Authors on the Hill Presents Prof. Giovanni Spani

Professor Giovanni Spani of the World Languages, Literatures, and Cultures Department at the College of the Holy Cross will present his work on Dante\u27s Florence, a multimedia educational app for Android and iOS.https://crossworks.holycross.edu/aoth/1009/thumbnail.jp

Inversion of the Coupling Absorption at the Two-Photon Resonance in a Coupling-Probe-Spectroscopy Experiment

Using probe and coupling lasers, a system characterized by electromagnetically induced absorption was investigated. A switch of the EIA peak of the coupling laser to a dip was measured as function of the laser intensities

Spectral measurement of the caesium D₂ line with a tunable heterodyne interferometer

The optical properties of a caesium atomic beam driven on a resonant hyperfine transition in the D2 line were studied as a function of the probe laser frequency. Using a third off-resonant laser system, a heterodyne interferometer allowed simultaneous absorption and phase shift measurements of either the probe or the coupling laser. The signal features of the probe and coupling laser transmitted intensities showed strong differences in the vicinity of the hyperfine transitions excited by the probe laser. Regular absorption signals and electromagnetically induced transparency were found in either transmitted intensities. Furthermore, light induced birefringence of the probe laser was measured

Realisation of transparency below the one-photon absorption level for a coupling laser driving a lambda system under EIT conditions

The concept of parametric spectra in electromagnetically induced transparency is clarified. In this context, the possibility for a coupling laser to reach absorption levels below the one-photon absorption is experimentally In this sense, the first results of electromagnetically induced transparency for a coupling laser in a coherent-populition-trapping dominated system are presented

Role of the coupling laser in electromagnetically induced absorption

The cesium D2 line closed hyperfine transition F=4F=5 was simultaneously coupled and probed in a hot atomic beam. We experimentally showed that, when the probe laser frequency approached that of the two-photon-resonance corresponding to electromagnetically induced absorption conditions, an enhanced transparency of the coupling laser appeared, combined with a further central absorption peak at zero probe laser detuning. Simultaneously, the coupling laser parametric dispersion showed a broad negative pattern together with a narrower steep positive phase shift in correspondence with the two-photon resonance, with sub-Doppler half-widths down to about 10 kHz

Giant Kerr effect in degenerate closed transitions

Giant Kerr nonlinearities about twelve orders of magnitudes greater than in glass were measured under negligible absorption conditions within two different closed transitions of the cesium D2 line characterized by electromagnetically induced transparency or absorption

Switching from „absorption within transparency“ to “transparency within transparency” in an electromagnetically induced absorption dominated transition

The absorption of a resonant coupling laser driving a closed degenerate two-level system in an atomic cesium beam was investigated as a function of the detuning of a second laser probing the same transition. The measurements were performed for four different polarization combinations of the two laser beams. Except for the beams of counterrotating polarizations all coupling-laser absorption profiles showed “absorption within transparency,” i.e., the absorption in the region around the two-photon resonance was smaller than the absorption corresponding to the one-photon transition induced by the coupling laser, and an extra absorption peak was observed on this curve at the two-photon resonance. With regard to the beams of counterrotating polarizations we observed a switch from absorption within transparency to “transparency within transparency” when the probe-laser power exceeded the constant coupling-laser power. In other words, the cesium ensemble became mostly transparent to the coupling-laser beam at the two-photon resonance

Giant Kerr effect in closed degenerate two-level transitions

Extremely large optical Kerr non-linearities (n2) and (n4) were measured in two closed degenerate two-level transitions in the caesium D2 line when a probe and a coupling laser simultaneously probed and coupled the hyperfine structure in an atomic beam. The magnitude of the measured non-linearities in both transitions were found to be a function of the coupling laser intensity and of the probe detuning from the two-photon resonance. In a figure of merit, the ratio between the non-unitarian part of the refractive index and the absorption coefficient measured in conditions of electromagnetically induced transparency showed a maximum value for a probe detuning of 160 kHz from the two-photon resonance and resulted in being 105 times larger than in the absence of the coupling laser field

Nonlinear spectroscopy of closed degenerate two-level systems

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A 3D journey on virtual surfaces and inner structure of ossa genitalia in Primates by means of a non-invasive imaging tool

Novel bio-imaging techniques such as micro-Computed Tomography provide an opportunity to investigate animal anatomy and morphology by overcoming limitations imposed by traditional anatomical drawings. The primate genital bones are complex anatomical structures whose occurrence in both male penis (baculum) and female clitoris (baubellum) may be difficult to assess in individual cadavers. We tested a 3-step methodological protocol, including different techniques ranging from inexpensive/simple to more expensive/sophisticated ones, by applying it to a sample of primate species, and resulting in different levels of data complexity: (1) presence/absence manual palpation method; (2) 2D X-ray plates; 3) 3D micro-CT scans. Manual palpation failed on 2 out of 23 specimens by detecting 1 false negative and 1 false positive; radiography failed once confirming the false positive, however firmly disproved by micro-CT; micro-CT analysis reported the presence of 9 bacula out of 11 male specimens and 1 baubellum out of 12 female specimens. A different baculum position was identified between strepsirrhine and haplorrhine species. We also aim to assess micro-CT as a non-invasive technique providing updated anatomical descriptions of primate ossa genitalia. Micro-CT 3D volumes showed the surface of some bones as rough, with a jagged appearance, whereas in others the surface appeared very smooth and coherent. In addition, four main types of bone internal structure were identified: 1) totally hollow; 2) hollow epiphyses and solid diaphysis with few or several channels inside; 3) totally solid with intricate Haversian channels; 4) totally solid with some channels (structure of single baubellum scanned). Ossa genitalia appeared as a living tissue having its own Haversian-like channels. The high resolution of micro-CT 3D-images of primate genital bones disclosed additional form variability to that available from genital bone 2D images of previous studies, and showed for the first time new internal and external morphological characters. Moreover, micro-CT non-invasive approach proved appropriate to recover much of scientific knowledge still hidden and often neglected in both museum specimens and primate cadavers only destined to necropsy