A MEMS Light Modulator Based on Diffractive Nanohole Gratings

We present the design, fabrication, and testing of a microelectromechanical systems (MEMS) light modulator based on pixels patterned with periodic nanohole arrays. Flexure-suspended silicon pixels are patterned with a two dimensional array of 150 nm diameter nanoholes using nanoimprint lithography. A top glass plate assembled above the pixel array is used to provide a counter electrode for electrostatic actuation. The nanohole pattern is designed so that normally-incident light is coupled into an in-plane grating resonance, resulting in an optical stop-band at a desired wavelength. When the pixel is switched into contact with the top plate, the pixel becomes highly reflective. A 3:1 contrast ratio at the resonant wavelength is demonstrated for gratings patterned on bulk Si substrates. The switching time is 0.08 ms and the switching voltage is less than 15V.

Communicating Severity of Hazard with the Signal Word on a Safety Sign

An experiment examined five signal words on safety signs for effectiveness at communicating information about severity of a hazard. Perceived severity was rated by 59 college students for the signal words Deadly, Danger, Warning, Caution, and Notice. Results indicated that Deadly communicated the highest ratings for severity. Danger was second. Warning and Caution were tied for third. The lowest ratings were for Notice.

Comparison of Student Versus Employee Test Populations for Warning Sign Research Based on Severity Ratings for Signal Words

Most studies of warning signs involve undergraduate students as subjects. This paper reports a direct comparison of findings from an undergraduate population and an employed population. The 48 employed subjects from this study were compared with 59 undergraduate subjects from a companion study. Subjects from both populations were shown the same signs and asked to rate the severity level connoted by each sign. The signs differed only in signal word. Results for each population indicated that signal word had a highly significant effect on severity ratings. When the two populations were compared for ratings of each signal word, the only significant difference was for Caution. Median ratings of each population were the same: Deadly (4), Danger (3), Warning (2), Caution (1), and Notice (0).

Photonics Crystals: The Future of Microwave Signal Processing

The ability of cryogenic photonic crystals to carry out high performance microwave signal processing operations has been developed into systems that can: rapidly record broadband microwave spectra with fine resolution and high dynamic range; search for patterns in 40 gigabits per second data streams; and communicate via spread- spectrum signals that are well below the noise floor. The basic concepts of the technology and its many applications, along with an overview of university-industry partnerships and the growing photonics industry in Bozeman, will be presented.