Advances in Liquid Crystal on Silicon (LCOS) spatial light modulator technology

Abstract

LCOS (Liquid Crystal on Silicon) is a reflective microdisplay technology based on a single crystal silicon pixel controller backplane which drives a liquid crystal layer. Using standard CMOS processes, microdisplays with extremely small pixels, high fill factor (pixel aperture ratio) and low fabrication costs are created. Recent advances in integrated circuit design and liquid crystal materials have increased the application of LCOS to displays and other optical functions. Pixel pitch below 3 µm, resolution of 8K x 4K, and sequential contrast ratios of 100K:1 have been achieved. These devices can modulate light spatially in amplitude or phase, so they act as an active dynamic optical element. Liquid crystal materials can be chosen to modulate illumination sources from the UV through far IR. The new LCOS designs have reduced power consumption to make portable displays and viewing elements more viable. Also innovative optical system elements including image and illumination waveguides and laser illuminators have been combined into LCOS based display systems for HMD, HUD, projector, and image analysis/surveillance direct view monitor applications. Dynamic displays utilizing the fine pixel pitch and phase mode operation of LCOS are advancing the development of true holographic displays. The paper will review these technology advances of LCOS and the display applications and related system implementation.

Micro-displays for Holography

“…Phase SLM "HEX" of the company MEADOWLARK OPTICS has the disc-shaped working aperture and 127 pixels of the hexagonal form, and this SLM as a phase-only mask can correct linearly polarized wave front after its passing through the aberrational medium. [2,3,[5][6][7][8] Pixels in the reflective micro-display are addressed by means of electronic keys formed in the silicon wafer using CMOS technology. At the top level of metallization on the silicon, they create the matrix system of aluminum mirrors acting as control electrodes for each individual LC electro-optical cells and at the same time reflecting the light incident to this cell.…”

“…One can expect also, that properties of SLMs will allow real time forming the information blocks as the digital holograms that can be reconstructed directly from a micro-display screen [1,2].…”

“…The following types of micro-displays can be used for spatial light modulation [2][3][4][5][6][7]:  AM LCD -light transmitting liquid crystal displays with Nematic Liquid-Crystal (NLC) as the electro-optical display medium, and Active-Matrix addressing scheme based on thin-film-transistor drivers on the glass surface;…”

LCoS SLM Study and Its Application in Wavelength Selective Switch

“…In recent years, liquid crystal on silicon (LCoS) [1,2] displays have become the most attractive micro-displays for all sorts of spatial light modulation (SLM) applications, as in diffractive optics [3], optical storage [4], optical metrology [5], reconfigurable interconnects [6,7], quantum optical computing [8], and wave shaper technology for optical signal processing and signal monitoring [9], thanks to their very high spatial resolution, very high light efficiency, and their phase-only modulation capability [10,11]. In this article, we focus on the characteristics of LCoS SLM for wavelength selective switch (WSS) systems used in reconfigurable optical add/drop multiplexers (ROADM) in wavelength division multiplexed (WDM) optical networks.…”

Active LSP based structure for Holographic 3D Video Display

“…MIT Spatial Imaging Group headed by Stephen Benton brought holography from the age of film to the digital age in 1989 and this is a remarkably transition. Since then R&D on the devices for true holographic video display is advanced [1,2,3]. Heart of the holographic video is the devices that modulate the light by some kinds of spatial light modulators (SLMs).…”