Recently, Bi_(4)Br_(4) is proved to be a member of topological insulators and is expected to be a promising candidate for ultrafast photonic device. However, experimental studies on the nonlinear optical properties of...Recently, Bi_(4)Br_(4) is proved to be a member of topological insulators and is expected to be a promising candidate for ultrafast photonic device. However, experimental studies on the nonlinear optical properties of Bi_(4)Br_(4) are limited, and its broadband absorption capabilities have not been validated. This study presents the first preparation of Bi_(4)Br_(4) samples using the chemical vapor transport method, resulting in a saturable absorber(SA) with a high modulation depth(46.23%) and low non-saturable loss(6.5%). The optical nonlinearity ranks among the best in similar studies. Additionally, this work applies Bi_(4)Br_(4)-SA for the first time in 1-μm fiber laser, developing a ring-cavity mode-locked fiber laser with a central wavelength of 1029.79 nm, a pulse duration of 442 fs, and a maximum output power of 90.83 m W. And a linear-cavity mode-locked fiber laser with a central wavelength of 1031.24 nm, a pulse duration of 511 fs, and a maximum output power of 92.81 m W is constructed. It is worth noting that the optical-to-optical conversion efficiency has reached about 11.54% and 33.58%.This study verifies Bi_(4)Br_(4)-SA's modulation effectiveness for 1-μm pulse lasers and provides a powerful reference for the design of high-efficiency fiber lasers.展开更多
Capturing ultrafast dynamics over a large momentum space is critical for revealing the relationship between the electronic and structural modulations in quantum materials.Here,by performing time-and angle-resolved pho...Capturing ultrafast dynamics over a large momentum space is critical for revealing the relationship between the electronic and structural modulations in quantum materials.Here,by performing time-and angle-resolved photoemission spectroscopy measurements at the Synergetic Extreme Condition User Facility(SECUF)equipped with an extreme ultraviolet light source,we reveal the ultrafast dynamics of a charge-density wave(CDW)material,1T-TiSe_(2),upon photoexcitation.Pump-induced CDW melting is revealed from two aspects:gap closing of the CDW at the Brillouin zone(BZ)center and weakening of the CDW folded band at the BZ boundary.By comparing the transient electronic structure and spectral weight over a large momentum space,we further reveal the carrier redistribution involving the excitation of electrons from theГpoint to the M point.This study provides a comprehensive picture of the physics and ultrafast dynamics of a CDW material across the entire BZ.展开更多
基金Project supported by the Beijing Natural Science Foundation (Grant No. JQ21019)the National Key Research and Development Program of China (Grant Nos. 2022YFA1604200 and 2022YFA1204100)the Fund from Beijing Municipal Commission of Science and Technology (Grant No. Z231100006623006)。
文摘Recently, Bi_(4)Br_(4) is proved to be a member of topological insulators and is expected to be a promising candidate for ultrafast photonic device. However, experimental studies on the nonlinear optical properties of Bi_(4)Br_(4) are limited, and its broadband absorption capabilities have not been validated. This study presents the first preparation of Bi_(4)Br_(4) samples using the chemical vapor transport method, resulting in a saturable absorber(SA) with a high modulation depth(46.23%) and low non-saturable loss(6.5%). The optical nonlinearity ranks among the best in similar studies. Additionally, this work applies Bi_(4)Br_(4)-SA for the first time in 1-μm fiber laser, developing a ring-cavity mode-locked fiber laser with a central wavelength of 1029.79 nm, a pulse duration of 442 fs, and a maximum output power of 90.83 m W. And a linear-cavity mode-locked fiber laser with a central wavelength of 1031.24 nm, a pulse duration of 511 fs, and a maximum output power of 92.81 m W is constructed. It is worth noting that the optical-to-optical conversion efficiency has reached about 11.54% and 33.58%.This study verifies Bi_(4)Br_(4)-SA's modulation effectiveness for 1-μm pulse lasers and provides a powerful reference for the design of high-efficiency fiber lasers.
基金supported by the Synergetic Extreme-Condition User Facility(SECUF)the National Key R&D Program of China(Grant Nos.2021YFA1400100,2020YFA0308800,and 2022YFA1604200)+2 种基金the National Natural Science Foundation of China(Grant Nos.12234011,92250305,52388201,11725418,and 11427903)supported by the China Postdoctoral Science Foundation(Grant Nos.2022M721886 and BX20230187)the Shuimu Tsinghua Scholar Program。
文摘Capturing ultrafast dynamics over a large momentum space is critical for revealing the relationship between the electronic and structural modulations in quantum materials.Here,by performing time-and angle-resolved photoemission spectroscopy measurements at the Synergetic Extreme Condition User Facility(SECUF)equipped with an extreme ultraviolet light source,we reveal the ultrafast dynamics of a charge-density wave(CDW)material,1T-TiSe_(2),upon photoexcitation.Pump-induced CDW melting is revealed from two aspects:gap closing of the CDW at the Brillouin zone(BZ)center and weakening of the CDW folded band at the BZ boundary.By comparing the transient electronic structure and spectral weight over a large momentum space,we further reveal the carrier redistribution involving the excitation of electrons from theГpoint to the M point.This study provides a comprehensive picture of the physics and ultrafast dynamics of a CDW material across the entire BZ.
