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Light-matter Interaction|16 Article(s)
Microstructured fluorescence in liquid crystals with femtosecond laser excitation
Xia Meng, Ping Jin, Shijun Ge, Jiao Liu, Bingxiang Li, Lei Wang, and Yanqing Lu
This study investigated direct fluorescence generation from a nematic liquid crystal (NLC) NJU-LDn-4 under femtosecond laser excitation. The absorption, transmittance, excitation, and emission spectra of the NLC were assessed. The relationship between the femtosecond pump power and fluorescence intensity was analyzed, revealing a quadratic increase and indicating that two-photon absorption (2PA) is the primary fluorescence mechanism. The LC microstructure was designed using photoalignment technology, allowing the generated fluorescence to reflect the corresponding structure. This research can establish a foundation for tunable LC microstructured fluorescence, with potential applications in fluorescence microscopy and optoelectronics. This study investigated direct fluorescence generation from a nematic liquid crystal (NLC) NJU-LDn-4 under femtosecond laser excitation. The absorption, transmittance, excitation, and emission spectra of the NLC were assessed. The relationship between the femtosecond pump power and fluorescence intensity was analyzed, revealing a quadratic increase and indicating that two-photon absorption (2PA) is the primary fluorescence mechanism. The LC microstructure was designed using photoalignment technology, allowing the generated fluorescence to reflect the corresponding structure. This research can establish a foundation for tunable LC microstructured fluorescence, with potential applications in fluorescence microscopy and optoelectronics.
Chinese Optics Letters
- Publication Date: Mar. 21, 2024
- Vol. 22, Issue 3, 033801 (2024)
Titanium hyperdoped black silicon prepared by femtosecond laser irradiation: first-principle calculations and experimental verification|Editors' Pick
Song Huang, Anmin Wu, Guanting Song, Jiaxin Cao, Jianghong Yao, Qiang Wu, Weiqing Gao, and Jingjun Xu
Black silicon materials prepared via microstructuring and hyperdoping by ultrafast laser irradiation have attracted immense attention owing to their high absorption and photon sensitivity across a broadband spectral range. However, a conflict exists between the repair requirements for the high amount of laser-induced damage and the thermally unstable hyperdoped impurities, resulting in low photon sensitivity and rapid decay at subbandgap wavelengths for the annealed black silicon. In this work, the properties of titanium (Ti) hyperdoped silicon have been explored using first-principle calculations. The findings of the study reveal that the interstitial Ti atoms exhibit a deep impurity band and low formation energy in silicon, which may be responsible for the stable subbandgap absorption that is achieved. Furthermore, femtosecond laser irradiation and rapid thermal annealing have been applied to manufacture Ti-hyperdoped black silicon (b-Si:Ti). The b-Si:Ti compound prepared by hyperdoping displayed high absorption across the visible and infrared ranges, with absorptance exceeding 90% for visible lights and 60% for subbandgap wavelengths. Additionally, the subbandgap absorption remains high even after intense thermal annealing, indicating a stable deep-level impurity of Ti in silicon. The experimental findings are consistent with the simulation results and complement each other to reveal the physical mechanisms responsible for the high performance of b-Si:Ti. The results thus demonstrate promising prospects for the application of black silicon in high-efficiency solar cells, photoelectric imaging, and flip-chip interconnection systems. Black silicon materials prepared via microstructuring and hyperdoping by ultrafast laser irradiation have attracted immense attention owing to their high absorption and photon sensitivity across a broadband spectral range. However, a conflict exists between the repair requirements for the high amount of laser-induced damage and the thermally unstable hyperdoped impurities, resulting in low photon sensitivity and rapid decay at subbandgap wavelengths for the annealed black silicon. In this work, the properties of titanium (Ti) hyperdoped silicon have been explored using first-principle calculations. The findings of the study reveal that the interstitial Ti atoms exhibit a deep impurity band and low formation energy in silicon, which may be responsible for the stable subbandgap absorption that is achieved. Furthermore, femtosecond laser irradiation and rapid thermal annealing have been applied to manufacture Ti-hyperdoped black silicon (b-Si:Ti). The b-Si:Ti compound prepared by hyperdoping displayed high absorption across the visible and infrared ranges, with absorptance exceeding 90% for visible lights and 60% for subbandgap wavelengths. Additionally, the subbandgap absorption remains high even after intense thermal annealing, indicating a stable deep-level impurity of Ti in silicon. The experimental findings are consistent with the simulation results and complement each other to reveal the physical mechanisms responsible for the high performance of b-Si:Ti. The results thus demonstrate promising prospects for the application of black silicon in high-efficiency solar cells, photoelectric imaging, and flip-chip interconnection systems.
Chinese Optics Letters
- Publication Date: Nov. 27, 2024
- Vol. 22, Issue 11, 113801 (2024)
High-gradient modulation of microbunchings using a minimized system driven by a vortex laser
Shufa Hao, Zhengxing Lv, Hao Dong, Jianzhi He, Nanshun Huang, Fengyu Sun, Zhiyong Shi, Hao Sun, Wenpeng Wang, Yuxin Leng, Ruxin Li, and Zhizhan Xu
This study entailed the development of a high-gradient modulation of microbunching for traditional radiation frequency accelerators using a minimized system driven by a relativistic Laguerre–Gaussian (LG) laser in three-dimensional particle-in-cell (PIC) simulations. It was observed that the LG laser could compress the transverse dimension of the beam to within a 0.7 µm radius (divergence≈4.3 mrad), which is considerably lower than the case tuned by a Gaussian laser. In addition, the electron beam could be efficiently modulated to a high degree of bunching effect (>0.5) within ∼21 fs (∼7 μm) in the longitudinal direction. Such a high-gradient density modulation driven by an LG laser for pre-bunched, low-divergence, and stable electron beams provides a potential technology for the system minimization of X-ray free-electron lasers (XFELs) and ultrashort-scale (attosecond) electron diffraction research. This study entailed the development of a high-gradient modulation of microbunching for traditional radiation frequency accelerators using a minimized system driven by a relativistic Laguerre–Gaussian (LG) laser in three-dimensional particle-in-cell (PIC) simulations. It was observed that the LG laser could compress the transverse dimension of the beam to within a 0.7 µm radius (divergence≈4.3 mrad), which is considerably lower than the case tuned by a Gaussian laser. In addition, the electron beam could be efficiently modulated to a high degree of bunching effect (>0.5) within ∼21 fs (∼7 μm) in the longitudinal direction. Such a high-gradient density modulation driven by an LG laser for pre-bunched, low-divergence, and stable electron beams provides a potential technology for the system minimization of X-ray free-electron lasers (XFELs) and ultrashort-scale (attosecond) electron diffraction research.
Chinese Optics Letters
- Publication Date: Aug. 23, 2023
- Vol. 21, Issue 9, 093801 (2023)
Effects of laser waveform on the generation of fast electrons in laser–solid interactions
Xiaomei Dong, Yuhan Du, Miaohua Xu, Yutong Li, Zhe Zhang, and Yingjun Li
In the scheme of fast ignition of inertial confinement fusion, the fuel temperature mainly relies on fast electrons, which act as an energy carrier, transferring the laser energy to the fuel. Both conversion efficiency from the laser to the fast electron and the energy spectrum of the fast electron are essentially important to achieve highly effective heating. In this study, a two-dimensional particle in cell simulation is applied to study the generation of fast electrons from solid-density plasmas with different laser waveforms. The results have shown that the slope of the rising edge has a significant effect on fast electron generation and energy absorption. For the negative skew pulse with a relatively slow rising edge, the J×B mechanism can most effectively accelerate the electrons. The overall absorption efficiency of the laser energy is optimized, and the fast electron yield in the middle- and low-energy range is also improved. In the scheme of fast ignition of inertial confinement fusion, the fuel temperature mainly relies on fast electrons, which act as an energy carrier, transferring the laser energy to the fuel. Both conversion efficiency from the laser to the fast electron and the energy spectrum of the fast electron are essentially important to achieve highly effective heating. In this study, a two-dimensional particle in cell simulation is applied to study the generation of fast electrons from solid-density plasmas with different laser waveforms. The results have shown that the slope of the rising edge has a significant effect on fast electron generation and energy absorption. For the negative skew pulse with a relatively slow rising edge, the J×B mechanism can most effectively accelerate the electrons. The overall absorption efficiency of the laser energy is optimized, and the fast electron yield in the middle- and low-energy range is also improved.
Chinese Optics Letters
- Publication Date: Jun. 06, 2023
- Vol. 21, Issue 6, 063801 (2023)
Generation and application of high-contrast laser pulses using plasma mirror in the SULF-1PW beamline
Cheng Jiang, Zongxin Zhang, Hao Dong, Zhiyong Shi, Jianzhi He, Shufa Hao, Fengyu Sun, Jiayan Gui, Jiayi Qian, Jiacheng Zhu, Wenpeng Wang, Yi Xu, Xiaoyan Liang, Yuxin Leng, and Ruxin Li
The plasma mirror system was installed on the 1 PW laser beamline of Shanghai Superintense Ultrafast Laser Facility (SULF) for enhancing the temporal contrast of the laser pulse. About 2 orders of magnitude improvement on pulse contrast was measured on picosecond and nanosecond time scales. The experiments show that high-contrast laser pulses can significantly improve the cutoff energy and quantity of proton beams. Then different target distributions are assumed in particles in cell simulations, which can qualitatively assume the expansion of nanometer-scale foil. The high-contrast laser enables the SULF-1PW beamline to generally be of benefit for many potential applications. The plasma mirror system was installed on the 1 PW laser beamline of Shanghai Superintense Ultrafast Laser Facility (SULF) for enhancing the temporal contrast of the laser pulse. About 2 orders of magnitude improvement on pulse contrast was measured on picosecond and nanosecond time scales. The experiments show that high-contrast laser pulses can significantly improve the cutoff energy and quantity of proton beams. Then different target distributions are assumed in particles in cell simulations, which can qualitatively assume the expansion of nanometer-scale foil. The high-contrast laser enables the SULF-1PW beamline to generally be of benefit for many potential applications.
Chinese Optics Letters
- Publication Date: Mar. 31, 2023
- Vol. 21, Issue 4, 043802 (2023)
Distinguishing high-harmonic generation from surface and bulk states in topological insulator Bi2Se3
Yang Jiang, Ya Bai, Zeyi Ye, Na Li, Candong Liu, and Peng Liu
We demonstrated a scheme to differentiate the high-harmonic generation (HHG) originating from the surface states and bulk states of the topological insulator Bi2Se3. By adopting two-color mid-infrared laser fields on Bi2Se3, we found that the nonlinear response sensitively depends on the relative phase of the driving fields. The even harmonics arise from the surface states with a clear signature, whose modulation period equals the cycle of the second-harmonic generation (SHG) field. We reveal that the weak SHG perturbs the nontrivial dipole phase of the electron-hole pair in surface states, and thus leads to the modulation of HHG. It provides a means to manipulate the ultrafast dynamics in surface states through adopting a weak perturbing laser field. We demonstrated a scheme to differentiate the high-harmonic generation (HHG) originating from the surface states and bulk states of the topological insulator Bi2Se3. By adopting two-color mid-infrared laser fields on Bi2Se3, we found that the nonlinear response sensitively depends on the relative phase of the driving fields. The even harmonics arise from the surface states with a clear signature, whose modulation period equals the cycle of the second-harmonic generation (SHG) field. We reveal that the weak SHG perturbs the nontrivial dipole phase of the electron-hole pair in surface states, and thus leads to the modulation of HHG. It provides a means to manipulate the ultrafast dynamics in surface states through adopting a weak perturbing laser field.
Chinese Optics Letters
- Publication Date: Apr. 04, 2023
- Vol. 21, Issue 4, 043801 (2023)
Trapping and revolving micron particles by transformable line traps of optical tweezers
Lingyao Yu, Yuan Jia, Xujin Hu, Shaofei Wang, Hongyu Chen, Shuai Liu, Hongchang Deng, Maowen Wang, and Jun Yin
Optical line tweezers have been an efficient tool for the manipulation of large micron particles. In this paper, we propose to create line traps with transformable configurations by using the transverse electromagnetic mode-like laser source. We designed an optical path to simulate the generation of the astigmatic beams and line traps with a series of lenses to realize the rotational transformation with respect to the rotation angle of cylindrical lenses. It is shown that the spherical particles with diameters ranging from 5 μm to 20 μm could be trapped, aligned, and revolved in experiment. The periodical trapping forces generated by transformable line traps might open an alternative way to investigate the mechanical properties of soft particles and biological cells. Optical line tweezers have been an efficient tool for the manipulation of large micron particles. In this paper, we propose to create line traps with transformable configurations by using the transverse electromagnetic mode-like laser source. We designed an optical path to simulate the generation of the astigmatic beams and line traps with a series of lenses to realize the rotational transformation with respect to the rotation angle of cylindrical lenses. It is shown that the spherical particles with diameters ranging from 5 μm to 20 μm could be trapped, aligned, and revolved in experiment. The periodical trapping forces generated by transformable line traps might open an alternative way to investigate the mechanical properties of soft particles and biological cells.
Chinese Optics Letters
- Publication Date: Mar. 30, 2022
- Vol. 20, Issue 5, 053801 (2022)
Femtosecond-laser-induced backward transfer of fluorinated ethylene propylene for fabrication of “lotus effect” surfaces
Kongyu Lou, Jing Qian, Xiaohan Yu, Zhaoyuan Xia, Danyang Shen, Guande Wang, and Quan-Zhong Zhao
“Lotus effect” glass surfaces with fluorinated ethylene propylene were successfully fabricated by using a femtosecond laser-induced backward transfer (LIBT) method. By space-selectively modifying both the surface morphology and surface chemistry in a single step, LIBT provides a convenient and flexible route to fabricate superhydrophobic surfaces with ultralow adhesion. A systematic mechanism responsible for the anisotropic wetting behaviors and adhesion modulation was proposed with a combination of the Cassie and Wenzel models. X-ray photoelectron spectroscopy revealed that oxidation and defluorination were induced by laser radiation. LIBT is proved to be a promising method for programmable manipulations of functional surfaces with diverse wettability. “Lotus effect” glass surfaces with fluorinated ethylene propylene were successfully fabricated by using a femtosecond laser-induced backward transfer (LIBT) method. By space-selectively modifying both the surface morphology and surface chemistry in a single step, LIBT provides a convenient and flexible route to fabricate superhydrophobic surfaces with ultralow adhesion. A systematic mechanism responsible for the anisotropic wetting behaviors and adhesion modulation was proposed with a combination of the Cassie and Wenzel models. X-ray photoelectron spectroscopy revealed that oxidation and defluorination were induced by laser radiation. LIBT is proved to be a promising method for programmable manipulations of functional surfaces with diverse wettability.
Chinese Optics Letters
- Publication Date: Feb. 18, 2022
- Vol. 20, Issue 4, 043801 (2022)
Femtosecond laser textured porous nanowire structured glass for enhanced thermal imaging|On the Cover
Tingni Wu, Zhipeng Wu, Yuchun He, Zhuo Zhu, Lingxiao Wang, and Kai Yin
Infrared (IR) thermal imaging has aroused great interest due to its wide application in medical, scientific, and military fields. Most reported approaches for regulating thermal radiation are aimed to realize IR camouflage and are not applicable to enhance thermal imaging. Here, we introduce a simple and effective method to process porous glass by femtosecond laser scanning, where distributed nanocavities and nanowires were produced, which caused improvement of the treated glass emissivity. The as-prepared sample possessed better IR thermal radiation performance but lower transmittance to visible light. We also demonstrated its applicability by placing it in different backgrounds, where the IR image temperature of laser-treated glass was closer to the actual environment, and this strategy may provide a new vision for enhanced thermal imaging. Infrared (IR) thermal imaging has aroused great interest due to its wide application in medical, scientific, and military fields. Most reported approaches for regulating thermal radiation are aimed to realize IR camouflage and are not applicable to enhance thermal imaging. Here, we introduce a simple and effective method to process porous glass by femtosecond laser scanning, where distributed nanocavities and nanowires were produced, which caused improvement of the treated glass emissivity. The as-prepared sample possessed better IR thermal radiation performance but lower transmittance to visible light. We also demonstrated its applicability by placing it in different backgrounds, where the IR image temperature of laser-treated glass was closer to the actual environment, and this strategy may provide a new vision for enhanced thermal imaging.
Chinese Optics Letters
- Publication Date: Feb. 02, 2022
- Vol. 20, Issue 3, 033801 (2022)
Rapid fabrication of microrings with complex cross section using annular vortex beams|On the Cover
Chenchu Zhang, Hanchang Ye, Rui Cao, Shengyun Ji, Heng Zhang, Linhan Zhao, Sizhu Wu, and Hua Zhai
A ring-shaped focus, such as a focused vortex beam, has played an important role in microfabrication and optical tweezers. The shape and diameter of the ring-shaped focus can be easily adjusted by the topological charge of the vortex. However, the flow energy is also related to the topological charge, making the individual control of diameter and flow energy of the vortex beam impossible. Meanwhile, the shape of the focus of the vortex beam remains in the hollow ring. Expanding the shape of focus of structural light broadens the applications of the vortex beam in the field of microfabrication. Here, we proposed a ring-shaped focus with controllable gaps by multiplexing the vortex beam and annular beam. The multiplexed beam has several advantages, such as the diameter and flow energy of the focal point can be individually controlled and are not affected by the zero-order beam, and the gap size and position are controllable. A ring-shaped focus, such as a focused vortex beam, has played an important role in microfabrication and optical tweezers. The shape and diameter of the ring-shaped focus can be easily adjusted by the topological charge of the vortex. However, the flow energy is also related to the topological charge, making the individual control of diameter and flow energy of the vortex beam impossible. Meanwhile, the shape of the focus of the vortex beam remains in the hollow ring. Expanding the shape of focus of structural light broadens the applications of the vortex beam in the field of microfabrication. Here, we proposed a ring-shaped focus with controllable gaps by multiplexing the vortex beam and annular beam. The multiplexed beam has several advantages, such as the diameter and flow energy of the focal point can be individually controlled and are not affected by the zero-order beam, and the gap size and position are controllable.
Chinese Optics Letters
- Publication Date: Oct. 14, 2021
- Vol. 20, Issue 2, 023801 (2022)
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