Phase cycling of extreme ultraviolet pulse sequences generated in rare gases

Abstract

The development of schemes for coherent nonlinear time-domain spectroscopy in the extreme-ultraviolet regime (XUV) has so far been impeded by experimental difficulties that arise at these short wavelengths. In this work we present a novel experimental approach, which facilitates the timing control and phase cycling of XUV pulse sequences produced by harmonic generation in rare gases. The method is demonstrated for the generation and high spectral resolution characterization of narrow-bandwidth harmonics (≈14 eV) in argon and krypton. Our technique simultaneously provides high phase stability and a pathway-selective detection scheme for nonlinear signals—both necessary prerequisites for all types of coherent nonlinear spectroscopy.

High-resolution two-dimensional electronic spectroscopy reveals homogeneous line profiles in isolated nanoparticles

“…This method combines carrier-envelope-phase modulation of the optical pulses on a shot-to-shot basis with efficient lock-in amplification, which suppresses phase noise in the interferometric measurement and greatly enhances the detection sensitivity (Details in Method section). These properties enabled several studies of highly dilute samples [39,33,40] and quantum interference measurements at extremely short wavelengths [41,42]. We use the method here with fluorescence detection to selectively extract the nonlinear 2DES signals as well as the linear absorption of the sample.…”

Extreme ultraviolet wave packet interferometry of the autoionizing HeNe dimer

“…The major technical obstacles are (i) the demand for extreme phase stability to perform XUV/Xray WPI, and (ii) the lack of selective/background-free probes to recover the weak nonlinear signals of interest. These ingredients were demonstrated in separate experiments: on the one hand, in XUV and soft X-ray interferometry [7][8][9][10][11][12][13][14][15], on the other hand, in backgroundfree NIR-XUV/X-ray four-wave-mixing schemes [16][17][18][19]. Only recently, the combination of both ingredients was achieved in a single experiment by introducing a phasecycling concept for XUV pulses [10,11].…”

A flexible and scalable, fully software-based lock-in amplifier for nonlinear spectroscopy

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