Over the last years our investigation on polaronic, photonic and plasmonic crystals has revealed photonic / plasmon effects that increase the magneto-optic response [see, e.g., References 1-8 below]. Additionally, we have demonstrated the nonreciprocal propagation of plasmons in the presence of magnetic fields [6]. All this research is relevant to achieving unidirectional propagation of spatially confined electromagnetic waves, indispensable for the development of on-chip optical communications in photonic circuitry.
Now we pursue different approaches that aim towards creating actively controllable nanophotonic devices based on topological photonic crystals, based on these ingredients:
(i) integration of electro- and magneto-optic materials into nanophotonic metasurfaces to enable using electric (magnetic) fields to control confined electromagnetic waves;
(ii) special topologies designed in the wavevector space that enable helical edge propagation of modes that flow unimpeded by imperfections or back-reflections. The latter are akin to quantum spin Hall in fermionic systems, which have been demonstrated in honeycomb photonic dielectric lattices.
Among other methodologies we exploit finite-difference time-domain (FDTD) simulations to design metasurfaces and topological photonic crystals and angle-resolved reflectance/transmission spectroscopy, which can resolve reciprocal space maps from near-IR to violet, with scanning beam sizes down to few microns. Beyond the more common real space imaging, this methodology enables the direct visualization of the photonic bands structure.
[1] Magnetophotonic Response of Three-Dimensional Opals. JM. Caicedo et al., ACS Nano, 2011. DOI: 10.1021/nn1035872
[2] Magneto-optical enhancement by plasmon excitations in nanoparticle/metal structures. Rubio-Roy et al., Langmuir 2012. DOI: 10.1021/la301239x
[3] Expanding Effective-Medium Theory to Optical Diamagnetic Responses in Magnetoplasmonic Colloids Vlasin et al., Physical Review Applied 2014. https://doi.org/10.1103/PhysRevApplied.2.054003
[4] Magnetopolaron-induced optical response in transition metal oxides. M. Caicedo, J. Fontcuberta, and G. Herranz, Physical Review B, 89 045121 (2014) http://dx.doi.org/10.1103/PhysRevB.89.045121
[5] Giant Optical Polarization Rotation Induced by Spin-Orbit Coupling in Polarons. Casals et al. Physical Review Letters 2016, https://doi.org/10.1103/PhysRevLett.117.026401
[6] Non-reciprocal diffraction in magnetoplasmonic gratings. R. Cichelero et al., Optics Express 26 34842-34852 (2018) https://doi.org/10.1364/OE.26.034842
[7] Spectral and Angle-Resolved Magneto-Optical Characterization of Photonic Nanostructures. Kataja, M., Cichelero, R., Herranz, G. . J. Vis. Exp. (153), e60094, doi:10.3791/60094 (2019)
[8] Solid-State Synapses Modulated by Wavelength-Sensitive Temporal Correlations in Optic Sensory Inputs. Yu Chen, Blai Casals, Florencio Sánchez and Gervasi Herranz. ACS Appl. Electron. Mater. (2019)
GERVASI HERRANZ'S LAB 