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Terahertz chiral subwavelength cavities breaking time-reversal symmetry via ultrastrong light-matter interaction
(2024)Physical Review BWe demonstrate terahertz chiral subwavelength cavities that break time-reversal symmetry by coupling the degenerate linearly polarized modes of two orthogonal sets of nanoantenna arrays using the inter-Landau-level transition of a two-dimensional (2D) electron gas in a perpendicular magnetic field, realizing normalized light-matter coupling rates up to ωR/ωcav=0.78 with a dispersion that is modified by the parasitic capacitive coupling ...Journal Article -
Third order nonlinear correlation of the electromagnetic vacuum at near-infrared frequencies
(2024)New Journal of PhysicsIn recent years, electro-optic sampling, which is based on Pockel's effect between an electromagnetic mode and a copropagating, phase-matched ultrashort probe, has been largely used for the investigation of broadband quantum states of light, especially in the mid-infrared and terahertz frequency range. The use of two mutually delayed femtosecond pulses at near-infrared frequencies allows the measurement of quantum electromagnetic radiation ...Journal Article -
Quantum cascade lasers as broadband sources via strong RF modulation
(2024)APL PhotonicsIn this work, we demonstrate that in a regime of strong modulation, by generating pulses of the length of the order of a few cavity lifetimes (hundreds of ps), a broadband quantum cascade laser can be driven to lase on a bandwidth (250 cm⁻¹) limited by the gain. In addition, the amplitude noise of the radiation was shown to be limited by the detector. A laser linewidth study has been performed under different operating conditions, finding ...Journal Article -
Impact of higher-order dispersion on frequency-modulated combs
(2024)Optics LettersFrequency-modulated (FM) combs form spontaneously in free-running semiconductor lasers and possess a vast potential for spectroscopic applications. Despite recent progress in obtaining a conclusive theoretical description, experimental FM combs often exhibit non-ideal traits, which prevents their widespread use. Here we explain this by providing a clear theoretical and experimental study of the impact of the higher-order dispersion on FM ...Other Journal Item -
Backscattering-Induced Dissipative Solitons in Ring Quantum Cascade Lasers
(2024)Physical Review LettersRing quantum cascade lasers have recently gained considerable attention, showing ultrastable frequency comb and soliton operation, thus opening a way to integrated spectrometers in the midinfrared and terahertz fingerprint regions. Thanks to a self-consistent Maxwell-Bloch model, we demonstrate, in excellent agreement with the experimental data, that a small but finite coupling between the counterpropagating waves arising from distributed ...Journal Article -
Single-mode, surface-emitting quantum cascade laser at 26 μm
(2024)Applied Physics LettersWe present the simulation, design, fabrication, and characterization of planarized double metal quantum cascade lasers based on InGaAs/GaAsSb. Intended for astrophysical heterodyne measurements and having the cavity embedded in benzocyclobutene, the devices are equipped with thermal bridges on either side of the ridge, in order to improve the heat dissipation. The lasers are shown to vertically emit a single mode around 26 μm in pulsed ...Journal Article -
Quantum Cascade Surface Emitting Lasers
(2024)Laser & Photonics ReviewsA low-cost single frequency laser, emitting in the mid-infrared spectral region and dissipating minimal electrical power, is a key ingredient for the next generation of portable gas sensors for high-volume applications involving chemical sensing of important greenhouse and pollutant gases. Herein, a Quantum Cascade Surface Emitting Laser (QCSEL) is proposed, which is implemented as a short linear cavity with high reflectivity coated ...Journal Article -
Probing vacuum field fluctuations and source radiation separately in space and time
(2023)Physical Review ResearchSource radiation (radiation reaction) and vacuum field fluctuations can be seen as two inseparable contributions to processes such as spontaneous emission, the Lamb shift, or the Casimir force. Here, we propose how they can be individually probed and their space-time structure revealed in electro-optic sampling experiments. This allows us to experimentally study causality at the single-photon level and to reveal space- and timelike ...Journal Article -
Frequency-Modulated Combs via Field-Enhancing Tapered Waveguides
(2023)Laser & Photonics ReviewsFrequency-modulated (FM) combs feature flat intensity spectra with a linear frequency chirp, useful for metrology and sensing applications. Generating FM combs in semiconductor lasers generally requires a fast saturable gain, usually limited by the intrinsic gain medium properties. Here, it is shown how a spatial modulation of the laser gain medium can enhance the gain saturation dynamics and nonlinearities to generate self-starting FM ...Journal Article -
Frequency Stabilization of a 4.7 THz Quantum Cascade Laser Using a Delay Line Frequency Discriminator
(2023)IEEE Transactions on Terahertz Science and TechnologyAstronomical heterodyne spectrometers, such as upGREAT on the SOFIA telescope, use a powerful quantum cascade laser (QCL) as local oscillator (LO) to observe the atomic oxygen line at 4.7 THz. The free-running laser, although temperature stabilized, is prone to broad effective linewidth and frequency drifts and lacks an absolute frequency reference. In this work, our successful frequency locking of a 4.7 THz QCL by employing a delay line ...Journal Article