Abstract
An improved implementation of the reverse phase contrast (RPC) method for rapid optical transformation of amplitude patterns into spatially similar phase patterns using a high-speed digital micromirror-array device (DMD) is presented. Aside from its fast response, the DMD also provides an electronically adjustable and inherently aligned input iris that simplifies the optimization of the RPC system. In the RPC optimization, we illustrate good agreement between experimentally obtained and theoretically predicted optimal iris size. Finally, we demonstrate the conversion of a binary amplitude grating encoded on the DMD into a binary (0-pi) phase grating.
Highlights
Reconfigurable two-dimensional (2D) phase patterns that can be imprinted onto a laser beam’s otherwise planar wavefront have a number of applications in optical engineering
The reverse phase contrast (RPC) method gives a number of advantages as it can make use of fixed amplitude masks and comparatively low-cost amplitude-only SLMs that create reconfigurable input patterns
We have shown the implementation of the reverse phase contrast (RPC) method using a digital mircromirror-array device (DMD)
Summary
Reconfigurable two-dimensional (2D) phase patterns that can be imprinted onto a laser beam’s otherwise planar wavefront have a number of applications in optical engineering. These include optical encryption-decryption [1,2,3], holographic optical memory or datastorage [4, 5], and optical joint-transform correlation (JTC) [6]. PO-SLMs may be liquid crystal (LC) or microelectromechanical system (MEMS) -based devices that generate phase profiles by spatial variation of the optical path of an incident wavefront. The former does it by a refractive index or birefringence variation while the latter does it by a geometrical path alteration. The DMD has significantly higher illumination power tolerances supporting several spectral regions from 350-2000 nm and has much less stringent requirement on the polarization of the incident field compared to LC-based SLMs
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