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Ultrafast Optics|54 Article(s)
Compact, folded multi-pass cells for energy scaling of post-compression
Arthur Schönberg, Supriya Rajhans, Esmerando Escoto, Nikita Khodakovskiy, Victor Hariton, Bonaventura Farace, Kristjan Põder, Ann-Kathrin Raab, Saga Westerberg, Mekan Merdanov, Anne-Lise Viotti, Cord L. Arnold, Wim P. Leemans, Ingmar Hartl, and Christoph M. Heyl
Combining high peak power and high average power has long been a key challenge of ultrafast laser technology, crucial for applications such as laser-plasma acceleration and strong-field physics. A promising solution lies in post-compressed ytterbium lasers, but scaling these to high pulse energies presents a major bottleneck. Post-compression techniques, particularly Herriott-type multi-pass cells (MPCs), have enabled large peak power boosts at high average powers but their pulse energy acceptance reaches practical limits defined by setup size and coating damage threshold. In this work, we address this challenge and demonstrate, to our knowledge, a novel type of compact, energy-scalable MPC (CMPC). By employing a novel MPC configuration and folding the beam path, the CMPC introduces a new degree of freedom for downsizing the setup length, enabling compact setups even for large pulse energies. We experimentally and numerically verify the CMPC approach, demonstrating post-compression of 8 mJ pulses from 1 ps down to 51 fs in atmospheric air using a cell roughly 45 cm in length at low fluence values. Additionally, we discuss the potential for energy scaling up to 200 mJ with a setup size reaching 2.5 m. Our work presents a new approach to high-energy post-compression, with up-scaling potential far beyond the demonstrated parameters. This opens new routes for achieving the high peak and average powers necessary for demanding applications of ultrafast lasers. Combining high peak power and high average power has long been a key challenge of ultrafast laser technology, crucial for applications such as laser-plasma acceleration and strong-field physics. A promising solution lies in post-compressed ytterbium lasers, but scaling these to high pulse energies presents a major bottleneck. Post-compression techniques, particularly Herriott-type multi-pass cells (MPCs), have enabled large peak power boosts at high average powers but their pulse energy acceptance reaches practical limits defined by setup size and coating damage threshold. In this work, we address this challenge and demonstrate, to our knowledge, a novel type of compact, energy-scalable MPC (CMPC). By employing a novel MPC configuration and folding the beam path, the CMPC introduces a new degree of freedom for downsizing the setup length, enabling compact setups even for large pulse energies. We experimentally and numerically verify the CMPC approach, demonstrating post-compression of 8 mJ pulses from 1 ps down to 51 fs in atmospheric air using a cell roughly 45 cm in length at low fluence values. Additionally, we discuss the potential for energy scaling up to 200 mJ with a setup size reaching 2.5 m. Our work presents a new approach to high-energy post-compression, with up-scaling potential far beyond the demonstrated parameters. This opens new routes for achieving the high peak and average powers necessary for demanding applications of ultrafast lasers.
Photonics Research
- Publication Date: Feb. 28, 2025
- Vol. 13, Issue 3, 761 (2025)
High-resolution, high-speed, chromotropic color printing based on fs-laser-induced gold/graphene HSFLs
Shiru Jiang, Woo-Bin Lee, Stuart Aberdeen, and Sang-Shin Lee
Through achieving high-spatial-frequency laser-induced periodic surface structures (HSFLs) on a gold/graphene hybrid film, we introduce a high-speed, high-resolution, and wide-gamut chromotropic color printing technique. This method effectively addresses the trade-off between throughput and resolution in laser coloring. To realize Au HSFL, disordered lattice structures and high transmittance of amorphous Au (a-Au) thin film are used to overcome the rapid hot-electron diffusion and loss of plasmonic coherence typically observed on low-loss metal surfaces, respectively. Coupled with crystallization in Au and modulated surface plasmon polaritons by artificial “seed” pre-structure growing in a SiO2/Si substrate, HSFL emerged with a period of 100 nm on crystalline Au after single and rapid femtosecond laser scanning. This equips the proposed color printing with high-resolution and high-speed features simultaneously. In addition, the crystallization process is demonstrated to initiate change in the complex refractive index of Au, which causes wide-gamut colors. The chromotropic capability, which facilitates the background color to be tailored in color as well as into desirable shapes independently, enables three-level anti-counterfeiting based on the proposed color printing. Therefore, the proposed color printing is amenable for practical implementation in diverse applications, including security marking and data storage, ranging from nanoscale to large-scale fabrication. Through achieving high-spatial-frequency laser-induced periodic surface structures (HSFLs) on a gold/graphene hybrid film, we introduce a high-speed, high-resolution, and wide-gamut chromotropic color printing technique. This method effectively addresses the trade-off between throughput and resolution in laser coloring. To realize Au HSFL, disordered lattice structures and high transmittance of amorphous Au (a-Au) thin film are used to overcome the rapid hot-electron diffusion and loss of plasmonic coherence typically observed on low-loss metal surfaces, respectively. Coupled with crystallization in Au and modulated surface plasmon polaritons by artificial “seed” pre-structure growing in a SiO2/Si substrate, HSFL emerged with a period of 100 nm on crystalline Au after single and rapid femtosecond laser scanning. This equips the proposed color printing with high-resolution and high-speed features simultaneously. In addition, the crystallization process is demonstrated to initiate change in the complex refractive index of Au, which causes wide-gamut colors. The chromotropic capability, which facilitates the background color to be tailored in color as well as into desirable shapes independently, enables three-level anti-counterfeiting based on the proposed color printing. Therefore, the proposed color printing is amenable for practical implementation in diverse applications, including security marking and data storage, ranging from nanoscale to large-scale fabrication.
Photonics Research
- Publication Date: Dec. 20, 2024
- Vol. 13, Issue 1, 125 (2025)
Parity effects in Rydberg-state excitation in intense laser fields
Yang Liu, Xiaopeng Yi, Qi Chen, Tian Sun, Hang Lv, Shilin Hu, Wilhelm Becker, Haifeng Xu, and Jing Chen
Conservation of parity plays a fundamental role in our understanding of various quantum processes. However, it is difficult to observe in atomic and molecular processes induced by a strong laser field due to their multiphoton character and the large number of states involved. Here we report an effect of parity in strong-field Rydberg-state excitation (RSE) by comparing the RSE probabilities of the N2 molecule and its companion atom Ar, which has a similar ionization potential but opposite parity of its ground state. Experimentally, we observe an oscillatory structure as a function of intensity with a period of about 50 TW/cm2 in the ratio between the RSE yields of the two species, which can be reproduced by simulations using the time-dependent Schrödinger equation (TDSE). We analyze a quantum-mechanical model, which allows for interference of electrons captured in different spatial regions of the Rydberg-state wave function. In the intensity-dependent RSE yield, it results in peaks with alternating heights with a spacing of 25 TW/cm2 and at the same intensity for both species. However, due to the opposite parities of their ground states, pronounced RSE peaks in Ar correspond to less pronounced peaks in N2 and vice versa, which leads to the period of 50 TW/cm2 in their ratio. Our work reveals a novel parity-related interference effect in the coherent-capture picture of the RSE process in intense laser fields. Conservation of parity plays a fundamental role in our understanding of various quantum processes. However, it is difficult to observe in atomic and molecular processes induced by a strong laser field due to their multiphoton character and the large number of states involved. Here we report an effect of parity in strong-field Rydberg-state excitation (RSE) by comparing the RSE probabilities of the N2 molecule and its companion atom Ar, which has a similar ionization potential but opposite parity of its ground state. Experimentally, we observe an oscillatory structure as a function of intensity with a period of about 50 TW/cm2 in the ratio between the RSE yields of the two species, which can be reproduced by simulations using the time-dependent Schrödinger equation (TDSE). We analyze a quantum-mechanical model, which allows for interference of electrons captured in different spatial regions of the Rydberg-state wave function. In the intensity-dependent RSE yield, it results in peaks with alternating heights with a spacing of 25 TW/cm2 and at the same intensity for both species. However, due to the opposite parities of their ground states, pronounced RSE peaks in Ar correspond to less pronounced peaks in N2 and vice versa, which leads to the period of 50 TW/cm2 in their ratio. Our work reveals a novel parity-related interference effect in the coherent-capture picture of the RSE process in intense laser fields.
Photonics Research
- Publication Date: Dec. 02, 2024
- Vol. 12, Issue 12, 3033 (2024)
All-optical control of high-order harmonic generation in correlated systems
Yang Wang, Jingsong Gao, Yu Liu, Pengzuo Jiang, Jingying Xiao, Zhuoyan Zhou, Hong Yang, Guowei Lu, Liang-You Peng, Yunquan Liu, Qihuang Gong, and Chengyin Wu
Solid-state high-order harmonic generation (HHG) presents a promising approach for achieving controllable broadband coherent light sources and dynamically detecting materials. In this study, we demonstrate the all-optical control of HHG in a strongly correlated system, vanadium dioxide (VO2), through photo-carrier doping. It has been discovered that HHG can be efficiently modified using a pump laser, achieving modulation depths approaching 100% (extinction ratio ≥40 dB) on femtosecond timescales. Quantitative analysis reveals that the driving forces behind pump-dependent HHG are attributed to two distinct many-body dynamics: the scattering-induced dephasing and the insulator-to-metal transition (IMT) caused by photo-induced electron shielding. These two dynamics play a crucial role in defining the intensity and transient response of the HHG. Furthermore, we demonstrate that it is possible to quantitatively extract the metallic phase fraction from time-resolved HHG (tr-HHG) signals throughout the IMT. This study highlights the benefits of utilizing many-body dynamics for controlling HHG and underscores the necessity for further theoretical research on HHG in strongly correlated systems. Solid-state high-order harmonic generation (HHG) presents a promising approach for achieving controllable broadband coherent light sources and dynamically detecting materials. In this study, we demonstrate the all-optical control of HHG in a strongly correlated system, vanadium dioxide (VO2), through photo-carrier doping. It has been discovered that HHG can be efficiently modified using a pump laser, achieving modulation depths approaching 100% (extinction ratio ≥40 dB) on femtosecond timescales. Quantitative analysis reveals that the driving forces behind pump-dependent HHG are attributed to two distinct many-body dynamics: the scattering-induced dephasing and the insulator-to-metal transition (IMT) caused by photo-induced electron shielding. These two dynamics play a crucial role in defining the intensity and transient response of the HHG. Furthermore, we demonstrate that it is possible to quantitatively extract the metallic phase fraction from time-resolved HHG (tr-HHG) signals throughout the IMT. This study highlights the benefits of utilizing many-body dynamics for controlling HHG and underscores the necessity for further theoretical research on HHG in strongly correlated systems.
Photonics Research
- Publication Date: Nov. 27, 2024
- Vol. 12, Issue 12, 2831 (2024)
Scheme for generation of spatiotemporal optical vortex attosecond pulse trains
Jiahao Dong, Liang Xu, Yiqi Fang, Hongcheng Ni, Feng He, Songlin Zhuang, and Yi Liu
The realization of spatiotemporal vortex structure of various physical fields with transverse orbital angular momentum (OAM) has attracted much attention and is expected to expand the research scope and open new opportunities in their respective fields. Here we present theoretically the first, to the best of our knowledge, study on the generation of attosecond pulse trains featuring a spatiotemporal optical vortex (STOV) structure by a two-color femtosecond light field, with each color carrying transverse OAM. Through careful optimization of relative phase and intensity ratio, we validate the efficient upconversion of the infrared pulse into its tens of order harmonics, showing that each harmonic preserves a corresponding intact topological charge. This unique characteristic enables the synthesis of an extreme ultraviolet attosecond pulse train with transverse OAM. In addition, we reveal that ionization depletion plays an outsize role therein. Our studies pave the way for the generation and utilization of light fields with STOV in the attosecond regime. The realization of spatiotemporal vortex structure of various physical fields with transverse orbital angular momentum (OAM) has attracted much attention and is expected to expand the research scope and open new opportunities in their respective fields. Here we present theoretically the first, to the best of our knowledge, study on the generation of attosecond pulse trains featuring a spatiotemporal optical vortex (STOV) structure by a two-color femtosecond light field, with each color carrying transverse OAM. Through careful optimization of relative phase and intensity ratio, we validate the efficient upconversion of the infrared pulse into its tens of order harmonics, showing that each harmonic preserves a corresponding intact topological charge. This unique characteristic enables the synthesis of an extreme ultraviolet attosecond pulse train with transverse OAM. In addition, we reveal that ionization depletion plays an outsize role therein. Our studies pave the way for the generation and utilization of light fields with STOV in the attosecond regime.
Photonics Research
- Publication Date: Oct. 01, 2024
- Vol. 12, Issue 10, 2409 (2024)
Less is more: surface-lattice-resonance-enhanced aluminum metasurface with giant saturable absorption for a wavelength-tunable Q-switched Yb-doped fiber laser
Hailun Xie, Lili Gui, Xiangxiang Zhou, Yue Zhou, and Kun Xu
Resonant metasurfaces provide a promising solution to overcome the limitations of nonlinear materials in nature by enhancing the interaction between light and matter and amplifying optical nonlinearity. In this paper, we design an aluminum (Al) metasurface that supports surface lattice resonance (SLR) with less nanoparticle filling density but more prominent saturable absorption effects, in comparison to a counterpart that supports localized surface plasmon resonance (LSPR). In detail, the SLR metasurface exhibits a narrower resonance linewidth and a greater near-field enhancement, leading to a more significant modulation depth (9.6%) at a low incident fluence of 25 μJ/cm2. As an application example, we have further achieved wavelength-tunable Q-switched pulse generation from 1020 to 1048 nm by incorporating the SLR-based Al metasurface as a passive saturable absorber (SA) in a polarization-maintaining ytterbium-doped fiber laser. Typically, the Q-switched pulse with a repetition rate of 33.7 kHz, pulse width of 2.1 μs, pulse energy of 141.7 nJ, and signal-to-noise ratio (SNR) of greater than 40 dB at the fundamental frequency can be obtained. In addition, we have investigated the effects of pump power and central wavelength of the filter on the repetition rate and pulse width of output pulses, respectively. In spite of demonstration of only using the Al metasurface to achieve a passive Q-switched fiber laser, our work offers an alternative scheme to build planar, lightweight, and broadband SA devices that could find emerging applications from ultrafast optics to neuromorphic photonics, considering the fast dynamics, CMOS-compatible fabrication, and decent nonlinear optical response of Al-material-based nanoplasmonics. Resonant metasurfaces provide a promising solution to overcome the limitations of nonlinear materials in nature by enhancing the interaction between light and matter and amplifying optical nonlinearity. In this paper, we design an aluminum (Al) metasurface that supports surface lattice resonance (SLR) with less nanoparticle filling density but more prominent saturable absorption effects, in comparison to a counterpart that supports localized surface plasmon resonance (LSPR). In detail, the SLR metasurface exhibits a narrower resonance linewidth and a greater near-field enhancement, leading to a more significant modulation depth (9.6%) at a low incident fluence of 25 μJ/cm2. As an application example, we have further achieved wavelength-tunable Q-switched pulse generation from 1020 to 1048 nm by incorporating the SLR-based Al metasurface as a passive saturable absorber (SA) in a polarization-maintaining ytterbium-doped fiber laser. Typically, the Q-switched pulse with a repetition rate of 33.7 kHz, pulse width of 2.1 μs, pulse energy of 141.7 nJ, and signal-to-noise ratio (SNR) of greater than 40 dB at the fundamental frequency can be obtained. In addition, we have investigated the effects of pump power and central wavelength of the filter on the repetition rate and pulse width of output pulses, respectively. In spite of demonstration of only using the Al metasurface to achieve a passive Q-switched fiber laser, our work offers an alternative scheme to build planar, lightweight, and broadband SA devices that could find emerging applications from ultrafast optics to neuromorphic photonics, considering the fast dynamics, CMOS-compatible fabrication, and decent nonlinear optical response of Al-material-based nanoplasmonics.
Photonics Research
- Publication Date: Sep. 20, 2024
- Vol. 12, Issue 10, 2198 (2024)
Ultrafast temporal-spectral analysis probes isomeric dynamics in a dissipative soliton resonator
Haoguang Liu, Yiyang Luo, Yixiang Sun, Yusong Liu, Yao Yao, Ran Xia, Gang Xu, Xiahui Tang, Qizhen Sun, and Perry Ping Shum
Self-assembly of dissipative solitons arouses versatile configurations of molecular complexes, enriching intriguing dynamics in mode-locked lasers. The ongoing studies fuel the analogy between matter physics and optical solitons, and stimulate frontier developments of ultrafast optics. However, the behaviors of multiple constituents within soliton molecules still remain challenging to be precisely unveiled, regarding both the intramolecular and intermolecular motions. Here, we introduce the concept of “soliton isomer” to elucidate the molecular dynamics of multisoliton complexes. The time-lens and time-stretch techniques assisted temporal-spectral analysis reveals the diversity of assembly patterns, reminiscent of the “isomeric molecule”. Particularly, we study the fine energy exchange during the intramolecular motions, therefore gaining insights into the degrees of freedom of isomeric dynamics beyond temporal molecular patterns. All these findings further answer the question of how far the matter-soliton analogy reaches and pave an efficient route for assisting the artificial manipulation of multisoliton structures. Self-assembly of dissipative solitons arouses versatile configurations of molecular complexes, enriching intriguing dynamics in mode-locked lasers. The ongoing studies fuel the analogy between matter physics and optical solitons, and stimulate frontier developments of ultrafast optics. However, the behaviors of multiple constituents within soliton molecules still remain challenging to be precisely unveiled, regarding both the intramolecular and intermolecular motions. Here, we introduce the concept of “soliton isomer” to elucidate the molecular dynamics of multisoliton complexes. The time-lens and time-stretch techniques assisted temporal-spectral analysis reveals the diversity of assembly patterns, reminiscent of the “isomeric molecule”. Particularly, we study the fine energy exchange during the intramolecular motions, therefore gaining insights into the degrees of freedom of isomeric dynamics beyond temporal molecular patterns. All these findings further answer the question of how far the matter-soliton analogy reaches and pave an efficient route for assisting the artificial manipulation of multisoliton structures.
Photonics Research
- Publication Date: Sep. 20, 2024
- Vol. 12, Issue 10, 2186 (2024)
Two-octave frequency combs from an all-silica-fiber implementation
Yanyan Zhang, Mingkun Li, Pan Zhang, Yueqing Du, Shibang Ma, Yuanshan Liu, Sida Xing, and Shougang Zhang
Mid-infrared frequency-comb spectroscopy enables measurement of molecules at megahertz spectral resolution, sub-hertz frequency accuracy, and microsecond acquisition speed. However, the widespread adoption of this technique has been hindered by the complexity and alignment sensitivity of mid-infrared frequency-comb sources. Leveraging the underexplored mid-infrared window of silica fibers presents a promising approach to address these challenges. In this study, we present the first, to the best of our knowledge, experimental demonstration and quantitative numerical description of mid-infrared frequency-comb generation in silica fibers. Our all-silica-fiber frequency comb spans over two octaves (0.8 μm to 3.4 μm) with a power output of 100 mW in the mid-infrared region. The amplified quantum noise is suppressed using four-cycle (25 fs) driving pulses, with the carrier-envelope offset frequency exhibiting a signal-to-noise ratio of 40 dB and a free-running bandwidth of 90 kHz. Our developed model provides quantitative guidelines for mid-infrared frequency-comb generation in silica fibers, enabling all-fiber frequency-comb spectroscopy in diverse fields such as organic synthesis, pharmacokinetics processes, and environmental monitoring. Mid-infrared frequency-comb spectroscopy enables measurement of molecules at megahertz spectral resolution, sub-hertz frequency accuracy, and microsecond acquisition speed. However, the widespread adoption of this technique has been hindered by the complexity and alignment sensitivity of mid-infrared frequency-comb sources. Leveraging the underexplored mid-infrared window of silica fibers presents a promising approach to address these challenges. In this study, we present the first, to the best of our knowledge, experimental demonstration and quantitative numerical description of mid-infrared frequency-comb generation in silica fibers. Our all-silica-fiber frequency comb spans over two octaves (0.8 μm to 3.4 μm) with a power output of 100 mW in the mid-infrared region. The amplified quantum noise is suppressed using four-cycle (25 fs) driving pulses, with the carrier-envelope offset frequency exhibiting a signal-to-noise ratio of 40 dB and a free-running bandwidth of 90 kHz. Our developed model provides quantitative guidelines for mid-infrared frequency-comb generation in silica fibers, enabling all-fiber frequency-comb spectroscopy in diverse fields such as organic synthesis, pharmacokinetics processes, and environmental monitoring.
Photonics Research
- Publication Date: Sep. 06, 2024
- Vol. 12, Issue 10, 2115 (2024)
Interaction of colliding laser pulses with gas plasma for broadband coherent terahertz wave generation
Yuxuan Chen, Yuhang He, Liyuan Liu, Zhen Tian, and Jianming Dai
Colliding of two counter-propagating laser pulses is a widely used approach to create a laser field or intensity surge. We experimentally demonstrate broadband coherent terahertz (THz) radiation generation through the interaction of colliding laser pulses with gas plasma. The THz radiation has a dipole-like emission pattern perpendicular to the laser propagation direction with a detected peak electric field 1 order of magnitude higher than that by single pulse excitation. As a proof-of-concept demonstration, it provides a deep insight into the physical picture of laser–plasma interaction, exploits an important option to the promising plasma-based THz source, and may find more applications in THz nonlinear near-field imaging and spectroscopy. Colliding of two counter-propagating laser pulses is a widely used approach to create a laser field or intensity surge. We experimentally demonstrate broadband coherent terahertz (THz) radiation generation through the interaction of colliding laser pulses with gas plasma. The THz radiation has a dipole-like emission pattern perpendicular to the laser propagation direction with a detected peak electric field 1 order of magnitude higher than that by single pulse excitation. As a proof-of-concept demonstration, it provides a deep insight into the physical picture of laser–plasma interaction, exploits an important option to the promising plasma-based THz source, and may find more applications in THz nonlinear near-field imaging and spectroscopy.
Photonics Research
- Publication Date: Aug. 28, 2023
- Vol. 11, Issue 9, 1562 (2023)
Impact of laser chirp on the polarization of terahertz from two-color plasma
Sen Mou, Luca Tomarchio, Annalisa D’Arco, Marta Di Fabrizio, Salvatore Macis, Alessandro Curcio, Luigi Palumbo, Stefano Lupi, and Massimo Petrarca
Two-color plasma, induced by two lasers of different colors, can radiate ultra-broadband and intense terahertz (THz) pulses, which is desirable in many technological and scientific applications. It was found that the polarization of the emitted THz depends on the phase difference between the fundamental laser wave and its second harmonic. Recent investigation suggests that chirp-induced change of pulse overlap plays an important role in the THz yield from two-color plasma. However, the effect of laser chirp on THz polarization remains unexplored. Hereby, we investigate the impact of laser chirp on THz polarization. It is unveiled that the chirp-induced phase difference affects THz polarization. Besides, positive and negative chirps have opposite effects on the variation of the THz polarization versus the phase difference. The polarization of THz generated by a positively chirped pump laser rotates clockwise with an increasing phase difference, while it rotates anticlockwise when generated by a negatively chirped pump laser. Two-color plasma, induced by two lasers of different colors, can radiate ultra-broadband and intense terahertz (THz) pulses, which is desirable in many technological and scientific applications. It was found that the polarization of the emitted THz depends on the phase difference between the fundamental laser wave and its second harmonic. Recent investigation suggests that chirp-induced change of pulse overlap plays an important role in the THz yield from two-color plasma. However, the effect of laser chirp on THz polarization remains unexplored. Hereby, we investigate the impact of laser chirp on THz polarization. It is unveiled that the chirp-induced phase difference affects THz polarization. Besides, positive and negative chirps have opposite effects on the variation of the THz polarization versus the phase difference. The polarization of THz generated by a positively chirped pump laser rotates clockwise with an increasing phase difference, while it rotates anticlockwise when generated by a negatively chirped pump laser.
Photonics Research
- Publication Date: May. 18, 2023
- Vol. 11, Issue 6, 978 (2023)
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