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Dändliker, René
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Dändliker, René
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33 Résultats
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- PublicationAccès libreFrequency-comb-referenced two-wavelength source for absolute distance measurement(2006)
; Holzwarth, RonaldWe propose a new tunable laser source concept for multiple-wavelength interferometry, offering an unprecedented large choice of synthetic wavelengths with a relative uncertainty better than 10−11 in vacuum. Two lasers are frequency stabilized over a wide range of frequency intervals defined by the frequency comb generated by a mode-locked fiber laser. In addition, we present experimental results demonstrating the generation of a 90 μm synthetic wavelength calibrated with an accuracy better than 0.2 parts in 106. With this synthetic wavelength we can resolve one optical wavelength, which opens the way to absolute distance measurement with nanometer accuracy. - PublicationAccès libreHigh Resolution Interference Microscopy: A Tool for Probing Optical Waves in the Far-Field on a Nanometric Length Scale(2006)
; High Resolution Interference Microscopy (HRIM) is a technique that allows the characterization of amplitude and phase of electromagnetic wave-fields in the far-field with a spatial accuracy that corresponds to a few nanometers in the object plane. Emphasis is put on the precise determination of topological features in the wave-field, called phase singularities or vortices, which are spatial points within the electromagnetic wave at which the amplitude is zero and the phase is hence not determined. An experimental tool working in transmission with a resolution of 20 nm in the object plane is presented and its application to the optical characterization of various single and periodic nanostructures such as trenches, gratings, microlenses and computer generated holograms is discussed. The conditions for the appearance of phase singularities are theoretically and experimentally outlined and it is shown how dislocation pairs can be used to determine unknown parameters from an object. Their corresponding applications to metrology or in optical data storage systems are analyzed. In addition, rigorous diffraction theory is used in all cases to simulate the interaction of light with the nano-optical structures to provide theoretical confirmation of the experimental results. - PublicationAccès libreMeasuring optical phase singularities at subwavelength resolution(2004)
; - PublicationAccès libreHigh-resolution measurement of phase singularities produced by computer-generated holograms(2004)
; We present measurements of the intensity as well as the phase distribution in the various diffraction orders of computer-generated holograms designed to generate a higher order Gauss–Laguerre beam. For the direct measurement of the phase distribution in the diffraction orders a high-resolution interferometer is used, which allows access to a lateral length scale for the localization of phase singularities below the wavelength. It is experimentally shown that in beams that carry multiple singularities, the dislocations do not degenerate. This effect cannot be seen by analyzing only the intensity distribution of the laser beam. - PublicationAccès librePropagation of the electromagnetic field in fully coated near-field optical probes(2003)
; Fully metal-coated near-field optical probes, based on a cantilever design, have been studied theoretically and experimentally. Numerical simulations prove that these structures allow nonzero modal emission of the electromagnetic field through a 60-nm-thick metallic layer, that is opaque when deposited on flat substrates. The far-field intensity patterns recorded experimentally correspond to the ones calculated for the fundamental and first excited LP modes. Moreover, this study demonstrates that a high confinement of the electromagnetic energy can be reached in the near-field, when illuminated with radially polarized light. Finally, it was verified that the confinement of the field depends on the volume of the probe apex. - PublicationAccès libreMicro-optical fiber switch for a large number of interconnects using a deformable mirror(2002)
; In this letter, we demonstrate the limitations for 1 × N free space optical switch with a moving macro-lens. We use a deformable mirror to overcome these limitations. The adaptive mirror corrects for the aberrations. Power coupling efficiencies between 6 and 3 dB (including losses due to the optical elements) are feasible for an optical switch allowing up to 3019 receiver fibers. - PublicationAccès libreOptical MEMS based on silicon-on-insulator (SOI) for monolithic microoptics(2002)
; - PublicationAccès libreApplications of SOI-based optical MEMS(2002)
; ; de Rooij, Nicolaas F.After microelectromechanical systems (MEMS) devices have been well established, components of higher complexity are now developed. Particularly, the combination with optical components has been very successful and have led to optical MEMS. The technology of choice for us is the silicon-on-insulator (SOI) technology, which has also been successfully used by other groups. The applications presented here give an overview over what is possible with this technology. In particular, we demonstrate four completely different devices: (a) a 2 × 2 optical cross connector (OXC)with an insertion loss of about 0.4 dB at a switching time of 500 μs and its extension to a 4 × 4 OXC, (b) a variable optical attenuators (VOA), which has an attenuation range of more than 50 dB (c) a Fourier transform spectrometer (FTS) with a spectral resolution of 6 nm in the visible, and (d) an accelerometer with optical readout that achieves a linear dynamic range of 40 dB over ±6 g. Except for the FTS, all the applications utilized optical fibers, which are held and self-aligned within the MEMS component by U-grooves and small leaf springs. All devices show high reliability and a very low power consumption. - PublicationAccès libreImproved red color with cholesteric liquid crystals in Bragg reflection mode(2002)
; - PublicationAccès libreMeasuring amplitude and phase distribution of fields generated by gratings with sub-wavelength resolution(2002)
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