Parallel optical tweezers with combining a diffractive optical element and a spatial light modulator for photonic DNA memory

To overcome the restriction of the density of optical memory systems due to diffraction limit, we have been studying photonic DNA memory, which utilizes photonic technologies and the DNA computing methodology. Our scheme is on the basis of local DNA reaction using laser irradiation and transportation of DNA using parallel optical tweezers with fabricating DNA clusters by attaching DNA onto beads. This paper reports on a new dynamic optical tweezers system, which combines a spatial light modulator (SLM) and a diffractive optical element (DOE) for manipulating DNA clusters. With this combination, real-time programmable manipulation of DNA clusters is achievable in a large spatial range. We also can choose simple patterns for the SLM, and decrease computation cost. In this experiment, a laser beam (633nm wavelength) illuminates a SLM (Hamamatsu Photonics K. K.; PPM8267), which is imaged on an 80-lp/mm transmission-type grating, then the beam is focused with a water immersible objective lens (× 100, NA 1). Simple blazed-phase patterns have different grating constants that are perpendicular to that of the grating are displayed on the SLM. We succeeded in lifting up three 6-micron-diameter polystyrene beads on a glass slide with light spots duplicated by the grating, then transporting the beads in three dimensions simultaneously with changing the grating constants on the SLM. We demonstrated that a same manipulation was implemented at different positions by duplicating a pattern that was generated when only using the SLM. This is usable in implementing a same operation for different data at multiple positions with a single instruction. The promising applications of the method include a nano-scale image memory with encryption.