1
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Chen Y, Lei H, Wang Q, Xie H, Zhang H, Lu X, Zhang N, Huang S, Wu Y, Liu J, Zhang Q, Liu Y, Zhao Z, Zhao J, Yao J. Multiphoton Resonance Meets Tunneling Ionization: High-Efficient Photoexcitation in Strong-Field-Dressed Ions. PHYSICAL REVIEW LETTERS 2024; 133:113201. [PMID: 39331982 DOI: 10.1103/physrevlett.133.113201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Accepted: 07/30/2024] [Indexed: 09/29/2024]
Abstract
Tunneling ionization, a fascinating quantum phenomenon, has played the key role in the development of attosecond physics. Upon absorption of a few tens of photons, tunneling ionization creates ions in different excited states and even enables the formation of population inversion between ionic states. However, the underlying physics is still being debated. Here, we demonstrate a significant enhancement in the efficiency of multiphoton excitation when ionization of neutral molecules and resonant excitation of ions coexist in strong laser fields. It facilitates the dramatic increase in population inversion and lasing radiation in N_{2}^{+} around 1000 nm pump wavelength. Utilizing the ionization-coupling theory, we discover that the synergistic interplay between tunneling ionization and multiphoton excitation enables the ionic coherence to be maximized by phase locking of the periodically created ionic dipoles and consistently maintain an optimal phase for the follow-up photoexcitation. This Letter provides new insights into the photoexcitation mechanism of ions in strong laser fields and opens up a route for optimizing ionic lasing radiations.
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2
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Gao J, Zhang X, Wang Y, Dong J, Lei M, Liu Y, Wu C, Gong Q, Jiang H. Controlling the Polarization of Nitrogen Ion Lasing. J Phys Chem Lett 2024; 15:3805-3811. [PMID: 38557052 DOI: 10.1021/acs.jpclett.4c00004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Air lasing provides a promising technique to remotely produce coherent radiation in the atmosphere and has attracted continuous attention. However, the polarization properties of N2+ lasing with seeding have not been understood since it was discovered 10 years ago, in which the polarization behaviors appear disordered and confusing. Here, we performed an experimental and theoretical investigation of the polarization properties of N2+ lasing and successfully revealed its underlying physical mechanism. We found that the optical gain is anisotropic, owing to the permanent alignment of N2+ induced by the preferential ionization of the pump light. As a result, the polarization of the N2+ lasing tends to align with that of the pump light after amplification, which becomes more pronounced as the amplification factor increases. Based on the permanent alignment of N2+, we built a theoretical model that analytically interpreted and numerically reproduced the experimental observations, which points out the key factors for controlling the polarization of N2+ lasing.
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Affiliation(s)
- Jingsong Gao
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Xiang Zhang
- Shanghai Key Lab of Modern Optical System, University of Shanghai for Science and Technology, Shanghai 200093, China
| | - Yang Wang
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Jiahao Dong
- Shanghai Key Lab of Modern Optical System, University of Shanghai for Science and Technology, Shanghai 200093, China
| | - Mingwei Lei
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Yi Liu
- Shanghai Key Lab of Modern Optical System, University of Shanghai for Science and Technology, Shanghai 200093, China
- CAS Center for Excellence in Ultra-intense Laser Science, Shanghai 201800, China
| | - Chengyin Wu
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Qihuang Gong
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Hongbing Jiang
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
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3
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Zyatikov IA, Losev VF. Parameters of 391 nm lasing from molecular nitrogen ions pumped by a 950 nm femtosecond laser pulse. APPLIED OPTICS 2023; 62:9133-9135. [PMID: 38108751 DOI: 10.1364/ao.508151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Accepted: 11/05/2023] [Indexed: 12/19/2023]
Abstract
The results of experimental studies of spectral, temporal, and spatial self-seed lasing characteristics at the wavelength of 391 nm in pure nitrogen at different values of specific pump power are presented. Pumping was carried out by a femtosecond radiation pulse at the wavelength of 950 nm. The possibility of obtaining lasing pulse duration close to transform-limited (1.83 ps) is presented. It is shown that far-field radiation divergence decreases with increasing lens focal length, and it correlates well with the geometric dimensions of laser plasma.
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4
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Mei H, Gao J, Wang K, Dong J, Gong Q, Wu C, Liu Y, Jiang H, Liu Y. Amplification of light pulses with orbital angular momentum (OAM) in nitrogen ions lasing. OPTICS EXPRESS 2023; 31:31912-31921. [PMID: 37859005 DOI: 10.1364/oe.500041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Accepted: 08/23/2023] [Indexed: 10/21/2023]
Abstract
Nitrogen ions pumped by intense femtosecond laser pulses give rise to optical amplification in the ultraviolet range. Here, we demonstrated that a seed light pulse carrying orbital angular momentum (OAM) can be significantly amplified in nitrogen plasma excited by a Gaussian femtosecond laser pulse. With the topological charge of ℓ = ±1, we observed an energy amplification of the seed light pulse by two orders of magnitude, while the amplified pulse carries the same OAM as the incident seed pulse. Moreover, we show that a spatial misalignment of the plasma amplifier with the OAM seed beam leads to an amplified emission of Gaussian mode without OAM, due to the special spatial profile of the OAM seed pulse that presents a donut-shaped intensity distribution. Utilizing this misalignment, we can implement an optical switch that toggles the output signal between Gaussian mode and OAM mode. This work not only certifies the phase transfer from the seed light to the amplified signal, but also highlights the important role of spatial overlap of the donut-shaped seed beam with the gain region of the nitrogen plasma for the achievement of OAM beam amplification.
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5
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Kleine C, Winghart MO, Zhang ZY, Richter M, Ekimova M, Eckert S, Vrakking MJJ, Nibbering ETJ, Rouzée A, Grant ER. Electronic State Population Dynamics upon Ultrafast Strong Field Ionization and Fragmentation of Molecular Nitrogen. PHYSICAL REVIEW LETTERS 2022; 129:123002. [PMID: 36179157 DOI: 10.1103/physrevlett.129.123002] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Revised: 07/20/2022] [Accepted: 08/10/2022] [Indexed: 06/16/2023]
Abstract
Air lasing from single ionized N_{2}^{+} molecules induced by laser filamentation in air has been intensively investigated and the mechanisms responsible for lasing are currently highly debated. We use ultrafast nitrogen K-edge spectroscopy to follow the strong field ionization and fragmentation dynamics of N_{2} upon interaction with an ultrashort 800 nm laser pulse. Using probe pulses generated by extreme high-order harmonic generation, we observe transitions indicative of the formation of the electronic ground X^{2}Σ_{g}^{+}, first excited A^{2}Π_{u}, and second excited B^{2}Σ_{u}^{+} states of N_{2}^{+} on femtosecond timescales, from which we can quantitatively determine the time-dependent electronic state population distribution dynamics of N_{2}^{+}. Our results show a remarkably low population of the A^{2}Π_{u} state, and nearly equal populations of the X^{2}Σ_{g}^{+} and B^{2}Σ_{u}^{+} states. In addition, we observe fragmentation of N_{2}^{+} into N and N^{+} on a timescale of several tens of picoseconds that we assign to significant collisional dynamics in the plasma, resulting in dissociative excitation of N_{2}^{+}.
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Affiliation(s)
- Carlo Kleine
- Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Max-Born-Straße 2a, 12489 Berlin, Germany
| | - Marc-Oliver Winghart
- Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Max-Born-Straße 2a, 12489 Berlin, Germany
| | - Zhuang-Yan Zhang
- Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Max-Born-Straße 2a, 12489 Berlin, Germany
| | - Maria Richter
- Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Max-Born-Straße 2a, 12489 Berlin, Germany
| | - Maria Ekimova
- Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Max-Born-Straße 2a, 12489 Berlin, Germany
| | - Sebastian Eckert
- Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Max-Born-Straße 2a, 12489 Berlin, Germany
| | - Marc J J Vrakking
- Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Max-Born-Straße 2a, 12489 Berlin, Germany
| | - Erik T J Nibbering
- Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Max-Born-Straße 2a, 12489 Berlin, Germany
| | - Arnaud Rouzée
- Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Max-Born-Straße 2a, 12489 Berlin, Germany
| | - Edward R Grant
- Department of Chemistry and Department of Physics and Astronomy, The University of British Columbia, 2036 Main Mall, Vancouver, British Columbia, Canada V6T 1Z1
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6
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Rastegari A, Diels JC, Kamer B, Liu LR, Arissian L. Measurement of delayed fluorescence in N 2 + with a streak camera. OPTICS EXPRESS 2022; 30:31498-31508. [PMID: 36242229 DOI: 10.1364/oe.468835] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Accepted: 08/03/2022] [Indexed: 06/16/2023]
Abstract
Using a streak camera, we directly measure time- and space-resolved dynamics of N 2 + emission from a self-seeded filament. Fluorescence emission does not start with ionization, but with a delay in the tenth of ps range.
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7
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Wan YX, Fu BT, Xie HQ, Yu SP, Lei HB, Zhang FB, Zhang ZH, Qiao LL, Li GH, Zhao J, Zhao ZX, Yao JP, Cheng Y. Observation of rotational coherence in an excited state of CO . OPTICS LETTERS 2021; 46:3893-3896. [PMID: 34388768 DOI: 10.1364/ol.432315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Accepted: 07/12/2021] [Indexed: 06/13/2023]
Abstract
The vacuum ultraviolet (VUV) radiation is generated in the strong-field-ionized CO molecules through 2+1 resonance excitation with two-color femtosecond laser pulses. When scanning the relative delay between two pump pulses, the rotational-resolved VUV radiations show periodic oscillations lasting as long as 500 ps. Fourier analysis reveals that these oscillations correspond to rotational beat frequencies of the A2Πi state of CO+, which is the result of multi-channel interference during the resonant excitation process. High resolution of Fourier transform spectra up to 0.067cm-1 allows us to obtain the fine energy levels of the A2Πi state. The theoretical calculation is in good agreement with the experimental observation. This work reveals the rotational coherence of the ionic excited state and shows the prospect of rotational coherence spectroscopy in measuring fine structures of molecular ions.
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8
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Miao Z, Zheng W, Wang Y, Dai C, Li Z, Wu C. Optical amplification from high vibrational states of ionized nitrogen molecules generated by 800-nm femtosecond laser pulses. OPTICS EXPRESS 2021; 29:2279-2287. [PMID: 33726426 DOI: 10.1364/oe.414843] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Accepted: 01/01/2021] [Indexed: 06/12/2023]
Abstract
We experimentally investigated the interaction between nitrogen molecules and intense femtosecond laser pulses. When irradiated by an 800-nm pump laser and a delayed 355-nm seed laser, the spectral lines around 353.3 nm and 353.8 nm are observed to be greatly amplified, no matter whether the pump laser is circularly or linearly polarized. The two spectral lines correspond to the transition of N2+ (B, ν' = 5 → X, ν = 4) and N2+ (B, ν' = 4 → X, ν = 3), respectively. In comparison with the spectral lines related with ground vibrational states of nitrogen molecular ion, the observed amplification exhibits different polarization dependence of the pump laser. This distinctive change can be explained by the population variation of high vibrational states caused by the pump laser with different polarizations.
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Li Z, Kuan YH, Mu X, Miao Z, Wu C, Liao WT. Ramsey interferometry through coherent A2Πu- X2Σg+- B2Σu+ coupling and population transfer in N2+ air laser. OPTICS LETTERS 2020; 45:6587-6590. [PMID: 33325846 DOI: 10.1364/ol.401800] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Accepted: 10/26/2020] [Indexed: 06/12/2023]
Abstract
Motivated by the hot debate on the mechanism of laser-like emission at 391 nm from N2 gas irradiated by a strong 800 nm pump laser and a weak 400 nm seed laser, we theoretically study the temporal profile, optical gain, and modulation of the 391 nm signal from N2+. Our calculation sheds light on the long standing controversy on whether population inversion is indispensable for optical gain and show the Ramsey fringes of the emission intensity at 391 nm formed by additionally injecting another 800 nm pump or 400 nm seed, which provides strong evidence for the coherence driven modulation of transition dipole moment and population transfer between the A2Πu(ν=2)-X2Σg+ states and the B2Σu+(ν=0)-X2Σg+ states. Our results show that the 391 nm optical gain is susceptible to the population inversion within N2+ states manipulated by the Ramsey technique and thus clearly reveal their symbiosis. This study reveals not only the physical picture of producing N2+ population inversion but also versatile control of the N2+ air laser.
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10
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Li H, Pan S, Chen F, Sun F, Li Z, Xu H, Wu J. Optimization of N 2+ lasing by waveform-controlled polarization-skewed pulses. OPTICS LETTERS 2020; 45:6591-6594. [PMID: 33325847 DOI: 10.1364/ol.410153] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Accepted: 11/07/2020] [Indexed: 05/20/2023]
Abstract
Optical ionization of N2 and subsequent population redistribution among the ground and excited states of N2+ in an intense laser field are commonly accepted to be fundamentally responsible for the generation of N2+ lasing. By finely controlling this two-step process, the optimization of N2+ lasing is possibly achieved. Here, we design a waveform-controlled polarization-skewed (PS) pumping pulse, in which the leading and falling edges are orthogonally polarized, and their relative field strength and phase can be well controlled. We demonstrate that precise manipulation of the N2+ lasing at 391 nm and 428 nm emissions can be achieved by modulating both the relative phase and amplitudes of the two orthogonally polarized components of the pumping PS pulse. We find that the optimization of N2+ lasing depends not only on the competitive balance between the ionization and post-ionization coupling that varies in different pumping energies but also on the phase with the maximum intensity appearing at the phase of nπ. Orders of magnitude enhancement in the N2+ lasing intensity is observed as the phase changes from (n+1/2)π to nπ. The PS pulse with a controllable spatiotemporal waveform provides us a robust and straightforward tool to efficiently enhance the N2+ lasing emission.
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11
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Understanding the Seeding Pulse-Induced Optical Amplification in
N
2
+
Pumped by 800 NM Femtosecond Laser Pulses. PHOTONICS 2020. [DOI: 10.3390/photonics7040099] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Nitrogen ions pumped by intense femtosecond laser pulses present an optical gain at 391.4 nm, evident by energy amplification of an injected resonant seeding pulse. We report a time-resolved measurement of the amplification process with seeding pulses having varying intensities. It is found that the amplification factor depends on the intensity of the seeding pulse and the effective temporal window for the optical gain becomes longer by applying more intense seeding pulses. These two features are in sharp contrast with classic pump-probe experiments, pinpointing the crucial role of macroscopic coherence and its dynamics during the lasing process. We further measure the temporal profile of the amplified emission for seeding pulse injected at different time delays. A complicated temporal behavior is observed, which highlights the nature of the superfluorescence.
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12
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Li G, Xie H, Zhang Q, Lei H, Zhou X, Wang X, Chen Z, Zhao Z. Enhanced resonant vibrational Raman scattering of N 2+ induced by self-seeding ionic lasers created in polarization-modulated intense laser fields. OPTICS LETTERS 2020; 45:5616-5619. [PMID: 33001962 DOI: 10.1364/ol.403110] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Accepted: 09/05/2020] [Indexed: 06/11/2023]
Abstract
We report on an experimental investigation of the five vibrational Raman lines at 358 nm, 388 nm, 391 nm, 428 nm, and 471 nm of N2+ resonantly driven by the self-seeding ionic lasers generated by a polarization-modulated (PM) or alternatively a linearly polarized (LP) femtosecond laser. It was found that the spectral intensities of several Raman lines can be dramatically enhanced by exploiting the PM laser pulses in comparison to the LP laser pulses. The evaluated Raman conversion efficiency reaches ∼10-2 for some lasing lines at suitable pressures. Moreover, the role of interplay between the seed amplification and the resonant vibrational Raman scattering processes in inducing the gain of N2+ lasing is characterized for the first time. The developed vibrational Raman spectroscopy with intense ultrafast lasers provides an additional approach to interrogate the products in a femtosecond filament, and it therefore can be a powerful tool for identifying chemical species at remote distances in the atmosphere.
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13
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Danylo R, Lambert G, Liu Y, Tikhonchuk V, Houard A, Mysyrowicz A. Quantum erasing of laser emission in N2. OPTICS LETTERS 2020; 45:4670-4673. [PMID: 32870827 DOI: 10.1364/ol.395261] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 07/18/2020] [Indexed: 06/11/2023]
Abstract
Cavity-free lasing of N2+ induced by a femtosecond laser pulse at 800 nm is nearly totally suppressed by a delayed twin control pulse. We explain this surprising effect within the V-scheme of lasing without population inversion. A fast transfer of population between nitrogen ionic states X2Σg+ and A2Πu, induced by the second pulse, terminates the conditions for amplification in the system. The appearance of short lasing bursts at delays corresponding to revivals of rotational wave packets is explained along the same lines.
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14
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Fu Y, Chen S, Wang S, Zhang W, Yao D, Zang H, Li H, Xu H. Asymmetric enhancement of N 2+ lasing in intense, birefringence-modulating elliptical laser fields. OPTICS EXPRESS 2020; 28:23274-23283. [PMID: 32752326 DOI: 10.1364/oe.389284] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Accepted: 07/14/2020] [Indexed: 06/11/2023]
Abstract
We experimentally demonstrate an asymmetric enhancement of the N2+ lasing at 391 nm for the transition between the B2Σu+ (v = 0) and X2Σg+ (v" = 0) states in an intense laser field with the ellipticity, ε, modulated by a 7-order quarter-wave plate (7-QWP). It is found that when the 7-QWP is rotated from α = 0 to 90°, where α is the angle between the polarization direction of the input laser and the slow axis of the 7-QWP, the intensity of the 391-nm lasing is optimized at ε ∼ 0.3 with α∼ 10°-20° and 70°-80° respectively, but the optimization intensity at α∼ 10°-20° is about 4 times smaller than that at α∼ 70°-80°. We interpret the asymmetric enhancement based on a post-ionization coupling model, in which the birefringence of the 7-QWP induces an opposite change in the relative amplitudes of the ordinary (Eo) and extraordinary (Ee) electric components under the two conditions, so that the same temporal separation of Eo and Ee leads to a remarkably different coupling strength for the population transfer from the X2Σg+ (v "=0) to A2Πu (v '=2) states.
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15
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Lei H, Li G, Xie H, Zhang Q, Wang X, Zhao J, Chen Z, Zhao Z. Mechanism and control of rotational coherence in femtosecond laser-driven N2. OPTICS EXPRESS 2020; 28:22829-22843. [PMID: 32752537 DOI: 10.1364/oe.398888] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Accepted: 07/10/2020] [Indexed: 06/11/2023]
Abstract
We investigate the formation of rotational coherence of N2+ resonantly interacting with an intense femtosecond laser field by numerical simulations based on a strong-field ionization-coupling model described with the density matrix formalism. The created N2+ system is unique in many aspects: the variable total population within the pump duration due to the intensity-dependent ionization injection, the readily accessible resonance owing to the effect of Stark shift, and the involvement of a few dozen of quantum states. By regarding the N2+ system as an open and non-stationary Λ-type cascaded multi-level system, we quantitatively studied the dependence of rotational coherence in different electronic-vibrational states of N2+ on the alignment angle θ and the pumping intensity. Our simulation results indicate that the quantum coherence between the neighbouring rotational states of J, J+2 in the vibrational state ν=0, 1 of the ground state of N2+ can be changed from a negative to a positive. The significant contribution of rotational coherence to inducing an extra gain or absorption of N2+ air lasing is further verified by solving the Maxwell's propagating equation. The finding provides crucial clues on how to manipulate N2+ lasing by controlling the rotational coherence and paves the way to studying strong-field quantum optics effects such as lasing without inversion and electromagnetically induced transparency in molecular ionic systems.
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16
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Zhao X, Nolte S, Ackermann R. Lasing of N2+ induced by filamentation in air as a probe for femtosecond coherent anti-Stokes Raman scattering. OPTICS LETTERS 2020; 45:3661-3664. [PMID: 32630924 DOI: 10.1364/ol.391989] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Accepted: 05/29/2020] [Indexed: 06/11/2023]
Abstract
We investigated ultrashort pulse filamentation and lasing action of N2+ for pump-probe experiments in gases. Using femtosecond coherent anti-Stokes Raman scattering, the white-light supercontinuum generated in the filament was used to excite ro-vibrational Raman transitions in air, CO2 and CH4. We show that the lasing pulse acts as a probe for the excited levels by detecting the corresponding anti-Stokes Raman spectroscopy signals. This feature may be applied to remote sensing applications, as the temporal and spatial alignment of the probe beam and the filament is intrinsically provided.
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17
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Ando T, Lötstedt E, Iwasaki A, Li H, Fu Y, Wang S, Xu H, Yamanouchi K. Rotational, Vibrational, and Electronic Modulations in N_{2}^{+} Lasing at 391 nm: Evidence of Coherent B^{2}Σ_{u}^{+}-X^{2}Σ_{g}^{+}-A^{2}Π_{u} Coupling. PHYSICAL REVIEW LETTERS 2019; 123:203201. [PMID: 31809116 DOI: 10.1103/physrevlett.123.203201] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Revised: 08/23/2019] [Indexed: 06/10/2023]
Abstract
We investigate lasing of a N_{2} gas induced by intense few-cycle near-IR laser pulses. By the pump-probe measurements, we reveal that the intensity of the B^{2}Σ_{u}^{+}-X^{2}Σ_{g}^{+} lasing emission of N_{2}^{+} oscillates at high (0.3-0.5 PHz), medium (50-75 THz), and low (∼3 THz) frequencies, corresponding to the energy separations between the rovibrational levels of the A^{2}Π_{u} and X^{2}Σ_{g}^{+} states. By solving the time-dependent Schrödinger equation, we reproduce the oscillations in the three different frequency ranges and show that the coherent population transfer among the three electronic states of N_{2}^{+} creates the population inversion between the B^{2}Σ_{u}^{+} and X^{2}Σ_{g}^{+} states, resulting in the lasing at 391 nm.
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Affiliation(s)
- Toshiaki Ando
- Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Erik Lötstedt
- Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Atsushi Iwasaki
- Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Helong Li
- State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China
| | - Yao Fu
- State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China
| | - Siqi Wang
- State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China
| | - Huailiang Xu
- State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
| | - Kaoru Yamanouchi
- Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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18
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Zheng W, Miao Z, Zhang L, Wang Y, Dai C, Zhang A, Jiang H, Gong Q, Wu C. Enhanced Coherent Emission from Ionized Nitrogen Molecules by Femtosecond Laser Pulses. J Phys Chem Lett 2019; 10:6598-6603. [PMID: 31603688 DOI: 10.1021/acs.jpclett.9b02581] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The forward emission spectra were experimentally measured for ionized nitrogen molecules by an 800 nm pump laser and a delayed seed laser. It was found that emission lines around both 428 and 391 nm are greatly enhanced upon use of a 391 or 428 nm seed laser. The emission lines around 391 and 428 nm can be assigned to the rotational transitions of N2+ [B2Σu+(v' = 0) → X2Σg+(v = 0)] and N2+ [B2Σu+(v' = 0) → X2Σg+(v = 1)], respectively. They originate from seed-induced superfluorescence and resonant stimulated Raman scattering. The genetic algorithm was utilized to simulate the experimental observations and determine the relative population of B2Σu+(v' = 0), X2Σg+(v = 1), and X2Σg+(v = 0). The result verifies that vibrational population inversion is achieved between B2Σu+(v' = 0) and X2Σg+(v = 0) by the 800 nm pump laser. Our finding provides new insights into controlling the coherent emission of ionized nitrogen molecules, which has promising application in filamentation-based remote atmospheric sensing.
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Affiliation(s)
- Wei Zheng
- State Key Laboratory for Mesoscopic Physics, School of Physics , Peking University , Beijing 100871 , China
| | - Zhiming Miao
- State Key Laboratory for Mesoscopic Physics, School of Physics , Peking University , Beijing 100871 , China
| | - Linlin Zhang
- State Key Laboratory for Mesoscopic Physics, School of Physics , Peking University , Beijing 100871 , China
| | - Yang Wang
- State Key Laboratory for Mesoscopic Physics, School of Physics , Peking University , Beijing 100871 , China
| | - Chen Dai
- State Key Laboratory for Mesoscopic Physics, School of Physics , Peking University , Beijing 100871 , China
| | - An Zhang
- State Key Laboratory for Mesoscopic Physics, School of Physics , Peking University , Beijing 100871 , China
| | - Hongbing Jiang
- State Key Laboratory for Mesoscopic Physics, School of Physics , Peking University , Beijing 100871 , China
- Collaborative Innovation Center of Extreme Optics , Shanxi University , Taiyuan , Shanxi 030006 , China
| | - Qihuang Gong
- State Key Laboratory for Mesoscopic Physics, School of Physics , Peking University , Beijing 100871 , China
- Collaborative Innovation Center of Quantum Matter , Beijing 100871 , China
- Collaborative Innovation Center of Extreme Optics , Shanxi University , Taiyuan , Shanxi 030006 , China
- Frontiers Science Center for Nano-optoelectronics , Peking University , Beijing 100871 , China
| | - Chengyin Wu
- State Key Laboratory for Mesoscopic Physics, School of Physics , Peking University , Beijing 100871 , China
- Collaborative Innovation Center of Quantum Matter , Beijing 100871 , China
- Collaborative Innovation Center of Extreme Optics , Shanxi University , Taiyuan , Shanxi 030006 , China
- Frontiers Science Center for Nano-optoelectronics , Peking University , Beijing 100871 , China
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19
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Ran P, Li G, Liu T, Hou H, Luo SN. Collision-mediated ultrafast decay of N 2 fluorescence during fs-laser-induced filamentation. OPTICS EXPRESS 2019; 27:19177-19187. [PMID: 31503681 DOI: 10.1364/oe.27.019177] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Accepted: 05/26/2019] [Indexed: 06/10/2023]
Abstract
We investigate experimentally spatiotemporal characteristics of fluorescence emission from fs-laser-induced filaments in air. Emissions accompanying the transitions of N2 (C3Πu-B3Πg) and N 2+ (B2Σu+-X2Σg+) are dominant. The decay dynamics of fluorescence from different radial positions and longitudinal sections of a filament column are obtained along with high resolution spectra. A decay curve contains two exponential components: a fast one (with a decay time constant ∼10s ps), and a slow one (∼sub-ns). The lifetime of the N 2 fluorescence is about three orders shorter than its spontaneous emission lifetime, indicating that most of the N 2 molecules in the excited state (C3Πu) are de-excited through collision. Different de-excitation mechanisms of N 2 (C3Πu) molecules contributing to fluorescence decay constants, e.g., the e --N2, N 2-N2, and O 2-N2 collisions, are elucidated. We analyze the variations of decay constants together with corresponding fluorescence intensities, and obtain temperature distributions by fitting band spectra of N 2 molecules and N 2+ ions with a synthetic spectral model. Our results suggest that the fast and slow decay processes originate from the e --N2 and O 2-N2 collisions, respectively.
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20
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Xu B, Yao J, Wan Y, Chen J, Liu Z, Zhang F, Chu W, Cheng Y. Vibrational Raman scattering from coherently excited molecular ions in a strong laser field. OPTICS EXPRESS 2019; 27:18262-18272. [PMID: 31252772 DOI: 10.1364/oe.27.018262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Accepted: 05/31/2019] [Indexed: 06/09/2023]
Abstract
We report on a pump-probe investigation of vibrational Raman scattering from coherently excited N2+ ions. It is found that the Raman signals produced by the inelastic scattering of the probe pulse from molecular ions can be dramatically enhanced when the probe laser is resonant with electronic transitions in N2+ ions. The Raman signal can be amplified at 428 nm wavelength due to the presence of population inversion in N2+ ions.
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21
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Zhang A, Lei M, Gao J, Wu C, Gong Q, Jiang H. Subfemtosecond-resolved modulation of superfluorescence from ionized nitrogen molecules by 800-nm femtosecond laser pulses. OPTICS EXPRESS 2019; 27:14922-14930. [PMID: 31163933 DOI: 10.1364/oe.27.014922] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Accepted: 05/02/2019] [Indexed: 06/09/2023]
Abstract
Superfluorescence emission around 391 nm is generated when nitrogen molecules are irradiated by a strong 800-nm pump laser and a delayed seed laser. The emission corresponds to the transition between N2+(B2Σu+,ν″=0) and N2+(X2Σg+,ν=0). When another weak 800-nm probe laser is injected and scanned after the pump laser, the superfluorescence intensity is observed to exhibit periodical modulation. The period is determined to be ~2.63 fs, corresponding to the transition frequency between N2+(A2Πu,ν'=2) and N2+(X2Σg+,ν=0). Based on theoretical derivation, these observations can be attributed to the laser-induced population transfer and polarization variation between the relevant electronic states of ionized nitrogen molecules.
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22
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Zhang A, Liang Q, Lei M, Yuan L, Liu Y, Fan Z, Zhang X, Zhuang S, Wu C, Gong Q, Jiang H. Coherent modulation of superradiance from nitrogen ions pumped with femtosecond pulses. OPTICS EXPRESS 2019; 27:12638-12646. [PMID: 31052802 DOI: 10.1364/oe.27.012638] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Accepted: 04/11/2019] [Indexed: 06/09/2023]
Abstract
Singly ionized nitrogen molecules in ambient air pumped by 800 nm femtosecond laser give rise to superradiant emission. Here, we study this superradiance by injecting a pair of resonant seeding pulses at different intensity ratios inside the nitrogen gas plasma. Strong modulation of the 391.4 nm superradiant emission with a period of 1.3 fs is observed when the delay between the two seeding pulses is finely tuned. The modulation contrast is increased and then decreased with the delay time when the second seed pulse is stronger than the first one, and the maximum modulation contrast occurs at longer delay time when the second seeding pulse is stronger. This reveals the increase of the macroscopic polarization with time after the seeding pulse. Moreover, these observations provide a new level of control on the "air lasing" based on nitrogen ions, which can find potential applications in optical remote sensing.
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23
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Li H, Hou M, Zang H, Fu Y, Lötstedt E, Ando T, Iwasaki A, Yamanouchi K, Xu H. Significant Enhancement of N_{2}^{+} Lasing by Polarization-Modulated Ultrashort Laser Pulses. PHYSICAL REVIEW LETTERS 2019; 122:013202. [PMID: 31012701 DOI: 10.1103/physrevlett.122.013202] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2018] [Indexed: 06/09/2023]
Abstract
We show that the intensity of self-seeded N_{2}^{+} lasing at 391 nm, assigned to the B^{2}Σ_{u}^{+}(v^{'}=0)→X^{2}Σ_{g}^{+}(v^{''}=0) emission, is enhanced by 2 orders of magnitude by modulating in time the polarization of an intense ultrashort near-IR (40 fs, 800 nm) laser pulse with which N_{2} is irradiated. We find that this dramatic enhancement of the 391 nm lasing is sensitive to the temporal variation of the polarization state within the laser pulse while the intensity of the spontaneous fluorescence emission at 391 nm is kept constant when the polarization state varies. We conclude that a postionization multiple-state coupling, through which the population can be transferred from the X^{2}Σ_{g}^{+} state of N_{2}^{+} to the first electronically excited A^{2}Π_{u} state, leads to the depletion of the population in the X^{2}Σ_{g}^{+} state, and consequently, to the population inversion between the X^{2}Σ_{g}^{+} state and the B^{2}Σ_{u}^{+} state.
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Affiliation(s)
- Helong Li
- State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China
| | - Mengyao Hou
- State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China
| | - Hongwei Zang
- State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China
| | - Yao Fu
- State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China
| | - Erik Lötstedt
- Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Toshiaki Ando
- Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Atsushi Iwasaki
- Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Kaoru Yamanouchi
- Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Huailiang Xu
- State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
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Xu B, Jiang S, Yao J, Chen J, Liu Z, Chu W, Wan Y, Zhang F, Qiao L, Lu R, Cheng Y, Xu Z. Free-space Ν2+ lasers generated in strong laser fields: the role of molecular vibration. OPTICS EXPRESS 2018; 26:13331-13339. [PMID: 29801358 DOI: 10.1364/oe.26.013331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Accepted: 05/03/2018] [Indexed: 06/08/2023]
Abstract
We investigate free-space lasing actions from molecular nitrogen ions (N2+) at the wavelengths of ~391 nm and ~428 nm. Our results show that pronounced gain can be measured at either 391 nm or 428 nm laser wavelength with a pump laser centered at 800 nm wavelength, whereas the gain at 391 nm laser wavelength completely disappears when the wavelength of the pump laser is tuned to 1500 nm. Our theoretical analysis reveals that the different gain behaviors can be attributed to the vibrational distribution of populations in X2Σg+(v=0) and X2Σg+(v=1) states as the N2+ ions are generated by photoionization in the laser fields, giving rise to more robust (i.e., less sensitive to the pump laser wavelength) population inversion for generating the 428 nm laser.
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