Widely tunable extreme UV frequency comb generation

Pinkert, T. J.; Kandula, D. Z.; Gohle, Christoph; Barmes, Itan; Morgenweg, J.; Eikema, K.S.E.

doi:10.1364/ol.36.002026

Cited by 8 publications

(4 citation statements)

References 15 publications

(20 reference statements)

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“…This is based on parametric amplification of two frequency-comb pulses combined with harmonic upconversion. A wide and continuous tunability from 85 to 51 nm was demonstrated for the method with spectroscopy in argon, neon, and helium [54]. In the current paper a full and detailed description is given of the precision spectroscopy performed in helium [53].…”

Section: Introductionmentioning

confidence: 99%

XUV frequency-comb metrology on the ground state of helium

et al. 2011

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The operation of a frequency comb at extreme ultraviolet (xuv) wavelengths based on pairwise amplification and nonlinear upconversion to the 15th harmonic of pulses from a frequency-comb laser in the near-infrared range is reported. It is experimentally demonstrated that the resulting spectrum at 51 nm is fully phase coherent and can be applied to precision metrology. The pulses are used in a scheme of direct-frequency-comb excitation of helium atoms from the ground state to the 1s4p and 1s5p 1 P 1 states. Laser ionization by auxiliary 1064 nm pulses is used to detect the excited-state population, resulting in a cosine-like signal as a function of the repetition rate of the frequency comb with a modulation contrast of up to 55%. Analysis of the visibility of this comb structure, thereby using the helium atom as a precision phase ruler, yields an estimated timing jitter between the two upconverted-comb laser pulses of 50 attoseconds, which is equivalent to a phase jitter of 0.38 (6) cycles in the xuv at 51 nm. This sets a quantitative figure of merit for the operation of the xuv comb and indicates that extension to even shorter wavelengths should be feasible. The helium metrology investigation results in transition frequencies of 5 740 806 993 (10) and 5 814 248 672 (6) MHz for excitation of the 1s4p and 1s5p 1 P 1 states, respectively. This constitutes an important frequency measurement in the xuv, attaining high accuracy in this windowless part of the electromagnetic spectrum. From the measured transition frequencies an eight-fold-improved 4 He ionization energy of 5 945 204 212 (6) MHz is derived. Also, a new value for the 4 He ground-state Lamb shift is found of 41 247 (6) MHz. This experimental value is in agreement with recent theoretical calculations up to order mα 6 and m 2 /Mα 5 , but with a six-times-higher precision, therewith providing a stringent test of quantum electrodynamics in bound two-electron systems.

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Section: Introductionmentioning

confidence: 99%

XUV frequency-comb metrology on the ground state of helium

et al. 2011

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“…Based on parametric amplification, Ramsey-comb spectroscopy combines high frequency precision with wide wavelength coverage at mJ-level pulse energy. Because of the high peak energy, the frequency range of this method can straightforwardly and efficiently be extended via nonlinear crystals to the ultraviolet, or with high-harmonic generation in a gas jet to the extreme ultraviolet [23] (taking T > 100 ns to avoid phase shifts from ionisation in the gas jet). Therefore there are many interesting targets for the Ramsey-comb method, such as the 1S-2S two-photon transition in He + to provide new information on the proton-size puzzle [24,25], or the twophoton X-EF transition in molecular hydrogen to put tighter constraints on speculative 5 th forces beyond the Standard Model [26].…”

Section: Figure 2: Schematic Of the Experimental Setupmentioning

confidence: 99%

Ramsey-comb spectroscopy with intense ultrashort laser pulses

Morgenweg¹,

Barmes²,

Eikema³

2013

Nature Phys

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Optical frequency combs based on mode-locked lasers have revolutionised the field of metrology and precision spectroscopy by providing precisely calibrated optical frequencies and coherent pulse trains. Amplification of the pulsed output from these lasers is very desirable, as nonlinear processes can then be employed to cover a much wider range of transitions and wavelengths for ultra-high precision, direct frequency comb spectroscopy. Therefore full repetition rate laser amplifiers and enhancement resonators have been employed to produce up to microjoule-level pulse energies. Here we show that the full frequency comb accuracy and resolution can be obtained by using only two frequency comb pulses amplified to the millijoule pulse energy level, orders of magnitude more energetic than what has previously been possible. The novel properties of this approach, such as cancellation of optical light-shift effects, is demonstrated on weak two-photon transitions in atomic rubidium and caesium, thereby improving the frequency accuracy up to thirty times.Comment: 16 pages (including supporting material), 6 figures and 2 table

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“…However, for our purposes we need spectra with no spurious or missing levels, which demands FC coverage from the visible to the mid-UV and, perhaps, even into the vacuum-UV or extreme-UV for ionized species. Such FCs already exist in the visible and near-IR, and rapid progress has been made in extending FCs to the mid-IR [27], to the VUV [28], and even into the XUV [29][30][31]. As this technology continues to improve, measuring the necessary spectra seems quite achievable.…”

Section: Sensitivity and Experimental Realizationmentioning

confidence: 99%

Proposed search forT-odd,P-even interactions in spectra of chaotic atoms

Morrison

Derevianko

2012

Phys. Rev. A

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Violation of fundamental symmetries in atoms is the subject of intense experimental and theoretical interest. P-odd, T-even transitions have been observed and are in excellent agreement with electroweak theory. Searches for permanent electric dipole moments have placed bounds on T-odd, P-odd interactions, constraining proposed extensions to the standard model of elementary particles. Here we propose a search for T-odd, P-even (TOPE) interactions in atoms. We consider open-shell atoms, such as rare-earth-metal atoms, which have dense, chaotic excitation spectra with strong level repulsion. The strength of the level repulsion depends on the underlying symmetries of the atomic Hamiltonian. TOPE interactions lead to enhanced level repulsion. We demonstrate how a statistical analysis of many chaotic spectra can determine the strength of level repulsion; in particular, the variance of the number of levels in an energy range has been shown to be a useful measure. We estimate that, using frequency comb spectroscopy, a sufficient number of chaotic levels could be measured to match or exceed the current experimental bounds on TOPE interactions.

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Widely tunable extreme UV frequency comb generation

Cited by 8 publications

References 15 publications

XUV frequency-comb metrology on the ground state of helium

XUV frequency-comb metrology on the ground state of helium

Ramsey-comb spectroscopy with intense ultrashort laser pulses

Proposed search forT-odd,P-even interactions in spectra of chaotic atoms

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