Jean-Michel Le Floch

Strong coupling between P1 diamond impurity centers and a three-dimensional lumped photonic microwave cavity

We report strong coupling between an ensemble of N impurity (P1) centers in diamond and microwave photons using a unique double-post reentrant cavity. The cavity is designed so that the magnetic component of the cavity field is spatially separated from the electric component and focused into the small volume in which the diamond sample is mounted. The novelty of the structure simultaneously allows the high magnetic filling factor (38.4%) and low frequencies necessary to interact, at low magnetic field, with transitions in diamond such as those in negatively charged nitrogen-vacancy and P1 centers. Coupling strength (or normal-mode splitting) of 51.42 MHz was achieved with P1 centers at 6.18 GHz and 220 mT in a centimeter-scale cavity, with a corresponding cooperativity factor of 4.7. This technique offers an alternative way, with some significant advantages, to couple 3D cavities to transitions in diamond and achieve the strong coupling necessary for applications to quantum information processing.

Three-dimensional cavity quantum electrodynamics with a rare-earth spin ensemble

We present cavity QED experiments with an Er:YSO crystal magnetically coupled to a 3D cylindrical sapphire loaded copper resonator. Such waveguide cavities are promising for the realization of a superconducting quantum processor. Here, we demonstrate the coherent integration of a rare-earth spin ensemble with the 3D architecture. The collective coupling strength of the Er

Cryogenic sapphire oscillator using a low- vibration design pulse-tube cryocooler: first results

^{3+}

Discovery of Bragg confined hybrid modes with high Q factor in a hollow dielectric resonator

spins to the 3D cavity is 21 MHz. The cylindrical sapphire loaded resonator allowed us to explore the anisotropic collective coupling between the rare-earth doped crystal and the cavity. This work shows the potential of spin doped solids in 3D quantum circuits for application as microwave quantum memories as well as for prospective microwave to optical interfaces.

Intercomparison of Permittivity Measurement Techniques for Ferroelectric Thin Layers

A cryogenic sapphire oscillator (CSO) has been implemented at 11.2 GHz using a low-vibration design pulse-tube cryocooler. Compared with a state-of-the-art liquid helium cooled CSO in the same laboratory, the square root Allan variance of their combined fractional frequency instability is ¿_y = 1.4 × 10^-5¿^-1/2 for integration times 1 < ¿ < 10 s, dominated by white frequency noise. The minimum ¿_y = 5.3 × 10^-16 for the two oscillators was reached at ¿ = 20 s. Assuming equal contributions from both CSOs, the single oscillator phase noise S_¿ ¿ -96 dB.rad²/Hz at 1 Hz set from the carrier.

Microwave properties of semi-insulating silicon carbide between 10 and 40 GHz and at cryogenic temperatures

The authors report on observation of Bragg confined mode in a hollow cylindrical dielectric cavity. A resonance was observed at 13.4GHz with an unloaded Q factor of order 2×105, which is more than a factor of 6 above the dielectric loss limit. Previously, such modes have only been realized from pure transverse electric modes with no azimuthal variations and only the Eϕ component. From rigorous numeric simulations, it is shown that the mode is a hybrid mode with nonzero azimuthal variations and with dominant Er and Eϕ electric field components and Hz magnetic field component.

Thin film materials characterization using TE modes cavity

The dielectric properties of a KTa0.65Nb0.35O3 (KTN) ferroelectric composition for a submicronic thin layer were measured in the microwave domain using different electromagnetic characterization methods. Complementary experimental techniques (broadband methods versus resonant techniques, waveguide versus transmission line) and complementary data processing procedures (quasi-static theoretical approaches versus full-wave analysis) were selected to investigate the best way to characterize ferroelectric thin films. The measured data obtained from the cylindrical resonant cavity method, the experimental method that showed the least sources of uncertainty, were taken as reference values for comparisons with results obtained using broadband techniques. The error analysis on the methods used is discussed with regard to the respective domains of validity for each method; this enabled us to identify the best experimental approach for obtaining an accurate determination of the microwave dielectric properties of ferroelectric thin layers.

Hollow-core resonator based on out-of-plane two-dimensional photonic band-gap crystal cladding at microwave frequencies

The complex permittivity of high-purity, semi-insulating, axis-aligned monocrystalline 4H-SiC has been determined over the frequency range 10–40 GHz and at temperatures from 40 up to 295 K using whispering gallery modes and quasi TE0, n, p modes in a dielectric resonator constructed from seven layers of a 375 μm thick wafer. The real part of the permittivity (in the plane of the wafers) was found to be nearly independent of frequency. The dielectric loss tangent of 4H-SiC increases with temperature above 100 K. All results were obtained for the semiconductor in darkness.

Low-loss materials for high Q-factor Bragg reflector resonators

This paper presents the characterization of thin film dielectric materials, labeled as LW 51 KTN and LW 48 KTN. The technique can be applied for lower temperatures. We briefly present the material process of both thin films, then the dielectric characterization using a conventional TE mode cavity method [1–5] with the help of a rigorous simulation software based on the method of lines [6]. We finally measured high permittivity and low loss-tangent materials within the microwave frequency range from 12 to 15 GHz.

Invited Article: Dielectric material characterization techniques and designs of high-Q resonators for applications from micro to millimeter-waves frequencies applicable at room and cryogenic temperatures

We report on the demonstration of a resonator based on electromagnetic field confinement in a hollow-core by implementing an out-of-plane two-dimensional ﲤ2Dﲥ photonic band-gap ﲤPBGﲥ crystal cladding. In contrast with in-plane 2D PBG crystal devices, the PBG crystal studied here is perpendicular to the propagation axis. A resonator was constructed with silica rods to prove the concept at frequencies around 30 GHz. We show that the technique has the potential to reach quality factors ﲤQﲥ of 5 ﲡ 105.