Laser Interference Patterning

Commercial polymer films can be easily microstructured using Laser Interference Patterning. In that way, the scope of the technique is increased since materials having well-known bulk and surface properties can be microstructured, allowing direct application, for example, in biomedical devices poly(etheretherketone) resists sterilization by radiation or heat treatment and it has been used to produce kidney dialysis machine components poly(etherimide) is used in harmonic scalpels polycarbonate (PC) is used in electrophysiology cathethers and poly(imide) (PI) is used in off pump coronary artery bypass devices.Moreover, the surface of already fabricated systems could be modified using this technique since it can be applied in air without altering the shape of the samples. 

Modification of polymer surfaces is used to improve biocompatibility or to provide medico-functionality of blood- and tissue-contacting medical devices. Yu et used Direct Laser Interference Patterning (DLIP) to prepare periodic micropatterns in polymers for study of contact guidance of mammalian cells. 

Kelly MK, Rogg J, Nebel CE, Stutzmann M, Katai S. (1998) High-resolution thermal processing of semiconductors using pulsed-laser interference patterning. Phys StatSol (a) 166 651-657. 

Lasagni A, Acevedo D, Barbero C, Mticklich F. (2006) One-step production of oiganized surface architectures on polymeric materials by direct laser interference patterning. Ado Eng Mater 99-103. 

Acevedo DF, Lasagni A, Barbero CA, Miicklich F. (2008) Micro/nano fabrication of surface architectures on polymers and copolymers using direct laser interference patterning. Proc Mat Res Soc Symp 1054 FF01-FF07. 

Fig. 40 Calculated constant-intensity surface in 4-beam laser interference patterns. The primitive units (contents of Wigner-Seitz unit cell) is shown inset in each case, a Scheme-1, high-index beam vectors interference, producing pattern of 922-nm lattice constant, b Scheme-2, low-index beam vectors interference, producing FCC pattern with 397-nm lattice constant. In both case, the use of 355-nm YAG laser was assumed. Scale bars 500 nm...

The application of interference techniques overcomes the limitations exerted by the large optical wavelengths. With commercial phase-measurement interference microscopes (PMIM), a surface resolution of the order of 0.6 nm can be achieved [33, 34]. In a microscope a laser beam is both reflected from the sample surface and from a semitransparent smooth reference surface (Fig. 3). The interference pattern is recorded on an area detector and modulated via the piezo-electric driven reference surface. The modulated interference pattern is fed into a computer to generate a two-dimensional phase map which is converted into a height level contour map of the sample surface. While the lateral resolution (typically of the... 

Fig. 2.6. Schematic illustration of the experimental setup for pump-probe anisotropic reflectivity measurements with fast scan method. PBS denotes polarizing beam splitter, PD1 and PD2, a pair of matched photodiodes to detect p- and s-polarized components of the reflected probe beam, PD3 another photodiode to detect the interference pattern of He-Ne laser in a Michelson interferometer to calibrate the scanning of the pump path length...

An experimental method based on the theories for rainbow phenomena has been applied to the measurement of droplet size and velocity and to the detection of non-sphericity.[7] In this method, a comparison between two droplet diameters is deduced from two different optical interference patterns observed in a rainbow that is created by a droplet scattering laser light. Once a rainbow pattern is... 

This effective Q,t-range overlaps with that of DLS. DLS measures the dynamics of density or concentration fluctuations by autocorrelation of the scattered laser light intensity in time. The intensity fluctuations result from a change of the random interference pattern (speckle) from a small observation volume. The size of the observation volume and the width of the detector opening determine the contrast factor C of the fluctuations (coherence factor). The normalized intensity autocorrelation function g Q,t) relates to the field amplitude correlation function g (Q,t) in a simple way g t)=l+C g t) if Gaussian statistics holds [30]. g Q,t) represents the correlation function of the fluctuat-... 

Rather than measuring the amount of material in the gel fraction, it might be easier to determine the time at which gelation of a network takes place. (For example, one could focus a laser beam on a sample and note when the speckle interference pattern freezes. ) Gelation occurs in a developing network if the crosslink fraction a exceeds a critical value a, given as(23)... 

Another important optical phenomena that relies on light interference and diffraction is holography, the process by which holograms (interference patterns) are produced. Whilst holograms are best known for the reproduction of near perfect 3D images of an object in the graphic arts, they also find apphcations in newer areas such as laser eye protection, LCDs, diffractive optical elements, optical processing... 

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