Multi-dimensional Imaging

Chapter 8Holographic Three-Dimensional Measurement of an Optically Trapped Nanoparticle

Yoshio Hayasaki

Center for Optical Research and Education (CORE), Utsunomiya University, Japan

8.1 Introduction

The “Optical tweezers” technique [1] is a well-known technique used to trap and manipulate minute objects in a liquid without contact. It has been used for manipulating viruses and bacteria [2], single RNA molecules [3, 4], and DNA molecules [5]. It has also been used to study the motion of the biological motor protein kinesin [6] and to sequence DNA [7]. It has been employed in not only biological applications but also for sorting objects in microfluidic systems [8–10], and measuring the mechanical properties [11] and shapes of microstructures [12]. Holographic optical tweezers [13–15] have also been used to create arbitrary three-dimensional structures [16–18].

In these applications, precise position measurement of the trapped object expands the ability to perform mechanical and structural measurements, and several methods have been developed. Position measurement with a quadrant photodiode (QPD) has been performed using spatial changes in light intensity according to the displacement of the trapped object with high temporal resolution and high sensitivity [1, 19–23]. However, it is difficult to measure many objects simultaneously and to measure a three-dimensional (3D) position.

The use of a camera was effective for measuring optically trapped objects three-dimensionally [24]. ...