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  • Quantitative imaging of microtubule alteration as an early marker of axonal degeneration after ischemia in neurons

     Psilodimitrakopoulos, Sotiris; Petegnief, Valerie; de Vera, Nuria; Hernandez, Oscar; Artigas Garcia, David; Planas, Ana Maria; Loza Alvarez, Pablo
    Biophysical journal
    Date of publication: 2013-03-05
    Journal article

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    Neuronal death can be preceded by progressive dysfunction of axons. Several pathological conditions such as ischemia can disrupt the neuronal cytoskeleton. Microtubules are basic structural components of the neuronal cytoskeleton that regulate axonal transport and neuronal function. Up-to-date, high-resolution observation of microtubules in living neuronal cells is usually accomplished using fluorescent-based microscopy techniques. However, this needs exogenous fluorescence markers to produce the required contrast. This is an invasive procedure that may interfere with the microtubule dynamics. In this work, we show, for the first time to our knowledge, that by using the endogenous (label-free) contrast provided by second harmonic generation (SHG) microscopy, it is possible to identify early molecular changes occurring in the microtubules of living neurons under ischemic conditions. This is done by measuring the intensity modulation of the SHG signal as a function of the angular rotation of the incident linearly polarized excitation light (technique referred to as PSHG). Our experiments were performed in microtubules from healthy control cultured cortical neurons and were compared to those upon application of several periods of oxygen and glucose deprivation (up to 120 min) causing ischemia. After 120-min oxygen and glucose deprivation, a change in the SHG response to the polarization was measured. Then, by using a three-dimensional PSHG biophysical model, we correlated this finding with the structural changes occurring in the microtubules under oxygen and glucose deprivation. To our knowledge, this is the first study performed in living neuronal cells that is based on direct imaging of axons and that provides the means of identifying the early symptoms of ischemia. Live observation of this process might bring new insights into understanding the dynamics and the mechanisms underlying neuronal degeneration or mechanisms of protection or regeneration.

  • Ultrashort laser pulse measurement for multiphoton microscopy  Open access

     Amat Roldan, Ivan
    Defense's date: 2013-06-21
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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    In this thesis, we address specific efforts towards developing the precise aspect of ultrashort laser pulse measurement in the context of biomedical research. The motivation for pursuing these new developments was triggered by the vision of developing fundamental tools that will enable to control matter by means of light with exquisite precision with the added difficulty of being next to biological samples which are extremely sensitive and fragile. For this, light matter interaction needs to be extremely well controlled to avoid undesired effects, like cell damage due to the high peak intensity values of ultrashort laser pulses, as well as promoting specific physical processes like two-photon fluorescence excitation of a desired fluorophore embedded in some biochemical environment. We focus in the two major bottlenecks regarding ultrashort laser pulse measurements for multiphoton microscopy, that aim for developing (1) new techniques for full characterization of ultrashort pulses under different experimental conditions and (2) new material with specific nonlinear properties that enable to obtain ultrashort pulse measurements that properly catch the temporal shape of light and at the same time can be readily found in biomedical lab, specially cost effective, non fragile and non-toxic. Combination of these two complementary strategies provides a new ground where it is possible to characterise an ultrashort pulse at the sample plane of a multiphoton microscope in a regular biomedical research facility. Importantly, we approach ultrashort pulse characterisation by developing a different theoretical framework to the state-of-the-art and we propose few initial experiments that preliminary support our theoretical statements in the form of new optical techniques. These findings are then experimentally tested under different conditions, such different optical setups and different pulsed regimes in order to evaluate the feasibility of the tools to measure ultrashort pulses in conditions that were prohibitive at the time this thesis was started. The scope of this thesis outlines the potential of such techniques, but further efforts shall be addressed to assess feasibility, robustness and further limitations.

  • Depth aberrations characterization in linear and nonlinear microscopy schemes using a Shack-Hartmann wavefront sensor

     Aviles Espinosa, Rodrigo; Andilla, Jordi; Porcar-Guezenec, Rafael; Levecq, Xavier; Artigas Garcia, David; Loza Alvarez, Pablo
    Three-Dimensional and Multidimensional Microscopy: Image Acquisition and Processing
    Presentation's date: 2012-02-09
    Presentation of work at congresses

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    The performance of imaging devices such as linear and nonlinear microscopes (NLM) can be limited by the optical properties of the imaged sample. Such an important aspect has already been described using theoretical models due to the difficulties of implementing a direct wavefront sensing scheme. However, these only stand for simple interfaces and cannot be generalized to biological samples given its structural complexity. This has leaded to the development of sensor-less adaptive optics (AO) implementations. In this approach, aberrations are iteratively corrected trough an image related parameter (aberrations are not measured), being prone of causing sample damage. In this work, we perform a practical implementation of a Shack-Hartman wavefront sensor to compensate for sample induced aberrations, demonstrating its applicability in linear and NLM. We perform an extensive analysis of wavefront distortion effects through different depths employing phantom samples. Aberration effects originated by the refractive index mismatch and depth are quantified using the linear and nonlinear guide-star concept. More over we analyze offaxis aberrations in NLM, an important aspect that is commonly overlooked. In this case spherical aberration behaves similarly to the wavefront error compared with the on-axis case. Finally we give examples of aberration compensation using epi-fluorescence and nonlinear microscopy.

  • Image formation by linear and nonlinear digital scanned light-sheet fluorescence microscopy with Gaussian and Bessel beam profiles

     Olarte, Omar E.; Licea Rodríguez, Jacob; Palero, Jonathan; Gualba, Emilio J.; Artigas Garcia, David; Mayer, Jürgen; Swoger, Jim; Sharpe, James; Rocha Mendoza, Israel; Rangel Rojo, Raul; Loza Alvarez, Pablo
    BIOMEDICAL OPTICS EXPRESS
    Date of publication: 2012-07-01
    Journal article

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    Effect of molecular organization on the image histograms of polarization SHG microscopy  Open access

     Psilodimitrakopoulos, Sotiris; Amat Roldan, Ivan; Loza Alvarez, Pablo; Artigas Garcia, David
    BIOMEDICAL OPTICS EXPRESS
    Date of publication: 2012
    Journal article

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    Based on its polarization dependency, second harmonic generation (PSHG) microscopy has been proven capable to structurally characterize molecular architectures in different biological samples. By exploiting this polarization dependency of the SHG signal in every pixel of the image, average quantitative structural information can be retrieved in the form of PSHG image histograms. In the present study we experimentally show how the PSHG image histograms can be affected by the organization of the SHG active molecules. Our experimental scenario grounds on two inherent properties of starch granules. Firstly, we take advantage of the radial organization of amylopectin molecules (the SHG source in starch) to attribute shifts of the image histograms to the existence of tilted off the plane molecules. Secondly, we use the property of starch to organize upon hydration to demonstrate that the degree of structural order at the molecular level affects the width of the PSHG image histograms. The shorter the width is the more organized the molecules in the sample are, resulting in a reliable method to measure order. The implication of this finding is crucial to the interpretation of PSHG images used for example in tissue diagnostics.

  • Coupling plasmons and dyakonons

     Takayama, Osamu; Artigas Garcia, David; Torner Sabata, Lluis
    Optics letters
    Date of publication: 2012-06-01
    Journal article

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    Practical dyakonons  Open access

     Takayama, Osamu; Artigas Garcia, David; Torner Sabata, Lluis
    Optics letters
    Date of publication: 2012-10-12
    Journal article

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    We show that engineered photonic metamaterials composed of alternating layers of suitable dielectrics and metals can support different kinds of surface waves (SWs) under robust and readily achievable experimental conditions. The supported SWs include Dyakonov SWs, hybrid plasmons, and Dyakonov plasmons. In particular, in contrast to conventional physical settings, we show that the high form birefringence exhibited by the metamaterials allows Dyakonov SWs, or dyakonons, to exist within large angular existence domains and levels of localization similar to plasmons, thus making dyakonons available for practical applications

  • Polarization Second Harmonic Imaging of Biological Samples

     Psilodimitrakopoulos, Sotirios
    Defense's date: 2012-12-14
    The Institute of Photonic Sciences, Universitat Politècnica de Catalunya
    Theses

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  • Ultrathin Metal Transparent Electrodes for the Optoelectronics Industry

     Sundar Ghosh, Dhriti
    Defense's date: 2012-10-11
    The Institute of Photonic Sciences, Universitat Politècnica de Catalunya
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  • MICRO-STRUCTURED FERROELECTRIC SUPERLATTICE FOR EFFICIENT ACOUSTO-OPTIC DEVICES  Open access

     Yudistira, Didit
    Defense's date: 2012-02-21
    The Institute of Photonic Sciences, Universitat Politècnica de Catalunya
    Theses

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    In this thesis we have investigated and proposed acoustic superLattices (ASLs) made of periodically poled ZX-cut lithium niobate (PPLN) associated ith coplanar electrodes as an effective alternative for surface acoustic wave (SAW) generation. In order to examine the acoustic transduction in the SL transducer we have developed and employed two modeling techniques. i.e . scalar approximation and finite element method (FEM) analysis (2-D nd 3-D modeling) implemented in COMSOL MULTIPHYSICS. Both techniques give similar results with respect to the characteristics of generated SAW modes. The calculated results obtained with the 3-D FEM simulation confirmed the Rayleigh nature of the generated SAW, showing that the excited SAW in the ASL is similar to that of the standard interdigitated transducer (IDT). From the propagation analysis in 2-D FEM simulation. we obtained that in addition to the SAW, the ASL transducer excites longitudinal bulk acoustic wave (L-BAW). Moreover. the 2-D model showed that the SAW excited by the ASL transducer does not propagate but it is rather confined within the transducer. Several ASL transducers, with different lattice periods, have been realized and characterized, also to validate the modeling and design tools . One and two-portelectrical measurements have been performed to evaluate the electro-acoustic response. In addition laser interferome try has been carried out o determine the out-of-plane component of the SAW displacement. With respect to the standard IDT configuration using the same crystal orientation, he efficiency of the SAW generation in the proposed designs is similar, while, for the same grating period, the resonance frequency that can be achieved is two times larger. In addition to the SAW, unlike its lOT counterparts, the ASL transducer can excite the L-BAW, as it had been predicted by the modeling. The two-port measurements have shown that the SAW signal collected at the receiver is small, indicating that the SAW energy remains essentially confined within the transmitter. This experimental result too is in agreement with the aforementioned theoretical predictions. After the experimental validation of the modeling, we designed and fabricated acousto-optic (AO) filters incorporating the ASL transducer. ASL struc tures with 20 tm period and coplanar electrodes have been realized along with 6 m wide Ti-LiNb03 optical channel waveguide. In that way monolithic and integrated (waveguide) SAW based AO filters and L-BAW based bulk AO filters have been demonstrated. As for integrated SAW based 0 filter, a 3-dB optical bandwidth of 2.5 nm, center wavelength of 1456 nm, and -20 dB distance of 14.49 nm are obtained at the SAW resonance frequency of 189.94 MHz. Such filter requires 1 W RF power to achieve nearly complete polarization conversion. As for the bulk AO filter. a center Wavelength of 1472.5 nm is measured at the L-BAW resonance frequency of 328 MHz. In the bulk AO filter. full conversion cannot be reached even at RF power up to 2 W. Comparing to the integrated (waveguide) filter. the efficiency of the bulk filter is significantly lower. The AO filter's central wavelength can be tuned by changing the RF power. We investigated several designs to improve the AO filter efficiency. By optimizing the ASL transducer (coplanar electrodes with electrode width of 70 urn and gap of 20 t m), nearly complete optical switching at very low electrical powers (50mW) has been obtained, this corresponding to an improvement factor of 20 compared to previous results. An appropriate mass-loading, placed on the surface and in between the electrodes of a coplanar LiNb03 ASL, has allowed achieving strong lateral confinement of the acoustic field, thus leading to a significant improvement of the AO filter performance.

  • High-Power, fiber-laser-pumped optical parametric oscillators from the visible to mid-infrared  Open access

     Suddapalli, Chaitanya Kumar
    Defense's date: 2012-01-18
    The Institute of Photonic Sciences, Universitat Politècnica de Catalunya
    Theses

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    High-power, continuous-wave (cw), mid-infrared (mid-IR) laser sources are of interest for variety of applications such as trace gas detection and remote sensing, which require broad spectral coverage to address the most prominent absorption features of a wide range of molecular species particularly in the mid-IR fingerprint region. On the other hand, surgical applications require high energy sources with unique pulse structure at specific wavelength in the mid-IR ranging from 6-6.5 m. Optical parametric oscillators (OPOs) offer potential sources for all the above applications. The output wavelengths of a singly-resonant oscillator (SRO) can be coarsely tuned over wide ranges through the adjustment of the nonlinear crystal temperature, phase-matching angle or, in the case of quasi-phase-matched (QPM) the first time. The high-energy CSP OPO marked the first demonstration of a compact, high-repetition-rate OPO synchronously pumped by a master oscillator power amplifier system at 1064 nm, generating an milli-joule pulses in the 6-6.5 m spectral range, which is technologically important for surgical applications. Additionally, we also demonstrated a fiber-based-green source at 532 nm, based on single-pass second harmonic generation (SHG) in MgO:sPPLT, as an alternative pump source for Ti:sapphire laser, pointing towards the future, compact fiber-laser pumped Ti:sapphire lasers. Further efforts to improve the SHG efficiency led to the development of a novel multi-crystal scheme, enabling single-pass SHG efficiency as high as 56%. This generic technique is simple and can be implemented at any wavelength. materials, the QPM grating period. The combination of SRO with a tunable pump laser allows the development of uniquely flexible and rapidly tunable class of mid-IR sources. In this thesis we have demonstrated several mid-IR OPOs in the cw as well as ultrafast picosecond regime pumped by fiber-lasers making them compact and robust. In the cw regime, we developed a high-power, Yb-fiber-laser pumped mid-IR OPO based on MgO:PPLN spanning 1506-1945 nm in the near-IR and 2304-3615 nm wavelength range in the mid-IR, efficiently addressing the thermal effects by implementing the optimum signal output coupling. Novel materials such a MgO:sPPLT, with better optical and thermal properties for cw mid-IR generation are explored. High-power broadband, cw mid-IR generation is also demonstrated by using the extended phase-matching properties of MgO:PPLN. Further, we also demonstrated a simple, inexpensive and novel interferometric technique for absolute optimization of output power from a ring optical oscillator. We deployed a picosecond Yb-fiber-laser pumped mid-IR OPO based on MgO:PPLN in ring cavity configuration to demonstrate this proof-of-principle experiment for

    Fuentes coherentes de luz continua y de alta potencia en el infrarrojo-medio (mid-IR) son de gran interés por su aplicación en la detección de gases, detección remota y la observación de imágenes. Estas aplicaciones requieren un ancho de banda amplio para evidenciar las características que ofrece la absorción de una gran variedad de especies moleculares, particularmente en la región “finger print” del mid-IR. Por otra parte, fuentes altamente energéticas con pulsos que posean estructuras peculiares en rangos específicos de longitud de onda en el mid-IR, entre 6-6.5 m. , prometen características únicas para nuevas aplicaciones en cirugía. Osciladores ópticos paramétricos (OPOs) constituyen fuentes de luz versátiles y apropiadas para todas las aplicaciones mencionadas anteriormente. La longitud de En el régimen ultrarápido, hemos demostrado una nueva técnica de interferometría para la optimización absoluta de la potencia de salida de un oscilador óptico con una cavidad de anillo. Como demostración de principio, implementamos, por primera vez, un OPO de picosegundos en el mid-IR basado en MgO:PPLN con una cavidad de anillo bombeado por un láser de fibra de Yb. Además, hemos desarrollado un nuevo OPO de alta energía en el mid-IR basado en el material nolineal CSP. Esto representa la primera demostración de un OPO compacto de alta repetición sincrónicamente bombeado por un láser de estado sólido a 1064 nm generando pulsos de milijulios en el rango espectral 6-6.5 m. Esta radiación es importante para aplicaciones en cirugía. Adicionalmente, hemos demostrado una fuente verde, 532 nm, basada en láseres de fibra. Esta radiación se obtiene por medio de la generación de segundo harmónico (SHG) en un paso individual en MgO:sPPLT. Esto representa una nueva alternativa de bombeo para los láseres de Ti:sapphire que los harán compactos en el futuro. Los esfuerzos para mejorar la eficiencia de segundo harmónico resultaron en el desarrollo de un novedoso esquema que utiliza múltiples cristales y permite eficiencias de SHG de paso individual del 56%. Este esquema es general y simple y puede ser implementado para cualquier longitud de onda. onda de un OPO puede ser sintonizada en regiones amplias del espectro cambiando la temperatura del cristal no-lineal, el ángulo de ajuste de fase o, al considerar materiales cuasi ajuste de fase (QPM), cambiando el periodo de red. En esta tesis, hemos demostrado una gran variedad de OPOs en el mid-IR en régimen continuo y de pulsos de picosegundo. Estos OPOs han sido bombeados por láseres de fibra permitiendo un diseño compacto y resistente. En el régimen de emisión continua, hemos implementado un OPO de alta potencia basado en MgO:PPLN bombeado por un láser de fibra. Este OPO es sintonízable en el rango 1506-1945 nm correspondiente al infrarrojo-cercano y en el rango 2304-3615 nm correspondiente al mid-IR. Esta capacidad de sintonización se logra al sobrepasar eficientemente los efectos térmicos optimizando el acoplamiento de salida. Materiales nuevos como el MgO:sPPLT, con propiedades ópticas y térmicas mejoradas para la generación de radiación continua en el mid-IR han sido estudiados. Utilizando las propiedades ajuste de la fase extendió del MgO:sPPLT, fuentes continuas de alta potencia con un gran ancho de banda en el infrarrojo-medio también han sido implementadas.

  • Multiphoton imaging with compact semiconductor disk lasers

     Loza Alvarez, Pablo; Aviles Espinosa, Rodrigo; Artigas Garcia, David; Hamilton, Craig; Malcolm, Graeme
    Proceedings of SPIE, the International Society for Optical Engineering
    Date of publication: 2012-01-23
    Journal article

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  • Three-dimensional polarization second harmonic generation (3D-PSHG) imaging: the effect of the tilted-off the plane SHG active structures

     Psilodimitrakopoulos, Sotiris; Amat Roldan, Ivan; Artigas Garcia, David; Loza Alvarez, Pablo
    Photonics West
    Presentation's date: 2011-01
    Presentation of work at congresses

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  • In-vivo third-harmonic generation microscopy at 1550nm three-dimensional long-term time-lapse studies in living C. elegans embryos

     Aviles Espinosa, Rodrigo; Santos, Susana; Brodschelm, Andreas; Kaenders, Wilhelm G.; Alonso Ortega, Cesar; Artigas Garcia, David; Loza Alvarez, Pablo
    Photonics West
    Presentation's date: 2011-01
    Presentation of work at congresses

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  • Compact ultrafast semiconductor disk laser for nonlinear imaging in living organisms

     Aviles Espinosa, Rodrigo; Filippidis, George; Hamilton, Craig; Malcolm, Graeme; Weingarten, Kurt J.; Südmeyer, Thomas; Barbarin, Yohan; Keller, Ursula; Artigas Garcia, David; Loza Alvarez, Pablo
    Photonics West
    Presentation's date: 2011-01
    Presentation of work at congresses

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  • Open-loop wavefront sensing scheme for specimen aberrations correction in two-photon excited fluorescence microscopy

     Aviles Espinosa, Rodrigo; Loza Alvarez, Pablo; Andilla, Jordi; Porcar-Guezenec, Rafael; Levecq, Xavier; Artigas Garcia, David
    Conference on Advanced Microscopy Techniques
    Presentation's date: 2011-05-24
    Presentation of work at congresses

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  • Portable semiconductor disk laser for in vivo tissue monitoring: a platform for the development of clinical applications

     Aviles Espinosa, Rodrigo; Filippidis, George; Hamilton, Craig; Malcolm, Graeme; Weingarten, Kurt J.; Südmeyer, Thomas; Barbarin, Yohan; Keller, Ursula; Artigas Garcia, David; Loza Alvarez, Pablo
    Conference on Medical Laser Applications and Laser-Tissue Interactions
    Presentation's date: 2011-05-25
    Presentation of work at congresses

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  • Imaging amylopectin's order in starch using 3-dimensional polarization SHG

     Psilodimitrakopoulos, Sotiris; Amat Roldan, Ivan; Artigas Garcia, David; Loza Alvarez, Pablo
    Conference on Advanced Microscopy Techniques
    Presentation's date: 2011-05-24
    Presentation of work at congresses

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  • Ultrastructural analysis of myocardiocyte sarcomeric changes in relation with cardiac dysfunction in human fetuses with intrauterine growth restriction

     Iruretagoyena, J.I.; Torre, Iratxe; Amat Roldan, Ivan; Psilodimitrakopoulos, Sotiris; Crispi, Fatima; Garcia Canadilla, Patricia; Nadal, Alfons; Eixarch, Elisenda; Loza Alvarez, Pablo; Artigas Garcia, David; Gratacos, Eduard
    American journal of obstetrics and gynecology
    Date of publication: 2011-01
    Journal article

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  • FIRST EXPERIMENTAL OBSERVATION OF DYAKONOV SURFACE WAVES

     Takayama, Osamu
    Defense's date: 2011-11-25
    The Institute of Photonic Sciences, Universitat Politècnica de Catalunya
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  • Compact ultrafast semiconductor disk laser: targeting GFP based nonlinear applications in living organisms

     Aviles Espinosa, Rodrigo; Filippidis, George; Hamilton, Craig; Malcolm, Graeme; Weingarten, Kurt J.; Südmeyer, Thomas; Barbarin, Yohan; Keller, Ursula; Santos, Susana I.C.O.; Artigas Garcia, David; Loza Alvarez, Pablo
    BIOMEDICAL OPTICS EXPRESS
    Date of publication: 2011-03-01
    Journal article

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    We present a portable ultrafast Semiconductor Disk Laser (SDL) (or vertical extended cavity surface emitting laser—VECSELs), to be used for nonlinear microscopy. The SDL is modelocked using a quantum-dot semiconductor saturable absorber mirror (SESAM), delivering an average output power of 287 mW, with 1.5 ps pulses at 500 MHz and a central wavelength of 965 nm. Specifically, despite the fact of having long pulses and high repetition rates, we demonstrate the potential of this laser for Two-Photon Excited Fluorescence (TPEF) imaging of in vivo Caenorhabditis elegans (C. elegans) expressing Green Fluorescent Protein (GFP) in a set of neuronal processes and cell bodies. Efficient TPEF imaging is achieved due to the fact that this wavelength matches the peak of the two-photon action cross section of this widely used fluorescent marker. The SDL extended versatility is shown by presenting Second Harmonic Generation images of pharynx, uterus, body wall muscles and its potential to be used to excite other different commercial dyes. Importantly this non-expensive, turn-key, compact laser system could be used as a platform to develop portable nonlinear bio-imaging devices.

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    Measurement and correction of in vivo sample aberrations employing a nonlinear guide-star in two-photon excited fluorescence microscopy  Open access

     Aviles Espinosa, Rodrigo; Andilla, Jordi; Porcar-Guezenec, Rafael; Olarte, Omar E.; Nieto, Marta; Levecq, Xavier; Artigas Garcia, David; Loza Alvarez, Pablo
    BIOMEDICAL OPTICS EXPRESS
    Date of publication: 2011-11-01
    Journal article

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    We demonstrate that sample induced aberrations can be measured in a nonlinear microscope. This uses the fact that two-photon excited fluorescence naturally produces a localized point source inside the sample: the nonlinear guide-star (NL-GS). The wavefront emitted from the NL-GS can then be recorded using a Shack-Hartmann sensor. Compensation of the recorded sample aberrations is performed by the deformable mirror in a single-step. This technique is applied to fixed and in vivo biological samples, showing, in some cases, more than one order of magnitude improvement in the total collected signal intensity.

  • Dyakonov surface wave resonant transmission

     Takayama, Osamu; Nikitin, A. Yu; Martin-Moreno, Luis; Torner Sabata, Lluis; Artigas Garcia, David
    Optics express
    Date of publication: 2011-03-28
    Journal article

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    The role of Dyakonov surface waves in the transmission through structures composed of birefringent media is theoretically explored. In the case of structures using prisms, unexpected high transmission above the critical angle due to resonant excitation of Dyakonov surface waves is predicted. This transmission is produced only when TE polarized incident wave reaches the interface supporting the surface waves within a narrow interval of angles, for both the angle of incidence and the angle with respect to the optic axis of the birefringent media. As a result, over 90% transmission for a single and isolated peak confined in the two transversal directions, with hybrid TE and TM polarization, can be obtained.

  • Signalling effect of NIR pulsed lasers on axonal growth

     Mathew, Manoj Vathalloor; Amat Roldan, Ivan; Andrés, Rosa; Santos, Susana I.C.O.; Artigas Garcia, David; Soriano, Eduardo; Loza Alvarez, Pablo
    Journal of neuroscience methods
    Date of publication: 2010-02-15
    Journal article

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  • A simple scanless two-photon fluorescence microscope using selective plane illumination

     Palero, Jonathan; Santos, Susana I.C.O.; Artigas Garcia, David; Loza Alvarez, Pablo
    Optics express
    Date of publication: 2010-04-12
    Journal article

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  • Spatial characterization of two-photon states

     Osorio Tamayo, Clara Inés
    Defense's date: 2010-03-12
    The Institute of Photonic Sciences, Universitat Politècnica de Catalunya
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  • Measurement of the spatial shape of photons

     González Rodríguez, Noelia
    Defense's date: 2010-01-15
    The Institute of Photonic Sciences, Universitat Politècnica de Catalunya
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    Third-harmonic generation for the study of Caenorhabditis elegans embryogenesis  Open access

     Aviles Espinosa, Rodrigo; Santos, Susana I.C.O.; Brodschelm, Andreas; Kaenders, Wilhelm G.; Alonso Ortega, Cesar; Artigas Garcia, David; Loza Alvarez, Pablo
    Journal of biomedical optics
    Date of publication: 2010-08
    Journal article

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    Live microscopy techniques i.e., differential interference contrast, confocal microscopy, etc. have enabled the understanding of the mechanisms involved in cells and tissue formation. In long-term studies, special care must be taken in order to avoid sample damage, restricting the applicability of the different microscopy techniques.We demonstrate the potential of using third-harmonic generation THG microscopy for morphogenesis/embryogenesis studies in living Caenorhabditis elegans C. elegans . Moreover, we show that the THG signal is obtained in all the embryo development stages, showing different tissue/structure information. For this research, we employ a 1550-nm femtosecond fiber laser and demonstrate that the expected water absorption at this wavelength does not severely compromise sample viability. Additionally, this has the important advantage that the THG signal is emitted at visible wavelengths 516 nm . Therefore, standard collection optics and detectors operating near maximum efficiency enable an optimal signal reconstruction. All this, to the best of our knowledge, demonstrates for the first time the noninvasiveness and strong potential of this particular wavelength to be used for highresolution four-dimensional imaging of embryogenesis using unstained C. elegans in vivo samples.

  • Estimating the helical pitch angle of amylopectin in starch using polarization second harmonic generation microscopy

     Psilodimitrakopoulos, Sotiris; Amat Roldan, Ivan; Loza Alvarez, Pablo; Artigas Garcia, David
    Journal of optics (Calcutta)
    Date of publication: 2010-08
    Journal article

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    Starch granules are among the brightest natural second harmonic generation (SHG) converters. They basically consist of amylose and amylopectin molecules and the source of the SHG signal is still undetermined. In the present study we perform polarization sensitive SHG (PSHG) imaging of wheat starch granules and we fit the SHG signal variation of each pixel of the PSHG images into a generalized biophysical model. By assuming that the SHG source molecule is a helix with cylindrical symmetry along its long axis, the model extracts the helical pitch angle of the SHG source for every pixel of the image. By displaying the pixel histogram representing this helical pitch angle we found a highly peaked histogram with maximum at θe = 36.1◦ and a width of θe = 9.3◦. This pitch angle corresponds to the strand of the parallel double helical structure, called amylopectin (as measured by a small angle x-ray scattering technique). This demonstrates amylopectin (and not amylose) as the source of SHG in starch. According to our knowledge, this is the first estimation of the amylopectin’s pitch angle in starch using PSHG.

  • Fast image analysis in polarization SHG microscopy

     Amat Roldan, Ivan; Psilodimitrakopoulos, Sotiris; Loza Alvarez, Pablo; Artigas Garcia, David
    Optics express
    Date of publication: 2010-08-02
    Journal article

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  • Discrimination between collagen and muscle using polarization second harmonic imaging with pixel resolution

     Psilodimitrakopoulos, S; Soria, G; Amat-Roldán, I; Artigas Garcia, David; Planas, A M; Loza-Álvarez, P
    Focus on Microscopy
    Presentation of work at congresses

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  • Complete optical quality analysis of a non-linear microscope

     Avilés-Espinosa, R; Porcar-Guezenec, R; Zalvidea, D; Artigas Garcia, David; Loza-Álvarez, P
    Focus on Microscopy
    Presentation of work at congresses

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  • Myosin helical pitch angle as a quantitative imaging biomarker for characterization of cardiac programming in fetal growth restriction measured by polarization second harmonic microscopy

     Amat-Roldán, I; Psilodimitrakopoulos, S; Eixarch, E; Torre, I; Wojtas, B; Crispi, F; Figueras, F; Artigas Garcia, David; Loza-Álvarez, P; Gratacós, E
    European Conferences on Biomedical Optics
    Presentation's date: 2009-06
    Presentation of work at congresses

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  • Observation of Dyakonov surface waves

     Takayama, O; Crasovan, I; Artigas Garcia, David; Torner Sabata, Lluis
    European Conference on Lasers and Electro-Optics / European Quantum Electronics Conference
    Presentation of work at congresses

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  • Polarization conversion spectroscopy of hybrid modes

     Nikitin, A. Yu; Artigas Garcia, David; Torner Sabata, Lluis; García Vidal, F. J.; Martín Moreno, L.
    Optics letters
    Date of publication: 2009-12
    Journal article

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  • Access to the full text
    Dyakonov surface waves  Open access

     Torner Sabata, Lluis; Artigas Garcia, David; Takayama, Osamu
    Optics and photonics news
    Date of publication: 2009
    Journal article

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  • Contrast enhancement in second harmonic imaging: discriminating between muscle and collagen

     Psilodimitrakopoulos, S; Amat-Roldán, I; Torre, I; Gratacós, E; Artigas Garcia, David; Loza-Álvarez, P
    European Conferences on Biomedical Optics
    Presentation's date: 2009-06
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  • Estimation of the effective orientation of the SHG source in primary cortical neurons

     Psilodimitrakopoulos, S; Petegnief, V; Soria, G; Amat-Roldán, I; Artigas Garcia, David; Planas, A M; Loza-Álvarez, P
    Optics express
    Date of publication: 2009-08
    Journal article

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  • Observation of Dyakonov surface waves

     Takayama, O; Crasovan, L; Artigas Garcia, David; Torner Sabata, Lluis
    Physical review letters
    Date of publication: 2009-01
    Journal article

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  • Quantitative discrimination between endogenous SHG sources in mammalian tissue, based on their polarization response

     Psilodimitrakopoulos, S; Artigas Garcia, David; Soria, G; Amat-Roldán, I; Planas, A M; Loza-Álvarez, P
    Optics express
    Date of publication: 2009-06
    Journal article

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  • In vivo, pixel-resolution mapping of thick filaments' orientation in nonfibrilar muscle using polarization-sensitive second harmonic generation microscopy

     Psilodimitrakopoulos, S; Santos, S I C O; Amat-Roldán, I; Thayil, A K N; Artigas Garcia, David; Loza-Álvarez, P
    Journal of biomedical optics
    Date of publication: 2009-01
    Journal article

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  • Polarization dependant in vivo second harmonic generation imaging of Caenorhabditis elegans vulval, pharynx, and body wall muscles

     Psilodimitrakopoulos, S; Santos, S; Amat-Roldán, I; Mathew, M; Thayil, A K N; Artigas Garcia, David; Loza-Álvarez, P
    SPIE Photonics West
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  • Two-photon fluorescence imaging and femtosecond laser microsurgery to study drosophila dorsal closure

     Thayil, A K N; Pereira, A; Mathew, M; Artigas Garcia, David; Martín-Blanco, E; Loza-Álvarez, P
    SPIE Photonics West
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  • Starch granules as a probe for the polarization at the sample plane of a high resolution multiphoton microscope

     Psilodimitrakopoulos, S; Amat-Roldán, I; Santos, S; Mathew, M; Thayil, A K N; Zalvidea, D; Artigas Garcia, David; Loza-Álvarez, P
    SPIE Photonics West
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  • Compact ultrafast laser sources based on novel quantum dot structures.

     Artigas Garcia, David; Rafailov, Edik; Loza Álvarez, P
    Participation in a competitive project

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  • Spatio-temporal Engineering of Light. Ultimate Multiphoton Microscopy.

     Artigas Garcia, David; Loza Álvarez, P
    Participation in a competitive project

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  • Polarization sensitive second harmonic generation imaging for pixel resolution mapping of thick filaments in living C. elegans

     Artigas Garcia, David
    New Frontiers in Micro and Nano Photonics
    Presentation's date: 2008-04-23
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  • Influence of distant femtosecond laser pulses on growth cone fillopodia

     Mathew, M; Amat-Roldán, I; Andrés, R; Cormack, I G; Artigas Garcia, David; Soriano, E; Loza-Álvarez, P
    Cytotechnology: international journal of cell culture and biotechnology
    Date of publication: 2008-10
    Journal article

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  • Dyakonov surface waves: a review

     Takayama, O; Crasovan, L C; Johansen, S K; Mihalache, D; Artigas Garcia, David; Torner Sabata, Lluis
    Electromagnetics
    Date of publication: 2008-03
    Journal article

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