Edoardo De Tommasi

• Researcher at Italian National Research Council

Diatoms represent the major component of phytoplankton and are responsible for about 20-25% of global primary production. Hundreds of millions of years of evolution led to tens of thousands of species differing in dimensions and morphologies. In particular, diatom porous silica cell walls, the frustules, are characterized by an extraordinary, speci...

The ability to control light at the nanoscale is at the basis of contemporary photonics and plasmonics. In particular, properly engineered periodic nanostructures not only allow the inhibition of propagation of light at specific spectral ranges or its confinement in nanocavities or waveguides, but make also possible field enhancement effects in vib...

The non‐trivial polarization topology of bound states in the continuum (BICs) provides new strategies in nanophotonics. The polarization topology depends on the geometric parameters and energy‐momentum dispersion of the system and can be engineered to add specific functionalities for light molding. Herein, such a possibility is investigated by stud...

Ordered, quasi-ordered, and even disordered nanostructures can be identified as constituent components of several protists, plants and animals, making possible an efficient manipulation of light for intra- and inter- species communication, camouflage, or for the enhancement of primary production. Diatoms are ubiquitous unicellular microalgae inhabi...

Nature provides various organisms with ordered or quasi-ordered dielectric nanostructures that enable several animals, plants, and protists to manipulate light, optimizing inter- and intra-species communication, camouflage, or solar light harvesting. In particular, diatom microalgae possess nanostructured silica cell walls, known as frustules, whic...

Spatially disordered but uniformly distributed point patterns characterized by so-called blue-noise long-range spatial correlations are of great benefit in computer graphics, especially in spatial dithering thanks to the spatial isotropy. Herein, the potential photonic properties of blue-noise disordered, homogeneous point processes based on farthe...

Evolution provided, through eras, several animal, vegetal, and protist species with sub-micrometric constituent structures able to manipulate light at the nanoscale in non trivial ways. In particular, diatoms are single-celled microalgae enclosed in a porous silica shell, the frustule, perforated by regular patterns of microand nano-pores and whose...

A new, simple digital holography-based polarization microscope for quantitative birefringence imaging of biological cells is presented. As a proof of concept, two different class of cells have been characterized by polarization sensitive digital holographic imaging (PSDHI). These two cases study reported are: differentiation of leukaemia cells and...

Several living organisms are able to synthesize complex nanostructures provided with peculiar physical and chemical properties by means of finely-tuned, genetically controlled biomineralization processes. Frustules, in particular, are micro- and nano-structured silica shells produced by ubiquitous diatom microalgae, whose optical properties have be...

Several species of diatoms, unicellular microalgae which constitute the main component of phytoplankton, are characterized by an impressive photosynthetic efficiency while presenting a noticeable tolerance versus exposure to detrimental UV radiation (UVR). In particular, the growth rate of the araphid diatom Ctenophora pulchella is not significantl...

Diatom frustules represent one of the most complex examples of micro- and nano-structured materials found in nature, being the result of a biomineralization process refined through tens of milions of years of evolution. They are constituted by an intricate, ordered porous silica matrix which recently found several applications in optoelectronics, s...

Abstract Diatoms can represent the major component of phytoplankton and contribute massively to global primary production in the oceans. Over tens of millions of years they developed an intricate porous silica shell, the frustule, which ensures mechanical protection, sorting of nutrients from harmful agents, and optimization of light harvesting. Se...

The frustule of diatoms, unicellular microalgae, shows very interesting photonic features, generally related to its complicated and quasi-periodic micro- and nano-structure. In order to simulate light propagation inside and through this natural structure, it is important to develop three-dimensional (3D) models for synthetic replica with high spati...

We present an approach enabling the representation of complex values using intensity only fields. The method can be used for imaging with structured illumination and allows the study of new propagating physical quantities with the classical coherent or incoherent light field playing the role of hidden variable. This approach can further be generali...

In this paper the imaging of extended targets by means of structured light and single-pixel detection is examined. In particular, different kinds of illumination patterns (discrete Hadamard; continuous sinusoidal; complex Laguerre-Gauss) are compared both numerically and experimentally in terms of obtainable resolution. Furthermore, a new approach...

Diatoms are ubiquitous monocellular microalgae, responsible for about 20–25% of the global oxygen produced by photosynthesis. Living in environments where sunlight is not so easily accessible, evolution shaped diatoms in order to exploit light with high efficiency. In particular, diatoms are provided with an external, micro-and nanopatterned silica...

Evolution shows that photonic structures are a constituent part of many animals and flora. These elements produce structural color and are useful in predator-prey interactions between animals and in the exploitation of light for photosynthetic organisms. In particular, diatoms have evolved patterned hydrated silica external valves able to confine l...

Some natural structures show three-dimensional morphologies on the micro- and nano- scale, characterized by levels of symmetry and complexity well far beyond those fabricated by best technologies available. This is the case of diatoms, unicellular microalgae, whose protoplasm is enclosed in a nanoporous microshell, made of hydrogenated amorphous si...

Diatoms are among the dominant phytoplankters in the world's oceans, and their external silica investments, resembling artificial photonic crystals, are expected to play an active role in light manipulation. Digital holography allowed studying the interaction with light of Coscinodiscus wailesii cell wall reconstructing the light confinement inside...

We report the generation of subdiffractive laser light focal spots in far-field regime, by means of the so-called Optical Eigenmodes (OEi) technique applied to the focusing properties of a single valve of Arachnoidiscus genus diatom. Diatoms are ubiquitous microalgae whose external walls are able to confine light in several hot-spots. We demonstrat...

In this work, we present a patented procedure that generates three dimensional (3D) image of a microscopic object with high definition, obtained by merging Scanning Electron Microscopy (SEM) and Digital Holography Microscopy (DHM) data. A high spatial resolution (up to rz=λ/20, ryx≅100nm) 3D model of the object is generated starting from two digita...

It is known that a properly arranged distribution of nanoholes on a metallic slab is able to produce, in far field conditions, light confinement at sub-diffraction and even sub-wavelength scale. The same effect can also be implemented by the use of Optical Eigenmode (OEi) technique. In this case, a spatial light modulator (SLM) encodes phase and am...

In this work, resonance phenomena in a negative photonic crystal are experimentally detected and discussed. Localized surface modes and guided mode resonances appear in the reflection spectrum of a photonic crystal slab interacting with external infrared radiation and can be connected with the negative refractive index of the sample . These phenome...

Advances in material science and laser sources renewed the interest in optical parametric oscillators (OPOs). A major attraction of OPOs is the possibility to coherently generate new frequencies over extended tunability ranges. These characteristics are of great interest for spectroscopic applications, which require stable cw highly-coherent radiat...

In this paper, experimental evidences about the resonance phenomena in a negative 2D photonic crystal are shown. Localized plasmon-like modes and guided mode resonances are detected in the reflectivity spectrum of a photonic crystal slab irradiated with out-of-plane incident radiation. The strong confinement of the radiation, in addition to the fie...

Diatoms are monocellular algae responsible of 20-25% of the global oxygen produced by photosynthetic processes. The protoplasm of every single cell is enclosed in an external wall made of porous hydrogenated silica, the frustule. In recent times, many effects related to photonic properties of diatom frustules have been discovered and exploited in a...

Photonic crystal metamaterial can exhibit negative index properties and this behaviour is well described by a resonator model. In this work, we present the experimental evidence that a Lorentz resonator correctly reconstruct data obtained with a negative refracting Photonic Crystal (PhC) by using a standard optical technique, such as ellipsometry....

In this paper, the presence of localized plasmon-like modes at the surface of a silicon two-dimensional photonic crystal slab is demonstrated. In analogy with surface plasmons supported in metals, we observe that, in a photonic crystal metamaterial, the electromagnetic surface waves arise from a negative effective permittivity. The proposed device...

Diatoms are among the dominant phytoplankters in the worl's ocean, and their external silica investments, resembling artificial photonics crystal, are expected to play an active role in light manipulation. Digital holography allowed studying the interaction with light of Coscinodiscus wailesii cell wall reconstructing the light confinement inside t...

We present a narrow-linewidth, singly-resonant cw optical parametric oscillator, emitting more than 1 W in the 2.7–4.2 µm range. The OPO is pumped by a narrow linewidth (40 kHz) fibre-laser system and the signal frequency is locked to a high-finesse Fabry–Pérot cavity in order to increase the spectral resolution, thus obtaining a residual linewidth...

We present a widely-tunable, singly-resonant optical parametric oscillator, emitting more than 1 W in the region between 2.7 and 4.2 μm. Two configurations have been studied in order to improve the frequency stability and the linewidth of the OPO emission. First, we stabilized the signal frequency to a high-finesse Fabry-Perot cavity. Then, we lock...

We present a widely-tunable, singly-resonant optical parametric oscillator, emitting more than 1 W between 2.7 and 4.2 μm, which is phase locked to a self-referenced frequency comb. Both pump and signal frequencies are directly phase-locked to the frequency comb of a NIR-emitting fs mode-locked fibre laser, linked, in turn, to the caesium primary s...

Several biological organisms, from some sea shells to butterflies, exhibit beautiful and sophisticated organs, developed during the evolution of each species, which properties are defined by their nanostructures. The marine diatoms are microscopic algae enclosed between two valves of hydrated amorphous silica. These intricate structures, called fru...

Porous silicon (PSi) is by far a very useful technological platform for optical monitoring of chemical and biological substances and due to its peculiar physical and morphological properties it is worldwide used in sensing experiments. On the other hand, we have discovered a natural material, the micro-shells of marine diatoms, ubiquitous unicellul...

The electric quadrupole fundamental (v=1←0) band of molecular deuterium around 3 μm is accessed by cavity ring-down spectroscopy using a difference-frequency-generation source linked to the Cs-clock primary standard via an optical frequency comb synthesizer. An absolute determination of the line position and strength is reported for the first two t...

Valves of Coscinodiscus wailesii diatoms, monocellular micro-algae characterized by a diameter between 100 and 200 mum, show regular pores patterns which confine light in a spot of few mum2. This effect can be ascribed to the superposition of diffracted wave fronts coming from the pores on the valve surface. We studied the transmission of partially...

The characterization of partially coherent light transmission by micrometer sized valves of marine diatoms is an interesting optical challenge and, from the biological point of view, is of outmost relevance in order to understand evolution mechanisms of such organisms. In the present work, we have studied the transmission of light coming from a mon...

In this work, we report on the fabrication of an hybrid material based on a porous silicon (PSi) layer infiltrated by an amino functionalized poly(ε-caprolattone) (PCL-NH2). The organic–inorganic structure has been characterized by variable angle spectroscopic ellipsometry, optical reflectometry and water contact angle measurements. Apolymer coated...

We have fabricated a microarray of porous silicon Bragg reflectors on a crystalline silicon substrate using a technological process based on standard photolithography and electrochemical anodization of the silicon. The array density is of 170 elements / cm ² and each element has a diameter of 200 μ m . The porous silicon structures have...

In this work, we have fabricated a porous silicon (PSi) Bragg reflectors microarray using a proper technological process based on photolithography and electrochemical anodization of silicon. Each element of the array is characterized by a diameter of 200 mum. The PSi structures have been used as platform to immobilize label-free DNA probe and a sim...

In this communication, we report some new results obtained in our laboratories in design, fabrication and characterization of silicon-based optical structures and devices, including metamaterials, raman light amplifiers, and biomatter-silicon interfaces for sensors and biochips.

Self-assembled monolayers are surfaces consisting of a single layer of molecules on a substrate: widespread examples of chemical and biological nature are alkylsiloxane, fatty acids, and alkanethiolate which can be deposited by different techniques on a large variety of substrates ranging from metals to oxides. We have found that a self-assembled b...

A crystalline silicon surface can be made biocompatible and chemically stable by a self-assembled biofilm of proteins, the hydrophobins (HFBs) purified from the fungus Pleurotus ostreatus. The protein-modified silicon surface shows an improvement in wettability and is suitable for immobilization of other proteins. Two different proteins were succes...

Porous silicon based one-dimensional photonic crystals, such as Bragg mirror and optical microcavity, has been modified by infiltration of a new biocompatible polymer, an amino functionalized poly( ε -caprolactone) ( PCL-NH ₂) , and characterized as optical biochemical sensors. The entrapped polymer adds strong chemical stability to the...

Several biological organisms, from some sea shells to butterflies, exhibit sophisticated optical systems, which have been developed during the evolution of each species. The diatoms are microscopic algae enclosed between two valves of hydrated amorphous silica. These intricate structures, called frustules, show quite symmetric patterns of micrometr...

In the last few years, silicon photonics has been characterized by a wide range of applications in several fields, from communications to sensing, from biophotonics to the development of new artificial materials. In this communication, we report a review of the main results obtained in our laboratories in design, fabrication and characterization of...

In the last few years, silicon photonics has been characterized by a wide range of applications in several fields, from communications to sensing, from biophotonics to the development of new artificial materials. In this communication, we report a review of the main results obtained in our laboratories in design, fabrication and characterization of...

Micro-ring resonators have been widely employed, in recent years, as wavelength filters, switches and frequency converters in optical communication circuits, but can also be successfully used as transducing elements in optical sensing and biosensing. Their operation is based on the optical coupling between a ring-shaped waveguide and one or more li...

Diatoms are monocellular micro-algae provided with external valves, the frustules, made of amorphous hydrated silica. Frustules present patterns of regular arrays of holes, the areolae, characterized by sub-micrometric dimensions. Frustules from centric diatoms are characterized by a radial disposition of areolae and exhibit several optical propert...

The protein–ligand molecular interactions imply strong geometrical and structural rearrangements of the biological complex which are normally detected by high sensitivity optical techniques such as time-resolved fluorescence microscopy. In this work, we have measured, by optical spectroscopic reflectometry in the visible–near-infrared region, the i...

We report on our preliminary results in the realization and characterization of a porous silicon (PSi) resonant mirror (RM) for optical biosensing. We have numerically and experimentally studied the coupling between the electromagnetic field, totally reflected at the base of a high refractive index prism, and the optical modes of a PSi waveguide. T...

Organic-inorganic hybrid devices for biochemical monitoring are gaining increasing interest due to the physical and chemical properties of polymers. On the other hand, porous silicon (PSi) is really a versatile material due to its peculiar morphological, physical and chemical features. In this work, we have synthesized biocompatible multiblock copo...

Diatoms are monocellular micro-algae provided with external valves, the frustules, made of amorphous hydrated silica. Frustules present patterns of regular arrays of holes, the areolae, characterized by sub-micrometric dimensions. In particular, frustules from centric diatoms are characterized by a radial disposition of areolae and exhibit several...

A direct laser writing process has been exploited to fabricate a high order Bragg grating on the surface of a porous silicon slab waveguide. The transmission spectrum of the structure, characterized by a pitch of 10 µm, has been investigated by end-fire coupling on exposure to vapor substances of environmental interest. The analyte molecules substi...

The development of label-free optical biosensors could have a great impact on life sciences as well as on screening techniques for medical and environmental applications. Peptide nucleic acid (PNA) is a nucleic acid analog in which the sugar phosphate backbone of natural nucleic acid has been replaced by a synthetic peptide backbone, resulting in a...

A solid phase oligonucleotide (ON) synthesis on porous silicon (PSi) chip is presented. The prepared Si-OH surface were analyzed by FT-IR and the OH functions were quantified by reaction with 3'-phosphoramidite nucleotide building block. Short ONs were synthesized on the chip surface and the coupling yields evaluated.

Micro-total-analysis-systems and lab-on-chip are more than promises in lot of social interest applications such as clinical diagnostic or environmental monitoring. There is an increasing demand of new and customized devices with better performances to be used in very specific applications. Nanostructured Porous silicon is a functional material and...

In this paper we report on an efficient approximation for the reconstruction and fitting of 2nd harmonic, wavelength-modulated, absorption spectra from Voigt profiles. The model consists in a proper combination of results recently obtained by other authors, concerning on one hand, Fourier analysis of signals resulting from wavelength modulation spe...

The interaction between an analyte and a biological recognition system is normally detected in biosensors by the transducer element which converts the molecular event into a measurable effect, such as an electrical or optical signal. Porous silicon microstructures have unique optical and morphological properties that can be exploited in biosensing....

In this work, an integrated optical microsystems for the continuous detection of flammable liquids has been fabricated and characterized. The proposed system is composed of a the transducer element, which is a vertical silicon/air Bragg mirror fabricated by silicon electrochemical micromachining, sealed with a cover glass anodically bonded on its t...

This paper reports on a compact analyzer for ammonia monitoring in the air based on near-infrared wavelength-modulation diode-laser absorption spectroscopy. Particular attention is devoted to the problem of residual amplitude modulation (RAM), which is responsible for the occurrence of the line profiles' distortions. The RAM effects are eliminated...

This paper reports on the development of a compact analyzer for ammonia monitoring in air, based on a distributed feedback diode laser at 2.005μm. A dual-beam long-path technique was combined with wavelength modulation detection of absorption in order to reach a detection limit of about 25ppb, with a 0.2-Hz equivalent noise bandwidth. Retrieval of...

We report the application of a cw distributed feedback quantum cascade laser to Lamb-dip spectroscopy of C O 2 at 4.3 μ m . With the laser operating in the free-running mode, we observed the sub-Doppler profile of the P ( 28 ) line of the ( 0 , 1 1 , 0 ) → ( 0 , 1 1 , 1 ) hot band by implementing a pump–probe scheme and using wavelength modulation...

By using soluble and insoluble glucose oxidase, the changes in intrinsic emission fluorescence in the visible spectral region were studied as a function of glucose concentration. Insoluble glucose oxidase (GOD) was obtained by entrapment in a gelatine membrane or by covalent attachment on an agarose membrane grafted with hexamethylendiamine. The in...