Leader : Marc De Micheli
PhD/Post-docs : Stepanenko Oleksandr
Financial supports : ANR PhoXcry (2010/2012)
Technological platforms : Integrated optics on lithium niobate
The last decade has witnessed significant breakthrough in the field of management of wave propagation in materials exhibiting periodic nano-structures, the so-called photonic and phononic crystals. Novel device geometries investigated theoretically or assessed experimentally have shown unmatched performance : highly efficient and compact electro-optical modulators can be quoted, amongst others.
The objective of this project is to demonstrate the viability of slow-photon based devices made of lithium niobate. It has already been demonstrated that slow light can induce an enhanced electro-optic effect. We will take advantage of this to fabricate ultra-compact, highly efficient electro-optic modulators with large “effective” interaction length between the optical wave and the modulating microwave. We will also investigate the acousto-optic counterpart of this phenomenon, first in conventional structures involving an acoustic modulation of the refractive index, then by combining phononic and photonic band gap effects in phoxonic crystals capable to simultaneously confine photons and phonons. For phoxonic crystals, the first objective is to find a crystal geometry with a simultaneous band gap for electromagnetic and elastic waves. The second is to ensure optimal guiding conditions for both types of waves. Eventually, the common confinement of elastic and optical waves needs to be modelled to get a better understanding of the new types of interactions expected in phoxonic crystals.
The technological objectives cover both to the realisation of the honeycomb structure constituting the photonic crystal and the fabrication of well-suited optical waveguides. The difficulty relies on the fact that the demanded aspect ratio of the nano-structure is very high (from 5 to 10) since the maximum of the optical mode in standard wave guides is at about 1.5 microns from the surface. We will use two ways of tackling this issue. The first is to improve our current etching technology based on FIB milling. We will also investigate large-scale production methods relying on Inductively Coupled Plasma RIE. The second is to make use of PE waveguides fabrication techniques inducing high index increase, and therefore tight confinement of the mode under the surface (mode core at about 0.5 µm).
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