Stable optical levitation of transparent hollow dielectric spheres has been demonstrated using TEM01 mode laser beams. The levitation of solid dielectric spheres has been made much more stable using highly convergent TEM00 mode beams. We have discovered the existence of two distinct stable regimes of levitation for solid spheres, one located above the beam focus, the other below it. A particle can be switched back and forth between these regimes. Three separate stable regimes are also possible.

Light can exert enough force to flip switches on a silicon chip. We can imagine using optical force to reroute light on the fly, allowing a photonic circuit to perform at a blindingly fast speed, far beyond anything that electronic controls can manage. This capability would go a long way toward realizing the dream of an all-optical computer, able to exploit the immense bandwidth of light to its fullest. Maybe if you left your hard drive at home, you could read it at a comfortable rate over the Internet-if we 're still using hard drives by that time! The most intractable bottleneck in today's high-end computers comes from having to use electronic signals to control photons. The sky will be the limit when we can at last use light to steer light.

The development of optical trapping by a single focused laser beam, also known as optical tweezers (1), has made it possible to manipulate various particles including biological cells, metallic particles (2), and low-refractive-index micro-objects (3). We recently reported the application of optical trapping to rotational manipulation of artificial micro-objects in micro-mechanical systems (4). Rotation was due to the optical torque from the optical radiation pressure exerted on the outside of micro-objects that had shape anisotropy. The axis of this rotation coincided with the incident laser beam axis (2, 4, 5). In an effort to change the direction of the optically induced torque, this paper investigates the possibility of optical trapping and simultaneous rotation about an axis perpendicular to the incident laser beam axis by illuminating an object with a strongly focused laser beam.

Light, visible light, or visible radiation is electromagnetic radiation that can be perceived by the human eye. Visible light spans the visible spectrum Light, visible light, or visible radiation is electromagnetic radiation that can be perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400–700 nanometers (nm), corresponding to frequencies of 750–420 terahertz. The visible band sits adjacent to the infrared (with longer wavelengths and lower frequencies) and the ultravi Light exerts physical pressure on objects in its path, a phenomenon which can be deduced by Maxwell's equations, but can be more easily explained by the particle nature of light: photons strike and transfer their momentum. Light pressure is equal to the power of the light beam divided by c, the speed of light. Due to the magnitude of c, the effect of light pressure is negligible for everyday objects. For example, a one-milliwatt laser pointer exerts a force of about 3.3 piconewtons on the object being illuminated; thus, one could lift a U.S. penny with laser pointers, but doing so would require about 30 billion 1-mW laser pointers. However, in nanometer-scale applications such as nanoelectromechanical systems (NEMS), the effect of light pressure is more significant and exploiting light pressure to drive NEMS mechanisms and to flip nanometer-scale physical switches in integrated circuits is an active area of research. At larger scales, light pressure can cause asteroids to spin faster, acting on their irregular shapes as on the vanes of a windmill. The possibility of making solar sails that would accelerate spaceships in space is also under investigation. Although the motion of the Crookes radiometer was originally attributed to light pressure, this interpretation is incorrect; the characteristic Crookes rotation is the result of a partial vacuum. This should not be confused with the Nichols radiometer, in which the (slight) motion caused by torque (though not enough for full rotation against friction) is directly caused by light pressure. As a consequence of light pressure, Einstein in 1909 predicted the existence of "radiation friction" which would oppose the movement of matter. He wrote, "radiation will exert pressure on both sides of the plate. The forces of pressure exerted on the two sides are equal if the plate is at rest. However, if it is in motion, more radiation will be reflected on the surface that is ahead during the motion (front surface) than on the back surface. The backwardacting force of pressure exerted on the front surface is thus larger than the force of pressure acting on the back. Hence, as the resultant of the two forces, there…

A single focus optical tweezer is formed when a laser beam is launched through a high numerical aperture immersion objective. This objective focuses the beam down to a diffraction-limited spot, which creates an optical trap where cells suspended in aqueous solutions can be held fixed. Spermatozoa, an often probative cell type in forensic investigations, can be captured inside this optical trap and dragged one by one across millimeter-length distances in order to create a cluster of cells which can be subsequently drawn up into a capillary for collection. Sperm cells are then ejected onto a ste

static pressure . Pressure exerted by radiant energy is called radiation pressure . pressure gage. A tide gage that is operated by the change in pressure at