arXiv subjects

J. C. de Aquino Carvalho

Publications and source records attributed to J. C. de Aquino Carvalho.

4 recordsLinked to original sources

arXiv2023

Spectrally Sharp Near-Field Thermal Emission: Revealing Some Disagreements between a Casimir-Polder Sensor and Predictions from Far-Field Emittance

Near-field thermal emission largely exceed blackbody radiation, owing to spectrally sharp emission in surface polaritons. We turn Casimir-Polder interaction between Cs(7P1/2) and a sapphire interface, into a sensor sharply filtering, at 24.687 THz, the near-field sapphire emission at ~ 24.5 THz. Temperature evolution of sapphire mode is demonstrated. The Cs sensor, sensitive to both dispersion and dissipation, suggests the polariton to be red-shifted and sharper, as compared, up to 1100 K, to predictions from far-field sapphire emission, affected by birefringence and multiple resonances.

physics.optics↗

arXiv2021

Linear probing of molecules at micrometric distances from a surface with sub-Doppler frequency resolution

We report on precision spectroscopy of sub-wavelength confined molecular gases. This was obtained by rovibrational selective reflection of $\mathrm{NH_3}$ and $\mathrm{SF_6}$ gases using a quantum cascade laser at $λ\approx 10.6 μm$. Our technique probes molecules at micrometric distances ($\approx λ/2π$) from the window of a macroscopic cell with sub-MHz resolution, allowing molecule-surface interaction spectroscopy. We exploit the linearity and high-resolution of our technique to gain novel spectroscopic information on the $\mathrm{SF_6}$ greenhouse gas, useful for enriching molecular databases. The natural extension of our work to thin-cells will allow compact frequency references and improved measurements of the Casimir-Polder interaction with molecules.

physics.optics↗

arXiv2021

The Surface response around a sharply resonant surface polariton mode is simply a Lorentzian

At the planar interface between a material and vacuum, the complex surface response S(omega)=[eps(omega) 1]/[eps(omega)+1], with eps(omega) the relative complex dielectric permittivity of the material, exhibit resonances, typical of the surface polariton modes, when eps(omega) ~ 1. We show that for a moderately sharp resonance, S(omega) is satisfactorily described with a mere (complex) Lorentzian, independently of the details affecting the various bulk resonances describing ) eps(omega). Remarkably, this implies a quantitative correlation between the resonant behaviors of Re[S(omega)] and Im[S(omega)], respectively associated to dispersive and dissipative effects in the surface near-field. We show that this "strong resonance" approximation easily applies, and discuss its limits, based upon published data for sapphire, CaF2 and BaF2. Extension to interfaces between two media or to a non planar interface is briefly considered.

physics.optics↗

arXiv2021

Velocity preserving transfer between highly excited atomic states: Black Body Radiation and Collisions

We study the excitation redistribution from cesium $7\mathrm{P}_{1/2}$ or $7\mathrm{P}_{3/2}$ to neighboring energy levels by Black Body Radiation (BBR) and inter atomic collisions using pump-probe spectroscopy inside a vapor cell. At low vapor densities we measure redistribution of the initial, velocity-selected, atomic excitation by BBR. This preserves the selected atomic velocities allowing us to perform high resolution spectroscopy of the $\mathrm{6D\rightarrow 7F}$ transitions. This transfer mechanism could also be used to perform sub-Doppler spectroscopy of the cesium highly-excited $\mathrm{nG}$ levels. At high densities we observe interatomic collisions redistributing the excitation within the cesium $\mathrm{7P}$ fine and hyperfine structure. We show that $\mathrm{7P}$ redistribution involves state-changing collisions that preserve the initial selection of atomic velocities. These redistribution mechanisms can be of importance for experiments probing high lying excited states in dense alkali vapor.

physics.atom-ph↗