Bismuth(Bi)-doped photonic materials, which exhibit broadband near-infrared(NIR) luminescence(1000–1600 nm), are evolving into interesting gain media. However, the traditional methods have shown their limitations in ...Bismuth(Bi)-doped photonic materials, which exhibit broadband near-infrared(NIR) luminescence(1000–1600 nm), are evolving into interesting gain media. However, the traditional methods have shown their limitations in enhancing Bi NIR emission, especially in the microregion. Consequently, the typical NIR emission has seldom been achieved in Bi-doped waveguides, which highly restricts the application of Bi-activated materials.Here, superbroadband Bi NIR emission is induced in situ instantly in the grating region by a femtosecond(fs)laser inside borosilicate glasses. A series of structural and spectroscopic characterizations are summoned to probe the generation mechanism. And we show how this novel NIR emission in the grating region can be enhanced significantly and erased reversibly. Furthermore, we successfully demonstrate Bi-activated optical waveguides.These results present new insights into Bi-doped materials and push the development of broadband waveguide amplification.展开更多
We present an ultrabroadband, high-speed wavelength-swept source based on a self-modulated femtosecond oscillator. Photonic crystal fiber was pumped by a mode-locked Yb:CaF2 laser, resulting in a strong spectral broad...We present an ultrabroadband, high-speed wavelength-swept source based on a self-modulated femtosecond oscillator. Photonic crystal fiber was pumped by a mode-locked Yb:CaF2 laser, resulting in a strong spectral broadening from 485 to 1800 nm. The pump laser cavity could be realigned in order to achieve total mode-locking of the longitudinal and transverse TEM00 and TEM01 electromagnetic modes. This led to spatial oscillations of the output beam, which induced modulation of the coupling efficiency to the fiber. Due to the fact that nonlinear spectral broadening was intensity dependent, this mechanism introduced wavelength sweeping at the fiber output. The sweeping rate could be adjusted between 7 and 21.5 MHz by changing the geometry of the pump cavity. By controlling the ratio of the transverse mode amplitudes, we were able to tune the sweeping bandwidth, eventually covering both the 1300 nm and 1700 nm bioimaging transparency windows. When compared with previously demonstrated wavelength-swept sources, our concept offers much broader tunability and higher speed. Moreover,it does not require an additional intensity modulator.展开更多
Chromatic aberration-free meta-devices(e.g.,achromatic meta-devices and abnormal chromatic meta-devices)play an essential role in modern science and technology.However,current efforts suffer the issues of low efficien...Chromatic aberration-free meta-devices(e.g.,achromatic meta-devices and abnormal chromatic meta-devices)play an essential role in modern science and technology.However,current efforts suffer the issues of low efficiency,narrow operating band,and limited wavefront manipulation capability.We propose a general strategy to design chromatic aberration-free meta-devices with high-efficiency and ultrabroadband properties,which is realized by satisfying the key criteria of desirable phase dispersion and high reflection amplitudes at the target frequency interval.The phase dispersion is tuned successfully based on a multiresonant Lorentz model,and high reflection is guaranteed by the presence of the metallic ground.As proof of the concept,two microwave meta-devices are designed,fabricated,and experimentally characterized.An achromatic meta-mirror is proposed within 8 to 12 GHz,and another abnormal chromatic meta-mirror can tune the reflection angle as a linear function.Both meta-mirrors exhibit very high efficiencies(85%to 94%in the frequency band).Our findings open a door to realize chromatic aberration-free meta-devices with high efficiency and wideband properties and stimulate the realizations of chromatic aberration-free metadevices with other functionalities or working at higher frequency.展开更多
基金Natural Science Foundation of Guangdong Province(2018B030308009)National Natural Science Foundation of China(NSFC)(51672085)+3 种基金Program for Innovative Research Team in University of Ministry of Education of China(IRT_17R38)Ministry of Education of the People's Republic of China(MOE)Local Innovative Research Team Project of "Pearl River Talent Plan"(2017BT01X137)Fundamental Research Funds for the Central Universities
文摘Bismuth(Bi)-doped photonic materials, which exhibit broadband near-infrared(NIR) luminescence(1000–1600 nm), are evolving into interesting gain media. However, the traditional methods have shown their limitations in enhancing Bi NIR emission, especially in the microregion. Consequently, the typical NIR emission has seldom been achieved in Bi-doped waveguides, which highly restricts the application of Bi-activated materials.Here, superbroadband Bi NIR emission is induced in situ instantly in the grating region by a femtosecond(fs)laser inside borosilicate glasses. A series of structural and spectroscopic characterizations are summoned to probe the generation mechanism. And we show how this novel NIR emission in the grating region can be enhanced significantly and erased reversibly. Furthermore, we successfully demonstrate Bi-activated optical waveguides.These results present new insights into Bi-doped materials and push the development of broadband waveguide amplification.
基金Narodowe Centrum Nauki(NCN)(2015/18/E/ST7/00296)Narodowe Centrum Badani Rozwoju(NCBR)(POIR.04.01.01-00-0037/17)+1 种基金Politechnika Wroclawska(PWr)(0402/0121/17)Fundacja na rzecz Nauki Polskiej(FNP)
文摘We present an ultrabroadband, high-speed wavelength-swept source based on a self-modulated femtosecond oscillator. Photonic crystal fiber was pumped by a mode-locked Yb:CaF2 laser, resulting in a strong spectral broadening from 485 to 1800 nm. The pump laser cavity could be realigned in order to achieve total mode-locking of the longitudinal and transverse TEM00 and TEM01 electromagnetic modes. This led to spatial oscillations of the output beam, which induced modulation of the coupling efficiency to the fiber. Due to the fact that nonlinear spectral broadening was intensity dependent, this mechanism introduced wavelength sweeping at the fiber output. The sweeping rate could be adjusted between 7 and 21.5 MHz by changing the geometry of the pump cavity. By controlling the ratio of the transverse mode amplitudes, we were able to tune the sweeping bandwidth, eventually covering both the 1300 nm and 1700 nm bioimaging transparency windows. When compared with previously demonstrated wavelength-swept sources, our concept offers much broader tunability and higher speed. Moreover,it does not require an additional intensity modulator.
基金This work was supported by the National Natural Science Foundation of China under Grant Nos.61871394,61901512,11604167,61625502,11961141010,61975176, 62071423Postdoctoral Innovation Talents Support Program of China under Grant No.BX20190293, Natural Science Foundation of Shaanxi Province under Grant No.2019JQ-013.
文摘Chromatic aberration-free meta-devices(e.g.,achromatic meta-devices and abnormal chromatic meta-devices)play an essential role in modern science and technology.However,current efforts suffer the issues of low efficiency,narrow operating band,and limited wavefront manipulation capability.We propose a general strategy to design chromatic aberration-free meta-devices with high-efficiency and ultrabroadband properties,which is realized by satisfying the key criteria of desirable phase dispersion and high reflection amplitudes at the target frequency interval.The phase dispersion is tuned successfully based on a multiresonant Lorentz model,and high reflection is guaranteed by the presence of the metallic ground.As proof of the concept,two microwave meta-devices are designed,fabricated,and experimentally characterized.An achromatic meta-mirror is proposed within 8 to 12 GHz,and another abnormal chromatic meta-mirror can tune the reflection angle as a linear function.Both meta-mirrors exhibit very high efficiencies(85%to 94%in the frequency band).Our findings open a door to realize chromatic aberration-free meta-devices with high efficiency and wideband properties and stimulate the realizations of chromatic aberration-free metadevices with other functionalities or working at higher frequency.
