My Note: Recently, I reached out to Dr. Willie Padilla, at Boston College regarding the amazing work he is doing at BC relating to the development of metamaterials which can be employed in the terahertz regime. Dr. Padilla along with his research assistants, graduate students, Claire M. Watts, and David Shrekenhamer, recently announced that they had created a revolutionary single-pixel imaging technique which takes images that are guided through a coded aperture using a semiconductor to guide and direct the reproduced image of an object once THz waves have passed through it. The BC team described this technique as depicted in the picture above in the following way:
"A new method for single pixel terahertz (THz) imaging developed by Boston College researchers uses a set of instructions delivered by a laser beam to tune THz waves in order to produce new types of THz images. During the imaging method devised by the team, THz waves pass through an object (a); then they strike a silicon semiconductor (b) given specific instructions about how to sample the image; that data is passed along in order to digitally reconstruct an image (c) of the original object in just a few seconds. "( Image credit: Claire M. Watts, Boston College).
Here is what I wrote to Dr. Padilla, and his response, which Ms Watts,
and Mr. Shrekenhamer,
assisted with answers to the following questions:
Dear Dr. Padilla,
Thank you for agreeing to answer a few
questions for me, and for readers of my blog, Terahertz Technology. As
I know, I am a layman, and please excuse any of my questions which may be
inartful, naïve or simply inane.
1. Are there names or other identifiers
for the specific metamaterials which you have created for use in THz? If so,
can you share that information, to give readers an idea of the number of
different materials which you have developed for use with terahertz radiation?
Metamaterials can be scaled across almost the entire electromagnetic
spectrum, from optical to microwave. What designates THz metamaterials is their
size, the unit cell dimensions being on the order of tens of microns.
Additionally, we choose to use materials that interact appropriately in the THz
regime. There are many different metamaterials that have been designed to
operate in THz, achieving many different electromagnetic responses. For example, we have developed perfect absorbers,
polarization sensitive and insensitive metamaterials, multi-frequency
metamaterials, and spatially patterned metamaterials. We and other researchers
have also created dynamic reconfigurable metamaterials whose material response
can be controlled through a variety of mechanisms including electronic,
optical, thermal, and mechanical.
2. Do the metamaterials you have
developed rely upon the use of either photons or electrons for the generation
of THz? Perhaps asked another way, would a device created with the use of your
metamaterials function in the realm of electronics or photonics, (both or
neither)?
THz metamaterials are typically fashioned
within the photonic domain having demonstrated the ability to tailor the
electromagnetic response in ways that are difficult and or expensive to find
within natural occurring materials.
3. How close or how far away (months or
years) are you from developing commercially viable uses for your single pixel
THz camera, enhanced by your coded aperture semiconductor?
There are a lot of aspects about our
imaging system that make it reasonably close to a commercially viable THz
camera. First, the masks are reconfigurable and easily changeable. This allows
us to image many different types of scenes. Second, the optics are easily transferable to a lens system, just like the one we see in
conventional cameras. Third, and most importantly, we use a very low power source
which makes our device easily adaptable to real world use.
4. Are there any plans to spin-off your
work into a private or publically held entity to further develop and market
your work?
We have no plans to spin off this work
into the private sector. We have, however, applied for various patents related
to our technology.
5. Are you involved in any way with
compressive sensing, (cs) and does your single pixel camera rely in any way
upon cs?
We are currently working on a few
projects using compressive sensing. This particular implementation of the
single pixel camera does not rely on CS, but rather uses Hadamard masks to
improve SNR over conventional raster scan masks. However, we are now
investigating several new designs that utilize CS methods in a single pixel
camera architecture, similar to the one we are using in this project. In these
single pixel cameras, the time of image acquisition is directly tied to the
number of measurements you take. Therefore, by using CS methods to reduce the
number of images, we can greatly reduce the image acquisition time. In the next
iteration of this project we plan to implement these methods to increase our
image frame rate.
6. Are you in contact with or do you do
you work with any of the current commercial ventures engaged in the sale of THz
products, Advantest, Coherent, Teraview, Advanced Photonix,
Agilent, Genia, etc.?
No.
I want to thank Dr. Padilla, and his team for taking time to answer these questions, relating to the amazing work they are doing. Cheers to them!
(for a related link see:
