A type of millimeter-wave antenna array with flexible design is proposed for a variety of applications at 60 GHz.The antenna array can be adjusted to be linearly or circularly polarized by simply changing the radiatio...A type of millimeter-wave antenna array with flexible design is proposed for a variety of applications at 60 GHz.The antenna array can be adjusted to be linearly or circularly polarized by simply changing the radiation part of the antenna array.High gain,wideband,and high radiation efficiency characteristics can be achieved by adopting a low insertion loss feeding network and broadband antenna elements.For the linearly polarized antenna array,simulation results show that the impedance bandwidth of the 2×2 antenna subarray reaches 21.6%,while the maximum gain achieves 15.1 dBi and has a fluctuation of less than 0.4 dBi within the working bandwidth.Simulation results of the 8×8 linearly polarized antenna array show a bandwidth of 21.6%and a gain of(26.1±1)dBi with an antenna efficiency of more than 80%.For the 8×8 circularly polarized antenna array,simulation results show that an impedance bandwidth of 18.2%and an axial ratio(AR)bandwidth of 13.3%are obtained.Gain and efficiency of up to 27.6 dBi and 80%are achieved,respectively.A prototype of antenna array is fabricated,and results are compared and analyzed.展开更多
In this paper,we demonstrate an all-fiber linearly polarized fiber laser oscillator.The single polarization of the oscillator is achieved through the careful designing of the active fiber coiling.The relationship betw...In this paper,we demonstrate an all-fiber linearly polarized fiber laser oscillator.The single polarization of the oscillator is achieved through the careful designing of the active fiber coiling.The relationship between fiber coiling diameter and polarization extinction ratio and optical efficiency is studied,whose results lead to an optimized system.The thermal management of the oscillator is also refined,which allows the oscillator to reach a maximum output power of44.1 W with an optical-to-optical efficiency of 57.9%.A high average polarization extinction ratio of 21.6 d B is achieved during a 2-hour stability test.The oscillator also owns a narrow 3-d B bandwidth of 0.1 nm,as well as near-diffraction-limit beam quality of M^2～ 1.14.展开更多
In this study, we demonstrate an all-fiber high-power linearly-polarized tunable Raman fiber laser system. An in- house high-power tunable fiber laser was employed as the pump source. A fiber loop mirror （FLM） servi...In this study, we demonstrate an all-fiber high-power linearly-polarized tunable Raman fiber laser system. An in- house high-power tunable fiber laser was employed as the pump source. A fiber loop mirror （FLM） serving as a high reflectivity mirror and a flat-cut endface serving as an output coupler were adopted to provide broadband feedback. A piece of 59-m commercial passive fiber was used as the Raman gain medium. The Raman laser had a 27.6 nm tuning range from 1112 nm to 1139.6 nm and a maximum output power of 125.3 W, which corresponds to a conversion efficiency of 79.4%. The polarization extinction ratio （PER） at all operational wavelengths was measured to be over 21 dB. To the best of our knowledge, this is the first report on a hundred-watt level linearly-polarized tunable Raman fiber laser.展开更多
In this paper, we propose a three-layered chiral metamaterial (CMM) that exhibits an asymmetric transmission effect for linearly polarized waves along forwardly and backwardly propagating in the microwave region, whic...In this paper, we propose a three-layered chiral metamaterial (CMM) that exhibits an asymmetric transmission effect for linearly polarized waves along forwardly and backwardly propagating in the microwave region, which not only realizes the asymmetric transmission effect of multi-frequency points for linearly polarized wave in microwave band, but also breaks through the limitation of single transformation from linear polarization to linear polarization. Numerical simulation results indicate that incident wave for linearly polarized waves will be converted and transmitted as a circularly polarized wave along the forward direction at 8.31 GHz. Moreover, the asymmetric transmission (AT) parameter Δ achieves 0.8 around 12 GHz, proving the existence of strong polarization conversion and diode-like function. The proposed CMM shows great potential applications in high performance linear polarization convertor and isolator in microwave frequency.展开更多
文摘A type of millimeter-wave antenna array with flexible design is proposed for a variety of applications at 60 GHz.The antenna array can be adjusted to be linearly or circularly polarized by simply changing the radiation part of the antenna array.High gain,wideband,and high radiation efficiency characteristics can be achieved by adopting a low insertion loss feeding network and broadband antenna elements.For the linearly polarized antenna array,simulation results show that the impedance bandwidth of the 2×2 antenna subarray reaches 21.6%,while the maximum gain achieves 15.1 dBi and has a fluctuation of less than 0.4 dBi within the working bandwidth.Simulation results of the 8×8 linearly polarized antenna array show a bandwidth of 21.6%and a gain of(26.1±1)dBi with an antenna efficiency of more than 80%.For the 8×8 circularly polarized antenna array,simulation results show that an impedance bandwidth of 18.2%and an axial ratio(AR)bandwidth of 13.3%are obtained.Gain and efficiency of up to 27.6 dBi and 80%are achieved,respectively.A prototype of antenna array is fabricated,and results are compared and analyzed.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFB1104500)the National Natural Science Foundation of China(Grant No.61675114)the Tsinghua University(THU)Initiative Scientific Research Program,China(Grant No.20151080709)
文摘In this paper,we demonstrate an all-fiber linearly polarized fiber laser oscillator.The single polarization of the oscillator is achieved through the careful designing of the active fiber coiling.The relationship between fiber coiling diameter and polarization extinction ratio and optical efficiency is studied,whose results lead to an optimized system.The thermal management of the oscillator is also refined,which allows the oscillator to reach a maximum output power of44.1 W with an optical-to-optical efficiency of 57.9%.A high average polarization extinction ratio of 21.6 d B is achieved during a 2-hour stability test.The oscillator also owns a narrow 3-d B bandwidth of 0.1 nm,as well as near-diffraction-limit beam quality of M^2～ 1.14.
基金Project supported by the Fok Ying-Tong Education Foundation,China(Grant No.151062)
文摘In this study, we demonstrate an all-fiber high-power linearly-polarized tunable Raman fiber laser system. An in- house high-power tunable fiber laser was employed as the pump source. A fiber loop mirror （FLM） serving as a high reflectivity mirror and a flat-cut endface serving as an output coupler were adopted to provide broadband feedback. A piece of 59-m commercial passive fiber was used as the Raman gain medium. The Raman laser had a 27.6 nm tuning range from 1112 nm to 1139.6 nm and a maximum output power of 125.3 W, which corresponds to a conversion efficiency of 79.4%. The polarization extinction ratio （PER） at all operational wavelengths was measured to be over 21 dB. To the best of our knowledge, this is the first report on a hundred-watt level linearly-polarized tunable Raman fiber laser.
文摘In this paper, we propose a three-layered chiral metamaterial (CMM) that exhibits an asymmetric transmission effect for linearly polarized waves along forwardly and backwardly propagating in the microwave region, which not only realizes the asymmetric transmission effect of multi-frequency points for linearly polarized wave in microwave band, but also breaks through the limitation of single transformation from linear polarization to linear polarization. Numerical simulation results indicate that incident wave for linearly polarized waves will be converted and transmitted as a circularly polarized wave along the forward direction at 8.31 GHz. Moreover, the asymmetric transmission (AT) parameter Δ achieves 0.8 around 12 GHz, proving the existence of strong polarization conversion and diode-like function. The proposed CMM shows great potential applications in high performance linear polarization convertor and isolator in microwave frequency.
