<title>New challenges for spatial light modulators: laser beam splitting and beam shaping, and reconstruction of digital holograms</title>

Abstract

Liquid crystal displays, operating in a linearized phase mode, can achieve a performance to be applicable as diffractive elements. We built up a Fourier-system with a Sony-LCD based spatial light modulator in order to realize dynamic diffraction patterns. The quality measures of our DOE in the output plane of the system are promising for a wide range of applications. The performance oftechnical beam splitters, realized as binary or 8-256 level diffractive elements will be discussed in the paper. Here we will focus on parameters as diffraction efficiency, signal to noise ratio and also speckle effects. Since the display is addressed directly from the graphics card series of diffraction patterns and animations can be realized. Furthermore, beam shaping elements, two-dimensional holograms and the reconstruction of digital holograms will be shown. The latter opens new possibilities for non-destructive testing devices especially in the field of holographic interferometry. The limiting parameters of the performance are mostly due to physical boundary conditions, such as pixel number and size, response time, transmission etc. . We can assume that the fast growing micro-structuring technology will serve us soon with displays of higher resolutions and efficiency. A discussion concerning requirements for medial or micro-fabrication applications, particularly due to the limited efficiency and the intensity-dependent modulation, will finish the paper.

Spatial light modulator system as dynamic diffractive element

“…A dynamic phase modulating system opens here new possibilities for non-destructive testing devices based on interferometry. This new approach is really the biggest challenge for SLMs, but the obtained results are more than just a feasibility study [10,12,13].…”

“…The result is again the realization of both optical functions, what is the same that happens with double exposure techniques in interferometry, fringes are visible. The addition of two digital phase masks leads in reconstruction to interference [10,12,13].…”

“…The LC 2002 could realize diffraction patterns of Fresnel holograms with a very high efficiency and a nearly totally reduced zero order intensity [8][9][10][11]. The space-bandwidth product is due to the pixel size of 32 µm and the 800x600 pixel resolution relatively weak and the reconstruction could just resolve the object in the mm region.…”

Phase effects of secondary reflections on the performance of reflective liquid-crystal cells

“…By using tiny arrays of electrodes, the light intensity can be varied across a given aperture, yielding a spatial light modulator [1]. Such spatial light modulators are used in a wide variety of applications, ranging from beam shaping [2,3] to arrayed optical switching devices [4,5].…”