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Zhu M, Xiao Z, Zhang H, Hua L, Liu Y, Zuo Z, Xu S, Liu X. Measurement of the linewidth of a home-built vacuum ultraviolet comb by frequency comb spectroscopy on NO 2. OPTICS LETTERS 2024; 49:3757-3760. [PMID: 38950260 DOI: 10.1364/ol.519912] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Accepted: 06/03/2024] [Indexed: 07/03/2024]
Abstract
Optical frequency comb in the vacuum ultraviolet (VUV)/extreme ultraviolet (XUV) region has attracted a great deal of attention, as it provides coherent VUV/XUV radiation source with a rather narrow bandwidth, facilitating precise spectroscopic measurements in the short wavelength regime. In this study, we report on the linewidth measurement of a home-built VUV comb centered at 148 nm using direct frequency comb spectroscopy with NO2. The measurement reveals that the upper bound of our comb linewidth is less than 28 MHz. Fitting the whole trace with different repetition rates shows that the center frequency of the excitation is 2 021.25 ± 0.24 THz (∼148.32 nm). Thus, we assigned this excitation to the transition from the 6a1 orbital (ν1'=0, ν2'=0) to the 3pσu orbital (ν1'=3, ν2'=8) in NO2. Our work demonstrates that VUV combs are potentially powerful tools for precision spectroscopic measurements in the short wavelength regime.
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Seres E, Seres J, Martinez-de-Olcoz L, Schumm T. Compact tunable 80 MHz repetition rate vacuum ultraviolet light source up to 10 eV: intracavity high harmonic generation by nonlinear reflection on a AlN nanofilm in a mode locked Ti:sapphire oscillator. OPTICS EXPRESS 2024; 32:17593-17605. [PMID: 38858940 DOI: 10.1364/oe.522309] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Accepted: 04/11/2024] [Indexed: 06/12/2024]
Abstract
We report the realization of an intra-oscillator high harmonic source based on a Kerr lens mode locked Ti:sapphire laser running at 80 MHz repetition rate. A nonlinear medium consisting of an AlN nanofilm on a thin sapphire substrate is placed inside the oscillator cavity. The harmonics are generated, in reflection geometry, on the AlN nanofilm, directing the harmonic beam out of the cavity. Exploiting the benefits of this approach, a compact size, tunable, high repetition rate and coherent vacuum ultraviolet light source with a spectrum up to the 7th harmonic has been achieved. In particular, the powerful 5th harmonic covering the 145-163 nm range aims to be an attractive tunable light source for spectroscopical applications.
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Gong Q, Tao S, Zhao C, Hang Y, Zhu S, Ma L. Structures and Properties of High-Concentration Doped Th:CaF 2 Single Crystals for Solid-State Nuclear Clock Materials. Inorg Chem 2024; 63:3807-3814. [PMID: 38345921 DOI: 10.1021/acs.inorgchem.3c04009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/27/2024]
Abstract
Thorium-doped vacuum ultraviolet (VUV) transparent crystals is a promising candidate for establishing a solid-state nuclear clock. Here, we report the research results on high-concentration doping of 232Th:CaF2 single crystals. The structures, defects, and VUV transmittance performances of highly doped Th:CaF2 crystals are investigated by theoretical and experimental methods. The defect configurations formed by Th and the charge compensation mechanism (Ca vacancy or interstitial F atoms) located at its first nearest neighbor position are mainly considered and studied. The preferred defect configuration is identified according to the doping concentration dependence of structural changes caused by the defects and the formation energies of the defects at different Ca or F chemical potentials. The cultivated Th:CaF2 crystals maintain considerable high VUV transmittance levels while accommodating high doping concentrations, showcasing an exceptional comprehensive performance. The transmittances of 1-mm-thick samples with doping concentrations of 1.91 × 1020 and 2.76 × 1020 cm-3 can reach ∼62% and 53% at 150 nm, respectively. The VUV transmittance exhibits a weak negative doping concentration dependence. The system factors that may cause distortion and additional deterioration of the VUV transmittance are discussed. Balancing and controlling the impacts of various factors will be of great significance for fully exploiting the advantages of Th:CaF2 and other Th-doped crystals for a solid-state nuclear optical clock.
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Affiliation(s)
- Qiaorui Gong
- Research Center of Laser Crystal, Key Laboratory of High-Power Laser Materials, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Siliang Tao
- Research Center of Laser Crystal, Key Laboratory of High-Power Laser Materials, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
| | - Chengchun Zhao
- Research Center of Laser Crystal, Key Laboratory of High-Power Laser Materials, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
| | - Yin Hang
- Research Center of Laser Crystal, Key Laboratory of High-Power Laser Materials, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
| | - Shining Zhu
- National Laboratory of Solid-State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, Jiangsu 210093, China
| | - Longsheng Ma
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
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Schönberg A, Salman HS, Tajalli A, Kumar S, Hartl I, Heyl CM. Below-threshold harmonic generation in gas-jets for Th-229 nuclear spectroscopy. OPTICS EXPRESS 2023; 31:12880-12893. [PMID: 37157438 DOI: 10.1364/oe.486338] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The generation of below-threshold harmonics in gas-jets constitutes a promising path towards optical frequency combs in the vacuum ultra-violet (VUV) spectral range. Of particular interest is the 150 nm range, which can be exploited to probe the nuclear isomeric transition of the Thorium-229 isotope. Using widely available high-power, high-repetition-rate Ytterbium-based laser sources, VUV frequency combs can be generated through the process of below-threshold harmonic generation, in particular 7th harmonic generation of 1030 nm. Knowledge about the achievable efficiencies of the harmonic generation process is crucial for the development of suitable VUV sources. In this work, we measure the total output pulse energies and conversion efficiencies of below-threshold harmonics in gas-jets in a phase-mismatched generation scheme using Argon and Krypton as nonlinear media. Using a 220 fs, 1030 nm source, we reach a maximum conversion efficiency of 1.1 × 10-5 for the 7th harmonic (147 nm) and 0.78 × 10-4 for the 5th harmonic (206 nm). In addition, we characterize the 3rd harmonic of a 178 fs, 515 nm source with a maximum efficiency of 0.3%.
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Zhang C, Li P, Jiang J, von der Wense L, Doyle JF, Fermann ME, Ye J. Tunable VUV frequency comb for 229mTh nuclear spectroscopy. OPTICS LETTERS 2022; 47:5591-5594. [PMID: 37219278 DOI: 10.1364/ol.473006] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Accepted: 10/10/2022] [Indexed: 05/24/2023]
Abstract
Laser spectroscopy of the 229mTh nuclear clock transition is necessary for the future construction of a nuclear-based optical clock. Precision laser sources with broad spectral coverage in the vacuum ultraviolet are needed for this task. Here, we present a tunable vacuum-ultraviolet frequency comb based on cavity-enhanced seventh-harmonic generation. Its tunable spectrum covers the current uncertainty range of the 229mTh nuclear clock transition.
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Fischer J, Drs J, Labaye F, Modsching N, Müller M, Wittwer VJ, Südmeyer T. Efficient XUV-light out-coupling of intra-cavity high harmonics by a coated grazing-incidence plate. OPTICS EXPRESS 2022; 30:30969-30979. [PMID: 36242190 DOI: 10.1364/oe.458946] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Accepted: 06/07/2022] [Indexed: 06/16/2023]
Abstract
We experimentally demonstrate an efficient and broadband extreme-ultraviolet light (XUV) out-coupling mechanism of intra-cavity generated high harmonics. The mechanism is based on a coated grazing-incidence plate (GIP), which utilizes the enhanced reflectivity of s-polarized light in comparison to p-polarized light for large angles of incidence (AoI). We design and produce a 60°-AoI coated GIP, tailored specifically for the high demands inside a sub-50-fs Kerr-lens mode-locked Yb:YAG thin-disk laser oscillator in which high harmonic generation (HHG) is driven at ∼450 MW peak power and 17 MHz repetition rate. The coated GIP features an XUV out-coupling efficiency of >25% for photon energies ranging from 10 eV to 60 eV while being anti-reflective for the driving laser field. The XUV spectra reach up to 52 eV in argon and 30 eV in xenon. In a single harmonic, we out-couple 1.3 µW of XUV average power at 37 eV in argon and 5.4 µW at 25 eV in xenon. The combination of an improved HHG driving laser performance and the out-coupling via the coated GIP enabled us to increase the out-coupled XUV average power in a single harmonic by a factor of 20 compared to previous HHG inside ultrafast laser oscillators. Our source approaches the state-of-the-art out-coupled XUV power levels per harmonic of femtosecond enhancement cavities operating at comparable photon energies.
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Turnbaugh C, Axelrod JJ, Campbell SL, Dioquino JY, Petrov PN, Remis J, Schwartz O, Yu Z, Cheng Y, Glaeser RM, Mueller H. High-power near-concentric Fabry-Perot cavity for phase contrast electron microscopy. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2021; 92:053005. [PMID: 34243315 PMCID: PMC8159438 DOI: 10.1063/5.0045496] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Accepted: 05/02/2021] [Indexed: 06/13/2023]
Abstract
Transmission electron microscopy (TEM) of vitrified biological macromolecules (cryo-EM) is limited by the weak phase contrast signal that is available from such samples. Using a phase plate would thus substantially improve the signal-to-noise ratio. We have previously demonstrated the use of a high-power Fabry-Perot cavity as a phase plate for TEM. We now report improvements to our laser cavity that allow us to achieve record continuous wave intensities of over 450 GW/cm2, sufficient to produce the optimal 90° phase shift for 300 keV electrons. In addition, we have performed the first cryo-EM reconstruction using a laser phase plate, demonstrating that the stability of this laser phase plate is sufficient for use during standard cryo-EM data collection.
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Affiliation(s)
| | | | | | | | - Petar N. Petrov
- Department of Physics, 366 Physics MS 7300, University of California-Berkeley, Berkeley, California 94720, USA
| | - Jonathan Remis
- California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, California 94720, USA
| | - Osip Schwartz
- Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Zanlin Yu
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California 94158, USA
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Nauta J, Oelmann JH, Borodin A, Ackermann A, Knauer P, Muhammad IS, Pappenberger R, Pfeifer T, Crespo López-Urrutia JR. XUV frequency comb production with an astigmatism-compensated enhancement cavity. OPTICS EXPRESS 2021; 29:2624-2636. [PMID: 33726454 DOI: 10.1364/oe.414987] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Accepted: 12/21/2020] [Indexed: 06/12/2023]
Abstract
We have developed an extreme ultraviolet (XUV) frequency comb for performing ultra-high precision spectroscopy on the many XUV transitions found in highly charged ions (HCI). Femtosecond pulses from a 100 MHz phase-stabilized near-infrared frequency comb are amplified and then fed into a femtosecond enhancement cavity (fsEC) inside an ultra-high vacuum chamber. The low-dispersion fsEC coherently superposes several hundred incident pulses and, with a single cylindrical optical element, fully compensates astigmatism at the w0 = 15 µm waist cavity focus. With a gas jet installed there, intensities reaching ∼ 1014 W/cm2 generate coherent high harmonics with a comb spectrum at 100 MHz rate. We couple out of the fsEC harmonics from the 7th up to the 35th (42 eV; 30 nm) to be used in upcoming experiments on HCI frequency metrology.
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