BEGIN:VCALENDAR VERSION:2.0 PRODID:Icfo X-PUBLISHED-TTL:P1W BEGIN:VEVENT UID:69e88e840532f DTSTART:20221202T100000Z SEQUENCE:0 TRANSP:OPAQUE LOCATION:ICFO Auditorium SUMMARY:ICFO | GERARD JIMÉNEZ MACHADO CLASS:PUBLIC DESCRIPTION:This thesis\, mostly experimental\, is based on two fundamental pillars: nonlinear interferometers and Optical Coherence Tomography (OCT) . Nonlinear interferometers are a class of interferometers that exhibit no nclassical phenomena brought on by nonlinear elements\, such as optical pa rametric amplifiers and parametric down-conversion (PDC) nonlinear crystal s. OCT is a non-invasive imaging technique that allows to obtain images wi th high axial and cross-sectional resolution of a wide variety of samples. \nThe first novel contribution of this thesis is an experimental scheme th at combines the two ideas: an OCT scheme based on a nonlinear interferomet er. In these new approach the reflectivity of the sample translates in a l oss of first-order coherence between two beams\, that is the variable that is measured. In addition\, it allows probing the sample with a wavelength different from the one that is measured. In this way\, the penetration de pth in the sample can be enhanced using longer wavelengths while using lig ht at the optimal wavelength for detection.\nWe present and implement two different experimental configurations. The first is a nonlinear interferom eter based on induced coherence\, or Mandel-type interferometer\, that wor ks in the low parametric gain regime of parametric down-conversion (PDC). The results presented here are a proof-of-concept\, that can potentially o ffer new applications for OCT\, but that are not meant to substitute tradi tional OCT systems. \;\nThe second OCT scheme overcomes some of the li mitations of the first scheme discussed above. It is an SU(1\,1)\, or Yurk e-type interferometer\, that operates in the high parametric gain regime o f parametric down-conversion. In addition to taking advantage of the salut ary features of this new approach\, it also enables obtaining values of po wer and axial resolution comparable to those of conventional OCT.\nThe sec ond novel contribution of this thesis is related to fundamental aspects at the heart of nonlinear interferometers. We discuss two experiments that s tudy two important concepts behind the idea of induced coherence: quantum distinguishability and parametric amplification (stimulated emission). In the first experiment we propose a new experimental measure of quantum dist inguishability and derive a complementarity relation between distinguishab ility and first-order coherence. In the second experiment\, we contribute to the ongoing debate about the true role of quantum distinguishability an d stimulated emission in explaining the induced coherence effect.\nFinally \, we put forward theoretically a new scheme to retrieve transverse spatia l information of a sample using a nonlinear interferometer\, based on proj ecting the outgoing photons in selected spatial modes. We call this new pr oposal spatial spectroscopy\, and it does not require a physical mechanica l scan of the sample. We demonstrate the feasibility of the technique with a simple example. This last contribution constitutes a future proposal to be carried out with nonlinear interferometers\, evidencing their great ve rsatility and potential applications in new areas.\nThesis Director: Prof Dr. Juan Pé\;rez Torres DTSTAMP:20260422T090156Z END:VEVENT END:VCALENDAR