32 research outputs found
Strain-induced pseudomagnetic field and Landau levels in photonic structures
Magnetic effects at optical frequencies are notoriously weak. This is
evidenced by the fact that the magnetic permeability of nearly all materials is
unity in the optical frequency range, and that magneto-optical devices (such as
Faraday isolators) must be large in order to allow for a sufficiently strong
effect. In graphene, however, it has been shown that inhomogeneous strains can
induce 'pseudomagnetic fields' that behave very similarly to real fields. Here,
we show experimentally and theoretically that, by properly structuring a
dielectric lattice, it is possible to induce a pseudomagnetic field at optical
frequencies in a photonic lattice, where the propagation dynamics is equivalent
to the evolution of an electronic wavepacket in graphene. To our knowledge,
this is the first realization of a pseudomagnetic field in optics. The induced
field gives rise to multiple photonic Landau levels (singularities in the
density of states) separated by band gaps. We show experimentally and
numerically that the gaps between these Landau levels give rise to transverse
confinement of the optical modes. The use of strain allows for the exploration
of magnetic effects in a non-resonant way that would be otherwise inaccessible
in optics. Employing inhomogeneous strain to induce pseudomagnetism suggests
the possibility that aperiodic photonic crystal structures can achieve greater
field-enhancement and slow-light effects than periodic structures via the high
density-of-states at Landau levels. Generalizing these concepts to other
systems beyond optics, for example with matter waves in optical potentials,
offers new intriguing physics that is fundamentally different from that in
purely periodic structures.Comment: 24 pages including supplementary information section, 4 figure
All-optical routing and switching for three-dimensional photonic circuitry
The ability to efficiently transmit and rapidly process huge amounts of data has become almost indispensable to our daily lives. It turned out that all-optical networks provide a very promising platform to deal with this task. Within such networks opto-optical switches, where light is directed by light, are a crucial building block for an effective operation. In this article, we present an experimental analysis of the routing and switching behaviour of light in two-dimensional evanescently coupled waveguide arrays of Y- and T-junction geometries directly inscribed into fused silica using ultrashort laser pulses. These systems have the fundamental advantage of supporting three-dimensional network topologies, thereby breaking the limitations on complexity associated with planar structures while maintaining a high dirigibility of the light. Our results show how such arrays can be used to control the flow of optical signals within integrated photonic circuits