Displacement measurement of optically trapped particles by a laser diode phase sensor

A method of sensing single particles in liquid using a diode laser for both trapping and phase measurement is proposed. Optical trapping makes it possible to fix a single particle in liquid and optical feedback effect of the laser diode is used to measure the wave-front of the scattered light. An analysis method of obtaining the position information from the laser intensity signal is described. Experimental results of measured displacement of optically trapped particles by the proposed phase sensing method are shown.