PRECISION RAMSEY-COMB SPECTROSCOPY OF MOLECULAR HYDROGEN IN THE DEEP-UV

High-precision spectroscopy experiments with simple atomic and molecular systems provide important benchmarks for tests of bound-state Quantum Electrodynamics (QED). In recent years there has been significant progress in both experiment [1,2] and theory [3] for QED tests in H$_{2}$. Even investigations of the proton radius puzzle [4] might become feasible in this molecule if the dissociation energy can be determined at a level of 10 kHz [3]. For this latter target, we developed an excitation method, Ramsey-comb spectroscopy, that enables kHz-level precision spectroscopy in the deep-UV. The method is based on excitation with amplified and upconverted frequency comb laser pulses [5]. It has allowed us to measure the $EF^{1} \Sigma_{g}^{+} - X^{1} \Sigma_{g}^{+}(0,0)$ Q1 two-photon transition at 202 nm with an accuracy of 73 kHz [6]. This result is two orders of magnitude better than obtained with previous experiments, and combined with future improved measurements of the EF ionization energy, this could lead to a dissociation energy with an uncertainty below 100 kHz. New measurements from V=1 and N=0 are now in preparation. Moreover, a new setup has been constructed to extend Ramsey-comb spectroscopy to the vacuum- and extreme-ultraviolet spectral region through high-harmonic generation, and an experiment is in preparation to demonstrate this. \newline \newline [1] J. Liu et al., J. Chem. Phys. 130, 174306 (2009) \newline [2] W. Ubachs et al., J. Mol. Spectr. 320, 1-12 (2016) \newline [3] M. Puchalski et al., Phys. Rev. A 95, 052506 (2017) \newline [4] R. Pohl et al., Science 353, 669 (2016) \newline [5] J. Morgenweg et al., Nature Physics 10, 30-33 (2014) \newline [6] R.K. Altmann et al., Phys. Rev. Lett. 120, 043204 (2018) \newlin

Precision measurements in helium at 58 nm: Ground state Lamb shift and the 1 S-1 2 P-1 transition isotope shift

A source of narrow bandwidth (<800 MHz) tunable laser radiation at 58.4 nm has been developed and is applied to record the 11S-21P transition in 3He and 4He. From the 4He transition frequency of 171 134.8936(58) cm-1 a fivefold improved ground state Lamb shift of 1.3763(58) cm-1 is deduced, in good agreement with the theoretical value of 1.3755(10) cm-1. The measured 11S-21P transition isotope shift of 263410(7) MHz presents a more than 2 order of magnitude improvement over a previous value and agrees with a theoretical value of 263411.26(11) MHz

High-power parametric amplification of 11.8-fs laser pulses with carrier-envelope phase control

Phase-stable parametric chirped-pulse amplification of ultrashort pulses from a carrier-envelope phase-stabilized mode-locked Ti:sapphire oscillator (11.0 fs) to 0.25 mJ/pulse at 1 kHz is demonstrated. Compression with a grating compressor and a LCD shaper yields near-Fourier-limited 11.8-fs pulses with an energy of 0.12 mJ. The amplifier is pumped by 532-nm pulses from a synchronized mode-locked laser, Nd:YAG amplifier system. This approach is shown to be promising for the next generation of ultrafast amplifiers aimed at producing terawatt-level phase-controlled few-cycle laser pulses. (C) 2005 Optical Society of America

NARROW-BAND EXTREME-ULTRAVIOLET LASER-RADIATION TUNABLE IN THE RANGE 90.5-95-NM - APPLICATION TO THE SPECTROSCOPY OF N2

Abstract. Tunable, narrowband extreme ultraviolet radiation in the range 90.5-95 nm with only limited intensity variations is produced by frequency-tripling ultraviolet light from a frequency-doubled dye laser in a gas-jet of xenon, Acetylene gas is found to be an efficient medium for thirdharmonic generation in this wavelength range as well. The extreme-ultraviolet radiation is applied in a spectroscopic study of the blH~, v = 6-8 andv = 10-12, oIH~, v = 0 and b ~ 1 r~, + v = 9 states of molecular nitrogen. From linewidth measurements a value kp = 6 x 10 l ° s-1 for the predissoci-ation rate of the b 1H,~, v = 11 state is deduced. PACS: 42.65.Ky, 33.20.Ni, 95.30.Ky In recent years various nonlinear optical wave-mixing techniques have been explored for the generation of coherent Extreme-UltraViolet (XUV) radiation at wavelengths belo

Frequency comb generation by CW laser injection into a quantum-dot mode-locked laser

100 GHz) RF generation and telecommunication applications. (C) 2012 Optical Society of Americ

Phase stability of terawatt-class ultrabroadband parametric amplification

The phase stability of broadband (280 nm bandwidth) terawatt-class parametric amplification was measured, for the first time to our knowledge, with a combination of spatial and spectral interferometry. Measurements at four different wavelengths from 750 to 900 nm were performed in combination with numerical modeling. The phase stability is better than 1/23 rms of an optical cycle for all the measured wavelengths, depending on the phase-matching conditions in the amplifier. (C) 2007 Optical Society of America

Frequency comb laser spectroscopy in the vacuum-ultraviolet region

1/30 of a vuv cycle). The produced vuv pulses are well suited to perform frequency comb spectroscopy with sub-MHz accuracy, which is experimentally verified using a Ramsey-type quantum interference scheme to excite a transition in xenon at 125 nm. The achieved resolution constitutes an improvement of six orders of magnitude compared to previous demonstrations of frequency domain quantum interference in this wavelength range