Research

Efficient illumination of spatial light modulators for optical trapping and manipulation.

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Abstract

Energy efficiency is always desirable. This is particularly true with lasers that find many applications in research and industry. Combined with spatial light modulators (SLMs) lasers are used for optical trapping and manipulation, sorting, microscopy or biological stimulation1. Besides efficiency, one wants to uniformly illuminate a specific shape such as the addressable area of an SLM. The common practice of truncating an expanded Gaussian source, however, is inefficient2. The Generalized Phase Contrast (GPC) enables illumination that inherits the efficiency advantages of phase-only light shaping while maintaining the speckle-free, high-contrast qualities of amplitude masking. Compared to a hard truncated Gaussian, a GPC Light Shaper (LS) saves up to 93% of typical losses3. We experimentally demonstrated shaped illumination with ~80% efficiency, ~3x intensity gain, and ~90% energy savings4. We have also shown dynamic SLM-generated patterns for materials processing and biological research. To efficiently illuminate an SLM, we used a compact pen-sized GPC-LS in place of an iris. For the same input power, hologram reconstructions are ~3x brighter or alternatively ~3x more focal spots can be addressed. This allows better response or increased parallel addressing for e.g. optical manipulation and sorting. Simple yet effective, a GPC-LS could save substantial power in applications that truncate lasers to a specific shape.