Massachusetts Institute of Technology

Vladimir Liberman

Mordechai Rothschild

Shaun R Berry

Robert W Haupt

Charles G Doll, Jr

Juejun Hu

Jeffrey Chou

William D Herzog

Yifei Zhang

Jason Stewart

Christopher Roberts

Kenneth Diest

Alloys of GeSbSeTe (GSST) can be used to make actively tunable infrared transmission filters that are small, fast, and solid-state. These filters can be used for hyperspectral imaging, 3D LIDAR, portable bio/chem sensing systems, thermal emission control, and tunable filters. GSST is a low-loss phase-change material that can switch from a low-index (n=3), amorphous state to a high-index (n=4.5), hexagonal state with low loss (k&#x3c;0.3) over a wavelength range of 2-10 microns or more. The GSST thickness can be selected to provide pure phase modulation, pure amplitude modulation, or coupled phase and amplitude modulation. GSST can be switched thermally in an oven, optically with visible light, or electrically via Joule heating at speeds from kilohertz to Gigahertz. It operates with reversible and polarization independent transmission switching over a wide incident angle (e.g., 0-60 degrees).

Methods and apparatus for modulating light with phase change materials

A seismic wave damping structure can include a structural arrangement including at least one pair of elements, each angled with respect to a vertical and extending into the earth and toward a protection zone. The elements thus form a tapered aperture, the structural arrangement defining the protection zone at an upper portion of the aperture. Each element defines an inner volume and contains a medium resistant to passage of an anticipated seismic wave in earth having a wavelength at least one order of magnitude greater than a cross-sectional dimension of the inner volume of each of the elements. The medium is at least one of air, gas, water, and viscous fluid. The structural arrangement is configured to attenuate power from the anticipated seismic wave within the protection zone relative to power from the anticipated seismic wave external to the protection zone.

Wave damping structures

A seismic, water, or acoustic wave damping structure can include a structural arrangement of at least two elements, each with an inner volume and containing a medium resistant to passage of an anticipated wave. Example elements can be earth boreholes or water pylons. The structural arrangement can taper from an upper aperture to a lower aperture, the structural arrangement defining a protection zone at the upper aperture. The structural arrangement can be configured to attenuate power from the anticipated wave within the protection zone relative to power from the anticipated wave external to the protection zone. A grouping may include elements that form acute or obtuse angles with a direction of a wave to attenuate wave power. High-value buildings or other structure in a protection zone on land or in water can be substantially shielded from seismic or water waves.

An embodiment according to the invention provides an optical filter that combines narrow spectral bandwidth and high rejection of out-of-band radiation with a wide acceptance angle. These filters are based on the nanoscale engineering of materials ('metamaterials') that possess predefined birefringence determined by a combination of their geometry and material composition. These metamaterials are combined into a functional optical filter that can exhibit true zero crossing, with acceptance angle effectively decoupled from bandwidth, at practically any wavelength of interest.

Optical filters with engineered birefringence

There is provided an optical limiter device for protecting an object from incident light having a wavelength in the visible, infrared or ultraviolet spectrum. The device comprises a plurality of nanoparticles of a metallic material including free electrons that undergo collective oscillations when exposed to the incident light. The plurality of nanoparticles of the metallic material include a plurality of nanoparticles of a non-spherical particle geometry, which may include a geometry having a plurality of sharp protrusions on a spherical body. The metallic material may include gold, silver, aluminum, indium or copper. The device further comprises a structurally rigid transparent medium in which the plurality of nanoparticles of the metallic material are embedded; and a mechanical support mounting the transparent medium between the incident light and the object.

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Reading, MA, United States of America

Vladimir Liberman