In recent years, the ability to pattern large areas at the micro- and nano-scale with stimuli-responsive materials has opened the opportunity to engineer surface structures and trigger peculiar properties such as complex optical functionalities or surface properties by laser-matter interactions. The use of light-sensitive materials, such as azobenzene compounds, can open the opportunity to active manipulate in terms of morphology, physical and mechanical properties a pre-patterned architectures, which are intrinsically static once fabricated.
We employ azopolymers, in which the rapid and reversible photoisomerization reaction of azobenzene molecules can actuate mass transport phenomena typically parallel to the light polarization. The azopolymeric film is patterned by soft-imprinting as an array of micro-holes showing a well-defined isotropic round pores. Upon a linearly polarized illumination (365 nm, 150 W/cm2), we observe a deformation of the initial holes along the polarization direction, in such a way that the circular pores are transformed into long closed slits. A rotation of the polarization by 90° triggers a reconfiguration of the pristine round shape, with a good degree of control of the photo-induced pore reshaping. Due to the polarized-directionality of the photo-manipulation we demonstrate the possibility to tune the pristine morphology and properties along specific directions, providing a smart engineered platform with different reshaped micro-patterns. The light-induced contraction and expansion reshaping strategy of a porous polymeric structures shows exciting potential for a number of applications including microfluidics, lithography and tissue engineering. Tuning cells behavior in response to material manipulation cues is a promising goal in biology
In this work we investigate new degrees of freedom in controlling the physical properties of structured photo-sensitive materials that can be usefully exploited in many application fields. We employ azopolymers, a class of light responsive materials, which are structured in micro-pillar array. A reversible and controlled change in morphology of a pre-patterned polymeric film under properly polarized illumination is demonstrated to provide the opportunity to engineer surface structures and dynamically tune their properties. We exploit the laser process taking advantage of the light-induced deformation of a micro-textured azopolymeric film in order to modify the surface hydrophobicity along specific direction.
KEYWORDS: Diamond, Surface plasmons, Near infrared, Quantum information, Single photon, Confocal microscopy, Polarization, Chemical vapor deposition, Color centers, Quantum optics
Single-photon sources (SPS) play a key-role in many applications, spanning from quantum metrology, to quantum information and to the foundations of quantum mechanics. Even if an ideal SPS (i. e. emitting indistinguishable, ”on-demand” single photons, at an arbitrarily fast repetition rate) is far to be realized due to real-world deviations from the ideality, much effort is currently devoted to improving the performance of real sources. With regards to the emission probability, it appears natural to employ sources that are in principle deterministic in the single- photon emission (single quantum emitters such as single atoms, ions, molecules, quantum dots, or color centers in diamond) as opposed to probabilistic ones (usually heralded SPS based on parametric down-conversion). We present an overview of our latest results concerning a work-in-progress NIR pulsed single photon source based on single quantum emitters (color centers in diamond) exploiting recently reported centers. They are particularly interesting because of the narrow emission line (tipically less than 5 nm), the shorter excited state lifetime with respect to NV centres (1 - 2 ns compared to 12 ns, allowing a ten-fold photon emission rate upon saturation) and the polarized emission.
Laser-matter interaction is a unique and simple approach to structure materials or locally modify their properties at the
micro and nanoscale level. Playing with the pulse duration and the laser wavelength, a broad range of materials and
applications can be addressed. Direct irradiation of surfaces with laser beam through a standard optical beam setup
allows an easy and fast structuring of these surfaces in the range of few micrometers. However, the irradiation of
materials through an array of dielectric nanospheres provides a unique opportunity to break the diffraction limit and to
realize structures in the range of hundred of nanometers. This simple, fast and low-cost near-field nanolithography
technique is presented and discussed, as well as its great potential.
The theoretical aspects of the near-field enhancement effects underneath the particles have been studied with a simple
model based on the Mie theory. A commercial FDTD software has also been used to study the influence of the substrate
and the surrounding media, on the energy profile of the photonic jet generated under the sphere. A specific study has
been dedicated to the influence of the dispersion of the sphere diameter on the morphology of the ablation craters. This
technique has been used for patterning bi-layer substrates. The process leads to the formation of a nanoporous membrane
which has been used to realize an array of gold nanodots on silicon. We have also associated the Laser-Induced Forward
Transfer (LIFT) process with the near-field nanolithography to print, in a single laser shot, an array of metallic
nanobumps.
In this proceedings we will present a research project financed by Piedmont regional government (Italy) and finalized to
the realization and commercialization of functional devices for cellular bio-sensing based on diamond. Partners of the
project are: Crisel Instruments, Torino University, Torino Polytechnic, INRIM, Politronica, Bionica Tech, Ulm
University
Here the main features of the final devices will be briefly summarized.
We envisage an active diamond-based cellular substrate that can simultaneously stimulate and detect a variety of signals
(chemical, optical, electrical) to and from neuroendocrine cells, in a fully biocompatible environment for the cellular
system under test. Such a device can be realized by fully exploiting the peculiar properties of diamond: optical
transparency, biocompatibility, chemical inertness, accessibility to a conductive graphite-like phase; properties that will
be further explored and tested during the project.
An easy and effective technique for locally oxidize, melt or remove Porous Silicon layers is presented and discussed. The method takes advantage from the very low thermal conductivity of Porous Silicon. With the aid of a focused laser beam, it is possible to reach temperatures of several hundreds °C at the illuminated spot. Results on fabrication of all-porous planar waveguides are presented and discussed. Preliminary results on the application of this technique for fabricating 2D and 3D photonic crystals are reported.
Porous silicon (PS) has been known for quite a long time for its photoluminescence and for its usage as a sensing element. However, only in recent years this material has been proposed as a substrate for integrated optoelectronic devices and, despite the low fabrication costs and the possibility to tailor the refractive index varying the material porosity, its usage is still at the very beginning. In this paper we present the fabrication of integrated waveguides in PS and we describe our efforts to reduce the propagation losses. Different fabrication approaches have been studied: the first one uses selective anodization to obtain layers with different porosity and thus different refractive index. Another one exploits the different oxidation grades of the various porous layers to fabricate dense oxidized porous silicon waveguides. A detailed characterization of the obtained waveguides is reported. In particular, propagation losses as low as 7 dB/cm have been obtained in simple non-optimized multimode planar waveguides at the optical communication wavelength of 1.55 micrometers . This encouraging result paves the way to the next realization of porous silicon-based integrated optical devices for communication and sensing purposes. Finally, the results concerning a completely new approach, based on a laser ablation technique, to define the rib structure of porous silicon channel waveguides is presented.
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