Schilt, Stephane

2022-4-4, Komagata, Kenichi N., Gianella, Michele, Jouy, Pierre, Kapsalidis, Filippos, Shahmohammadi, Mehran, Beck, Mattias, Matthey-De-L'Endroit, Renaud, 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.

2015-6-1, Matthey-De-L'Endroit, Renaud, Gruet, Florian, Schilt, Stephane, Mileti, Gaetano

Combining light modulation and frequency conversion techniques, a compact and simple frequency-stabilized optical frequency comb spanning over 45 nm in the 1.56-μm wavelength region is demonstrated. It benefits from the high-frequency stability achievable from rubidium atomic transitions at 780 nm probed in a saturation absorption scheme, which is transferred to the 1.56-μm spectral region via a second-harmonic generation process. The optical frequency comb is generated by an electro-optic modulator enclosed in a Fabry–Perot cavity that is injected by the fundamental frequency stabilized laser. Frequency stability better than 2 kHz has been demonstrated on time scales between 1000 s and 2 days both at 1560 nm, twice the rubidium wavelength, and for a comb line at 1557 nm.

2013, Tombez, Lionel, Schilt, Stephane, Hofstetter, D, Südmeyer, Thomas

2013, Klenner, Alexander, Emaury, Florian, Schriber, Cinia, Diebold, Andreas, Saraceno, Clara Jody, Schilt, Stephane, Keller, Ursula, Südmeyer, Thomas

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.

2013-7-17, Tombez, Lionel, Cappelli, Francesco, Schilt, Stephane, Di Domenico, Gianni, Bartalini, Saverio, Hofstetter, Daniel

We report on the wavelength tuning dynamics in continuous-wave distributed feedback quantum cascade lasers (QCLs). The wavelength tuning response for direct current modulation of two mid-IR QCLs from different suppliers was measured from 10 Hz up to several MHz using ro-vibrational molecular resonances as frequency-to-intensity converters. Unlike the output intensity, which can be modulated up to several gigahertz, the frequency-modulation bandwidth was found to be on the order of 200 kHz, limited by the laser thermal dynamics. A non-negligible roll-off and a significant phase shift are observed above a few hundred hertz already and explained by a thermal model.

2013, Hoffmann, Martin, Schilt, Stephane, Südmeyer, Thomas

2016-7-4, Matthey-De-L'Endroit, Renaud, Moreno, William, Gruet, Florian, Brochard, Pierre, Schilt, Stephane, Mileti, Gaetano

We have developed a compact rubidium-stabilized laser system to serve as optical frequency reference in the 1.55-m wavelength region, in particular for CO2 monitoring at 1572 nm. The light of a fiber-pigtailed distributed feedback (DFB) laser emitting at 1560 nm is frequency-doubled and locked to a sub-Doppler rubidium transition at 780 nm using a 2-cm long vapor glass cell. Part of the DFB laser light is modulated with an electro-optical modula-tor enclosed in a Fabry-Perot cavity, generating an optical frequency comb with spectral cover-age extending from 1540 nm to 1580 nm. A second slave DFB laser emitting at 1572 nm and offset-locked to one line of the frequency comb shows a relative frequency stability of 1·10-11at 1 s averaging time and <4·10-12 from 1 hour up to 3 days.

2013, Schilt, Stephane, Tombez, Lionel, Di Domenico, Gianni, Hofstetter, Daniel

2013, Dolgovskiy, Vladimir, Schilt, Stephane, Bucalovic, Nikola, Di Domenico, Gianni, Grop, Serge, Dubois, Benoît, Giordano, Vincent, Südmeyer, Thomas