1
|
Chen YH, Wise F. Unified and vector theory of Raman scattering in gas-filled hollow-core fiber across temporal regimes. APL PHOTONICS 2024; 9:030902. [PMID: 38533268 PMCID: PMC10961736 DOI: 10.1063/5.0189749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Accepted: 02/06/2024] [Indexed: 03/28/2024]
Abstract
Raman scattering has found renewed interest owing to the development of gas-filled hollow-core fibers, which constitute a unique platform for exploration of novel ultrafast nonlinear phenomena beyond conventional solid-core-fiber and free-space systems. Much progress has been made through models for particular interaction regimes, which are delineated by the relation of the excitation pulse duration to the time scales of the Raman response. However, current experimental settings are not limited to one regime, prompting the need for tools spanning multiple regimes. Here, we present a theoretical framework that accomplishes this goal. The theory allows us to review recent progress with a fresh perspective, makes new connections between distinct temporal regimes of Raman scattering, and reveals new degrees of freedom for controlling Raman physics. Specific topics that are addressed include transient Raman gain, the interplay of electronic and Raman nonlinearities in short-pulse propagation, and interactions of short pulses mediated by phonon waves. The theoretical model also accommodates vector effects, which have been largely neglected in prior works on Raman scattering in gases. The polarization dependence of transient Raman gain and vector effects on pulse interactions via phonon waves is investigated with the model. Throughout this Perspective, theoretical results are compared to the results of realistic numerical simulations. The numerical code that implements the new theory is freely available. We hope that the unified theoretical framework and numerical tool described here will accelerate the exploration of new Raman-scattering phenomena and enable new applications.
Collapse
Affiliation(s)
- Yi-Hao Chen
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
| | - Frank Wise
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
| |
Collapse
|
2
|
Ushakov A, Chizhov P, Bukin V, Dolmatov T, Garnov S. Narrow intensity range optical anisotropy in air induced by a femtosecond laser breakdown. APPLIED OPTICS 2023; 62:8000-8006. [PMID: 38038094 DOI: 10.1364/ao.501842] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Accepted: 09/20/2023] [Indexed: 12/02/2023]
Abstract
In this paper, we study the optical anisotropy induced by femtosecond laser radiation in air during an optical breakdown. Using a transverse pump-probe technique, we demonstrate that this anisotropy appears in a narrow range of pump intensities, which are close to the optical breakdown threshold in air and lead to a phase shift of probe radiation, polarized collinear to the pump. The intensity range where an induced intense anisotropy occurs makes it possible to estimate the magnitude of the 5th-order Kerr nonlinear refractive index component in air.
Collapse
|
3
|
Cruz CD, Stephenson JC, Engmann S, Bittle EG, Wahlstrand JK. Pump-probe phase spectroscopy with submilliradian sensitivity and nanosecond time delay using Michelson interferometers. OPTICS EXPRESS 2023; 31:14299-14307. [PMID: 37157297 DOI: 10.1364/oe.483358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Using two Michelson interferometers, we describe an experimental scheme for sensitive pump-probe spectral interferometry measurements at long time delays. It has practical advantages over the Sagnac interferometer method typically used when long-time delays are required. First, with the Sagnac interferometer, achieving many nanosecond delays requires expanding the size of the interferometer so that the reference pulse arrives before the probe pulse. Because the two pulses still pass through the same region of the sample, long-lived effects can still affect the measurement. In our scheme, the probe and reference pulses are spatially separated at the sample, alleviating the need for a large interferometer. Second, in our scheme, a fixed delay between probe and reference pulses is straightforward to produce and is continuously adjustable while maintaining alignment. Two applications are demonstrated. First, transient phase spectra are presented in a thin tetracene film with up to 5 ns probe delay. Second, impulsive stimulated Raman measurements are presented in Bi4Ge3O12. The signal-to-noise using the double Michelson technique is comparable to previously described methods with the added advantage of arbitrarily long pump-probe time delays.
Collapse
|
4
|
Nie Z, Nambu N, Marsh KA, Welch E, Matteo D, Zhang C, Wu Y, Patchkovskii S, Morales F, Smirnova O, Joshi C. Cross-polarized common-path temporal interferometry for high-sensitivity strong-field ionization measurements. OPTICS EXPRESS 2022; 30:25696-25706. [PMID: 36237094 DOI: 10.1364/oe.463424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Accepted: 06/17/2022] [Indexed: 06/16/2023]
Abstract
Absolute density measurements of low-ionization-degree or low-density plasmas ionized by lasers are very important for understanding strong-field physics, atmospheric propagation of intense laser pulses, Lidar etc. A cross-polarized common-path temporal interferometer using balanced detection was developed for measuring plasma density with a sensitivity of ∼0.6 mrad, equivalent to a plasma density-length product of ∼2.6 × 1013 cm-2 if using an 800 nm probe laser. By using this interferometer, we have investigated strong-field ionization yield versus intensity for various noble gases (Ar, Kr, and Xe) using 800 nm, 55 fs laser pulses with both linear (LP) and circular (CP) polarization. The experimental results were compared to the theoretical models of Ammosov-Delone-Krainov (ADK) and Perelomov-Popov-Terent'ev (PPT). We find that the measured phase change induced by plasma formation can be explained by the ADK theory in the adiabatic tunneling ionization regime, while PPT model can be applied to all different regimes. We have also measured the photoionization and fractional photodissociation of molecular (MO) hydrogen. By comparing our experimental results with PPT and MO-PPT models, we have determined the likely ionization pathways when using three different pump laser wavelengths of 800 nm, 400 nm, and 267 nm.
Collapse
|
5
|
Fu Y, Cao J, Wang S, Chen S, Zang H, Li H, Lötstedt E, Ando T, Iwasaki A, Yamanouchi K, Xu H. Extremely enhanced N 2+ lasing in a filamentary plasma grating in ambient air. OPTICS LETTERS 2021; 46:3404-3407. [PMID: 34264224 DOI: 10.1364/ol.428065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Accepted: 06/21/2021] [Indexed: 06/13/2023]
Abstract
Cavity-free air lasing offers a promising route towards the realization of atmospheric lasers for various applications such as remote sensing and standoff spectroscopy; however, achieving efficient generation and control of air lasing in ambient air is still a challenge. Here we show the experimental realization of a giant lasing enhancement by three to four orders of magnitude in ambient air for the self-seeded N2+ lasing at 428 nm, assigned to the B2Σu+(ν'=0) and X2Σg+(ν''=1) emission, by modulating the spatiotemporal overlap of ultrashort near-infrared control-pump pulses in a filamentary plasma grating; meanwhile, the spontaneous emission from the same transition is only enhanced by three to four times. We find that this enhancement is sensitive to the relative polarization and interference time of the two pulses, and reveal that the formation of the plasma grating induces different population variations in the B2Σu+(ν'=0) and X2Σg+(ν''=1) levels, resulting in an enormous population inversion between the two levels, thereby a higher gain for the giant enhancement of N2+ lasing in ambient air.
Collapse
|
6
|
Beetar JE, Nrisimhamurty M, Truong TC, Liu Y, Chini M. Thermal effects in molecular gas-filled hollow-core fibers. OPTICS LETTERS 2021; 46:2437-2440. [PMID: 33988603 DOI: 10.1364/ol.422983] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Accepted: 04/14/2021] [Indexed: 06/12/2023]
Abstract
Few-cycle sources with high average powers are required for applications to attosecond science. Raman-enhanced spectral broadening of Yb-doped laser amplifiers in molecular gases can yield few-cycle pulses, but thermal excitation of vibrational and rotational degrees of freedom may preclude high-power operation. Here we investigate changes in the spectral broadening associated with repetitive laser interactions in an ${{\rm{N}}_2}{\rm{O}}$-filled hollow-core fiber. By comparing experimental measurements of the spectrum associated with each laser pulse to simulations based on a density matrix model, we find that losses in a spectral bandwidth and transmission are largely dominated by thermal excitation of the gas.
Collapse
|
7
|
Tofighi S, Munera N, Reichert M, Hagan DJ, Van Stryland EW. Transient mid-IR nonlinear refraction in air. OPTICS EXPRESS 2021; 29:10863-10878. [PMID: 33820210 DOI: 10.1364/oe.414495] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Accepted: 03/10/2021] [Indexed: 06/12/2023]
Abstract
We use the polarization-sensitive, time-resolved Beam-Deflection technique to measure the nonlinear refraction of air, exciting in both the near and mid-IR and probing in the mid-IR. This gives us the first measurements for air using both excitation and probe in the mid-IR, and we find no dispersion of the bound-electronic nonlinear refractive index, n2,el(λp;λe), assuming, as has been shown earlier, that the nuclear rotational nonlinear refraction is nearly dispersionless. From these data, we can model the pulsewidth dependence of the effective nonlinear refractive index, n2,eff, i.e., as would be measured by a single beam. Interestingly, n2,eff is maximized for a pulsewidth of approximately 0.5 ps. The position of this maximum is nearly independent of pressure while its magnitude decreases with increasing pressure and temperature. From the measurements and modeling, we predict the nonlinear refraction in the atmosphere at different altitudes.
Collapse
|
8
|
Hancock SW, Zahedpour S, Milchberg HM. Transient-grating single-shot supercontinuum spectral interferometry (TG-SSSI). OPTICS LETTERS 2021; 46:1013-1016. [PMID: 33649642 DOI: 10.1364/ol.417803] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Accepted: 01/26/2021] [Indexed: 06/12/2023]
Abstract
We present a technique for the single-shot measurement of the spatiotemporal (1D space+time) amplitude and phase of an ultrashort laser pulse. The method, transient grating single-shot supercontinuum spectral interferometry (TG-SSSI), is demonstrated by the space-time imaging of short pulses carrying spatiotemporal optical vortices. TG-SSSI is well suited for characterizing ultrashort laser pulses that contain singularities associated with spin/orbital angular momentum or polarization.
Collapse
|
9
|
Tolliver J, Zahedpour S, Wahlstrand JK, Milchberg HM, Kolesik M. Nonlinearity and ionization in Xe: experiment-based calibration of a numerical model. OPTICS LETTERS 2020; 45:5780-5783. [PMID: 33057283 PMCID: PMC8218235 DOI: 10.1364/ol.408403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Accepted: 09/14/2020] [Indexed: 06/11/2023]
Abstract
Recently proposed universality of the nonlinear response is put to the test and used to improve a previously designed model for xenon. Utilizing accurate measurements resolving the nonlinear polarization and ionization in time and space, we calibrate the scaling parameters of the model and demonstrate agreement with several experiments spanning the intensity range relevant for applications in nonlinear optics at near-infrared and mid-infrared wavelengths. Applications to other species including small molecules are discussed, suggesting a self-consistent way to calibrate light-matter interaction models.
Collapse
Affiliation(s)
- J. Tolliver
- College of Optical Sciences, University of Arizona, Tucson, Arizona 85712, USA
| | - S. Zahedpour
- Institute for Research in Electronics & Applied Physics, University of Maryland, College Park, Maryland 20742, USA
| | - J. K. Wahlstrand
- Institute for Research in Electronics & Applied Physics, University of Maryland, College Park, Maryland 20742, USA
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | - H. M. Milchberg
- Institute for Research in Electronics & Applied Physics, University of Maryland, College Park, Maryland 20742, USA
| | - M. Kolesik
- College of Optical Sciences, University of Arizona, Tucson, Arizona 85712, USA
| |
Collapse
|
10
|
Rosenthal EW, Larkin I, Goffin A, Produit T, Schroeder MC, Wolf JP, Milchberg HM. Dynamics of the femtosecond laser-triggered spark gap. OPTICS EXPRESS 2020; 28:24599-24613. [PMID: 32906999 DOI: 10.1364/oe.398836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 07/20/2020] [Indexed: 06/11/2023]
Abstract
We present space and time resolved measurements of the air hydrodynamics induced by femtosecond laser pulse excitation of the air gap between two electrodes at high potential difference. We explore both plasma-based and plasma-free gap excitation. The former uses the plasma left in the wake of femtosecond filamentation, while the latter exploits air heating by multiple-pulse resonant excitation of quantum molecular wavepackets. We find that the cumulative electrode-driven air density depression channel plays the dominant role in the gap evolution leading to breakdown. Femtosecond laser heating serves mainly to initiate the depression channel; the presence of filament plasma only augments the early heating.
Collapse
|
11
|
Beetar JE, Nrisimhamurty M, Truong TC, Nagar GC, Liu Y, Nesper J, Suarez O, Rivas F, Wu Y, Shim B, Chini M. Multioctave supercontinuum generation and frequency conversion based on rotational nonlinearity. SCIENCE ADVANCES 2020; 6:eabb5375. [PMID: 32937367 PMCID: PMC7442354 DOI: 10.1126/sciadv.abb5375] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Accepted: 07/08/2020] [Indexed: 05/17/2023]
Abstract
The field of attosecond science was first enabled by nonlinear compression of intense laser pulses to a duration below two optical cycles. Twenty years later, creating such short pulses still requires state-of-the-art few-cycle laser amplifiers to most efficiently exploit "instantaneous" optical nonlinearities in noble gases for spectral broadening and parametric frequency conversion. Here, we show that nonlinear compression can be much more efficient when driven in molecular gases by pulses substantially longer than a few cycles because of enhanced optical nonlinearity associated with rotational alignment. We use 80-cycle pulses from an industrial-grade laser amplifier to simultaneously drive molecular alignment and supercontinuum generation in a gas-filled capillary, producing more than two octaves of coherent bandwidth and achieving >45-fold compression to a duration of 1.6 cycles. As the enhanced nonlinearity is linked to rotational motion, the dynamics can be exploited for long-wavelength frequency conversion and compressing picosecond lasers.
Collapse
Affiliation(s)
- John E Beetar
- Department of Physics, University of Central Florida, Orlando FL 32816, USA
| | - M Nrisimhamurty
- Department of Physics, University of Central Florida, Orlando FL 32816, USA
| | - Tran-Chau Truong
- Department of Physics, University of Central Florida, Orlando FL 32816, USA
| | - Garima C Nagar
- Department of Physics, Applied Physics and Astronomy, Binghamton University, Binghamton NY 13902, USA
| | - Yangyang Liu
- Department of Physics, University of Central Florida, Orlando FL 32816, USA
| | - Jonathan Nesper
- Department of Physics, University of Central Florida, Orlando FL 32816, USA
| | - Omar Suarez
- Department of Physics, University of Central Florida, Orlando FL 32816, USA
| | - Federico Rivas
- Department of Physics, University of Central Florida, Orlando FL 32816, USA
| | - Yi Wu
- Department of Physics, University of Central Florida, Orlando FL 32816, USA
- Institute for the Frontier of Attosecond Science and Technology, University of Central Florida, Orlando FL 32816, USA
- CREOL, the College of Optics and Photonics, University of Central Florida, Orlando FL 32816, USA
| | - Bonggu Shim
- Department of Physics, Applied Physics and Astronomy, Binghamton University, Binghamton NY 13902, USA
| | - Michael Chini
- Department of Physics, University of Central Florida, Orlando FL 32816, USA.
- CREOL, the College of Optics and Photonics, University of Central Florida, Orlando FL 32816, USA
| |
Collapse
|
12
|
Mashiko H, Chen MC, Asaga K, Oshima A, Katayama I, Takeda J, Nishikawa T, Oguri K. Spatially resolved spectral phase interferometry with an isolated attosecond pulse. OPTICS EXPRESS 2020; 28:21025-21034. [PMID: 32680150 DOI: 10.1364/oe.393922] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 06/22/2020] [Indexed: 06/11/2023]
Abstract
We demonstrate spatially resolved supercontinuum spectral phase interferometry with an isolated attosecond pulse (IAP). The measured spatial-spectral interferogram over the broadband region indicates a high degree of IAP coherence in both spatial and spectral domains. In addition, the spectral-delay interferogram shows periodic temporal oscillations over the full IAP continuous spectrum, which indicates high temporal coherence. The supercontinuum spectral phase interferometry with broadband IAP will contribute to exploring spatiotemporal dispersive electronic dynamics through phase-based spectroscopy in the future.
Collapse
|
13
|
Larkin I, Griff-McMahon J, Schweinsberg A, Goffin A, Valenzuela A, Milchberg HM. Full path single-shot imaging of femtosecond pulse collapse in air turbulence. OPTICS LETTERS 2020; 45:2518-2521. [PMID: 32356805 DOI: 10.1364/ol.389495] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Accepted: 03/23/2020] [Indexed: 06/11/2023]
Abstract
In a single shot, we measure the full propagation path, including the evolution to pulse collapse, of a high power femtosecond laser pulse propagating in air. Our technique enables examination of the effect of parameters that fluctuate on a shot-to-shot basis, such as pulse energy, pulse duration, and air turbulence-induced refractive index perturbations. We find that even in lab air over relatively short propagation distances, turbulence plays a significant role in determining the location of pulse collapse.
Collapse
|
14
|
Schroeder MC, Larkin I, Produit T, Rosenthal EW, Milchberg H, Wolf JP. Molecular quantum wakes for clearing fog. OPTICS EXPRESS 2020; 28:11463-11471. [PMID: 32403657 DOI: 10.1364/oe.389393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Accepted: 03/26/2020] [Indexed: 06/11/2023]
Abstract
High intensity laser filamentation in air has recently demonstrated that, through plasma generation and its associated shockwave, fog can be cleared around the beam, leaving an optically transparent path to transmit light. However, for practical applications like free-space optical communication (FSO), channels of multi-centimeter diameters over kilometer ranges are required, which is extremely challenging for a plasma based method. Here we report a radically different approach, based on quantum control. We demonstrate that fog clearing can also be achieved by producing molecular quantum wakes in air, and that neither plasma generation nor filamentation are required. The effect is clearly associated with the rephasing time of the rotational wave packet in N2.Pump excitation provided in the form of resonant trains of 8 pulses separated by the revival time are able to transmit optical data through fog with initial extinction as much as -6 dB.
Collapse
|
15
|
Zahedpour S, Hancock SW, Milchberg HM. Ultrashort infrared 2.5-11 μm pulses: spatiotemporal profiles and absolute nonlinear response of air constituents. OPTICS LETTERS 2019; 44:843-846. [PMID: 30768001 DOI: 10.1364/ol.44.000843] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Accepted: 12/26/2018] [Indexed: 06/09/2023]
Abstract
We measure the detailed spatiotemporal profiles of femtosecond laser pulses in the infrared wavelength range of λ=2.5-11 μm and the absolute nonlinear response of major air constituents (N2, O2, and Ar) over this range. The spatiotemporal measurements reveal wavelength-dependent pulse front tilt and temporal stretching in the infrared pulses.
Collapse
|
16
|
Wahlstrand JK, Jhajj N, Milchberg HM. Controlling femtosecond filament propagation using externally driven gas motion. OPTICS LETTERS 2019; 44:199-202. [PMID: 30644860 PMCID: PMC6547820 DOI: 10.1364/ol.44.000199] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Accepted: 11/29/2018] [Indexed: 06/09/2023]
Abstract
The thermal density depression (or "density hole") produced by a high-repetition-rate femtosecond filament in air acts as a negative lens, altering the propagation of the filament. We demonstrate the effects of externally driven gas motion on these density holes and the resulting filament steering, and we derive an expression for the gas velocity that maximizes the effect. At gas velocities more than ∼3 times this value, the density hole is displaced from the filament, and it no longer affects filament propagation. We demonstrate density hole displacement using an audio speaker-driven sound wave, leading to a controllable, repeatable deflection of the filament. Applications are discussed, including quasi-phase matching in gas-based nonlinear optics. To the best of our knowledge, this is the first demonstration of femtosecond filament propagation control through controlled motion of the nonlinear medium.
Collapse
Affiliation(s)
- J. K. Wahlstrand
- lnstitutefor Research in Electronics and Applied Physics, University of Maryland, College Park, MD 20742, USA
- Currently with Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | - N. Jhajj
- lnstitutefor Research in Electronics and Applied Physics, University of Maryland, College Park, MD 20742, USA
| | - H. M. Milchberg
- lnstitutefor Research in Electronics and Applied Physics, University of Maryland, College Park, MD 20742, USA
| |
Collapse
|
17
|
Vu DT, Jang D, Kim KY. Simplified chirp characterization in single-shot supercontinuum spectral interferometry. OPTICS EXPRESS 2018; 26:20572-20581. [PMID: 30119366 DOI: 10.1364/oe.26.020572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Accepted: 07/19/2018] [Indexed: 06/08/2023]
Abstract
Single-shot supercontinuum spectral interferometry (SSSI) is an optical technique that can measure ultrafast transients in the complex index of refraction. This method uses chirped supercontinuum reference/probe pulses that need to be pre-characterized prior to use. Conventionally, the spectral phase (or chirp) of those pulses can be determined from a series of phase or spectral measurements taken at various time delays with respect to a pump-induced modulation. Here we propose a novel method to simplify this process and characterize reference/probe pulses up to the third order dispersion from a minimum of 2 snapshots taken at different pump-probe delays. Alternatively, without any pre-characterization, our method can retrieve both unperturbed and perturbed reference/probe phases, including the pump-induced modulation, from 2 time-delayed snapshots. From numerical simulations, we show that our retrieval algorithm is robust and can achieve high accuracy even with 2 snapshots. Without any apparatus modification, our method can be easily applied to any experiment that uses SSSI.
Collapse
|
18
|
Wahlstrand JK, Zahedpour S, Bahl A, Kolesik M, Milchberg HM. Bound-Electron Nonlinearity Beyond the Ionization Threshold. PHYSICAL REVIEW LETTERS 2018; 120:183901. [PMID: 29775376 PMCID: PMC6074032 DOI: 10.1103/physrevlett.120.183901] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2018] [Indexed: 05/25/2023]
Abstract
We present absolute space- and time-resolved measurements of the ultrafast laser-driven nonlinear polarizability in argon, krypton, xenon, nitrogen, and oxygen up to ionization fractions of a few percent. These measurements enable determination of the strongly nonperturbative bound-electron nonlinear polarizability well beyond the ionization threshold, where it is found to remain approximately quadratic in the laser field, a result normally expected at much lower intensities where perturbation theory applies.
Collapse
Affiliation(s)
- J. K. Wahlstrand
- Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD 20742
- Engineering Physics Division, National Institute of Standards and Technology, Gaithersburg, MD 20899
| | - S. Zahedpour
- Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD 20742
| | - A. Bahl
- College of Optical Sciences, University of Arizona, Tucson, AZ 85712
| | - M. Kolesik
- College of Optical Sciences, University of Arizona, Tucson, AZ 85712
| | - H. M. Milchberg
- Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD 20742
| |
Collapse
|
19
|
Rosenthal EW, Jhajj N, Larkin I, Zahedpour S, Wahlstrand JK, Milchberg HM. Energy deposition of single femtosecond filaments in the atmosphere. OPTICS LETTERS 2016; 41:3908-3911. [PMID: 27519120 DOI: 10.1364/ol.41.003908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Accepted: 08/01/2016] [Indexed: 06/06/2023]
Abstract
We present spatially resolved measurements of energy deposition into atmospheric air by femtosecond laser filaments. Single filaments formed with varying laser pulse energy and pulsewidth were examined using longitudinal interferometry, sonographic probing, and direct energy loss measurements. We measure peak and average energy absorption of ∼4 μJ/cm and ∼1 μJ/cm for input pulse powers up to ∼6 times the critical power for self-focusing.
Collapse
|
20
|
Romanov DA, Odhner JH, Levis RJ. Modification of chirped laser pulses via delayed rotational nonlinearity. J Chem Phys 2016; 144:124313. [PMID: 27036454 DOI: 10.1063/1.4944527] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
To interpret single-shot measurements of rotational revival patterns in molecular gases excited by an ultrashort laser pulse, an analytical description of the probe pulse modulation by the impulsively excited medium is developed. A femtosecond pump laser pulse prepares a rotational wavepacket in a gas-phase sample, and the resulting periodic revivals are mapped into the frequency domain by using a substantially chirped continuum probe pulse. Since the standard approximate descriptions of probe pulse propagation are inapplicable (such as the slowly varying envelope approximation and the slowly evolving wave approximation), we propose an approach capable of incorporating both the substantial chirp of the pulse and the temporal dispersion of the medium response. Theory is presented for the case where the frequency change of the probe during the probe pulse duration is comparable with the carrier frequency. Analytical expressions are obtained for the probe signal modulation over the pump-probe interaction region and for the resulting heterodyned transient birefringence spectra. The approach is illustrated using the case of nitrogen gas.
Collapse
Affiliation(s)
- D A Romanov
- Department of Physics, Temple University, Philadelphia, Pennsylvania 19122, USA
| | - J H Odhner
- Center for Advanced Photonics Research, Temple University, Philadelphia, Pennsylvania 19122, USA
| | - R J Levis
- Center for Advanced Photonics Research, Temple University, Philadelphia, Pennsylvania 19122, USA
| |
Collapse
|
21
|
Point G, Thouin E, Mysyrowicz A, Houard A. Energy deposition from focused terawatt laser pulses in air undergoing multifilamentation. OPTICS EXPRESS 2016; 24:6271-6282. [PMID: 27136820 DOI: 10.1364/oe.24.006271] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Laser filamentation is responsible for the deposition of a significant part of the laser pulse energy in the propagation medium. We found that using terawatt laser pulses and moderately strong focusing conditions in air, more than 60 % of the pulses energy is transferred to the medium, eventually degrading into heat. This results in a strong hydrodynamic reaction of air with the generation of shock waves and associated underdense channels for each of the generated multiple filaments. In the focal zone, where filaments are close to each other, these discrete channels eventually merge to form a single cylindrical low-density tube over a ~ 1 µs timescale. We measured the maximum lineic deposited energy to be more than 1 J·m-1.
Collapse
|
22
|
Kaya N, Kaya G, Sayrac M, Boran Y, Anumula S, Strohaber J, Kolomenskii AA, Schuessler HA. Probing nonadiabatic molecular alignment by spectral modulation. OPTICS EXPRESS 2016; 24:2562-2576. [PMID: 26906829 DOI: 10.1364/oe.24.002562] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We investigated molecular alignment wakes of femtosecond laser pulses. Evolution of nonadiabatic molecular alignment in nitrogen gas has been measured via its nonlinear interaction effects with a variably delayed probe pulse. The induced rotational wave packet was mapped as a function of the angular difference between polarization directions of femtosecond pump and probe pulses as well as their relative delay and the plot of the variations of the rotational wave packet, i.e. "quantum carpet", was found to be in good agreement with the calculated angular and temporal dependencies of molecular alignment parameter.
Collapse
|
23
|
Zahedpour S, Wahlstrand JK, Milchberg HM. Measurement of the nonlinear refractive index of air constituents at mid-infrared wavelengths. OPTICS LETTERS 2015; 40:5794-5797. [PMID: 26670514 DOI: 10.1364/ol.40.005794] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We measure the nonlinear refractive index coefficients in N₂, O₂, and Ar from visible through mid-infrared wavelengths (λ=0.4-2.4 μm). The wavelengths investigated correspond to transparency windows in the atmosphere. Good agreement is found with theoretical models of χ((3)). Our results are essential for accurately simulating the propagation of ultrashort mid-infrared pulses in the atmosphere.
Collapse
|
24
|
Goers AJ, Hine GA, Feder L, Miao B, Salehi F, Wahlstrand JK, Milchberg HM. Multi-MeV Electron Acceleration by Subterawatt Laser Pulses. PHYSICAL REVIEW LETTERS 2015; 115:194802. [PMID: 26588390 DOI: 10.1103/physrevlett.115.194802] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Indexed: 06/05/2023]
Abstract
We demonstrate laser-plasma acceleration of high charge electron beams to the ∼10 MeV scale using ultrashort laser pulses with as little energy as 10 mJ. This result is made possible by an extremely dense and thin hydrogen gas jet. Total charge up to ∼0.5 nC is measured for energies >1 MeV. Acceleration is correlated to the presence of a relativistically self-focused laser filament accompanied by an intense coherent broadband light flash, associated with wave breaking, which can radiate more than ∼3% of the laser energy in a ∼1 fs bandwidth consistent with half-cycle optical emission. Our results enable truly portable applications of laser-driven acceleration, such as low dose radiography, ultrafast probing of matter, and isotope production.
Collapse
Affiliation(s)
- A J Goers
- Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742, USA
| | - G A Hine
- Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742, USA
| | - L Feder
- Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742, USA
| | - B Miao
- Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742, USA
| | - F Salehi
- Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742, USA
| | - J K Wahlstrand
- Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742, USA
| | - H M Milchberg
- Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742, USA
| |
Collapse
|
25
|
Reichert M, Zhao P, Reed JM, Ensley TR, Hagan DJ, Van Stryland EW. Beam deflection measurement of bound-electronic and rotational nonlinear refraction in molecular gases. OPTICS EXPRESS 2015; 23:22224-22237. [PMID: 26368195 DOI: 10.1364/oe.23.022224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
A polarization-resolved beam deflection technique is used to separate the bound-electronic and molecular rotational components of nonlinear refractive transients of molecular gases. Coherent rotational revivals from N(2), O(2), and two isotopologues of carbon disulfide (CS(2)), are identified in gaseous mixtures. Dephasing rates, rotational and centrifugal distortion constants of each species are measured. Polarization at the magic angle allows unambiguous measurement of the bound-electronic nonlinear refractive index of air and second hyperpolarizability of CS(2). Agreement between gas and liquid phase second hyperpolarizability measurements is found using the Lorentz-Lorenz local field correction.
Collapse
|
26
|
Yuan S, Wang TJ, Pan H, Zheng L, Chin SL, Zeng H. Pulse polarization evolution and control in the wake of molecular alignment inside a filament. OPTICS EXPRESS 2015; 23:5582-5589. [PMID: 25836790 DOI: 10.1364/oe.23.005582] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The polarization evolution and control of a femtosecond laser pulse in the wake of molecular alignment inside a laser filament was investigated. A weak probe pulse was delayed with respect to the field-free revivals of the pre-excited rotational wave-packets created by an infrared filamenting pulse in nitrogen gas. 30° was set between the pump and probe's initial linear polarization directions in order to control the output probe's polarization ellipse. The detailed physical response of the probe's polarization states was analyzed in the wake of alignment and dephasing of molecular N(2). The probe's polarization was modulated by varying the retarded time between the pump and probe pulses.
Collapse
|
27
|
Zahedpour S, Wahlstrand JK, Milchberg HM. Quantum control of molecular gas hydrodynamics. PHYSICAL REVIEW LETTERS 2014; 112:143601. [PMID: 24765959 DOI: 10.1103/physrevlett.112.143601] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Indexed: 06/03/2023]
Abstract
We demonstrate that strong impulsive gas heating or heating suppression at standard temperature and pressure can occur from coherent rotational excitation or deexcitation of molecular gases using a sequence of nonionizing laser pulses. For the case of excitation, subsequent collisional decoherence of the ensemble leads to gas heating significantly exceeding that from plasma absorption under the same laser focusing conditions. In both cases, the macroscopic hydrodynamics of the gas can be finely controlled with ∼40 fs temporal sensitivity.
Collapse
Affiliation(s)
- S Zahedpour
- Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742, USA
| | - J K Wahlstrand
- Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742, USA
| | - H M Milchberg
- Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742, USA
| |
Collapse
|
28
|
Abstract
Femtosecond laser filamentation occurs as a dynamic balance between the self-focusing and plasma defocusing of a laser pulse to produce ultrashort radiation as brief as a few optical cycles. This unique source has many properties that make it attractive as a nonlinear optical tool for spectroscopy, such as propagation at high intensities over extended distances, self-shortening, white-light generation, and the formation of an underdense plasma. The plasma channel that constitutes a single filament and whose position in space can be controlled by its input parameters can span meters-long distances, whereas multifilamentation of a laser beam can be sustained up to hundreds of meters in the atmosphere. In this review, we briefly summarize the current understanding and use of laser filaments for spectroscopic investigations of molecules. A theoretical framework of filamentation is presented, along with recent experimental evidence supporting the established understanding of filamentation. Investigations carried out on vibrational and rotational spectroscopy, filament-induced breakdown, fluorescence spectroscopy, and backward lasing are discussed.
Collapse
Affiliation(s)
- Johanan Odhner
- Department of Chemistry and Center for Advanced Photonics Research, Temple University, Philadelphia, Pennsylvania 19122
| | - Robert Levis
- Department of Chemistry and Center for Advanced Photonics Research, Temple University, Philadelphia, Pennsylvania 19122
| |
Collapse
|
29
|
McCole ET, Odhner JH, Romanov DA, Levis RJ. Spectral-to-temporal amplitude mapping polarization spectroscopy of rotational transients. J Phys Chem A 2013; 117:6354-61. [PMID: 23651318 DOI: 10.1021/jp402135t] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
A new implementation of pump-probe polarization spectroscopy is presented where the revivals of an impulsively excited rotational wavepacket are mapped onto a broad-band, chirped continuum pulse to measure a long temporal window without the need for delay scanning. Experimental measurements and a theoretical framework for spectral-temporal amplitude mapping polarization spectroscopy (STAMPS) as applied to impulsive rotational motion are presented. In this technique, a femtosecond laser pulse is used to prepare a rotational wavepacket in a gas-phase sample at room temperature. The rotational revivals of the wavepacket are then mapped onto a chirped continuum (400-800 nm) pulse created by laser filamentation in argon. Nearly single-shot time-resolved rotational spectra are recorded over a 65 ps time window. The transient birefringence spectra are simulated by including terms for polarization rotation of the probe as well as cross-phase modulation. Measurements and simulations are presented for the cylindrically symmetric N2, O2, and CO2 molecules. The long time window of the method allows measurement of rotational spectra for asymmetric top molecules, and here we present measurements for ethylene and methanol.
Collapse
Affiliation(s)
- Erin T McCole
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, USA
| | | | | | | |
Collapse
|
30
|
Cheng YH, Wahlstrand JK, Jhajj N, Milchberg HM. The effect of long timescale gas dynamics on femtosecond filamentation. OPTICS EXPRESS 2013; 21:4740-4751. [PMID: 23482007 DOI: 10.1364/oe.21.004740] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Femtosecond laser pulses filamenting in various gases are shown to generate long- lived quasi-stationary cylindrical depressions or 'holes' in the gas density. For our experimental conditions, these holes range up to several hundred microns in diameter with gas density depressions up to ~20%. The holes decay by thermal diffusion on millisecond timescales. We show that high repetition rate filamentation and supercontinuum generation can be strongly affected by these holes, which should also affect all other experiments employing intense high repetition rate laser pulses interacting with gases.
Collapse
Affiliation(s)
- Y-H Cheng
- Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742, USA
| | | | | | | |
Collapse
|
31
|
Wahlstrand JK, Cheng YH, Milchberg HM. High field optical nonlinearity and the Kramers-Kronig relations. PHYSICAL REVIEW LETTERS 2012; 109:113904. [PMID: 23005631 DOI: 10.1103/physrevlett.109.113904] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Indexed: 06/01/2023]
Abstract
The nonlinear optical response to high fields is absolutely measured for the noble gas atoms He, Ne, Ar, Kr, and Xe. We find that the response is quadratic in the laser field magnitude up to the ionization threshold of each gas. Its size and quadratic dependence are well predicted by a Kramers-Kronig analysis employing known ionization probabilities, and the results are consistent with calculations using the time-dependent Schrödinger equation.
Collapse
Affiliation(s)
- J K Wahlstrand
- Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742, USA
| | | | | |
Collapse
|
32
|
Wahlstrand JK, Cheng YH, Chen YH, Milchberg HM. Optical nonlinearity in Ar and N2 near the ionization threshold. PHYSICAL REVIEW LETTERS 2011; 107:103901. [PMID: 21981503 DOI: 10.1103/physrevlett.107.103901] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2011] [Indexed: 05/31/2023]
Abstract
We directly measure the nonlinear optical response in argon and nitrogen in a thin gas target to laser intensities near the ionization threshold. No instantaneous negative nonlinear refractive index is observed, nor is saturation, in contrast with a previous measurement [Opt. Express 17, 13429 (2009)] and calculations [Phys. Rev. Lett. 106, 183902 (2011)]. In addition, we are able to cleanly separate the instantaneous and rotational components of the nonlinear response in nitrogen. In both Ar and N2, the peak instantaneous index response scales linearly with the laser intensity until the point of ionization, whereupon the response turns abruptly negative and ∼constant, consistent with plasma generation.
Collapse
Affiliation(s)
- J K Wahlstrand
- Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742, USA
| | | | | | | |
Collapse
|
33
|
Feng Y, Pan H, Liu J, Chen C, Wu J, Zeng H. Direct measurement of field-free molecular alignment by spatial (de)focusing effects. OPTICS EXPRESS 2011; 19:2852-2857. [PMID: 21369106 DOI: 10.1364/oe.19.002852] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We directly measure the field-free molecular alignment of various room-temperature molecular gases based on alignment-induced spatial focusing and defocusing effects. By imaging the spatial profile of a time-delayed probe pulse with increased and decreased local intensity at the beam center, the parallel and perpendicular molecular alignments are clearly characterized. Meanwhile, the electronic Kerr effect, weak plasma contribution and field-free molecular alignment impact could be distinguished from the measured signals.
Collapse
Affiliation(s)
- Yahui Feng
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
| | | | | | | | | | | |
Collapse
|
34
|
Chen YH, Varma S, Antonsen TM, Milchberg HM. Direct measurement of the electron density of extended femtosecond laser pulse-induced filaments. PHYSICAL REVIEW LETTERS 2010; 105:215005. [PMID: 21231313 DOI: 10.1103/physrevlett.105.215005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2010] [Indexed: 05/30/2023]
Abstract
We present direct time- and space-resolved measurements of the electron density of femtosecond laser pulse-induced plasma filaments. The dominant nonlinearity responsible for extended atmospheric filaments is shown to be field-induced rotation of air molecules.
Collapse
Affiliation(s)
- Y-H Chen
- Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742, USA
| | | | | | | |
Collapse
|
35
|
Shu CC, Yuan KJ, Hu WH, Cong SL. Field-free molecular orientation with terahertz few-cycle pulses. J Chem Phys 2010; 132:244311. [PMID: 20590197 DOI: 10.1063/1.3458913] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Chuan-Cun Shu
- Department of Physics, Dalian University of Technology, Dalian 116024, China.
| | | | | | | |
Collapse
|
36
|
Negro M, Vozzi C, Calegari F, De Silvestri S, Stagira S. Polarization pulse shaping induced by impulsive molecular alignment in optical filamentation and application to high-order harmonic generation. OPTICS LETTERS 2010; 35:1350-1352. [PMID: 20436565 DOI: 10.1364/ol.35.001350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We investigated theoretically and experimentally the ultrafast birefringence induced by impulsive alignment in a molecular gas during optical filamentation. This phenomenon is able to substantially affect the polarization state of an ultrashort laser pulse that propagates through the aligned medium at suitable delays from a first aligning pulse. We exploited this modulation of the polarization state in order to effectively control the high-order harmonic generation (HHG) process, which is strongly dependent on the driving pulse polarization. These results open new and fascinating perspectives for the tailoring of strong-field phenomena by means of polarization pulse shaping.
Collapse
Affiliation(s)
- M Negro
- Dipartimento di Fisica, Politecnico di Milano & CNR-IFN, Piazza Leonardo da Vinci, 32, 20133 Milano, Italy
| | | | | | | | | |
Collapse
|
37
|
Wu J, Cai H, Tong Y, Zeng H. Measurement of field-free molecular alignment by cross-defocusing assisted polarization spectroscopy. OPTICS EXPRESS 2009; 17:16300-16305. [PMID: 19724629 DOI: 10.1364/oe.17.016300] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We demonstrate the measurement of field-free molecular alignment of nitrogen by a cross-(de)focusing assisted polarization spectroscopy technique, allowing us to distinguish the transient orientation of prealigned molecules on the basis of the relative ratio of the adjacent revival peaks of the measured signal. For impulsive excitation with high pump intensities, the involved orientation-dependent ionization of the neutral molecules contributes to the signal.
Collapse
Affiliation(s)
- Jian Wu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China.
| | | | | | | |
Collapse
|
38
|
York AG. Laser-driven clockwise molecular rotation for a transient spinning waveplate. OPTICS EXPRESS 2009; 17:13671-13676. [PMID: 19654775 DOI: 10.1364/oe.17.013671] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Our simulations show a copropagating pair of laser pulses polarized in two different directions can selectively excite clockwise or counterclockwise molecular rotation in a gas of linear molecules. The resulting birefringence of the gas rotates on a femtosecond timescale and shows a periodic revival structure. The total duration of the pulse pair can be subpicosecond, allowing molecular alignment at the high densities and temperatures necessary to create a transient spinning waveplate.
Collapse
Affiliation(s)
- Andrew G York
- Institute for Research in Electronics and Applied Physics University of Maryland, College Park, MD 20742, USA.
| |
Collapse
|
39
|
Varma S, Chen YH, Milchberg HM. Trapping and destruction of long-range high-intensity optical filaments by molecular quantum wakes in air. PHYSICAL REVIEW LETTERS 2008; 101:205001. [PMID: 19113345 DOI: 10.1103/physrevlett.101.205001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2008] [Indexed: 05/27/2023]
Abstract
We report the first observation of the strong effect of quantum rotational wave packets in atmospheric air on the long-range filamentary propagation of intense femtosecond laser pulses. In a pump-probe experiment, we find that the probe filament can be sucked into the pump filament's molecular quantum wake and trapped or be destroyed by it.
Collapse
Affiliation(s)
- S Varma
- Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742, USA
| | | | | |
Collapse
|
40
|
York AG, Milchberg HM. Broadband terahertz lasing in aligned molecules. OPTICS EXPRESS 2008; 16:10557-105645. [PMID: 18607470 DOI: 10.1364/oe.16.010557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
No broadband amplifying medium has been demonstrated yet for terahertz radiation. We present simulations showing that laser-aligned molecules can amplify broadband terahertz radiation, allowing high-energy amplification of few-cycle pulses at terahertz frequencies.
Collapse
Affiliation(s)
- Andrew G York
- Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD 20742, USA.
| | | |
Collapse
|