Transmissive light valves based on voltage-tunable color-selective absorption of light in surface plasmons are undergoing development. Like other surface-plasmon-based devices reported in a number of recent articles in NASA Tech Briefs, these light valves could be constructed in many different configurations and concatenated with other optical and electronic components to produce a variety of display and color-filtering devices. These devices would be compatible with, and could be incorporated into, monolithic integrated circuits for use in display, addressing, and interface applications.
As shown in Figure 1, a basic transmissive surface-plasmon light valve would include a substrate made of glass or other suitable transparent material, a metal film (e.g., a thin layer of metal or of indium tin oxide), a layer of electro-optical material (typically a liquid crystal), and another metal film as top electrode. White light would be introduced from the bottom; some of this light would pass through the bottom electrode and impinge on the top electrode, where it would excite surface plasmons at the interface between the metal films and the liquid crystal.
Figure 1. This Light Valve would exploit voltage-tunable color-selective absorption of light in surface plasmons. Light of the color complementary to that of the surface-plasmon absorption resonance would be transmitted.
The surface plasmons would absorb some light in a resonance wavelength band determined partly by the index of refraction of the electro-optical material. The light not absorbed in the surface plasmons would pass through the top metal film. The color of this transmitted light would be complementary to that of the reflected light. As in the previously reported surface-plasmon devices, the index of refraction of the electro-optical material, and thus the absorption wavelength band, would depend on the electric field imposed by applying an electric potential between the electrodes. Therefore, one could control the transmitted complementary color by controlling the applied voltage.
Figure 2. Multiple Light Valves could be arrayed by fabricating a common upper electrode plus multiple side-by-side lower electrode segments. The voltage applied between the common upper electrode and each lower electrode segment would control the color of light transmitted through that segment.
Figure 2 illustrates part of a flat-panel display device comprising one of the many different possible combinations of surface-plasmon light valves. This device would be similar to that of Figure 1, except that the lower electrode would be divided into segments that could, for example, correspond to pixels of a display. The colors in each segment could be controlled, independently of the other segments, by applying a distinct voltage between the common upper electrode and the lower electrode for that segment. The electronic circuitry for controlling the voltages on the lower electrode segments could be fabricated on the transparent substrate.
This work was done by Yu Wang, Randy Shimabukuro, and Stephen Russell of Caltech for NASA's Jet Propulsion Laboratory.
In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to
Technology Reporting Office
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Refer to NPO-20280
This Brief includes a Technical Support Package (TSP).
Transmissive surface-plasmon light valves
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Overview
The document is a technical support package from NASA detailing advancements in transmissive surface-plasmon light valves, which are innovative optical devices that can modulate light transmission based on applied voltage. The invention is particularly significant for its potential applications in optical filtering and display technologies.
The core structure of these light valves consists of a transparent substrate, a bottom electrode, an electro-optic material, and a top electrode. The design allows for the modulation of the resonant frequency of surface plasmons at the interface between the electro-optic material and the top electrode. By applying a voltage between the electrodes, the optical properties of the device can be controlled, enabling selective absorption and transmission of light.
The document describes various embodiments of the light valve, including configurations with multiple top and bottom electrodes. These configurations can be aligned or misaligned, allowing for flexibility in design and application. The light valves can be optically coupled to various optical detectors, such as charge-coupled devices and photomultiplier tubes, making them versatile for different technological needs.
One of the key advantages of these transmissive devices is their ability to function as voltage-selective optical filters, which can control the grayscale and color of transmitted light. This capability opens up new possibilities for applications in displays and imaging systems, where precise control over light properties is essential.
The document also emphasizes the compatibility of these devices with silicon-on-insulator (SOI) technology, which is advantageous for integrating them into existing electronic systems. SOI technology offers benefits such as lower parasitic capacitance and improved performance in high-speed and radiation-hardened environments.
Overall, the transmissive surface-plasmon light valves represent a significant advancement in optical technology, with the potential to enhance display systems and other optical applications. The research highlights the innovative approaches being explored at NASA's Jet Propulsion Laboratory, showcasing the intersection of optics and electronics in developing next-generation devices.
