404 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
Quantum frequency conversion and strong coupling of photonic modes using four-wave mixing in integrated microresonators
Single photon-level quantum frequency conversion has recently been
demonstrated using silicon nitride microring resonators. The resonance
enhancement offered by such systems enables high-efficiency translation of
quantum states of light across wide frequency ranges at sub-watt pump powers.
Using a quantum-mechanical Hamiltonian formalism, we present a detailed
theoretical analysis of the conversion dynamics in these systems, and show that
they are capable of converting single- and multi-photon quantum states.
Analytic formulas for the conversion efficiency, spectral conversion
probability density, and pump power requirements are derived which are in good
agreement with previous theoretical and experimental results. We show that with
only modest improvement to the state of the art, efficiencies exceeding 95% are
achievable using less than 100 mW of pump power. At the critical driving
strength that yields maximum conversion efficiency, the spectral conversion
probability density is shown to exhibit a flat-topped peak, indicating a range
of insensitivity to the spectrum of a single photon input. Two alternate
theoretical approaches are presented to study the conversion dynamics: a
dressed mode approach that yields a better intuitive picture of the conversion
process, and a study of the temporal dynamics of the participating modes in the
resonator, which uncovers a regime of Rabi-like coherent oscillations of single
photons between two different frequency modes. This oscillatory regime arises
from the strong coupling of distinct frequency modes mediated by coherent
pumps.Comment: 14 pages, 7 figure
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
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
Second harmonic generation in gallium phosphide photonic crystal nanocavities with ultralow continuous wave pump power
We demonstrate second harmonic generation in photonic crystal nanocavities
fabricated in the semiconductor gallium phosphide. We observe second harmonic
radiation at 750 nm with input powers of only nanowatts coupled to the cavity
and conversion efficiency .
The large electronic band gap of GaP minimizes absorption loss, allowing
efficient conversion. Our results are promising for integrated, low-power light
sources and on-chip reduction of input power in other nonlinear processes
Scalable squeezed light source for continuous variable quantum sampling
We propose a novel squeezed light source capable of meeting the stringent
requirements of continuous variable quantum sampling. Using the effective
interaction induced by a strong driving beam in the presence of the
response in an integrated microresonator, our device is compatible
with established nanophotonic fabrication platforms. With typical realistic
parameters, squeezed states with a mean photon number of 10 or higher can be
generated in a single consistent temporal mode at repetition rates in excess of
100MHz. Over 15dB of squeezing is achievable in existing ultra-low loss
platforms
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
Stimulated Emission Tomography: Beyond Polarization
In this work we demonstrate the use of stimulated emission tomography to
characterize a hyper-entangled state generated by spontaneous parametric
down-conversion in a CW-pumped source. In particular, we consider the
generation of hyper-entangled states consisting of photon pairs entangled in
polarisation and path. These results extend the capability of stimulated
emission tomography beyond the polarisation degree of freedom, and demonstrate
the use of this technique to study states in higher dimension Hilbert spaces
- …