126 research outputs found
Electromagnetic Field Enhancement in Bloch Surface Waves
We present a systematic comparison between guided modes supported by slab
waveguides and Bloch Surface Waves (BSWs) propagating at the surface of
truncated periodic multilayers. We show that, contrary to common belief, the
best surface field enhancement achievable for guided modes in a slab waveguide
is comparable to that observed for BSWs. At the same time, we demonstrate that,
if one is interested in maximizing the electromagnetic energy density at a
generic point of a dielectric planar structure, BSWs are often preferable to
modes in which light is confined uniquely by total internal reflection. Since
these results are wavelength independent and have been obtained by considering
a very wide range of refractive indices of the structure constituent materials,
we believe they can prove helpful in the design of future structures for the
control and the enhancement of the light-matter interaction.Comment: 8 pages, 6 figure
Optical resonators based on Bloch surface waves
A few recent works suggest the possibility of controlling light propagation
at the interface of periodic multilayers supporting Bloch surface waves (BSWs),
but optical resonators based on BSWs are yet to demonstrate. Here we discuss
the feasibility of exploiting guided BSWs in a ring resonator configuration. In
particular, we investigate the main issues related to the design of these
structures, and we discuss about their limitations in terms of quality factors
and dimensions. We believe these results might be useful for the development of
a complete BSW-based platform for application ranging from optical sensing to
the study of the light-matter interaction in micro and nano structures.Comment: 10 pages, 10 figures. To be published in JOSA
Long-range Bloch Surface Waves in Photonic Crystal Ridges
We theoretically study light propagation in guided Bloch surface waves (BSWs)
supported by photonic crystal ridges. We demonstrate that low propagation
losses can be achieved just by a proper design of the multilayer to obtain
photonic band gaps for both light polarizations. We present a design strategy
based on a Fourier analysis that allows one to obtain intrinsic losses as low
as 5 dB/km for a structure operating in the visible spectral range. These
results clarify the limiting factors to light propagation in guided BSWs and
represent a fundamental step towards the development of BSW-based integrated
optical platforms.Comment: v2: figures revise
Coherence in parametric fluorescence
We investigate spontaneous four wave mixing (SFWM) in a single-channel
side-coupled integrated spaced sequence of resonators (SCISSOR). Analytic
expressions for the number of photon pairs generated, as well as the biphoton
wave function (joint spectral amplitude) describing the pairs, are derived and
numerically computed for different pump pulse durations and numbers of ring
resonators. In the limit of a long input pump pulse, we show a strong analogy
between super-linear scaling of generation efficiency with respect to the
number of rings in the structure and Dicke superradiance. More generally, we
discuss in detail the factors that influence the shape of the biphoton wave
function, as well as the conditions for observing super-SFWM
A Green function method to study thin diffraction gratings
The anomalous features in diffraction patterns first observed by Wood over a
century ago have been the subject of many investigations, both experimental and
theoretical. The sharp, narrow structures - and the large resonances with which
they are sometimes associated - arise in numerous studies in optics and
photonics. In this paper we present an analytical method to study diffracted
fields of optically thin gratings that highlights the nonanalyticities
associated with the anomalies. Using this approach we can immediately derive
diffracted fields for any polarization in a compact notation. While our
equations are approximate, they fully respect energy conservation in the
electromagnetic field, and describe the large exchanges of energy between
incident and diffracted fields that can arise even for thin gratings.Comment: 19 pages, 8 figure
Generation of photon pairs by spontaneous four-wave mixing in linearly uncoupled resonators
We present a detailed study of the generation of photon pairs by spontaneous
four-wave mixing in a structure composed of two linearly uncoupled resonators,
where energy can be transferred from one resonator to another only through a
nonlinear interaction. Specifically, we consider the case of two
racetrack-shaped resonators connected by a coupler designed to guarantee that
the resonance comb of each resonator can be tuned independently, and to allow
the nonlinear interaction between modes that belong to different combs. We show
that such a coupler can be realized in at least two ways: a directional coupler
or a Mach-Zehnder interferometer. For these two scenarios, we derive analytic
expressions for the pair generation rate via single-pump spontaneous four-wave
mixing, and compare these results with that achievable in a single ring
resonator
Programmable integrated source of polarization and frequency-bin hyperentangled photon pairs
We present a system of four ring resonators capable of generating
programmable polarization and frequency-bin entangled photon pairs on an
integrated photonic device. Each ring is pumped with a continuous wave,
generating photon pairs with the same polarization in two pairs of frequency
bins via spontaneous fourwave mixing. We show that the density operator of the
generated state represents a hyperentangled state in the polarization and
frequency bin degrees of freedom. We also calculate the generation rate of the
state.Comment: 9 pages, 4 figure
Stimulated and spontaneous four-wave mixing in silicon-on-insulator coupled photonic wire nano-cavities
We report on four-wave mixing in coupled photonic crystal nano-cavities on a
silicon-on-insulator platform. Three photonic wire cavities are side-coupled to
obtain three modes equally separated in energy. The structure is designed to be
self-filtering, and we show that the pump is rejected by almost two orders of
magnitudes. We study both the stimulated and the spontaneous four-wave mixing
processes: owing to the small modal volume, we find that signal and idler
photons are generated with a hundred-fold increase in efficiency as compared to
silicon micro-ring resonators
Strong coupling between excitons in organic semiconductors and Bloch Surface Waves
We report on the strong coupling between the Bloch surface wave supported by
an inorganic multilayer structure and -aggregate excitons in an organic
semiconductor. The dispersion curves of the resulting polariton modes are
investigated by means of angle-resolved attenuated total reflection as well as
photoluminescence experiments. The measured Rabi splitting is 290 meV. These
results are in good agreement with those obtained from our theoretical model
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