Giacomo Corrielli, 2 Andrea Crespi, 2 Roberto Osellame, 2, ∗ Riccardo Geremia, Roberta Ramponi, 2... more Giacomo Corrielli, 2 Andrea Crespi, 2 Roberto Osellame, 2, ∗ Riccardo Geremia, Roberta Ramponi, 2 Linda Sansoni, Andrea Santinelli, Paolo Mataloni, 4 and Fabio Sciarrino 4, † Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche (IFN-CNR), Piazza Leonardo da Vinci 32, I-20133 Milano, Italy Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 5, I-00185 Roma, Italy Istituto Nazionale di Ottica, Consiglio Nazionale delle Ricerche (INO-CNR), Largo Enrico Fermi 6, I-50125 Firenze, Italy
The efficacy of tumor photodynamic therapy (PDT) with haematoporphyrin derivative (HpD) as the ph... more The efficacy of tumor photodynamic therapy (PDT) with haematoporphyrin derivative (HpD) as the photosensitizer is now established. However, photosensitizing drugs with a higher absorption at the longer wavelengths that can penetrate more deeply into tissues are likely to improve PDT therapeutic efficiency.
Laser-Based Micro- and Nanopackaging and Assembly Vi, 2012
ABSTRACT We have fabricated entirely by femtosecond micromachining a plastic optofluidic chip wit... more ABSTRACT We have fabricated entirely by femtosecond micromachining a plastic optofluidic chip with integrated microfluidics and optical excitation/detection. First a microfluidic channel and two fiber grooves were ablated on one surface of the PMMA substrate. In order to collect and focus the fluorescence signal onto a detector, two binary Fresnel lenses were micromachined on the back surface of the substrate. The operatio of the integrated optofluidic chip was demonstrated by filling the channel with different Rhodamine 6G solution, and a limit of detection of 50 nM was achieved.
ISOT 2009 - International Symposium on Optomechatronic Technologies, 2009
Lab-on-a-chips (LOCs) are becoming one of the most powerful tools of analytical chemistry, with a... more Lab-on-a-chips (LOCs) are becoming one of the most powerful tools of analytical chemistry, with a broad application in life sciences, biotechnology and drug development. They incorporate in a single substrate the functions of a biological laboratory (i.e. microfluidic channels, reservoirs, valves, pumps and sensors). Their main advantages include the possibility of working with small sample quantities (from nano-to picoliters), high sensitivity, speed of analysis and the possibility of measurement automation and standardization. Direct on-chip integration of photonic devices for detection of biomolecules flowing in the microchannels is one of the main objectives of current research in this field, which becomes particularly challenging in case of analytes that cannot be chemically labeled. In fact in this case an interferometric detection is often needed and optical devices, such as interferometers, have to be integrated. Ultrafast laser writing of waveguides in glasses proves to be a very flexible, simple and well suited method also for this kind of applications. As a post-processing technique it doesn't affect the fabrication of the fluidic part and its unique threedimensional capabilities allow realization of devices with complex design. In this work we report on the use of femtosecond laser pulses to fabricate a Mach-Zehnder interferometer, integrated with a microfluidic channel; this provides label-free sensing, by means of refractive index measurements, of samples flowing in the microchannel.
ABSTRACT form only given. In 1958 P.W. Anderson predicted that the wave-function of a quantum par... more ABSTRACT form only given. In 1958 P.W. Anderson predicted that the wave-function of a quantum particle can be localized in the presence of a static disordered potential [1]. This phenomenon arises from the destructive interference of waves propagating in static disordered media. As a consequence, in these conditions, particle and energy transport through a disordered medium are expected to be strongly suppressed and an initially localized wave packet does not spread out with time. In this work we experimentally study the localization properties of a pair of non-interacting particles obeying bosonic/fermionic statistics by simulating a one-dimensional QW of a two-photon polarization-entangled state in a disordered medium. Quantum walk is the quantum counterpart of classical random walk: a walker jumping between different sites of a lattice with a given probability. In the quantum case the walker is a quantum system, whose quantum properties affect the transport. When multi-particle walkers travel within the QW their bosonic or fermionic nature strongly affects the transport. Here we implement different quantum statistics by exploiting of the polarization-entangled bi-photon input state. The QW circuit has been experimentally realized by femtosecond laser writing which provides a perfect phase stability [2]. In particular, we realized an 8-step quantum walk circuit composed by an array of polarization independent beam splitters arranged in a cascade configuration of Mach-Zehnder (MZ) interferometers (see Fig.1a).
Abstract We demonstrate active waveguide writing by a compact diode-pumped cavity dumped femtosec... more Abstract We demonstrate active waveguide writing by a compact diode-pumped cavity dumped femtosecond Yb: glass oscillator. The waveguides are perfectly mode-matched to standard single-mode telecom fibers at 1.55 mm and show internal gain and laser action.
We present here a fully integrated fluorescence activated cell sorter (FACS), able to perform ana... more We present here a fully integrated fluorescence activated cell sorter (FACS), able to perform analysis at single cell level. This optofluidic device is obtained on a fused silica substrate with the use of femtosecond laser micromachining.
2014 16th International Conference on Transparent Optical Networks (ICTON), 2014
ABSTRACT Femtosecond laser microfabrication is a versatile method able to form surface ablated fe... more ABSTRACT Femtosecond laser microfabrication is a versatile method able to form surface ablated features in any material, buried waveguides and microchannels in transparent glasses, and 3D microstructures in photoresists via two photon polymerization. In this paper, we describe the fundamentals of each of these three important modalities of the femtosecond laser micromachining method and present several novel devices that have application in lab on a chip, biosensing and display industries.
Surface texturing of silicon substrates is performed by femtosecond laser irradiation at high rep... more Surface texturing of silicon substrates is performed by femtosecond laser irradiation at high repetition rates. Various fabrication parameters are optimized in order to achieve very high absorptance in the visible region from the micro-structured silicon wafer as compared to the unstructured one. A 70-fold reduction of the processing time is demonstrated by increasing the laser repetition rate from 1 kHz to 200 kHz. Further scaling up to 1 MHz can be foreseen.
We report on a direct experimental observation of dynamic localization (DL) of light in sinusoida... more We report on a direct experimental observation of dynamic localization (DL) of light in sinusoidallycurved Lithium-Niobate waveguide arrays which provides the optical analog of DL for electrons in periodic potentials subjected to ac electric fields as originally proposed by Dunlap and Kenkre [D.H. Dunlap and V.M. Kenkre, Phys. Rev. B 34, 3625 (1986)]. The theoretical condition for DL in a sinusoidal field is experimentally demonstrated.
An optical visualization of the semiclassical dynamics of a multiband Bloch particle subjected to... more An optical visualization of the semiclassical dynamics of a multiband Bloch particle subjected to an external time-dependent force is experimentally reported using an array of tunneling-coupled lithium-niobate optical waveguides with a curved axis. It is shown that a Gaussian beam injected into the array breaks into wave packets belonging to different bands of the array which propagate as semiclassical Bloch particles in a timedependent force simulated by the waveguide axis curvature. According to the semiclassical analysis and to numerical simulations of the scalar beam propagation equation, the paths followed by the wave packets is proven to depend on the initial momentum, which is controlled by varying the incidence angle of the Gaussian beam. In particular, we study in detail, both theoretically and experimentally, the wave packet refocusing dynamics which occurs in the presence of a semicycle sinusoidal force and reveal its deep difference with respect to Bloch oscillations in a dc field.
Interaction between femtosecond laser pulses and semiconductor nanocrystals is thoroughly studied... more Interaction between femtosecond laser pulses and semiconductor nanocrystals is thoroughly studied. Absorption, Raman, and photoluminescence spectra together with transmission electron microscopy images are presented for irradiated regions and compared to those of the pristine material. A simple model based on charge transfer to the glass matrix from the nanocrystals is adopted to explain the strong color changes and the photoluminescence
Optical parametric generation in dispersion-engineered waveguides fabricated by proton exchange i... more Optical parametric generation in dispersion-engineered waveguides fabricated by proton exchange in periodically poled lithium niobate is numerically investigated as a means for producing widely tunable midinfrared ultrashort pulses starting from low energy pump pulses at a 1.55 m wavelength and with 100 fs duration, which are typical parameters of amplified Er-fiber oscillators. Numerical evidence is given about the generation of sub-100 fs nearly transform-limited pulses in the 2.4-4.4 m spectral range.
Room-temperature cw second-harmonic generation from telecom wavelengths, with 30% W −1 cm −2 effi... more Room-temperature cw second-harmonic generation from telecom wavelengths, with 30% W −1 cm −2 efficiency and second-harmonic power levels up to 41 mW, was achieved in buried waveguides fabricated by reverse-proton exchange in 1% MgO-doped stoichiometric lithium tantalate without any evidence of optical damage. The technology proves suitable for the realization of efficient nonlinear frequency converters and all-optical devices.
Buried waveguides with nearly symmetrical refractive index profile and high homogeneity were obta... more Buried waveguides with nearly symmetrical refractive index profile and high homogeneity were obtained by applying the reverse-proton-exchange technique to MgO doped stoichiometric lithium tantalate, a promising nonlinear material due to its low coercive field and high damage threshold. By characterizing several samples fabricated under different experimental conditions, we identified a fabrication procedure in which the annealing and the reverse-exchange processes are performed at the same temperature, and the diffusion of hydrogen ions towards the substrate is negligible during the burial step. These fabrication conditions are simpler than the conventional ones used for lithium niobate. Accurate empirical laws were found, relating the fabrication conditions to the optical parameters.
We studied the cascading of two second order processes and its use for frequency conversion (gene... more We studied the cascading of two second order processes and its use for frequency conversion (generation of a pulse at frequency wp-A w from a signal at wp + A w under the action of a pump at to 0) in a planar Ti-indiffused lithium niobate waveguide. Consistently with the predictions of a numerical model based on the fabrication parameters of the waveguide and the substrate refractive index, we find that the TE~ mode best serves as the intermediate sum-frequency field for the TM o signals and pump. With a propagation length of 17 ram, pulses of 20 ps time duration and A ~ 1.1 txm, we observed wavelength conversion with 4% efficiency when the energy of the pump pulse per unit width was about 20 ixJ/m.
Giacomo Corrielli, 2 Andrea Crespi, 2 Roberto Osellame, 2, ∗ Riccardo Geremia, Roberta Ramponi, 2... more Giacomo Corrielli, 2 Andrea Crespi, 2 Roberto Osellame, 2, ∗ Riccardo Geremia, Roberta Ramponi, 2 Linda Sansoni, Andrea Santinelli, Paolo Mataloni, 4 and Fabio Sciarrino 4, † Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche (IFN-CNR), Piazza Leonardo da Vinci 32, I-20133 Milano, Italy Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 5, I-00185 Roma, Italy Istituto Nazionale di Ottica, Consiglio Nazionale delle Ricerche (INO-CNR), Largo Enrico Fermi 6, I-50125 Firenze, Italy
The efficacy of tumor photodynamic therapy (PDT) with haematoporphyrin derivative (HpD) as the ph... more The efficacy of tumor photodynamic therapy (PDT) with haematoporphyrin derivative (HpD) as the photosensitizer is now established. However, photosensitizing drugs with a higher absorption at the longer wavelengths that can penetrate more deeply into tissues are likely to improve PDT therapeutic efficiency.
Laser-Based Micro- and Nanopackaging and Assembly Vi, 2012
ABSTRACT We have fabricated entirely by femtosecond micromachining a plastic optofluidic chip wit... more ABSTRACT We have fabricated entirely by femtosecond micromachining a plastic optofluidic chip with integrated microfluidics and optical excitation/detection. First a microfluidic channel and two fiber grooves were ablated on one surface of the PMMA substrate. In order to collect and focus the fluorescence signal onto a detector, two binary Fresnel lenses were micromachined on the back surface of the substrate. The operatio of the integrated optofluidic chip was demonstrated by filling the channel with different Rhodamine 6G solution, and a limit of detection of 50 nM was achieved.
ISOT 2009 - International Symposium on Optomechatronic Technologies, 2009
Lab-on-a-chips (LOCs) are becoming one of the most powerful tools of analytical chemistry, with a... more Lab-on-a-chips (LOCs) are becoming one of the most powerful tools of analytical chemistry, with a broad application in life sciences, biotechnology and drug development. They incorporate in a single substrate the functions of a biological laboratory (i.e. microfluidic channels, reservoirs, valves, pumps and sensors). Their main advantages include the possibility of working with small sample quantities (from nano-to picoliters), high sensitivity, speed of analysis and the possibility of measurement automation and standardization. Direct on-chip integration of photonic devices for detection of biomolecules flowing in the microchannels is one of the main objectives of current research in this field, which becomes particularly challenging in case of analytes that cannot be chemically labeled. In fact in this case an interferometric detection is often needed and optical devices, such as interferometers, have to be integrated. Ultrafast laser writing of waveguides in glasses proves to be a very flexible, simple and well suited method also for this kind of applications. As a post-processing technique it doesn't affect the fabrication of the fluidic part and its unique threedimensional capabilities allow realization of devices with complex design. In this work we report on the use of femtosecond laser pulses to fabricate a Mach-Zehnder interferometer, integrated with a microfluidic channel; this provides label-free sensing, by means of refractive index measurements, of samples flowing in the microchannel.
ABSTRACT form only given. In 1958 P.W. Anderson predicted that the wave-function of a quantum par... more ABSTRACT form only given. In 1958 P.W. Anderson predicted that the wave-function of a quantum particle can be localized in the presence of a static disordered potential [1]. This phenomenon arises from the destructive interference of waves propagating in static disordered media. As a consequence, in these conditions, particle and energy transport through a disordered medium are expected to be strongly suppressed and an initially localized wave packet does not spread out with time. In this work we experimentally study the localization properties of a pair of non-interacting particles obeying bosonic/fermionic statistics by simulating a one-dimensional QW of a two-photon polarization-entangled state in a disordered medium. Quantum walk is the quantum counterpart of classical random walk: a walker jumping between different sites of a lattice with a given probability. In the quantum case the walker is a quantum system, whose quantum properties affect the transport. When multi-particle walkers travel within the QW their bosonic or fermionic nature strongly affects the transport. Here we implement different quantum statistics by exploiting of the polarization-entangled bi-photon input state. The QW circuit has been experimentally realized by femtosecond laser writing which provides a perfect phase stability [2]. In particular, we realized an 8-step quantum walk circuit composed by an array of polarization independent beam splitters arranged in a cascade configuration of Mach-Zehnder (MZ) interferometers (see Fig.1a).
Abstract We demonstrate active waveguide writing by a compact diode-pumped cavity dumped femtosec... more Abstract We demonstrate active waveguide writing by a compact diode-pumped cavity dumped femtosecond Yb: glass oscillator. The waveguides are perfectly mode-matched to standard single-mode telecom fibers at 1.55 mm and show internal gain and laser action.
We present here a fully integrated fluorescence activated cell sorter (FACS), able to perform ana... more We present here a fully integrated fluorescence activated cell sorter (FACS), able to perform analysis at single cell level. This optofluidic device is obtained on a fused silica substrate with the use of femtosecond laser micromachining.
2014 16th International Conference on Transparent Optical Networks (ICTON), 2014
ABSTRACT Femtosecond laser microfabrication is a versatile method able to form surface ablated fe... more ABSTRACT Femtosecond laser microfabrication is a versatile method able to form surface ablated features in any material, buried waveguides and microchannels in transparent glasses, and 3D microstructures in photoresists via two photon polymerization. In this paper, we describe the fundamentals of each of these three important modalities of the femtosecond laser micromachining method and present several novel devices that have application in lab on a chip, biosensing and display industries.
Surface texturing of silicon substrates is performed by femtosecond laser irradiation at high rep... more Surface texturing of silicon substrates is performed by femtosecond laser irradiation at high repetition rates. Various fabrication parameters are optimized in order to achieve very high absorptance in the visible region from the micro-structured silicon wafer as compared to the unstructured one. A 70-fold reduction of the processing time is demonstrated by increasing the laser repetition rate from 1 kHz to 200 kHz. Further scaling up to 1 MHz can be foreseen.
We report on a direct experimental observation of dynamic localization (DL) of light in sinusoida... more We report on a direct experimental observation of dynamic localization (DL) of light in sinusoidallycurved Lithium-Niobate waveguide arrays which provides the optical analog of DL for electrons in periodic potentials subjected to ac electric fields as originally proposed by Dunlap and Kenkre [D.H. Dunlap and V.M. Kenkre, Phys. Rev. B 34, 3625 (1986)]. The theoretical condition for DL in a sinusoidal field is experimentally demonstrated.
An optical visualization of the semiclassical dynamics of a multiband Bloch particle subjected to... more An optical visualization of the semiclassical dynamics of a multiband Bloch particle subjected to an external time-dependent force is experimentally reported using an array of tunneling-coupled lithium-niobate optical waveguides with a curved axis. It is shown that a Gaussian beam injected into the array breaks into wave packets belonging to different bands of the array which propagate as semiclassical Bloch particles in a timedependent force simulated by the waveguide axis curvature. According to the semiclassical analysis and to numerical simulations of the scalar beam propagation equation, the paths followed by the wave packets is proven to depend on the initial momentum, which is controlled by varying the incidence angle of the Gaussian beam. In particular, we study in detail, both theoretically and experimentally, the wave packet refocusing dynamics which occurs in the presence of a semicycle sinusoidal force and reveal its deep difference with respect to Bloch oscillations in a dc field.
Interaction between femtosecond laser pulses and semiconductor nanocrystals is thoroughly studied... more Interaction between femtosecond laser pulses and semiconductor nanocrystals is thoroughly studied. Absorption, Raman, and photoluminescence spectra together with transmission electron microscopy images are presented for irradiated regions and compared to those of the pristine material. A simple model based on charge transfer to the glass matrix from the nanocrystals is adopted to explain the strong color changes and the photoluminescence
Optical parametric generation in dispersion-engineered waveguides fabricated by proton exchange i... more Optical parametric generation in dispersion-engineered waveguides fabricated by proton exchange in periodically poled lithium niobate is numerically investigated as a means for producing widely tunable midinfrared ultrashort pulses starting from low energy pump pulses at a 1.55 m wavelength and with 100 fs duration, which are typical parameters of amplified Er-fiber oscillators. Numerical evidence is given about the generation of sub-100 fs nearly transform-limited pulses in the 2.4-4.4 m spectral range.
Room-temperature cw second-harmonic generation from telecom wavelengths, with 30% W −1 cm −2 effi... more Room-temperature cw second-harmonic generation from telecom wavelengths, with 30% W −1 cm −2 efficiency and second-harmonic power levels up to 41 mW, was achieved in buried waveguides fabricated by reverse-proton exchange in 1% MgO-doped stoichiometric lithium tantalate without any evidence of optical damage. The technology proves suitable for the realization of efficient nonlinear frequency converters and all-optical devices.
Buried waveguides with nearly symmetrical refractive index profile and high homogeneity were obta... more Buried waveguides with nearly symmetrical refractive index profile and high homogeneity were obtained by applying the reverse-proton-exchange technique to MgO doped stoichiometric lithium tantalate, a promising nonlinear material due to its low coercive field and high damage threshold. By characterizing several samples fabricated under different experimental conditions, we identified a fabrication procedure in which the annealing and the reverse-exchange processes are performed at the same temperature, and the diffusion of hydrogen ions towards the substrate is negligible during the burial step. These fabrication conditions are simpler than the conventional ones used for lithium niobate. Accurate empirical laws were found, relating the fabrication conditions to the optical parameters.
We studied the cascading of two second order processes and its use for frequency conversion (gene... more We studied the cascading of two second order processes and its use for frequency conversion (generation of a pulse at frequency wp-A w from a signal at wp + A w under the action of a pump at to 0) in a planar Ti-indiffused lithium niobate waveguide. Consistently with the predictions of a numerical model based on the fabrication parameters of the waveguide and the substrate refractive index, we find that the TE~ mode best serves as the intermediate sum-frequency field for the TM o signals and pump. With a propagation length of 17 ram, pulses of 20 ps time duration and A ~ 1.1 txm, we observed wavelength conversion with 4% efficiency when the energy of the pump pulse per unit width was about 20 ixJ/m.
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Papers by R. Ramponi