Marek W. Kowarz

Conformal grating electromechanical system (GEMS) for high-speed digital light modulation

A diffractive optical MEMS device for spatial and temporal light modulation is described that is capable of high-speed digital operation. The device contains electromechanical ribbons suspended flat above a silicon substrate by a periodic series of intermediate supports. When actuated electrostatically, the ribbons conform around the support substructure to produce a grating. The device has optical switching times of less than 50 nsec, sub-nanosecond jitter, high optical contrast and efficiency, and reliable actuation in contact mode. The fine gray levels needed for digital imaging systems are produced by pulse width modulation.

High-Resolution Laser-Projection Display System Using a Grating Electromechanical System (GEMS)

Eastman Kodak Company has developed a diffractive-MEMS spatial-light modulator for use in printing and display applications, the grating electromechanical system (GEMS). This modulator contains a linear array of pixels capable of high-speed digital operation, high optical contrast, and good efficiency. The device operation is based on deflection of electromechanical ribbons suspended above a silicon substrate by a series of intermediate supports. When electrostatically actuated, the ribbons conform to the supporting substructure to produce a surface-relief phase grating over a wide active region. The device is designed to be binary, switching between a reflective mirror state having suspended ribbons and a diffractive grating state having ribbons in contact with substrate features. Switching times of less than 50 nanoseconds with sub-nanosecond jitter are made possible by reliable contact-mode operation. The GEMS device can be used as a high-speed digital-optical modulator for a laser-projection display system by collecting the diffracted orders and taking advantage of the low jitter. A color channel is created using a linear array of individually addressable GEMS pixels. A two-dimensional image is produced by sweeping the line image of the array, created by the projection optics, across the display screen. Gray levels in the image are formed using pulse-width modulation (PWM). A high-resolution projection display was developed using three 1080-pixel devices illuminated by red, green, and blue laser-color primaries. The result is an HDTV-format display capable of producing stunning still and motion images with very wide color gamut.

Vector diffraction from subwavelength optical disk structures: two-dimensional modeling of near-field profiles, far-field intensities, and detector signals from a dvd

Rigorous two-dimensional vector-diffraction patterns of a focused beam incident on an optical disk, specifically, a digital versatile disk (DVD), are examined both in the near field and in the far field. An efficient finite-difference frequency-domain method is developed for calculating the electromagnetic fields in the neighborhood of subwavelength dielectric and metallic structures. The results of vector-diffraction theory are compared with those of scalar-diffraction theory for pressed DVD features that consist of pits or of bumps. The sum (data) and difference (tracking) signals from a split photodetector are also calculated for different disk features and for different polarizations. The subwavelength features of a DVD result in considerable vector-diffraction effects both in the near-field profiles and in the detector signals, depending not only on the polarization of illumination but also on whether the features are pits or bumps. This paper provides important insight into the vector-diffraction effects encountered in high-density optical data storage systems.

Vector diffraction from subwavelength optical disk structures: Two-dimensional near-field profiles

An efficient finite-difference frequency-domain method is developed for calculating electromagnetic fields in the neighborhood of subwavelength dielectric and metallic structures. The method is used to investigate two-dimensional near-field and far-field patterns of a focused beam diffracted from an optical disk, specifically from a DVD (Digital Versatile Disk). It is shown that the polarization of illumination has a significant impact on diffraction patterns as expected and that scalar theory does not provide an accurate analysis of diffraction from a DVD.

67.2: Line‐Scanned Laser Display Architectures Based on GEMS Technology: From Three‐Lens Three‐Chip Systems to Low‐Cost Optically Efficient Trilinear Systems

The device structure of our grating electromechanical system (GEMS) linear array modulator enables unique optical architectures for line-scanned laser displays. We describe the optical system of our three-chip, front-projection GEMS prototype and a design for a high-performance, trilinear system that combines the simplicity of a single-chip system with the optical efficiency and image quality of a three-chip system.

MEMS programmable spectral imaging system for remote sensing

ITT Industries Space Systems Division and Eastman Kodak Company have developed a scalable, data- and power-efficient imaging spectrometer system with a digitally tunable optical filter capability, which enables the rapid selection of high-quality user-defined optical spectral band(s) of interest. The system utilizes a custom-designed, high-contrast diffractive MEMS device with 50 independent spectral switches at the image plane of a double-pass dispersive/de-dispersive spectrometer. The custom MEMS device is based on grating electromechanical system (GEMS) display technology, which provides very high image contrast (2000:1), fast optical switching speeds (< 100 ns), and a large active area with a very high fill factor. The system enables the selection of arbitrary, narrow or wide spectral bands of interest across the visible spectrum with a sampling resolution of 5 nm, without any moving mechanical parts. The resulting optical filter quality and performance is comparable to conventional fixed-band dichroic filters used in current remote sensing systems. The brassboard systems are designed for rapid transition to space-based, electro-optical (EO) remote sensing missions that utilize large format linear TDI scanning sensors and large format area staring arrays in the visible band. This technology addresses numerous capabilities to meet future EO system requirements for rapidly selecting and utilizing a high quality imaging optical bandpass of interest. The system concept provides capability for a >20X scan rate advantage over conventional hyperspectral imagers as a result of the compatibility with TDI scanning. The image quality is comparable to current MSI and HSI systems.

Tilt analysis of readback signals from DVD-ROM media

Tilt is a major source of distortion for the DVD channel. This paper is aimed at understanding the effect of tilt on the readback signal. Equalized signals were collected from DVD-ROM media on an optical spin stand with a variable tilt stage. A simulated version of duty cycle correction (DCC) was applied to each signal to cancel the baseline drift. The pulse response, which characterizes the signal under the linear superposition assumption, was extracted for each signal. The pulse response of the DVD-ROM channel is shown to be highly affected by tangential tilt while the effect of radial tilt is minimal.

Microfabricated electrochemical sensors for combustion applications

A new design for the miniaturization of an existing oxygen sensor is proposed based on the application of silicon microfabrication technologies to a cm sized O2 sensor demonstrated by Argonne National Laboratory and The Ohio State University which seals a metal/metal oxide within the structure to provide an integrated oxygen reference. The structural and processing changes suggested will result in a novel MEMS-based device meeting the semiconductor industry standards for cost efficiency and mass production. The MEMS design requires thin film depositions to create a YSZ membrane, palladium oxide reference and platinum electrodes. Pt electrodes are studied under operational conditions ensuring film conductivity over prolonged usage. SEM imaging confirms void formation after extended tests, consistent with the literature. Furthermore, hydrophilic bonding of pairs of silicon die samples containing the YSZ membrane and palladium oxide is discussed in order to create hermetic sealed cavities for oxygen reference. The introduction of tensile Si3N4 films to the backside of the silicon die generates bowing of the chips, compromising bond quality. This effect is controlled through the application of pressure during the initial bonding stages. In addition, KOH etching of the bonded die samples is discussed, and a YSZ membrane that survives the etching step is characterized by Raman spectroscopy.