Showing papers by "Pietro Ferraro published in 2010"
TL;DR: A simple way to draw attolitre liquid droplets from one or multiple sessile drops or liquid film reservoirs using a pyroelectrohydrodynamic dispenser, which is expected to have many applications in biochemical assays and various transport and mixing processes.
Abstract: Manipulating and dispensing liquids on the micrometre- and nanoscale is important in biotechnology and combinatorial chemistry, and also for patterning inorganic, organic and biological inks. Several methods for dispensing liquids exist, but many require complicated electrodes and high-voltage circuits. Here, we show a simple way to draw attolitre liquid droplets from one or multiple sessile drops or liquid film reservoirs using a pyroelectrohydrodynamic dispenser. Local pyroelectric forces, which are activated by scanning a hot tip or an infrared laser beam over a lithium niobate substrate, draw liquid droplets from the reservoir below the substrate, and deposit them on the underside of the lithium niobate substrate. The shooting direction is altered by moving the hot tip or laser to form various patterns at different angles and locations. Our system does not require electrodes, nozzles or circuits, and is expected to have many applications in biochemical assays and various transport and mixing processes.
236 citations
TL;DR: Strain measurements are reported at the 10−13ε-Hz–1/2 level using a fiber Bragg-grating resonator with a diode-laser source that is stabilized against a quartz-disciplined optical frequency comb, thus approaching detection limits set by thermodynamic phase fluctuations in the fiber.
Abstract: The measurement of relative displacements and deformations is important in many fields such as structural engineering, aerospace, geophysics, and nanotechnology. Optical-fiber sensors have become key tools for strain measurements, with sensitivity limits ranging between 10(-9) and 10(-6)e hertz (Hz)(-1/2) (where e is the fractional length change). We report on strain measurements at the 10(-13)e-Hz(-1/2) level using a fiber Bragg-grating resonator with a diode-laser source that is stabilized against a quartz-disciplined optical frequency comb, thus approaching detection limits set by thermodynamic phase fluctuations in the fiber. This scheme may provide a route to a new generation of strain sensors that is entirely based on fiber-optic systems, which are aimed at measuring fundamental physical quantities; for example, in gyroscopes, accelerometers, and gravity experiments.
203 citations
TL;DR: It is shown that 3D dynamic scenes can be projected as an alternative to complicated and heavy computations needed to generate realistic-looking computer generated holograms.
Abstract: A 3D scene is synthesized combining multiple optically recorded digital holograms of different objects. The novel idea consists of compositing moving 3D objects in a dynamic 3D scene using a process that is analogous to stop-motion video. However in this case the movie has the exciting attribute that it can be displayed and observed in 3D. We show that 3D dynamic scenes can be projected as an alternative to complicated and heavy computations needed to generate realistic-looking computer generated holograms. The key tool for creating the dynamic action is based on a new concept that consists of a spatial, adaptive transformation of digital holograms of real-world objects allowing full control in the manipulation of the object’s position and size in a 3D volume with very high depth-of-focus. A pilot experiment to evaluate how viewers perceive depth in a conventional single-view display of the dynamic 3D scene has been performed.
106 citations
TL;DR: A completely numerical method, named digital self-referencing holography, is described to easily accomplish a quantitative phase microscopy for microfluidic devices by a digital holographic microscope.
Abstract: A completely numerical method, named digital self-referencing holography, is described to easily accomplish a quantitative phase microscopy for microfluidic devices by a digital holographic microscope. The approach works through an appropriate numerical manipulation of the retrieved complex wavefront. The self-referencing is obtained by folding the retrieved wavefront in the image plane. The folding operation allows us to obtain the correct phase map by subtracting from the complex region of interest a flat area outside the microfluidic channel. To demonstrate the effectiveness of the method, quantitative phase maps of bovine spermatozoa and in vitro cells are retrieved.
80 citations
TL;DR: The optical reconstruction in the visible range (0.532 microm) of digital holograms recorded at long IR wavelengths by means of a spatial light modulator is demonstrated and the high NA achievable at a long IR wavelength allows us to image large objects at reasonable distances.
Abstract: We demonstrate the optical reconstruction in the visible range (0.532μm) of digital holograms recorded at long IR wavelengths (10.6μm) by means of a spatial light modulator. By using an integrated recording-reconstruction system, it is, in fact, feasible to achieve direct imaging of holograms acquired outside the visible range, i.e., in the IR spectrum. By choosing a Fourier recording configuration, the reconstructed image, obtained at about a 20 times shorter wavelength than the acquisition image, exhibits minor aberrations, which do not significantly affect the optical reconstruction. The high NA achievable at a long IR wavelength allows us to image large objects at reasonable distances.
49 citations
TL;DR: An overview on high-resolution and fast interrogation of optical-fiber sensors relying on laser reflection spectroscopy is given and results on detection performances are presented.
Abstract: An overview on high-resolution and fast interrogation of optical-fiber sensors relying on laser reflection spectroscopy is given Fiber Bragg-gratings (FBGs) and FBG resonators built in fibers of different types are used for strain, temperature and acceleration measurements using heterodyne-detection and optical frequency-locking techniques Silica fiber-ring cavities are used for chemical sensing based on evanescent-wave spectroscopy Various arrangements for signal recovery and noise reduction, as an extension of most typical spectroscopic techniques, are illustrated and results on detection performances are presented
41 citations
TL;DR: It is shown that 1D and 2D patterning of PDMS gratings can be achieved and can pave the way for realizing PDMS micro-structures with high degree of flexibility that avoids the need of moulds fabrication.
Abstract: A new method for direct patterning of Poly(dimethylsiloxane) (PDMS) microstructures is developed by taking advantage of photorefractive effect in a functionalized substrate. Here we show that when a x-cut Iron doped Lithium Niobate (LN) crystal is exposed to appropriate structured laser light, a charge density pattern builds-up in the crystal and a space charge field arise that is able to induce self-patterning of the PDMS liquid film deposited on its surface via the dielectrophoretic effects. Proper heating treatment allows to achieve polymeric linking process creating a solid and stable PDMS microstructures. The self-patterned structures replicate the illuminating light pattern. We show that 1D and 2D patterning of PDMS gratings can be achieved. This new soft-lithographic approach can pave the way for realizing PDMS micro-structures with high degree of flexibility that avoids the need of moulds fabrication.
30 citations
TL;DR: Efficient cw high-power second harmonic generation in a periodically poled LiTaO3 crystal placed in a resonant enhancement cavity and photo-thermal effect induced by photon absorption at the mirrors and in the crystal is observed, which however does not affect stable operation of the cavity.
Abstract: We report on efficient cw high-power second harmonic generation in a periodically poled LiTaO3 crystal placed in a resonant enhancement cavity. We tested three configurations, differing in the coupling mirror reflectivity, and a maximum conversion efficiency of about 76%, corresponding to 6.1 W of green light with 8.0 W of fundamental power, was achieved. This is, to the best of our knowledge, the highest cw power ever reported using a periodically-poled crystal in an external cavity. We observed photo-thermal effect induced by photon absorption at the mirrors and in the crystal, which however does not affect stable operation of the cavity. A further effect arises for two out of the three configurations, at higher values of the input power, which degrades the performance of the locked cavity. We suggest this effect is due to the onset of competing nonlinearities in the same crystal.
23 citations
TL;DR: In the infrared (IR) range, a much higher stability, a wider view angle, and shorter acquisition distances are achievable, allowing easier acquisition of large object holograms as discussed by the authors.
Abstract: Digital Holography (DH) in the infrared (IR) range presents some peculiar aspects compared with the more common DH in the visible range. The current major drawback is due to the size of the pixel pitch of presently available thermal cameras, which is rather large compared to what would be optimal, and what is possible with analog films. However, since the ${\hbox{CO}}_{2}$ laser wavelength is 15 times longer than average visible wavelength, a much higher stability, a wider view angle, and shorter acquisition distances are achievable, allowing easier acquisition of large object holograms.
20 citations
TL;DR: This Letter investigates a method to compress DHs using a sparse matrix representation and demonstrates that using sparse representation allows for a high compression factor with minimal loss in the quality of the reconstructed image.
Abstract: Efficient storage and transmission of digital holograms (DHs) requires the development of appropriate compression techniques for such a special class of images. In this Letter, we investigate a method to compress DHs using a sparse matrix representation. Using digital holography to numerically manage complex wave fields, we are able to apply an adaptive mask, based on a threshold filter, to the object wave field. From there, we store the result of this filtering by sparse representation. In this Letter, we demonstrate that using sparse representation allows for a high compression factor with minimal loss in the quality of the reconstructed image. This technique is efficient for storage and transmission of DHs.
19 citations
TL;DR: In this article, the authors review the activities which took place in analog holography and illustrate the results achieved, referring to the opportunities this technique offers, and the challenges it presents.
Abstract: In analog holography, the infrared (IR) range received quite some attention, since it could provide interesting information, not achievable otherwise. Since digital sensors in this band became recently available and affordable, also digital holography (DH) expanded its feasibility beyond the visible wavelengths. In fact, the IR range allows shorter recording distances, unparalleled larger field of view and less stringent requirements on system stability, together with some specific characteristics, like e.g. the possibility to test IR glasses or other materials transparent to IR radiation, which cannot be controlled in visible range. In this paper we review the activities which took place in this field and illustrate the results achieved, referring to the opportunities this technique offers, and the challenges it presents. We show efficient reconstructions of holograms of objects of various materials, recorded with different resolution digital thermal cameras, in various configurations, and moreover we demonstrate optical holographic display through a liquid crystal based Spatial Light Modulator which gives the chance to get direct 3D imaging and display of long IR range. Moreover we believe this opens the route toward holography in THz region.
TL;DR: An alternative approach to get multiple images in microscopy is reported, exploiting the capabilities of both a lithium niobate diffraction grating and digital holographic technique, overcoming the many constrains imposed by the grating parameters in multi-imaging with Talbot effect or Talbot array illuminators.
Abstract: In this Letter we report on an alternative approach to get multiple images in microscopy, exploiting the capabilities of both a lithium niobate diffraction grating and digital holographic technique. We demonstrate that multi-imaging can be achieved in a lensless configuration by using a hexagonal diffraction grating but overcoming, thanks to digital holography (DH), the many constrains imposed by the grating parameters in multi-imaging with Talbot effect or Talbot array illuminators. In fact, DH permits the numerical reconstruction of the optical field diffracted by the grating, thus obtaining in-focus multiple images in a plane different from the fractional or entire Talbot ones.
TL;DR: This work reports the result of a pilot experiment to evaluate how viewers perceive depth in a conventional single-view display of dynamic 3D scenes synthesized by an opportune numerical hologram deformation.
Abstract: A synthetic scene of real-word objects is obtained through the multiplexing of several digital holograms. Moreover, by an opportune numerical hologram deformation, it is possible to synthesize 3D dynamic scenes that can be displayed by means of a spatial light modulator. In fact, the spatial adaptive deformation of digital holograms allows the control of the object position and size in a 3D volume with a high depth of focus. Through this novel technique a 3D dynamic scenes can be projected as an alternative to difficult and heavy computations needed to generate realistic-looking computer generated holograms. Finally we report the result of a pilot experiment to evaluate how viewers perceive depth in a conventional single-view display of these dynamic 3D scenes.
12 Jul 2010
TL;DR: The Real 3D project as discussed by the authors is a three-year effort to facilitate the entry of a new technology (digital holography) into the 3D capture and display markets.
Abstract: “Digital holography for 3D and 4D real-world objects' capture, processing, and display” (acronym “Real 3D”) is a research project funded under the Information and Communication Technologies theme of the European Commission's Seventh Framework Programme, and brings together nine participants from academia and industry (see www.digitalholography.eu). This three-year project marks the beginning a long-term effort to facilitate the entry of a new technology (digital holography) into the three-dimensional capture and display markets. Its progress at the end of year 2 is summarised.
TL;DR: In this paper, adaptive deformation of digital holograms is used to manage and control the depth of focus in 3D imaging, where objects lying at different distances can be set simultaneously in focus.
Abstract: Through adaptive deformation of digital holograms it is possible to manage and control the depth of focus in 3D imaging. Objects lying at different distances can be set simultaneously in-focus. The method is applied to maintain in focus the reconstructed image of a MEMS subjected to thermal load that changes its position during the hologram acquisition.
01 Feb 2010
TL;DR: In this article, an adaptive deformation of a digital hologram is applied to the original hologram with the aim to change the reconstruction distance and recover the extended focus image (EFI) of a tilted object.
Abstract: We show here that through an adaptive deformation of a digital hologram, it is possible to manage the depth of focus in 3D imaging reconstruction. For Fresnel holograms, a linear deformation is applied to the original hologram with the aim to change the reconstruction distance. On the other hand, by a quadratic deformation of spatial coordinates of a digital hologram acquired in Fourier configuration, it is possible to recover the extended focus image (EFI) of a tilted object.
24 Oct 2010
TL;DR: In this paper, a pyroelectric effect activated by IR laser is used for streaming liquid nano-pico-droplets through pyro electric effect activated with IR laser for 2D and 3D manipulation of nano-drops and liquid printing.
Abstract: A new opto-nanofluidic approach named Pyro-EHD is presented for streaming liquid nano-pico-droplets through pyroelectric effect activated by IR laser. Manipulation in 2-D and 3-D of nano-drops and liquid printing with atto-Liter drops is demonstrated
TL;DR: Nano and pico-droplets have been extracted and dispensed from sessile drop or liquid film reservoirs through pyroelectric effect activated by a hot tip or an IR laser source on polar dielectric substrates as discussed by the authors.
Abstract: Nano- and pico-droplets have been extracted and dispensed from sessile drop or liquid film reservoirs through pyroelectric effect activated by a hot tip or an IR laser source on polar dielectric substrates.
TL;DR: In this paper, a non-invasive electrodeless configuration using the electric field generated by the pyroelectric effect into a dielectric crystal is presented for dispensing liquid nano-and pico-droplets.
Abstract: A new and simple method is presented here for dispensing liquid nano- and pico-droplets through a non-invasive electrode-less configuration using the electric field generated by the pyroelectric effect into a dielectric crystal.
TL;DR: In this paper, a direct patterning of polydimethylsiloxane (PDMS) thin film is demonstrated, in which linear periodic and radial arrays of microchannels are fabricated by changing the wettability on the LN crystal surface.
Abstract: Direct patterning of Polydimethylsiloxane (PDMS) thin film is demonstrated. A procedure is implemented to induce
PDMS self-patterning in one and two dimensional geometries based on surface-charge lithography by means of the
photorefractive properties of iron doped Lithium Niobate (LN) crystal. Linear periodic and radial arrays of microchannels
are fabricated by changing the wettability on the LN crystal surface. The substrate is x-cut Fe+ doped LN
crystal, the covering substance is PDMS. Fabrication process is divided in three stages: PDMS spinning on the substrate,
PDMS reshaping and PDMS curing. After spinning step the sample is inserted in an optical setup. We employ an Argon
laser whose wavelength is 514nm. Light passes trough an amplitude grating that is imaged by a lens. The sample is
positioned in the conjugate plane of the grating. Light impinging on the lower LN surface is spatially inhomogenous and
excites the charge carriers inside the crystal. The space-charge field generate inside the material modulate the refractive
index via electro-optic effect and cause lateral forces near the upper surface able to manipulate and trap liquids. PDMS
moves on the crystal surface trapping itself and gathering up in stripes to form geometries with the same period of the
phase grating written inside the crystal.
While the light source generate the PDMS structure, a thermal treatment applied to the crystal, induces the cross-linking
of the PDMS, leading to a stable and reliable PDMS pattern. We propose an alternative one step patterning process based
on light driven self assembly.