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Broadband femtosecond lasers enable efficient two-photon excitation of the ultranarrow linewidth singlet 1s2s state in helium

Shashank Kumar1,*, Justin D. Piel1, Chris H. Greene1,2, and Niranjan Shivaram1,2,†

  • *Contact author: kumar414@purdue.edu
  • †Contact author: niranjan@purdue.edu
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Phys. Rev. Research 8, 013009 – Published 8 January, 2026

DOI: https://doi.org/10.1103/nfbf-h6hc

Abstract

We propose a broadband, femtosecond two-photon excitation scheme for efficient population transfer to the ultranarrow linewidth 1s2s1S0 metastable state in helium. Using 120 nm vacuum ultraviolet femtosecond laser pulses, we theoretically demonstrate that a direct two-photon excitation process can achieve a population transfer efficiency of 25%–30%, even when photoionization losses are included. The use of broadband pulses enables multiple excitation pathways to populate the excited state, in addition to compensating for significant ac Stark shifts occurring within the pulse duration. Furthermore, we introduce a two-color two-photon extreme-ultraviolet-near-infrared (XUV-IR) excitation scheme that will further reduce ionization losses and can achieve significantly higher transfer efficiencies of ∼70%. These results demonstrate that high excitation probability of ultranarrow linewidth (∼50Hz) excited states can be achieved using experimentally accessible femtosecond laser sources with bandwidth in the terahertz range.

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References (61)

  1. X. Shi, J. Sinanan-Singh, K. DeBry, S. L. Todaro, I. L. Chuang, and J. Chiaverini, Long-lived metastable-qubit memory, Phys. Rev. A 111, L020601 (2025).
  2. S. Pucher, V. Klüsener, F. Spriestersbach, J. Geiger, A. Schindewolf, I. Bloch, and S. Blatt, Fine-structure qubit encoded in metastable strontium trapped in an optical lattice, Phys. Rev. Lett. 132, 150605 (2024).
  3. T. P. Harty, D. T. C. Allcock, C. J. Ballance, L. Guidoni, H. A. Janacek, N. M. Linke, D. N. Stacey, and D. M. Lucas, High-fidelity preparation, gates, memory, and readout of a trapped-ion quantum bit, Phys. Rev. Lett. 113, 220501 (2014).
  4. G. Unnikrishnan, P. Ilzhöfer, A. Scholz, C. Hölzl, A. Götzelmann, R. K. Gupta, J. Zhao, J. Krauter, S. Weber, N. Makki, H. P. Büchler, T. Pfau, and F. Meinert, Coherent control of the fine-structure qubit in a single Alkaline-earth atom, Phys. Rev. Lett. 132, 150606 (2024).
  5. Y. Wang, M. Um, J. Zhang, S. An, M. Lyu, J.-N. Zhang, L.-M. Duan, D. Yum, and K. Kim, Single-qubit quantum memory exceeding ten-minute coherence time, Nat. Photonics 11, 646 (2017).
  6. P. Wang, C.-Y. Luan, M. Qiao, M. Um, J. Zhang, Y. Wang, X. Yuan, M. Gu, J. Zhang, and K. Kim, Single ion qubit with estimated coherence time exceeding one hour, Nat. Commun. 12, 233 (2021).
  7. A. Aeppli, K. Kim, W. Warfield, M. S. Safronova, and J. Ye, Clock with 8×10−19 systematic uncertainty, Phys. Rev. Lett. 133, 023401 (2024).
  8. M. A. Bohman, S. G. Porsev, D. B. Hume, D. R. Leibrandt, and M. S. Safronova, Enhancing divalent optical atomic clocks with the S01↔P23 transition, Phys. Rev. A 108, 053120 (2023).
  9. S. R. Jefferts, T. P. Heavner, T. E. Parker, J. H. Shirley, E. A. Donley, N. Ashby, F. Levi, D. Calonico, and G. A. Costanzo, High-accuracy measurement of the blackbody radiation frequency shift of the ground-state hyperfine transition in Cs133, Phys. Rev. Lett. 112, 050801 (2014).
  10. K. Beeks, T. Sikorsky, T. Schumm, J. Thielking, M. V. Okhapkin, and E. Peik, The thorium-229 low-energy isomer and the nuclear clock, Nat. Rev. Phys. 3, 238 (2021).
  11. C. Zhang, T. Ooi, J. S. Higgins, J. F. Doyle, L. von der Wense, K. Beeks, A. Leitner, G. A. Kazakov, P. Li, P. G. Thirolf, T. Schumm, and J. Ye, Frequency ratio of the Th229m nuclear isomeric transition and the Sr87 atomic clock, Nature (London) 633, 63 (2024).
  12. J. Shapiro and G. Breit, Metastability of 2s states of hydrogenic atoms, Phys. Rev. 113, 179 (1959).
  13. M. H. Prior, Lifetime of the 2s state of He+, Phys. Rev. Lett. 29, 611 (1972).
  14. C. A. Kocher, J. E. Clendenin, and R. Novick, Lifetime of the 22S12 state of singly ionized helium, Phys. Rev. Lett. 29, 615 (1972).
  15. E. A. Hinds, J. E. Clendenin, and R. Novick, Decay rate of the 22S12 state of singly ionized helium, Phys. Rev. A 17, 670 (1978).
  16. R. S. Van Dyck, C. E. Johnson, and H. A. Shugart, Radiative lifetime of the 21S0 metastable state of helium, Phys. Rev. A 4, 1327 (1971).
  17. S. S. Hodgman, R. G. Dall, L. J. Byron, K. G. H. Baldwin, S. J. Buckman, and A. G. Truscott, Metastable helium: A new determination of the longest atomic excited-state lifetime, Phys. Rev. Lett. 103, 053002 (2009).
  18. E. A. Hildum, U. Boesl, D. H. McIntyre, R. G. Beausoleil, and T. W. Hansch, Measurement of the 1S-2S frequency in atomic hydrogen, Phys. Rev. Lett. 56, 576 (1986).
  19. M. Niering, R. Holzwarth, J. Reichert, P. Pokasov, T. Udem, M. Weitz, T. W. Hänsch, P. Lemonde, G. Santarelli, M. Abgrall, P. Laurent, C. Salomon, and A. Clairon, Measurement of the hydrogen 1S−2S transition frequency by phase coherent comparison with a microwave cesium fountain clock, Phys. Rev. Lett. 84, 5496 (2000).
  20. C. G. Parthey, A. Matveev, J. Alnis, B. Bernhardt, A. Beyer, R. Holzwarth, A. Maistrou, R. Pohl, K. Predehl, T. Udem, T. Wilken, N. Kolachevsky, M. Abgrall, D. Rovera, C. Salomon, P. Laurent, and T. W. Hänsch, Improved measurement of the hydrogen 1S–2S transition frequency, Phys. Rev. Lett. 107, 203001 (2011).
  21. M. Ahmadi, B. X. R. Alves, C. J. Baker, W. Bertsche, A. Capra, C. Carruth, C. L. Cesar, M. Charlton, S. Cohen, R. Collister, et al., Characterization of the 1S–2S transition in antihydrogen, Nature (London) 557, 71 (2018).
  22. M. Lipeles, R. Novick, and N. Tolk, Direct detection of two-photon emission from the metastable state of singly ionized helium, Phys. Rev. Lett. 15, 690 (1965).
  23. A. Dalgarno and D. R. Bates, Two-photon decay of singlet metastable helium, Mon. Not. R. Astron. Soc. 131, 311 (1966).
  24. G. W. F. Drake, G. A. Victor, and A. Dalgarno, Two-photon decay of the singlet and triplet metastable states of helium-like ions, Phys. Rev. 180, 25 (1969).
  25. A. T. Bondy, D. C. Morton, and G. W. F. Drake, Two-photon decay rates in heliumlike ions: Finite-nuclear-mass effects, Phys. Rev. A 102, 052807 (2020).
  26. Y. Wang, S. Pandey, C. H. Greene, and N. Shivaram, Attosecond entangled photons from two-photon decay of metastable atoms: A source for attosecond experiments and beyond, Phys. Rev. Res. 4, L032038 (2022).
  27. A. Grinin, A. Matveev, D. C. Yost, L. Maisenbacher, V. Wirthl, R. Pohl, T. W. Hänsch, and T. Udem, Two-photon frequency comb spectroscopy of atomic hydrogen, Science 370, 1061 (2020).
  28. T. Mossberg, A. Flusberg, R. Kachru, and S. R. Hartmann, Tri-level echoes, Phys. Rev. Lett. 39, 1523 (1977).
  29. J.-H. Choi, B. Knuffman, T. C. Liebisch, A. Reinhard, and G. Raithel, Cold Rydberg atoms, in Advances in Atomic, Molecular, and Optical Physics, Vol. 54 (Academic Press, 2007), pp. 131–202.
  30. U. Gaubatz, P. Rudecki, S. Schiemann, and K. Bergmann, Population transfer between molecular vibrational levels by stimulated Rraman scattering with partially overlapping laser fields. A new concept and experimental results, J. Chem. Phys. 92, 5363 (1990).
  31. K. Bergmann, H. Theuer, and B. W. Shore, Coherent population transfer among quantum states of atoms and molecules, Rev. Mod. Phys. 70, 1003 (1998).
  32. N. V. Vitanov, A. A. Rangelov, B. W. Shore, and K. Bergmann, Stimulated Rraman adiabatic passage in physics, chemistry, and beyond, Rev. Mod. Phys. 89, 015006 (2017).
  33. L. P. Yatsenko, B. W. Shore, T. Halfmann, K. Bergmann, and A. Vardi, Source of metastable H(2s) atoms using the Stark chirped rapid-adiabatic-passage technique, Phys. Rev. A 60, R4237(R) (1999).
  34. L. P. Yatsenko, V. R. Romanenko, B. W. Shore, T. Halfmann, and K. Bergmann, Two-photon excitation of the metastable 2s state of hydrogen assisted by laser-induced chirped Stark shifts and continuum structure, Phys. Rev. A 71, 033418 (2005).
  35. T. Rickes, L. P. Yatsenko, S. Steuerwald, T. Halfmann, B. W. Shore, N. V. Vitanov, and K. Bergmann, Efficient adiabatic population transfer by two-photon excitation assisted by a laser-induced Stark shift, J. Chem. Phys. 113, 534 (2000).
  36. E. Appi, C. C. Papadopoulou, J. L. Mapa, N. Wesavkar, C. Jusko, P. Mosel, S. Ališauskas, T. Lang, C. M. Heyl, B. Manschwetus, et al., A synchronized VUV light source based on high-order harmonic generation at FLASH, Sci. Rep. 10, 6867 (2020).
  37. K. Konishi, D. Akai, Y. Mita, M. Ishida, J. Yumoto, and M. Kuwata-Gonokami, Tunable third harmonic generation in the vacuum ultraviolet region using dielectric nanomembranes, APL Photonics 5, 066103 (2020).
  38. L. Misoguti, S. Backus, C. G. Durfee, R. Bartels, M. M. Murnane, and H. C. Kapteyn, Generation of broadband VUV light using third-order cascaded processes, Phys. Rev. Lett. 87, 013601 (2001).
  39. R. Forbes, P. Hockett, Q. Leterrier, and R. Lausten, Efficient (∼10%) generation of vacuum ultraviolet femtosecond pulses via four-wave mixing in hollow-core fibers, Opt. Lett. 49, 3178 (2024).
  40. J. M. Dudley, G. Genty, and S. Coen, Supercontinuum generation in photonic crystal fiber, Rev. Mod. Phys. 78, 1135 (2006).
  41. Y.-C. Cheng, C.-H. Lu, Y.-Y. Lin, and A. H. Kung, Supercontinuum generation in a multi-plate medium, Opt. Express 24, 7224 (2016).
  42. S.-J. Im, A. Husakou, and J. Herrmann, High-power soliton-induced supercontinuum generation and tunable sub-10-fs VUV pulses from Kagome-lattice HC-PCFs, Opt. Express 18, 5367 (2010).
  43. N. Y. Joly, J. Nold, W. Chang, P. Hölzer, A. Nazarkin, G. K. L. Wong, F. Biancalana, and P. S. J. Russell, Bright spatially coherent wavelength-tunable deep-UV laser source using an Ar-filled photonic crystal fiber, Phys. Rev. Lett. 106, 203901 (2011).
  44. K. F. Mak, J. C. Travers, P. Hölzer, N. Y. Joly, and P. S. J. Russell, Tunable vacuum-UV to visible ultrafast pulse source based on gas-filled Kagome-PCF, Opt. Express 21, 10942 (2013).
  45. F. Belli, A. Abdolvand, W. Chang, J. C. Travers, and P. S. Russell, Vacuum-ultraviolet to infrared supercontinuum in hydrogen-filled photonic crystal fiber, Optica 2, 292 (2015).
  46. F. Köttig, F. Tani, C. M. Biersach, J. C. Travers, and P. S. Russell, Generation of microjoule pulses in the deep ultraviolet at megahertz repetition rates, Optica 4, 1272 (2017).
  47. A. Ermolov, K. F. Mak, M. H. Frosz, J. C. Travers, and P. S. J. Russell, Supercontinuum generation in the vacuum ultraviolet through dispersive-wave and soliton-plasma interaction in a noble-gas-filled hollow-core photonic crystal fiber, Phys. Rev. A 92, 033821 (2015).
  48. J. C. Travers, T. F. Grigorova, C. Brahms, and F. Belli, High-energy pulse self-compression and ultraviolet generation through soliton dynamics in hollow capillary fibres, Nat. Photonics 13, 547 (2019).
  49. M. Aymar, C. H. Greene, and E. Luc-Koenig, Multichannel Rydberg spectroscopy of complex atoms, Rev. Mod. Phys. 68, 1015 (1996).
  50. B. Kaufman, T. Rozgonyi, P. Marquetand, and T. Weinacht, Adiabatic elimination in strong-field light-matter coupling, Phys. Rev. A 102, 063117 (2020).
  51. P. L. Knight, M. A. Lauder, and B. J. Dalton, Laser-induced continuum structure, Phys. Rep. 190, 1 (1990).
  52. A. Tóth, S. Borbély, Y. Zhou, and A. Csehi, Role of dynamic Stark shifts in strong-field excitation and subsequent ionization, Phys. Rev. A 107, 053101 (2023).
  53. J. N. Bruhnke, E. Olofsson, A. Stenquist, and J. M. Dahlström, Giant counter-rotating oscillations on the attosecond timescale, Phys. Rev. Res. 7, L042019 (2025).
  54. D. Nobis, H. G. Sansom, and S. W. Magennis, Pulse-shaped broadband multiphoton excitation for single-molecule fluorescence detection in the far field, Methods Appl. Fluoresc. 11, 017001 (2023).
  55. D. Meshulach and Y. Silberberg, Coherent quantum control of multiphoton transitions by shaped ultrashort optical pulses, Phys. Rev. A 60, 1287 (1999).
  56. J. Murphy and C. Pellegrini, Free electron lasers for the XUV spectral region, Nucl. Instrum. Methods Phys. Res. Sect. A 237, 159 (1985).
  57. P. Radcliffe, M. Arbeiter, W. B. Li, S. Düsterer, H. Redlin, P. Hayden, P. Hough, V. Richardson, J. T. Costello, T. Fennel, and M. Meyer, Atomic photoionization in combined intense XUV free-electron and infrared laser fields, New J. Phys. 14, 043008 (2012).
  58. P. Finetti, H. Höppner, E. Allaria, C. Callegari, F. Capotondi, P. Cinquegrana, M. Coreno, R. Cucini, M. B. Danailov, A. Demidovich, et al., Pulse duration of seeded free-electron lasers, Phys. Rev. X 7, 021043 (2017).
  59. M. M. Bidhendi, I. J. Bermudez Macias, R. Ivanov, M. V. Yurkov, and S. Düsterer, FEL pulse duration evolution along undulators at FLASH, Appl. Sci. 12, 7048 (2022).
  60. M. Rafiq, S. Hussain, M. Saleem, M. A. Kalyar, and M. A. Baig, Measurement of photoionization cross section from the 3s3p P11 excited state of magnesium, J. Phys. B: At. Mol. Opt. Phys. 40, 2291 (2007).
  61. G. Reitsma, J. Hummert, J. Dura, V. Loriot, M. J. J. Vrakking, F. Lépine, and O. Kornilov, Delayed relaxation of highly excited cationic states in naphthalene, J. Phys. Chem. A 123, 3068 (2019).

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Phys. Rev. Research 8, 013009– Published 8 January, 2026
  • Received 18 September 2025
  • Accepted 10 December 2025
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