<title>Writing diffractive structures by optical trapping</title>

Abstract

Optical forces, such as radiation pressure and the gradient force, are used to trap microscopic size dielectric particles. Regular arrays of optical traps can be constructed interferometrically, and more complex assemblages of traps could be made through holographic-type set-ups. Such opticalwell arrays are useflul in writing and erasing dynamic gratings. Two-dimensional "optical crystals", composed of monodispersed polystyrene spheres in water, display high diffraction efficiencies and low noise level, thanks respectively to a very high index modulation, and to the very small size dispersion ofthe scatterers. Many dielectric microobjects can be arranged in such trap assemblies to form difi1active stmctures. This is the case in particular for biological materials such as bacteria or other organisms currently trapped with laser tweezers.The possibilities ofmanufacturing 3-D diffiactive structures are explored.

Miniaturized high-NA focusing-mirror multiple optical tweezers

“…Several multiple optical trapping schemes have already been proposed relying on very different techniques, including diffractive elements [9,10], interfering beams [11,12], VCSEL arrays [13], microlens arrays [14] or optical fiber-bundles [15]. Certain optical trapping schemes even allow generating multiple traps that are computer-reconfigurable using laser scanning [16] or spatial light modulators [17,18].…”

Optical electrostriction

“…This was followed by sporadic investigations involving different methods. [15][16][17][18][19][20] The advent of sufficient laser intensities to study these forces are now routinely available, encouraging new interest; indeed, there is now good reason to expect significant effects to be experimentally demonstrable at much lower intensity levels than originally expected. In 2005 the UEA quantum electrodynamics group published the first fully comprehensive theory of optically induced inter-particle force, based on QED.…”

Orientation of Red Blood Cells and Rouleaux Disaggregation in Interference Laser Fields

“…There are two main approaches towards multiple optical trapping: one based on strongly focused beams using the high numerical aperture objectives [6][7][8][9][10] and another based on interference methods when particles are trapped by interference field [11][12][13][14][15][16][17]. The first type systems were created by a number of means: by fast single beam scanning [6], by two counterpropagating Gaussian light beams [7], with methods of spatial light modulation, e.g., computer-generated holography [8] or generalized phase-contrast method [9], and with multiple light sources [10].…”

“…The creation of two-dimensional array of microparticles by means of interference field was demonstrated for the first time in [11][12][13]. The simplest case of two-beam interference forms a pattern of linear interference fringes with easily adjustable width [14].…”