Johns Hopkins University

United States of America As Represented by the Administrator of Nasa

Charles L Bennett

Edward J Wollack

David T Chuss

Lingzhen Zeng

Haiquan Guo

Mary Ann Meador

Tobias Marriage

Thomas M Essinger-Hileman

The present invention relates to broadband and tunable infrared (IR)-blocking optical filters for millimeter and sub-millimeter astronomy composed of small diffusely scattered particles embedded in an aerogel substrate. The size of the scattering particles included in the aerogel filters can be tuned to give variable cutoff frequencies. In one embodiment, the aerogel scattering optical filters of the present invention have ultra-low density and index of refraction (typically n&#x3c;1.15), removing the need for anti-reflection coatings that limit bandwidth and increase filter complexity, and allowing for high transmission across an ultra-broad band from zero frequency to above 1 THz, and as much as 10 THz.

Optical filter having polyimide aerogel substrate and infrared radiation scattering particles

A device for at least one of receiving and transmitting electromagnetic radiation includes a feedhorn having a substantially smooth, electrically conducting inner surface extending from an open end to a feed end, the inner surface being substantially rotationally symmetrical about a longitudinal axis, wherein an orthogonal distance from a point on the longitudinal axis to the substantially smooth, electrically conducting inner surface increases monotonically as the point on the longitudinal axis is selected at successively greater distances from the feed end of the feedhorn towards the open end of the feedhorn such that a profile of the substantially smooth, electrically conducting inner surface of the feedhorn is monotonically increasing. The feedhorn has an operating bandwidth and the feedhorn provides a maximum of &#x2212;30 dB cross polarization response over at least 15% of the operating bandwidth. A method of producing a feedhorn for receiving or transmitting electromagnetic radiation includes determining a profile of an inner surface of the feedhorn based on constraints required to achieve a plurality of operating parameters, providing a pre-machined feedhorn having an initial inner surface, and machining the initial inner surface of the pre-machined feedhorn to substantially match the profile determined to achieve the plurality of operating parameters for the feedhorn. The determining the profile includes a constraint for the profile to be a monotonically increasing profile relative to a rotational symmetry axis of the inner surface of the feedhorn going from a narrow end to a wide end of the feedhorn.

Smooth-walled feedhorn

A device for at least one of receiving and transmitting electromagnetic radiation includes a feedhorn having a substantially smooth, electrically conducting inner surface extending from an open end to a feed end, the inner surface being substantially rotationally symmetrical about a longitudinal axis, wherein an orthogonal distance from a point on the longitudinal axis to the substantially smooth, electrically conducting inner surface increases monotonically as the point on the longitudinal axis is selected at successively greater distances from the feed end of the feedhorn towards the open end of the feedhorn such that a profile of the substantially smooth, electrically conducting inner surface of the feedhorn is monotonically increasing. The feedhorn has an operating bandwidth and the feedhorn provides a maximum of &#x2212;30 dB cross polarization response over at least 15% of the operating bandwidth.

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Baltimore, MD, United States of America

Charles L Bennett