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Brochard, Pierre

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Brochard, Pierre
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https://libra.unine.ch/handle/123456789/1021

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  • Publication
    Accès libre
    Carrier-envelope offset frequency stabilization of a gigahertz semiconductor disk laser
    Jornod, Nayara 
    ;
    Gürel, Kutan
    ;
    Wittwer, Valentin 
    ;
    Brochard, Pierre 
    ;
    Hakobyan, Sargis 
    ;
    Schilt, Stephane 
    ;
    Waldburger, Dominik
    ;
    Keller, Ursula
    ;
    Südmeyer, Thomas 
    Optical frequency combs based on ultrafast lasers have enabled numerous scientific breakthroughs. However, their use for commercial applications is limited by the complexity and cost of femtosecond laser technology. Ultrafast semiconductor lasers might change this issue as they can be mass produced in a cost-efficient way while providing large spectral coverage from a single technology. However, it has not been proven to date if ultrafast semiconductor lasers are suitable for stabilization of their carrier-envelope offset (CEO) frequency. Here we present what we believe to be the first CEO frequency stabilization of an ultrafast semiconductor disk laser (SDL). The optically pumped SDL is passively modelocked by a semiconductor saturable absorber mirror. It operates at a repetition rate of 1.8 GHz and a center wavelength of 1034 nm. The 273 fs pulses of the oscillator are amplified to an average power level of 6 W and temporally compressed down to 120 fs. A coherent octave-spanning supercontinuum spectrum is generated in a photonic crystal fiber. The CEO frequency is detected in a standard ƒ–to–2ƒ interferometer and phase locked to an external reference by feedback applied to the current of the SDL pump diode. This proof-of-principle demonstrates that ultrafast SDLs are suitable for CEO stabilization and constitutes a key step for further developments of this comb technology expected in the coming years.
  • Publication
    Accès libre
    Carrier-envelope offset frequency stabilization of a thin-disk laser oscillator operating in the strongly self-phase modulation broadened regime
    Modsching, Norbert 
    ;
    Paradis, Clément 
    ;
    Brochard, Pierre 
    ;
    Jornod, Nayara 
    ;
    Gürel, Kutan
    ;
    Kränkel, Christian
    ;
    Schilt, Stephane 
    ;
    Wittwer, Valentin 
    ;
    Südmeyer, Thomas 
    We demonstrate the carrier-envelope offset (CEO) frequency stabilization of a Kerr lens mode-locked Yb:Lu2O3 thin-disk laser oscillator operating in the strongly self-phase modulation (SPM) broadened regime. This novel approach allows overcoming the intrinsic gain bandwidth limit and is suited to support frequency combs from sub-100-fs pulse trains with very high output power. In this work, strong intra-oscillator SPM in the Kerr medium enables the optical spectrum of the oscillating pulse to exceed the bandwidth of the gain material Yb: Lu2O3 by a factor of two. This results in the direct generation of 50-fs pulses without the need for external pulse compression. The oscillator delivers an average power of 4.4 W at a repetition rate of 61 MHz. We investigated the cavity dynamics in this regime by characterizing the transfer function of the laser output power for pump power modulation, both in continuous-wave and mode-locked operations. The cavity dynamics in mode-locked operation limit the CEO modulation bandwidth to ~10 kHz. This value is sufficient to achieve a tight phase-lock of the CEO beat via active feedback to the pump current and yields a residual in-loop integrated CEO phase noise of 197 mrad integrated from 1 Hz to 1 MHz.
  • Publication
    Accès libre
    First investigation of the noise and modulation properties of the carrier-envelope offset in a modelocked semiconductor laser
    Brochard, Pierre 
    ;
    Jornod, Nayara 
    ;
    Schilt, Stephane 
    ;
    Wittwer, Valentin 
    ;
    Hakobyan, Sargis 
    ;
    Waldburger, Dominik
    ;
    Link, Sandro M
    ;
    Alfieri, Cesare G. E
    ;
    Golling, Matthias
    ;
    Devenoges, Laurent 
    ;
    Morel, Jacques
    ;
    Keller, Ursula
    ;
    Südmeyer, Thomas. Laboratoire Temps-Fréquence, Université de Neuchâtel, Switzerland
    We present the first characterization of the noise properties and modulation response of the carrier-envelope offset (CEO) frequency in a semiconductor modelocked laser. The CEO beat of an optically-pumped vertical external-cavity surface-emitting laser (VECSEL) at 1030 nm was characterized without standard ƒ-to-2ƒ interferometry. Instead, we used an appropriate combination of signals obtained from the modelocked oscillator and an auxiliary continuous-wave laser to extract information about the CEO signal. The estimated linewidth of the free-running CEO beat is approximately 1.5 MHz at 1-s observation time, and the feedback bandwidth to enable a tight CEO phase lock to be achieved in a future stabilization loop is in the order of 300 kHz. We also characterized the amplitude and phase of the pump current to CEO-frequency transfer function, which showed a 3-dB bandwidth of ∼300 kHz for the CEO frequency modulation. This fulfills the estimated required bandwidth and indicates that the first self-referenced phase-stabilization of a modelocked semiconductor laser should be feasible in the near future.
  • Publication
    Accès libre
    Frequency comb metrology with an optical parametric oscillator
    Balskus, K
    ;
    Schilt, Stephane 
    ;
    Wittwer, Valentin 
    ;
    Brochard, Pierre 
    ;
    Ploetzing, T
    ;
    Jornod, Nayara 
    ;
    McCracken, R. A
    ;
    Zhang, Z
    ;
    Bartels, A
    ;
    Reid, D. T
    ;
    Südmeyer, Thomas 
    We report on the first demonstration of absolute frequency comb metrology with an optical parametric oscillator (OPO) frequency comb. The synchronously-pumped OPO operated in the 1.5-μm spectral region and was referenced to an H-maser atomic clock. Using different techniques, we thoroughly characterized the frequency noise power spectral density (PSD) of the repetition rate frep, of the carrier-envelope offset frequency fCEO, and of an optical comb line νN. The comb mode optical linewidth at 1557 nm was determined to be ~70 kHz for an observation time of 1 s from the measured frequency noise PSD, and was limited by the stability of the microwave frequency standard available for the stabilization of the comb repetition rate. We achieved a tight lock of the carrier envelope offset frequency with only ~300 mrad residual integrated phase noise, which makes its contribution to the optical linewidth negligible. The OPO comb was used to measure the absolute optical frequency of a near-infrared laser whose second-harmonic component was locked to the F = 2→3 transition of the 87Rb D2 line at 780 nm, leading to a measured transition frequency of νRb = 384,228,115,346 ± 16 kHz. We performed the same measurement with a commercial fiber-laser comb operating in the 1.5-μm region. Both the OPO comb and the commercial fiber comb achieved similar performance. The measurement accuracy was limited by interferometric noise in the fibered setup of the Rb-stabilized laser.