired applications and manufacturing photonic crystals.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10874250, 10674183 and 10804131)National Basic Research Program of China (Grant No 2004CB719804)
文摘We analyse surface solitons at the interface between a one-dimensional photonic superlattice and a uniform medium with weak nonlocal nonlinearity. We demonstrate that in deep lattices there exist three kinds of surface solitons when the propagation constant exceeds a critical value, including two on-site solitons and one off-site soliton. These three kinds of surface solitons have unique dynamical properties. If the relative depth of the superlattice is low, there is only one kind of off-site soliton; however, the solitons of this kind can propagate stably, unlike their deep superlattice counterparts. Dipole surface solitons are also investigated, and the stable domain is given.
基金Supported by the National Natural Science Foundation of China under Grant No.69977008.
文摘The transient photoluminescence(PL)of DO-PPV(poly-(2,5-dioctyloxy-1,4-phenylene vinylene))solution in chloroform was investigated by picosecond time-resolved PL spectroscopy.An ultrafast rise of PL and the following single exponential decay with a time constant about 400ps were assigned to the formation of intrachain exciton and its decay process,respectively.The redshift of the PL emission spectrum with time was caused by the subsequent exciton migration among the different conjugated segments in the DO-PPV polymer.
基金Supported by the National Natural Science Foundation of China under Grant No.19574077the National Reseach Project of 863-416 High Technology,and the Guangdong Natural Science Foundation.
文摘The fluorescent decays and spectra of pump power density dependent emission demonstrated that the excitation power density was enhanced in Rh640 dye solution containing scattering nanoparticles.Lasing in disordered scattering medium with low threshold,narrow bandwidth,and short duration was observed.The mechanism of this enhancement,together with the lasing properties of low threshold and narrow bandwidth,was discussed.
基金Project supported by the National Natural Science Foundation of China (Grant No 10774031)Natural Science Foundation of Guangdong Province of China (Grant No 07001790)
文摘We study the surface defect gap solitons in an interface between a defect of one-dimensional dual-frequency lattices and the uniform media. Some unique properties are revealed that such lattices can broaden the region of semi-finite gap, and the semi-finite gap exists not only in the positive and zero defects but also in the negative defect; unlike in the regular lattices, the semi-finite gap exists in the positive and zero defects but does not exist in the negative defect. In particular, stable solitons exist almost in the whole semi-finite gap for the positive and zero defects. These properties are different from other lattices with defects. In addition, it is found that the existence of surface dual-frequency lattice solitons does not need a threshold power.
