Full phase and amplitude control of holographic optical tweezers with high efficiency

Abstract

Recently we demonstrated the applicability of a holographic method for shaping complex wavefronts to spatial light modulator (SLM) systems. Here we examine the potential of this approach for optical micromanipulation. Since the method allows one to shape both amplitude and phase of a trapping light field independently and thus provides full control over scattering and gradient forces, it extends the possibilities of commonly used holographic tweezers systems. We utilize two cascaded phase-diffractive elements which can actually be display side-by-side on a single programmable phase modulator. Theoretically the obtainable light efficiency is close to 100%, in our case the major practical limitation arises from absorption in the SLM. We present data which demonstrate the ability to create user-defined "light pathways" for microparticles driven by transverse radiation pressure.

Time-reversed optical focusing through scattering media by digital full phase and amplitude recovery using a single phase-only SLM

“…Due to the CGH's ability to recover complex shapes of varied patterns, the G-S algorithm has been widely used in varied applications such as optical tweezers and laser beam forming. 11 In such applications, the G-S algorithm iteratively Fourier transforms the light propagation between the plane of computed hologram and its Fourier plane, where the desired pattern is supposed to be. In the meantime, a speci¯c constraint (for example, the desired pattern of an optical tweezers, or the desired shape of an output laser beam) is added at any plane to con¯ne the output pattern.…”

“…2.1, a setup for TR optical focusing through scattering media is proposed for discussion, 11 as shown in Fig. 3.…”

Experimentally generating any desired partially coherent Schell-model source using phase-only control

“…For GSM synthesizers, this element is naturally a Gaussian amplitude filter. [28][29][30]39,40,[44][45][46][47][49][50][51] For more general source shapes, another SLM (either amplitude or phase-only) could be used; [53][54][55][56] however, aligning the SLMs can be difficult and is a potential source of error.…”

White light wavefront control with a spatial light modulator

“…Spatial light modulators (SLMs) are now standard tools for the shaping and control of light, having found applications in fields ranging from holographic optical trapping and tweezing [1][2][3][4], laser beam shaping and characterization [5][6][7][8][9] and imaging [10] to name but a few. These devices are primarily limited in two ways.…”