Monolithically integrated optical displacement sensor based on triangulation and optical beam deflection.

A monolithically integrated optical displacement sensor based on triangulation and optical beam deflection is reported. This sensor is simple and consists of only a laser diode, a polyimide waveguide, and a split detector (a pair of photodiodes) upon a GaAs substrate. The resultant prototype device is extremely small (750 microm x 800 microm). Experiments have shown that this sensor can measure the displacement of a mirror with resolution of better than 4 nm. Additionally, we have experimentally demonstrated both axial and lateral displacement measurements when we used a cylindrical micromirror (diameter, 125 microm) as a movable external object.

Monolithic-integrated microlaser encoder.

We have developed an extremely small integrated microencoder whose sides are less than 1 mm long. It is 1/100 the size of conventional encoders. This microencoder consists of a laser diode, monolithic photodiodes, and fluorinated polyimide waveguides with total internal reflection mirrors. The instrument can measure the relative displacement between a grating scale and the encoder with a resolution of the order of 0.01 microm; it can also determine the direction in which the scale is moving. By using the two beams that were emitted from the two etched mirrors of the laser diode, by monolithic integration of the waveguide and photodiodes, and by fabrication of a step at the edge of the waveguide, we were able to eliminate conventional bulky optical components such as the beam splitter, the quarter-wavelength plate, bulky mirrors, and bulky photodetectors.

Optical trapping of low-refractive-index microfabricated objects using radiation pressure exerted on their inner walls.

Optical trapping of transparent ring-shaped micrometer-sized objects with a refractive index lower than that of the surrounding medium has been demonstrated by use of a strongly focused TEM(00)-mode laser beam. Axial trapping of these objects is a result of the upward radiation pressure induced when the incident light strikes the inner wall and transmitted light leaves from the bottom. Transverse trapping of these objects occurs because the total repulsive radiation pressure exerted on the inner wall of the object is directed toward the laser beam axis. Three-dimensional manipulation of f luorinated polyimide micro-objects (refractive index n(1)= 1.525, outer diameter 10 microm, inner diameter 5 microm, and thickness 5.7 microm) in a high-refractive-index liquid (n(2)= 1.605) was experimentally shown to be possible by use of an objective lens with a wide range of numerical apertures from 1.25 to 0.5.