We present linear and non linear optical applications of solid and hollow silica microresonators. Hollow microresonators or microbubble resonators combine the unique properties of whispering gallery mode resonators (WGMR) with the intrinsic capability of integrated microfluidics. Microbubbles were filled with water and aqueous solutions of ethanol in order to test the refractive index sensing capabilities of such resonators. We also tested the potential of microbubbles as nonlinear enhancement platform of both the filling material (Rhodamine 6G and Fluorescein) and the glass bubble.
We report on a new source able to provide probe pulses in the UV visible range and on the demonstration of its
application to hyperspectral (fluorescence lifetime) imaging measurements. The source is able to generate UV (down to
300 nm) and blue light exploiting high-order mode propagation in a microstructured fiber pumped by a Ti:Sapphire laser.
We believe that further optimization of pump wavelength, fiber length and fiber zero-dispersion wavelength could
generate light well below 300 nm using a simple and stable set-up and become a useful tool for biomedical imaging. We
demonstrated its versatility using the source for FLIM-FRET measurement a 460 nm and hyperspectral FRET-FLIM
Cell-to-cell contacts are crucial for cell differentiation. The promyogenic cell surface protein, Cdo, functions as a component of multiprotein clusters to mediate cell adhesion signaling. Connexin43, the main connexin forming gap junctions, also plays a key role in myogenesis. At least part of its effects are independent of the intercellular channel function, but the mechanisms underlying are unknown. Here, using multiple optical approaches, we provided the first evidence that Cx43 physically interacts with Cdo to form dynamic complexes during myoblast differentiation, offering clues for considering this interaction a structural basis of the channel-independent function of Cx43.
In this paper we report imaged neuronal rat cells in a confocal laser scanning microscope by simultaneous generation of
the three requested wavelengths obtained by a UV-extended supercontinuum source. This is to the best of our
knowledge that such a measure was performed using a microstructured fiber pumped by a standard Ti:Sapphire laser.
We observed efficient UV light generation when a novel pumping scheme was used. The pump wavelength is close to
the zero-dispersion wavelength of the fiber first high-order mode and offset axial pumping is used. By tuning the pump
wavelength and power level we were able to generate mW-power levels in the visible wavelength interval down and of
about hundreds of microwatt in the UV wavelength interval down to 300 nm. The pump alignment was very simple and
very stable. We believe that further optimization of pump wavelength, fiber length and fiber zero-dispersion wavelength
could generate light well below 300 nm using a simple and stable set-up. To demonstrate the potentiality of this
technique we imaged neuronal rat cells in a confocal laser scanning microscope by simultaneous generation of the three
Optical sensors have a large impact in the fields of life science research, drug discovery and medical diagnostics. The
recent advances in nanotechnology and photonics have led to a new generation of nanotools, capable of probing even the
single cell: it has already been demonstrated that nanobiosensors can detect biochemical targets and proteins inside living
single cells. Here we provide a brief overview of the field of nanoprobes consisting of tapered, metal-coated optical
fibers having nanosize tips, such as those which were originally developed for use in near-field optical microscopy.
Moreover we present some preliminary results concerning the characterization of the experimental sensing system which
exploits such nanoprobes for intracellular biomedical diagnostics. The feasibility of using the Fluorescence Lifetime
Imaging Microscopy (FLIM) technique as a dynamic diagnostics tool with these nanoprobes has been demonstrated.
We report on the application of a simple white light source based on the supercontinuum generation from commercial
photonic crystal fibres to confocal fluorescence microscopy and fluorescence lifetime imaging (FLIM) microscopy. The
coherent white light can be tuned by varying the wavelength and intensity of the pump, a Ti:Sapphire laser. There are
several advantages jn the use of SC sources: spatially coherent white radiation, tuning ranges of approximately 400 nm,
high brightness, a robust compact system (potentially all-fibre) and relatively low cost. Being pulsed, SC sources are
suitable for FLIM and may be used for multiple excitation.
Nonlinear optical microscopy is a relatively new and rapidly growing field of optical engineering, where Ti:sapphire ultrafast laser sources and technologies are finding a wide application. Diagnostic techniques addressed to this kind of application have been widely developed in the last few years. Research efforts have been focused on the evaluation and eventual correction of laser pulse duration widening due to group velocity dispersion of microscope optics, and devices have been specially designed to perform second-order autocorrelation measurements at the objective focal plane. In the present work, innovative, simple setups and procedures are reported that make the best use of all the facilities and characteristics of the microscope itself, so that only a few optical components are needed to temporal characterize the laser pulse at the specimen plane.
Multiphoton microscopy is a relatively new and rapidly growing field of applied optics where Ti:Sapphire ultrafast laser sources and related technology find a wide application. Laser beam diagnostic techniques specially devoted to this kind of application has been widely developed in these last years. Research efforts have been addressed to the evaluation and the eventual correction of the laser pulse duration widening due to group velocity dispersion caused by the microscope optics. Temporal characterization is thus a fundamental task when operating a ultrafast laser system for multiphoton microscopy applications and it is carried out by means of autocorrelators specially designed to perform pulse width measurements at the focus of the microscope objective. In the present communication, an innovative autocorrelator set-up and a simple metrological procedure are reported.
Planar waveguides have been realized in lithium fluoride crystals by ion-beam irradiation. Ion bombardment produces color centers in the LiF crystal, increasing locally the refractive index. Confocal microscopy is applied to the characterization of the waveguides in order to assess the uniformity and distribution of color centers through the measurement of the photoluminescence emission.
Optical waveguides in lithium fluoride (LiF) crystals have been obtained by He<sup>+</sup> ion beam irradiation. The waveguides
have been characterized by several techniques. In particular, we describe here the application of confocal microscopy to their characterization and show the first results obtained. We have also carried out a preliminary evaluation of the potential of this technique for the assessment of structural and spectroscopic characteristics of the waveguides.
The basic elements of a fairly complete optomechanical kit based on the use of LEGO<SUP>TM</SUP> is presented. Through a careful exploitation of the many standard LEGO elements, and adding a few new simple components made of plexiglass, we demonstrate that almost all of the mechanical parts of an optical setup can be built with little effort and at an extremely reduced cost. Several systems and experiments are presented, mainly in the fields of optical filtering and interferometry, to show that the proposed mountings are perfectly suitable for didactic purposes, and can often be employed even in more demanding scientific applications.
In this work we report on a novel angular and positional sensor based on the phenomenon of attenuated total reflection that occurs at a metal-dielectric interface when the conditions for the excitation of a surface plasma wave in Kretschmann configuration are satisfied. The reflectivity of the metallic surface exhibits a very sharp dip at an angle of incidence corresponding to the phase-matching condition for the coupling of energy from the incident beam to the resonant surface mode. The typical width of the resonance is a few mrad, thus making feasible the direct measurement of small angular movements by just detecting the intensity of the reflected light. By means of a simple optical setup this sensitivity can be exploited to build a position-sensitive detector capable of nanometric resolution. Tests have been carried out on several Ag depositions. The angular resolution obtained has been in the 0.2 to 0.4 arcsecs range; the sensitivity to linear displacements has been tested monitoring the motion of piezoelectric actuators and is better than 5 nm over a range of a few microns. We have verified that the proposed method does not require beams of high optical quality and permits in principle a considerable simplification over interferometric systems. Well-established technological processes might be used for its implementation, keeping its cost at a competitive level with respect to other devices of the same potential sensitivity.
This work relates to the glass polishing process in optical workshops, classically based on pitch lapping of ground surfaces. The process progressively removes the asperities and lowers the surface toward the bottom of the remaining pits. According to Preston's hypothesis, the polishing rate is proportional to the velocity of the lap and to its pressure on the area of contact. A computerized imaging technique is here reported to monitor the progress of the polishing action. A Nomarski microscope with a 16X objective has been equipped with a TV camera connected to a personal computer. A frame grabber provides image data that are elaborated to work out the surface features. Statistics are obtained on the fractional area covered by the residual pits. Referring to the Preston's hypothesis, the measured parameter is related to the actual finish grade of the surface inspected.
A homodyne interferometer is described, using a He-Ne laser source and working in Twyman- Green configuration. By means of proper retardation plates and polarizing beam splitters, three signals at 90 degree(s) phase lag are made available. Such signals are digitized and fed into a desktop computer. Fitting procedures and computing algorithms are then implemented working out a phase angle; monitoring such a phase provides information on the optical path difference between the two arms of the interferometer. The general features of the approach are reviewed; examples of application are given, monitoring the fine displacement of mechanical parts and measuring the optical thickness variation of a soap film in air.
After being processed by an optical system, either in reflection or in transmission, a probe wavefront contains information on the induced aberrations that are conveniently reported by interferometry. Yet, the probe beam also includes diffuse light, mostly produced by scattering at the optical surfaces. The actual disturbance that is studied via interferometry is a partially developed speckle field, made of a strong bias phaser plus the weak random contribution due to scattering. The standard deviation of the random contribution, normalized to the modulus of the bias phaser, is assumed as a characteristic parameter of the speckle field. Such a parameter has been measured with digital phase-shift interferometric techniques on a series of selected samples, corresponding to different optical finish. In excess of 120 samples have been studied, referred to a traceable polishing process. The results are interpreted on the basis of available models of polishing mechanisms. Data fitting to the equation of the theory is reported; the results are in fair agreement with the theory.
Phaseshifting interferometry applied to speckle fields is described. Experimental cases of both weak and strong scatterers are investigated. Statistical parameters are sought on timing of the polishing process of optical sample surfaces. 1 .