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Schilt, Stephane
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Absolute frequency referencing in the long wave infrared using a quantum cascade laser frequency comb
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.
Compact rubidium-stabilized multi-frequency reference source in the 1.55-μm region
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.
Phase-stabilization of the carrier-envelope-offset frequency of a SESAM modelocked thin disk laser
2013, Klenner, Alexander, Emaury, Florian, Schriber, Cinia, Diebold, Andreas, Saraceno, Clara Jody, Schilt, Stephane, Keller, Ursula, Südmeyer, Thomas
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.
Wavelength tuning and thermal dynamics of continuous-wave mid-IR distributed feedback quantum cascade laser
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.
Rb-stabilized laser at 1572 nm for CO2 monitoring
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.
Active linewidth-narrowing of a mid-infrared quantum cascade laser without optical reference
2013, Tombez, Lionel, Schilt, Stephane, Hofstetter, D, Südmeyer, Thomas