Südmeyer, Thomas

2008, Rudin, Benjamin, Rutz, A, Hoffmann, Martin, Maas, Deran J. H. C., Bellancourt, Aude-Reine, Gini, E, Südmeyer, Thomas, Keller, Ursula

2010, Pekarek, Selina, Fiebig, Christian, Stumpf, Max, Oehler, Andreas Ernst Heinz, Paschke, Katrin, Erbert, Götz, Südmeyer, Thomas, Keller, Ursula

2021-6, Komagata, Kenichi N., Shehzad, Atif, Terrasanta, Giulio, Brochard, Pierre, Matthey-De-L'Endroit, 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.

, Jornod, Nayara, Gürel, Kutan, Wittwer, Valentin J, 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.

, Modsching, Norbert, Paradis, Clément, Labaye, François, Gaponenko, Maxim, Graumann, Ivan J, Diebold, Andreas, Emaury, Florian, Wittwer, Valentin J, Südmeyer, Thomas

We demonstrate the first Kerr lens mode-locked Yb:CaGdAlO₄ (Yb:CALGO) thin-disk laser oscillator. It generates pulses with a duration of 30 fs at a central wavelength of 1048 nm and a repetition rate of 124 MHz. The laser emits the shortest pulses generated by a thin-disk laser oscillator, equal to the shortest pulse duration obtained by Yb-doped bulk oscillators. The average output power is currently limited to 150 mW by the low gain and limited disk quality. We expect that more suitable Yb:CALGO disks will enable substantially higher power levels with similar pulse durations.

2022-4-4, Komagata, Kenichi N., Gianella, Michele, Jouy, Pierre, Kapsalidis, Filippos, Shahmohammadi, Mehran, Beck, Mattias, Matthey-De-L'Endroit, Wittwer, Valentin, Hugi, Andreas, Faist, Jérôme, Emmenegger, Lukas, Südmeyer, Thomas, Schilt, Stephane

Optical frequency combs (OFCs) based on quantum cascade lasers (QCLs) have transformed mid-infrared spectroscopy. However, QCL-OFCs have not yet been exploited to provide a broadband absolute frequency reference. We demonstrate this possibility by performing comb-calibrated spectroscopy at 7.7 µm (1305 cm−1) using a QCL-OFC referenced to a molecular transition. We obtain 1.5·10−10 relative frequency stability (100-s integration time) and 3·10−9 relative frequency accuracy, comparable with state-of-the-art solutions relying on nonlinear frequency conversion. We show that QCL-OFCs can be locked with sub-Hz-level stability to a reference for hours, thus promising their use as metrological tools for the mid-infrared.

2013, Emaury, Florian, Dutin, Coralie Fourcade, Saraceno, Clara Jody, Trant, Mathis, Heckl, Oliver Hubert, Wang, Yang Y, Schriber, Cinia, Gerome, Frederic, Südmeyer, Thomas, Benabid, Fetah

2012, Pekarek, Selina, Klenner, Alexander, Südmeyer, Thomas, Fiebig, Christian, Paschke, Katrin, Erbert, Götz, Keller, Ursula

, Tombez, Lionel, Schilt, Stephane, Hofstetter, Daniel, Südmeyer, Thomas

We report on a technique for frequency noise reduction and linewidth-narrowing of a distributed-feedback mid-IR quantum cascade laser (QCL) that does not involve any optical frequency reference. The voltage fluctuations across the QCL are sensed, amplified and fed back to the temperature of the QCL at a fast rate using a near-IR laser illuminating the top of the QCL chip. A locking bandwidth of 300 kHz and a reduction of the frequency noise power spectral density by a factor of 10 with respect to the free-running laser are achieved. From 2 MHz for the free-running QCL, the linewidth is narrowed below 700 kHz (10 ms observation time).

2007, Maas, Deran J. H. C., Bellancourt, Aude-Reine, Rudin, Benjamin, Golling, Matthias, Unold, HJ, Südmeyer, Thomas, Keller, Ursula