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Search Results: 1 - 10 of 1185 matches for " Giacomo Scalari "
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InGaAs/AlInGaAs THz Quantum Cascade Lasers operating up to 195 K in strong magnetic field
Federico Valmorra,Giacomo Scalari,Keita Ohtani,Mattias Beck,Jerome Faist
Physics , 2014, DOI: 10.1088/1367-2630/17/2/023050
Abstract: Terahertz quantum cascade lasers based on InGaAs wells and quaternary AlInGaAs barriers were measured in magnetic field. This study was carried out on a four quantum well active region design with photon energy of 14.3 meV processed both with Au and Cu waveguides. The heterostructure operates up to 148 K at B=0 T and in a Cu waveguide. The complete magneto-spectroscopic study allowed the comparison of emission and transport data. Increasing the magnetic field, the low effective mass of the InGaAs wells allowed us to reach the very strong confinement regime. At B=12 T, where the cyclotron transition is almost resonant with the LO-phonon, we recorded a maximum operating temperature of 195 K for the devices with Cu waveguide. Additional lasing at 5.9 meV was detected for magnetic fields between 7.3 and 7.7 T.
High quality factor, fully switchable THz superconducting metasurface
Giacomo Scalari,Curdin Maissen,Sara Cibella,Roberto Leoni,Jerome Faist
Physics , 2014, DOI: 10.1063/1.4905199
Abstract: We present a complementary THz metasurface realised with Niobium thin film which displays a quality factor Q=54 and a fully switchable behaviour as a function of the temperature. The switching behaviour and the high quality factor are due to a careful design of the metasurface aimed at maximising the ohmic losses when the Nb is above the critical temperature and minimising the radiative coupling. The superconductor allows the operation of the cavity with an high Q and inductive elements with an high aspect ratio. Comparison with three dimensional finite element simulations highlights the crucial role of the inductive elements and of the kinetic inductance of the Cooper pairs in achieving the high quality factor and the high field enhancement.
Ultra strong coupling regime and plasmon-polaritons in parabolic semiconductor quantum wells
Markus Geiser,Fabrizio Castellano,Giacomo Scalari,Mattias Beck,Laurent Nevou,Jér?me Faist
Physics , 2011, DOI: 10.1103/PhysRevLett.108.106402
Abstract: Ultra strong coupling is studied in a modulation-doped parabolic potential well coupled to an inductance-capacitance resonant circuit. In this system, in accordance to Kohn's theorem, strong reduction of the energy level separation caused by the electron-electron interaction compensates the depolarization shift. As a result, a very large ratio of 27% of the Rabi frequency to the center resonance frequency as well as a polariton gap of width 2? ? 670GHz are observed, suggesting parabolic quantum wells as the system of choice in order to explore the ultra-strong coupling regime.
Sub-cycle measurement of intensity correlations in the Terahertz range
Ileana-Cristina Benea-Chelmus,Curdin Maissen,Giacomo Scalari,Mattias Beck,Jér?me Faist
Physics , 2015,
Abstract: The Terahertz frequency range bears intriguing opportunities, beyond very advanced applications in spectroscopy and matter control. Peculiar quantum phenomena are predicted to lead to light emission by non-trivial mechanisms. Typically, such emission mechanisms are unraveled by temporal correlation measurements of photon arrival times, as demonstrated in their pioneering work by Hanbury Brown and Twiss. So far, the Terahertz range misses an experimental implementation of such technique with very good temporal properties and high sensitivity. In this paper, we propose a room-temperature scheme to measure photon correlations at THz frequencies based on electro-optic sampling. The temporal resolution of 146 fs is faster than one cycle of oscillation and the sensitivity is so far limited to ~1500 photons. With this technique, we measure the photon statistics of a THz quantum cascade laser. The proposed measurement scheme allows, in principle, the measurement of ultrahigh bandwidth photons and paves the way towards THz quantum optics.
Octave-spanning semiconductor laser
Markus R?sch,Giacomo Scalari,Mattias Beck,Jér?me Faist
Physics , 2014, DOI: 10.1038/nphoton.2014.279
Abstract: We present here a semiconductor injection laser operating in continuous wave with an emission covering more than one octave in frequency, and displaying homogeneous power distribution among the lasing modes. The gain medium is based on a heterogeneous quantum cascade structure operating in the THz range. Laser emission in continuous wave takes place from 1.64 THz to 3.35 THz with optical powers in the mW range and more than 80 modes above threshold. Free-running beatnote investigations on narrow waveguides with linewidths of 980 Hz limited by jitter indicate frequency comb operation on a spectral bandwidth as wide as 624 GHz, making such devices ideal candidates for octave-spanning semiconductor-laser-based THz frequency combs.
Room temperature terahertz polariton emitter
Markus Geiser,Giacomo Scalari,Fabrizio Castellano,Mattias Beck,Jér?me Faist
Physics , 2012, DOI: 10.1063/1.4757611
Abstract: The strong-coupling regime between an electronic transition and the photonic mode of a optical resonator manifests itself in the lifting of the degeneracy between the two modes and the creation of two polariton states with mixed optical and electronic character. This phenomenon has been studied in atoms, excitons in semiconductors and quantum electrodynamics circuits based on Josephson junctions. Recently, there is also strong interest to study similar e?ects using intersubband transitions in quantum wells in the terahertz, where the ultra strong coupling regime can be reached and new physical e?ects have been predicted. An other interesting feature of this system is that, in contrast to systems based on superconductors, the ultra strong coupling regime can be maintained up to room temperature. In this work, we demonstrate that parabolic quantum wells coupled to LC circuit resonators in the ultra strong coupling regime can achieve terahertz emission up to room temperature.
Observation of Zone-Folded Acoustic Phonons in Terahertz Quantum Cascade Lasers using Picosecond Ultrasonics
Axel Bruchhausen,Mike Hettich,James Lloyd-Hughes,Milan Fischer,Mattias Beck,Giacomo Scalari,Jér?me Faist,Thomas Dekorsy
Physics , 2010,
Abstract: We have investigated the time-resolved vibrational properties of terahertz quantum cascade lasers by means of ultra-fast laser spectroscopy. By the observation of the acoustic folded branches, and by analyzing the involved phonon modes it is possible to extract accurate structural information of these devices, which are essential for their design and performance.
Quantum Cascade Laser Frequency Combs
Jér?me Faist,Gustavo Villares,Giacomo Scalari,Markus R?sch,Christopher Bonzon,Andreas Hugi,Mattias Beck
Physics , 2015,
Abstract: It was recently demonstrated that broadband quantum cascade lasers can operate as frequency combs. As such, they operate under direct electrical pumping at both mid-infrared and THz frequencies, making them very attractive for dual-comb spectroscopy. Performance levels are continuously improving, with average powers over 100 mW and frequency coverage of 100 cm$^{-1}$ in the mid-infrared. In the THz range, 10 mW of average power and 600 GHz of frequency coverage are reported. As a result of the very short upper state lifetime of the gain medium, the mode proliferation in these sources arises from four wave mixing rather than saturable absorption. As a result, their optical output is characterized by the tendency of small intensity modulation of the output power, and the relative phases of the modes to be similar to the ones of a frequency modulated laser. Recent results include the proof of comb operation down to a metrological level, the observation of a Schawlow-Townes broadened linewidth, as well as the first dual-comb spectroscopy measurements. The capability of the structure to integrate monolithically non-linear optical element as well as to operate as a detector show great promise for future chip integration of dual-comb systems.
Ultrastrong coupling of the cyclotron transition of a two-dimensional electron gas to a THz metamaterial
Giacomo Scalari,Curdin Maissen,Dana Turcinková,David Hagenmüller,Simone De Liberato,Cristiano Ciuti,Dieter Schuh,Christian Reichl,Werner Wegscheider,Mattias Beck,Jér?me Faist
Physics , 2011, DOI: 10.1126/science.1216022
Abstract: Artificial cavity photon resonators with ultrastrong light-matter interactions are attracting interest both in semiconductor and superconducting systems, due to the possibility of manipulating the cavity quantum electrodynamic ground state with controllable physical properties. We report here experiments showing ultrastrong light-matter coupling in a terahertz metamaterial where the cyclotron transition of a high mobility two-dimensional electron gas is coupled to the photonic modes of an array of electronic split-ring resonators. We observe a normalized coupling ratio $\frac{\Omega}{\omega_c}=0.58$ between the vacuum Rabi frequency $\Omega$ and the cyclotron frequency $\omega_c$. Our system appears to be scalable in frequency and could be brought to the microwave spectral range with the potential of strongly controlling the magnetotransport properties of a high-mobility 2DEG.
Ultrastrong Coupling in the Near-field of Complementary Split Ring Resonators
Curdin Maissen,Giacomo Scalari,Federico Valmorra,Sara Cibella,Roberto Leoni,Christian Reichl,Christohpe Charpentier,Werner Wegscheider,Mattias Beck,Jér?me Faist
Physics , 2014, DOI: 10.1103/PhysRevB.90.205309
Abstract: The ultrastrong light-matter interaction regime was investigated in metallic and superconducting complementary split ring resonators coupled to the cyclotron transition of two dimensional electron gases. The sub-wavelength light confinement and the large optical dipole moment of the cyclotron transition yield record high normalized coupling rates of up to $\frac{\Omega_R}{\omega_c}=$ 0.87. We observed a blue-shift of both polaritons due to the diamagnetic term of the interaction Hamiltonian.
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