Full-range, continuous, complex modulation by the use of two coupled-mode liquid-crystal televisions

Abstract

Switchable, continuous, complex-amplitude modulation is demonstrated with two cascaded, twisted nematic liquid-crystal televisions (LCTV's), both operating in phase- and amplitude-coupled modulation modes. The condition for full-range complex modulation is that one of the LCTV's must provide a 2π-range phase modulation. A look-up table encoding method is proposed that permits the compensation of phase-amplitude coupling and nonlinearity in the two individual LCTV modulations. Experimental techniques for determining the LCTV-device parameters, for maximizing the phase-mostly modulation range and the amplitude-mostly modulation contrast, and for testing the complex-amplitude modulation are developed. Optical complex-amplitude Fresnel holograms are shown.

Complex Fresnel hologram display using a single SLM

“…Thus, we can use two SLMs, one in AM mode and the other one in PM mode, to control the amplitude and the phase of the light, respectively. This is what has been done in [22][23][24], but cascading the two SLMs demands precise alignment. Alternatively, H cp can be separated into two parts,…”

“…Using two SLMs can display a complex hologram directly. This can be implemented by cascading two SLMs, one for amplitude modulation (AM) and the other for phase modulation (PM) [22][23][24]. Alternatively, a beam splitter can be applied to combine the beams from two SLMs, one for displaying the real part and the other the imaginary part of the complex hologram [25][26][27].…”

Laser Probe 3D Cameras Based on Digital Optical Phase Conjugation

“…Since these fundamental mode fields are separated from each other in space, they could be reconstructed using a pair of low resolution SLMs and a micro lens array (MLA) as illustrated in Fig.2. For the device in Fig.2 we may adjust the gray scale of each pixel of SLMs so that it modulates the amplitude and the phase of illuminating laser beam properly [Neto, et al 1996;Tudela, et al 2004] and reconstruct a conjugate field proportional to above decomposed fundamental mode field within each isolated single-mode waveguide at the right wide end. Due to reciprocity of an optical path the digitally reconstructed conjugate light field within each isolated single-mode waveguide would travel inversely to the left narrow end of the taper, combine and create an optical field proportional to the original incident optical field.…”

Teaching optics with a spatial light modulator

“…2,[7][8][9] We chose the former with some modifications 6,10,11 to avoid ambiguities in the determination of the parameters. The experimental procedure consists on the measurement of the cell transmission between polarizers (crossed ⊥ 7 and parallel || 7 ) when no voltage is applied, as a function of the angle rotated simultaneously by the polarizers axis, ψ 1 .…”