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Südmeyer, Thomas

Nom
Südmeyer, Thomas
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Email
thomas.sudmeyer@unine.ch
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https://libra.unine.ch/handle/123456789/816

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  • Publication
    Accès libre
    Frequency Noise Characterization of a 25-GHz Diode-Pumped Mode-Locked Laser With Indirect Carrier-Envelope Offset Noise Assessment
    Brochard, Pierre 
    ;
    Wittwer, Valentin Johannes
    ;
    Bilicki, Slawomir
    ;
    Resan, Bojan
    ;
    Weingarten, Kurt John
    ;
    Schilt, Stephane 
    ;
    Südmeyer, Thomas 
    We present a detailed frequency noise characterization of an ultrafast diode-pumped solid-state laser operating at 25-GHz repetition rate. The laser is based on the gain material Er:Yb:glass and operates at a wavelength of 1.55 μm. Using a beating measure-ment with an ultralow-noise continuous-wave laser in combination with a dedicated electrical scheme, we measured the frequency noise properties of an optical mode of the 25-GHz laser, of its repetition rate and indirectly of its carrier-envelope offset (CEO) signal without detecting the CEO frequency by the standard approach of nonlinear interferometry. We ob-served a strong anticorrelation between the frequency noise of the indirect CEO signal and of the repetition rate in our laser, leading to optical modes with a linewidth below 300 kHz in the free-running laser (at 100-ms integration time), much narrower than the individual contributions of the carrier envelope offset and repetition rate. We explain this behavior by the presence of a fixed point located close to the optical carrier in the laser spectrum for the dominant noise source.
  • Publication
    Accès libre
    Optical rectification of ultrafast Yb lasers: pushing power and bandwidth of terahertz generation in GaP
    Drs, Jakub 
    ;
    Modsching, Norbert 
    ;
    Paradis, Clément 
    ;
    Kränkel, Christian
    ;
    Wittwer, Valentin Johannes
    ;
    Razskazovskaya, Olga
    ;
    Südmeyer, Thomas 
    We demonstrate broadband high-power terahertz (THz) generation at megahertz repetition rates by optical rectification in GaP driven by an ultrafast Yb-based thin-disk laser (TDL) oscillator. We investigate the influence of pulse duration in the range of 50–220 fs and thickness of the GaP crystal on the THz generation. Optimization of these parameters with respect to the broadest spectral bandwidth yields a gap-less THz spectrum extending to nearly 7 THz. We further tailor the driving laser and the THz generation parameters for the highest average power, demonstrating 0.3 mW THz radiation with a spectrum extending to 5 THz. This was achieved using a 0.5 mm thick GaP crystal pumped with a 95 fs, 20 W TDL, operating at 48 MHz repetition rate. We also provide a simple method to estimate the THz spectrum, which can be used for design and optimization of similar THz systems.
  • Publication
    Accès libre
    Frequency Comb Stabilization of Ultrafast Lasers by Opto-Optical Modulation of Semiconductors
    Gürel, Kutan
    ;
    Hakobyan, Sargis 
    ;
    Wittwer, Valentin Johannes
    ;
    Schilt, Stephane 
    ;
    Südmeyer, Thomas 
    In this paper, we review the current state and discuss new developments in opto-optical modulation (OOM) of semiconductor elements for frequency comb self-referenced stabilization of ultrafast lasers. This method has been successfully used for carrier-envelope offset (CEO) frequency stabilization of diodepumped solid-state lasers operating in 1-μm and 1.5-μm regimes, providing high feedback bandwidth and resulting in low noise performance. We compare the achieved results for Er- and Yb-based laser materials and in different regimes of repetition rates up to 1 GHz. In addition, we present the first semiconductor OOM for CEO stabilization in an ultrafast fiber laser. Moreover, we discuss requirements and design guidelines for OOM chips. In most demonstrations, semiconductor saturable absorber mirrors have been used for OOM, which in parallel were also responsible for pulse formation. By separating the OOM functionality from the pulse formation, we expect that it will enable low-noise CEO stabilization in other types of ultrafast lasers, such as, for example, high-power Kerr-lens mode-locked thin disk lasers.
  • Publication
    Accès libre
    XUV Sources Based on Intra-Oscillator High Harmonic Generation with Thin-Disk Lasers: Current Status and Prospects
    Labaye, François
    ;
    Gaponenko, Maxim 
    ;
    Modsching, Norbert 
    ;
    Brochard, Pierre 
    ;
    Paradis, Clément 
    ;
    Schilt, Stephane 
    ;
    Wittwer, Valentin Johannes
    ;
    Südmeyer, Thomas 
    Ultrafast thin-disk laser (TDL) oscillators provide higher intracavity pulse energy, average power, and peak power levels than any other femtosecond laser oscillator technology. They are suitable for driving extreme nonlinear interactions directly inside the laser oscillator. High harmonic generation (HHG) driven inside ultrafast TDL oscillators is a very recent approach for the generation of coherent extreme ultraviolet (XUV) light at multi-megahertz repetition rates. In this paper, we review the current state of the development, discuss the technological potential, and give an outlook toward the future developments. We compare the current performance to established technologies and evalu-ate possible limitations. We discuss future improvements, such as reduction of the driving pulse duration and increase of the intracavity peak power, efficient extraction of the XUV light from the cavity, and carrier-envelope offset frequency stabilization of the generated XUV light. Due to the power scalability of the TDL concept and the possibility to operate in a spectrally broadened regime with pulse durations below the gain bandwidth limitation, intra-oscillator HHG with TDLs has a high potential for powerful table-top multi-megahertz coherent XUV light sources for science and applications.