With the aid of phase-only spatial light modulators (SLM), generalized phase contrast (GPC) has been applied with great success to the projection of binary light patterns through arbitrary-NA microscope objectives for real-time threedimensional manipulation of microscopic particles. Here, we review the analysis of the GPC method with emphasis on efficiently producing speckle-free two-dimensional grey-level light patterns. Numerical simulations are applied to construct 8-bit grey-level optical potential landscapes with high fidelity and optical throughput via the GPC method. Three types of patterns were constructed: geometric block patterns, multi-level optical trap arrays, and optical obstacle arrays. Non-periodic patterns were accurately projected with an average of 80% diffraction efficiency. Periodic patterns yielded even higher diffraction efficiencies, averaging 94%, by the utilization of large-aperture phase contrast filters.

Date Published: 5 September 2007
PDF: 9 pages
Proc. SPIE 6644, Optical Trapping and Optical Micromanipulation IV, 66440X (5 September 2007); doi: 10.1117/12.733956

Published in SPIE Proceedings Vol. 6644:
Optical Trapping and Optical Micromanipulation IV
Kishan Dholakia; Gabriel C. Spalding, Editor(s)