Optical trapping of small particles using a 1.3-microm compact InGaAsP diode laser

We describe the noncontact optical trapping of small particles by a single-beam gradient force using a near-infrared InGaAsP diode laser operating at 1.33 microm. The feasibility and reliability of diode-laser trapping was confirmed with polystyrene latex and glass spheres as well as with yeast cells. By moving small particles vertically to the laser beam axis, we measured the horizontal component of the trapping force based on the Stokes law. Thus a linear relationship between the trapping laser power and the horizontal trapping force is demonstrated and compared quantitatively with that for the Ar laser.