I got given the opportunity to write an article on any area of science I wanted to potentially be published in the first issue of the Cardiff University science magazine... So I stuck with Physics and ventured into the area of Photonic Metamaterials!
I would love to have the opportunity to work within science communication as I have been told I have a knack for explaining complex phenomena to people who have little to no scientific background and I enjoy teaching people (but I'm not fond of little people so don't want to go into primary or secondary education).
Either way here is the Article I wrote for the magazine:
Do you want
an Invisibility Cloak?
Sci-fi and fantasy films have invisibility cloaks throughout,
from Harry Potter’s cloak to Klingon cloaking devices. The reality is that the science
to make things invisible exists in the present day, although when I try to
explain this to people they think I am pulling their leg. So, to convince them
of this feat, I point out that it uses the negative refractive index and
cloaking properties of photonic metamaterials, and then I receive some rather
strange looks.
The field of complex photonic media (which encompasses
photonic metamaterials) is a new area of physics, engineering, material
science, and nanotechnology. So new that it is still very much experimental
with some interesting results in a lab, but
with no real life applications in use at the present moment. Unfortunately, due
to technological limitations, items can only be cloaked against certain types
of electromagnetic radiation (light), and these types of light are not within the
visible spectrum. This means that your invisibility cloak will not turn you
invisible to the human eye, yet. The closest scientists have been able to get
to visible light is with microwaves. So, if someone could see in microwaves, your cloak
would work and you would be invisible. The applications for this area are
extremely varied; they can be used to provide solutions for telecoms, imaging,
power, data-storage, computing, security and national defence.
You have probably read this and thought it all sounds good
but perhaps you are still wondering ‘What on earth are photonic metamaterials?’
So I shall explain. A metamaterial is a synthetic compound that exhibits
properties that are not seen in nature. Specifically, photonic metamaterials
react with light in such a way that they can be used to manipulate light to achieve
extraordinary results. Metamaterials, unlike materials found in nature which
receive their properties from their chemical compositions, exhibit these
bizarre properties because of the way their constituent parts are arranged.
Moving onto the invisibility part in detail, how does it
work? It works because these metamaterials have a negative refractive index. This
means that as the light passes through the material,
it ‘bends’ in the opposite direction to light passing through a normal
transparent medium, like a glass block. Using
rings made of the material you can build up several layers surrounding the
object you intend to render invisible. Once
you have sufficient layers arranged in the correct manner, the object should
become invisible to the appropriate wavelengths. Although, unfortunately, a few
problems have arisen when it comes to meeting the expectations on how well an
invisible cloak should work. These problems are that the object is not
perfectly invisible to the wavelength because there are imperfections in the layers
and secondly, the cloak is restricted to only one wavelength and visible light
is a broader range than just one wavelength.
The main challenge faced with making metamaterials is that the
structures that give it the material its exciting properties need to be
minuscule; they must be smaller than the wavelength of the electromagnetic
radiation they wish to manipulate. Making such small structures requires
advanced technology and this restricts the wavelengths to which we can cloak
materials from, as I mentioned earlier. The size of the structures used in
metamaterials need to be smaller than that of the waves they are looking to
manipulate. Microwaves are centimetres in length, which means that the
structures need to be of the millimetre size. By the standards of technology today,
structures of this size can be manufactured. With visible light however their
waves are a few hundred nanometres in size which makes them hundreds of
thousands times smaller than microwaves, their structures need to be in the
nanometre range. To create anything that is several nanometres in size is a technological
achievement in itself.
