Optics & Photonics News - September 2011

The researchers coated the side containing the bump with a 200-nm- thick layer of gold to provide a reflecting surface. Then they shone broadband terahertz radiation into the block at an incident angle of 45 degrees with respect to the reflect- ing surface. Underneath the bump, they placed a block of pressed lactose powder, which as a strong absorption feature at 0.53 THz. They performed similar tests with a flat reflecting surface, a chunk of lactose covered by a non-cloaking reflecting surface and a bare chunk of lactose.

Imaging of the reflected terahertz light showed that the cloaked block of lactose showed the same spectroscopic signature as the flat reflecting surface— no scattering or absorption of the rays. According to the researchers, the result demonstrates that the cloak has hidden

(Left) Terahertz cloaking structure ( 8. 5 x 4. 4 mm) made by researchers from Northwestern University and Oklahoma State University. Objects placed beneath the shallow concave “bump” in the middle of the bottom surface are rendered invisible. (Right) Micrograph of the bump region of the terahertz cloaking structure. The size variations in the holes, which extend through the entire structure, are a key feature that guides light around the bump, beneath which objects become invisible. The view is about 2 mm square.

both the geometrical and spectroscopic signatures of the concealed material.

Previous cloaking studies have focused
on the microwave and optical regions of
the spectrum, leaving a gap at terahertz
frequencies—a spectroscopically inter-
esting band that researchers have been
studying intensely for potential security
and industrial applications.

A Solid Performance.

The ability to create realistic, accurate, and detailed optomechanical models in FRED – Photon Engineering’s industry-leading system design and analysis software – has taken a solid step forward. Now, with our latest release, FRED has the ability to create composite solids using Boolean operations.

By giving you the power to perform true boolean operations, FRED improves the fidelity of your models and makes it even easier to build complex structures. You can also export your composite solids to STEP and IGES file formats for data exchange with CAD programs. Best of all, FRED's composite solids have the added flexibility of being dynamic; when you modify a component element, FRED automatically updates the composite solid.

Motion tracking assembly modeled using only composite solids.

Discover all the reasons FRED has been used for more than a decade by scientists and engineers worldwide for 3-D optomechanical design and analysis. Contact Photon Engineering today for a free demo version of FRED.