Giuseppe Molesini

Accurate polarization interferometer

A polarization interferometer which measures optical path differences with improved accuracy control is presented. The approach makes use of four signals in quadrature, computing the phase with an algorithm insensitive to laser power drifts. Experimental results of the interferometer’s performance are given under laser warmup conditions, and with long‐term monitoring of optical path differences.

Iterative algorithm for three flat test

Absolute planarity measurements by interferometry are classically made using three flats, compared two by two in the course of four or more tests. Data reduction is performed with various analytical methods. Here we present instead a data processing algorithm that converges to solution numerically by iteration. Examples are presented both on synthetic interferograms and on experimental data. High accuracy and versatility of the approach are demonstrated.

Viscous Behavior of Fused Silica at Room Temperature

Researchers are once again interested in using non-diffracting beams of light because of the possibility

Three-flat test with plates in horizontal posture

Measuring flats in the horizontal posture with interferometers is analyzed in detail, taking into account the sag produced by gravity. A mathematical expression of the bending is provided for a plate supported at three unevenly spaced locations along the edge. It is shown that the azimuthal terms of the deformation can be recovered from a three-flat measuring procedure, while the pure radial terms can only be estimated. The effectiveness of the iterative algorithm for data processing is also demonstrated. Experimental comparison on a set of three flats in horizontal and upright posture is provided.

Absolute planarity with three-flat test: an iterative approach with Zernike polynomials

An iterative algorithm to analyze three-flat test data for absolute planarity measurements is presented. Using the properties of Zernike polynomial representations, results are achieved in a fast and effective manner. Details and demonstrative examples are provided.

Design of optical-waveguide homogeneous refracting lenses

A class of multielement homogeneous refracting lenses for optical waveguides is presented, and their design procedure is described. These lenses appear to be particularly suitable for use in integrated optical processors, as they can be fabricated by fully planar photolithography and reliable diffusion processes either in glass or in lithium niobate; their optical characteristics can be very good. For example, the design of an f/3.3 waveguide optical system, constituted by five elements, with no field curvature and very well corrected up to a 20 degrees total field of view, is presented.

Telescopes of galileo.

The Florentine Istituto e Museo di Storia delta Scienza houses two complete telescopes and a single objective lens (reconstructed from several fragments) that can be attributed to Galileo. These optics have been partially dismantled and made available for optical testing with state-of-the-art equipment. The lenses were investigated individually; the focal length and the radii of curvature were measured, and the optical layout of the instruments was worked out. The optical quality of the surfaces and the overall performance of the two complete telescopes have been evaluated interferometrically at a wavelength of 633 nm (with a He-Ne laser source). It was found in particular that the optics of Galileo came close to attaining diffraction-limited operation.

Validation of absolute planarity reference plates with a liquid mirror

The use of a simplified version of the liquid mirror approach to validate absolute planarity reference flats is described in detail. It is shown that the approach can serve the purpose, providing a measurement of the peak-to-valley departure from planarity that in experiments is within 7 nm uncertainty (2σ) over a diameter of 90 mm.

Supercontinuum source tuned by an on-axis monochromator for fluorescence lifetime imaging

We report on the application of an optically tunable coherent white light source, based on the supercontinuum generation from microstructured optical fibres, to fluorescence lifetime imaging (FLIM) microscopy and Foerster resonance energy transfer (FRET). A prototype lens based on monotonic longitudinal chromatic aberration is used for tuning the supercontinuum wavelengths from 400 to 1000 nm and acts as an axial monochromator, suitable for fibre delivery in confocal microscopy.

Speckle interferometry experiments with a digital photocamera

We discuss a simple experiment for detecting small deformations by speckle interferometry. The optical setup uses a laser diode for the source together with a lens to expand the laser beam and a beam splitter dividing the beam and illuminating two scattering surfaces. A low-cost, commercial charge coupled device (CCD) photocamera provides images of the two superimposed speckle fields through the beam splitter. We first take a picture with the system at rest, and then take a second one after a deformation is made in a surface. By simple subtraction of the digital pictures, we obtain a fringe pattern that gives us information about the deformation.