Biphotons for nonlinear imagine

Overall aim of this research project is to investigate how entangled photons affect nonlinear imaging. Nonlinear
imaging plays a significant role in scientific development as it allows for the study of many biological systems.
More specifically, biological structures can be imaged in 3D resolution by nonlinear optical microscopy which
uses nonlinear interactions between light and matter. With the implementation of quantum optics in such
technologies we wish to enhance bioimaging to get a better look of the microscopic world.
To do so, biphoton fields will be utilized experimentally to examine nonlinear effects. The twin photons
generated by parametric down-conversion hold strong temporal correlations and can significantly increase the
two-photon absorption cross-section[1]
. When two-photon absorption occurs in materials such as fluorophores
or semiconductors, the cross-section of the absorbed biphotons is orders of magnitude higher than what is
observed with classical radiation. Moreover, the cross-section approaches that of one-photo process due to the
entangled nature of the photons and by utilizing this fact the project will study parametric interactions in thirdorder nonlinear media, such as self and cross-phase modulation, parametric amplification, and Raman
scattering. There is also significant interest in the investigation of biphoton induced enhancement of Kerr
nonlinearities where materials undergo a change in their refractive index after their interaction with an electric
field.
Lastly, this Ph.D. project has the goal of investigating phase front correlations caused by nonlinear phase
conjugation. Phase conjugation is used to describe the wavefront reversion of one beam after its interaction
with another counterpropagating beam which has identical transverse amplitude distribution as the first one[2]
.
Previous research indicates high phase-conjugation conversion efficiencies in various systems such as
graphene[3] and coupled plasmonic systems at the epsilon-near-zero condition[4]
. We shall focus on the latter
system where in thin metallic films the mode dispersion approaches the plasma frequency with the aim to
understand how biphotons excite plasmonic resonance.
The examples described above are only a rough idea to what we aim to investigate and further applications
and approaches will be explored to study optical nonlinearities enhanced by biphotons.