Amplified spontaneous emission （ASE）, including intensity and bandwidth, in a typical example of BuEH-PPV is calculated. For this purpose, the intensity rate equation is used to explain the reported experimental mea...Amplified spontaneous emission （ASE）, including intensity and bandwidth, in a typical example of BuEH-PPV is calculated. For this purpose, the intensity rate equation is used to explain the reported experimental measurements of a BuEH-PPV sample pumped at different pump intensities from Ip = 0.61 MW/cm2 to 5.2 MW/cm2. Both homogeneously and inhomogeneously broadened transition lines along with a model based on the geometrically dependent gain coefficient （GDGC） are examined and it is confirmed that for the reported measurements the homogeneously broadened line is responsible for the light-matter interaction. The calculation explains the frequency spectrum of the ASE output intensity extracted from the sample at different pump intensities, unsaturated and saturated gain coefficients, and ASE bandwidth reduction along the propagation direction. Both analytical and numerical calculations for verifying the GDGC model are presented in this paper. Although the introduced model has shown its potential for explaining the ASE behavior in a specific sample it can be universally used for the ASE study in different active media.展开更多
This paper proposes two types of integrated sound absorbing-insulating metamaterials with low thickness and efficient sound attenuation in the low-frequency bandwidth,i.e.,labyrinth-type metamaterial and multi-order r...This paper proposes two types of integrated sound absorbing-insulating metamaterials with low thickness and efficient sound attenuation in the low-frequency bandwidth,i.e.,labyrinth-type metamaterial and multi-order resonator metamaterial.The labyrinth-type metamaterial is designed through spatial dimension transfer,transferring the required dimension in the thickness direction to the planar thin layer.Based on the Helmholtz resonance,the metamaterial achieves noise reduction through the reflection of sound waves and the thermoviscous dissipation of holes and cavities.This mechanism enables its sound insulation performance to produce the same gain effect as absorption,thereby accomplishing the broadband absorbing-insulating integrated design.With a thickness of only 33 mm,it achieves both sound absorption and insulation effects over more than one octave.The multi-order resonator metamaterial has a larger working bandwidth than the labyrinth-type metamaterial.It is designed based on the multiorder resonance absorption mechanism,and consists of 9 different orders of resonator units.The metamaterial obtains a continuous sound absorption coefficient curve in the low-frequency range of 362–1712 Hz,and possesses high transmission loss(TL)above 346 Hz.In addition,this paper deeply explores the sound absorbing-insulating mechanism through the correlation analysis between the sound absorption coefficient and TL curves.The experimental results verify the continuous and efficient absorption effects of the two metamaterials,as well as their insulation performance that breaks the mass law.In low-frequency engineering applications,the two designed metamaterials demonstrate great potential and value at sub-wavelength dimensions.展开更多
A novel envelope design for an envelope tracking(ET)power amplifier(PA)based on its derivatives is proposed,which can trade well off between bandwidth reduc-tion and tracking accuracy.This paper theoretically analyzes...A novel envelope design for an envelope tracking(ET)power amplifier(PA)based on its derivatives is proposed,which can trade well off between bandwidth reduc-tion and tracking accuracy.This paper theoretically analyzes how to choose an envelope design that can track the original envelope closely and reduce its bandwidth,and then demonstrates an example to validate this idea.The generalized memory polynomial(GMP)model is applied to compensate for the nonlinearity of ET PA with the proposed envelope design.Experiments are carried out on an ET system that is operated with the center fre-quency of 3.5 GHz and excited by a 20 MHz LTE signal,which show that the proposed en-velope design can make a good trade-off between envelope bandwidth and efficiency,and satisfactory linearization performance can be realized.展开更多
文摘Amplified spontaneous emission （ASE）, including intensity and bandwidth, in a typical example of BuEH-PPV is calculated. For this purpose, the intensity rate equation is used to explain the reported experimental measurements of a BuEH-PPV sample pumped at different pump intensities from Ip = 0.61 MW/cm2 to 5.2 MW/cm2. Both homogeneously and inhomogeneously broadened transition lines along with a model based on the geometrically dependent gain coefficient （GDGC） are examined and it is confirmed that for the reported measurements the homogeneously broadened line is responsible for the light-matter interaction. The calculation explains the frequency spectrum of the ASE output intensity extracted from the sample at different pump intensities, unsaturated and saturated gain coefficients, and ASE bandwidth reduction along the propagation direction. Both analytical and numerical calculations for verifying the GDGC model are presented in this paper. Although the introduced model has shown its potential for explaining the ASE behavior in a specific sample it can be universally used for the ASE study in different active media.
基金Project supported by the National Natural Science Foundation of China(No.52250287)the Outstanding Youth Science Fund Project of Shaanxi Province of China(No.2024JC-JCQN-49)。
文摘This paper proposes two types of integrated sound absorbing-insulating metamaterials with low thickness and efficient sound attenuation in the low-frequency bandwidth,i.e.,labyrinth-type metamaterial and multi-order resonator metamaterial.The labyrinth-type metamaterial is designed through spatial dimension transfer,transferring the required dimension in the thickness direction to the planar thin layer.Based on the Helmholtz resonance,the metamaterial achieves noise reduction through the reflection of sound waves and the thermoviscous dissipation of holes and cavities.This mechanism enables its sound insulation performance to produce the same gain effect as absorption,thereby accomplishing the broadband absorbing-insulating integrated design.With a thickness of only 33 mm,it achieves both sound absorption and insulation effects over more than one octave.The multi-order resonator metamaterial has a larger working bandwidth than the labyrinth-type metamaterial.It is designed based on the multiorder resonance absorption mechanism,and consists of 9 different orders of resonator units.The metamaterial obtains a continuous sound absorption coefficient curve in the low-frequency range of 362–1712 Hz,and possesses high transmission loss(TL)above 346 Hz.In addition,this paper deeply explores the sound absorbing-insulating mechanism through the correlation analysis between the sound absorption coefficient and TL curves.The experimental results verify the continuous and efficient absorption effects of the two metamaterials,as well as their insulation performance that breaks the mass law.In low-frequency engineering applications,the two designed metamaterials demonstrate great potential and value at sub-wavelength dimensions.
文摘A novel envelope design for an envelope tracking(ET)power amplifier(PA)based on its derivatives is proposed,which can trade well off between bandwidth reduc-tion and tracking accuracy.This paper theoretically analyzes how to choose an envelope design that can track the original envelope closely and reduce its bandwidth,and then demonstrates an example to validate this idea.The generalized memory polynomial(GMP)model is applied to compensate for the nonlinearity of ET PA with the proposed envelope design.Experiments are carried out on an ET system that is operated with the center fre-quency of 3.5 GHz and excited by a 20 MHz LTE signal,which show that the proposed en-velope design can make a good trade-off between envelope bandwidth and efficiency,and satisfactory linearization performance can be realized.
