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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
    Coherently-averaged dual comb spectrometer at 7.7 µm with master and follower quantum cascade lasers
    (2021-6)
    Komagata, Kenichi N. 
    ;
    Shehzad, Atif 
    ;
    Terrasanta, Giulio
    ;
    Brochard, Pierre 
    ;
    Matthey-De-L'Endroit, Renaud 
    ;
    Gianella, Michele
    ;
    Jouy, Pierre
    ;
    Kapsalidis, Filippos
    ;
    Shahmohammadi Mehran, Mehran
    ;
    Beck Matthias, Matthias
    ;
    Wittwer, Valentin 
    ;
    Faist, Jérôme
    ;
    Emmenegger, Lukas
    ;
    Südmeyer, Thomas 
    ;
    Hugi, Andreas
    ;
    Schilt, Stephane 
    We demonstrate coherent averaging of the multi-heterodyne beat signal between two quantum cascade laser frequency combs in a master-follower configuration. The two combs are mutually locked by acting on the drive current to control their relative offset frequency and by radio-frequency extraction and injection locking of their intermode beat signal to stabilize their mode spacing difference. By implementing an analog common-noise subtraction scheme, a reduction of the linewidth of all heterodyne beat notes by five orders of magnitude is achieved compared to the free-running lasers. We compare stabilization and post-processing corrections in terms of amplitude noise. While they give similar performances in terms of signal-to-noise ratio, real-time processing of the stabilized signal is less demanding in terms of computational power. Lastly, a proof-of-principle spectroscopic measurement was performed, showing the possibility to reduce the amount of data to be processed by three orders of magnitude, compared to the free-running system.
  • Publication
    Accès libre
    Characterizing the carrier-envelope offset in an optical frequency comb without traditional f-to-2f interferometry
    Brochard, Pierre 
    ;
    Schilt, Stephane 
    ;
    Wittwer, Valentin 
    ;
    Südmeyer, Thomas 
    We present a new method to measure the frequency noise and modulation response of the carrier-envelope offset (CEO) beat of an optical frequency comb that does not make use of the traditional f-to-2f interferometry. Instead, we use an appropriate combination of different signals to extract the contribution of the CEO frequency without directly detecting it. We present a proof-of-principle validation realized with a commercial Er:fiber frequency comb and show an excellent agreement with the results obtained using a standard f-to-2f interferometer. This approach is attractive for the characterization of novel frequency comb technologies for which self-referencing is challenging, such as semiconductor mode-locked lasers, microresonator-based systems, or GHz repetition rate lasers.
  • 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
    Full stabilization and characterization of an optical frequency comb from a diode-pumped solid-state laser with GHz repetition rate
    Hakobyan, Sargis 
    ;
    Wittwer, Valentin 
    ;
    Brochard, Pierre 
    ;
    Gürel, Kutan
    ;
    Schilt, Stephane 
    ;
    Mayer, Aline S
    ;
    Keller, Ursula
    ;
    Südmeyer, Thomas 
    We demonstrate the first self-referenced full stabilization of a diode-pumped solid-state laser (DPSSL) frequency comb with a GHz repetition rate. The Yb:CALGO DPSSL delivers an average output power of up to 2.1 W with a typical pulse duration of 96 fs and a center wavelength of 1055 nm. A carrier-envelope offset (CEO) beat with a signal-to-noise ratio of 40 dB (in 10-kHz resolution bandwidth) is detected after supercontinuum generation and Æ’-to-2Æ’ interferometry directly from the output of the oscillator, without any external amplification or pulse compression. The repetition rate is stabilized to a reference synthesizer with a residual integrated timing jitter of 249 fs [10 Hz – 1 MHz] and a relative frequency stability of 10−12/s. The CEO frequency is phase-locked to an external reference via pump current feedback using home-built modulation electronics. It achieves a loop bandwidth of ∼150 kHz, which results in a tight CEO lock with a residual integrated phase noise of 680 mrad [1 Hz – 1 MHz]. We present a detailed characterization of the GHz frequency comb that combines a noise analysis of the repetition rate Æ’rep, of the CEO frequency Æ’CEO, and of an optical comb line at 1030 nm obtained from a virtual beat with a narrow-linewidth laser at 1557 nm using a transfer oscillator. An optical comb linewidth of about 800 kHz is assessed at 1-s observation time, for which the dominant noise sources of Æ’rep and Æ’CEO are identified.
  • 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.