40 research outputs found
Roadmap on holography
From its inception holography has proven an extremely productive and attractive area of research. While specific technical applications give rise to 'hot topics', and three-dimensional (3D) visualisation comes in and out of fashion, the core principals involved continue to lead to exciting innovations in a wide range of areas. We humbly submit that it is impossible, in any journal document of this type, to fully reflect current and potential activity; however, our valiant contributors have produced a series of documents that go no small way to neatly capture progress across a wide range of core activities. As editors we have attempted to spread our net wide in order to illustrate the breadth of international activity. In relation to this we believe we have been at least partially successful.This work was supported by Ministerio de EconomĂa, Industria y Competitividad (Spain) under projects FIS2017-82919-R (MINECO/AEI/FEDER, UE) and FIS2015-66570-P (MINECO/FEDER), and by Generalitat Valenciana (Spain) under project PROMETEO II/2015/015
Roadmap on holography
From its inception holography has proven an extremely productive and attractive area of research. While specific technical applications give rise to 'hot topics', and three-dimensional (3D) visualisation comes in and out of fashion, the core principals involved continue to lead to exciting innovations in a wide range of areas. We humbly submit that it is impossible, in any journal document of this type, to fully reflect current and potential activity; however, our valiant contributors have produced a series of documents that go no small way to neatly capture progress across a wide range of core activities. As editors we have attempted to spread our net wide in order to illustrate the breadth of international activity. In relation to this we believe we have been at least partially successful
Reply to the Comment on Spontaneously Ordered SolâGel Composites with Submicrometer Periodicity
Spontaneous Formation of Fractal Aggregates of Au Nanoparticles in Epoxy-Siloxane Films and Their Application as Substrates for NIR Surface Enhanced Raman Spectroscopy
We present a facile, inexpensive route to free-standing, thermo-mechanically robust and flexible epoxy-siloxane substrates embedded with fractal aggregates of Au nanoparticles, and demonstrate their efficiency as substrates for surface enhanced Raman spectroscopy (SERS) at NIR wavelengths. The metallodielectric films are prepared by generating Au nanoparticles through the in-situ reduction of gold (III) chloride trihydrate in epoxypropoxypropyl terminated polydimethyl siloxane (EDMS). The metal nanoparticles spontaneously aggregate into fractal structures in the colloid, which could then be drop-cast onto a substrate. Subsequent UV-initiated cationic polymerization of epoxide moieties in EDMS transforms the fluid colloid into a thin, free-standing film, which contains a dense distribution of fractal aggregates of Au nanoparticles. We used electron and optical microscopy as well as UVâVisâNIR spectrometry to monitor the evolution of nanoparticles and to optically and structurally characterize the resulting films. Raman spectroscopy of the chromophore Eosin Y adsorbed onto the metallodielectric films showed that they are excellent SERS substrates at NIR excitation with an enhancement factor of ~9.3 Ă 103
Self-Organized Lattices of Nonlinear Optochemical Waves in Photopolymerizable Fluids: The Spontaneous Emergence of 3-D Order in a Weakly Correlated System
Spontaneous Emergence of Nonlinear Light Waves and Self-Inscribed Waveguide Microstructure during the Cationic Polymerization of Epoxides
We report spontaneous pattern formation
due to modulation instability
(MI) of a broad, uniform, incandescent beam as it propagates through
a fluid medium undergoing cationic ring-opening polymerization of
epoxide moieties and show that the dynamics of the process can be
controlled through polymerization kinetics. By strong contrast, MI
in the half century-old field of nonlinear light propagation has until
now been described predominantly in terms of optical parameters such
as coherence, intensity and wavelength. The increase in refractive
index (Î<i>n</i>) originating from the cross-linking
polymerization of biscycloaliphatic epoxy monomers pushes the system
into a nonlinear regime, where normally negligible spatial noise becomes
greatly amplified. The perturbed optical field stabilizes by spontaneously
dividing into thousands of self-trapped filaments of light. Because
each filament inscribes a permanent microscopic channel along its
propagation path, the initially isotropic fluid medium solidifies
into a densely packed array of self-induced waveguides. These experiments
demonstrated the strong correlation between the kinetics of cationic
polymerization and dynamics of MI; the beam becomes unstable only
within a narrow parameter range where a critical balance is struck
between the photoresponse speed (determined by polymerization rate)
and the magnitude of Î<i>n</i> (determined by extent
of cross-linking). The former needs to be sufficiently fast to respond
to noise while the latter must be large enough to generate high-refractive
index seeds that trigger MI. Outside of this range, MI is entirely
suppressed. This study reveals that nonlinear waveforms emerge in
a familiar, widely employed epoxide photopolymer system, which for
the first time highlights the possibility of tuning MI through the
kinetics of a photochemical reaction