Blog #12: Say Cheese! Photographing light as a particle and a wave

We have all heard about the weird nature of elementary particles in the quantum world, especially the dual nature of light as both a particle and a wave.. Einstein's work on the photoelectric effect showed that light acts as discrete particles of light, called photons. However, other experiments, such as the double slit-experiment, shows light acting like, and having all the properties of a wave. Although at first this wave-particle duality was met with skepticism, today, it is accepted as fact.

However, although we now know that light acts as both a particle and a wave, the weird nature of quantum physics makes it so that the act of observing light determines whether or not you see its particulate properties, or its wave-like properties. We have never been able to see light act as both a particle and a wave at the same time!

This past year, however, scientists at the Swiss Federal Institute of Technology in Lausanne made headlines around the world after successfully capturing the first photograph of light acting as both a particle and a wave at the same time.

This is the first image captured that shows light to be both a particle and a wave.
Source: http://www.extremetech.com/extreme/200277-scientists-capture-first-ever-image-of-light-acting-as-a-particle-and-a-wave

This image captures the wave nature of light as a $sinc()$ function. However, the shadow on the bottom of the picture shows discrete particles.

So how did these scientists manage to capture a photograph of light acting as both a particle and a wave, especially since you need light to take a photo in the first place?

This is how the avian flu virus looks like under an electron
microscope.
Source: http://blog.silive.com/health/2008/10/avian-flu-virus.jpg

Well, they used a classic imaging technique of using a beam of electrons and it's interaction with the object it is imaging, to take a picture of light. This technique is most notably used in electron microscopes, which give us the scarily up-close images of the microscopic world that are light microscopes are not able to see.

Okay, well things underneath an electron microscope are not moving, so we can take pictures of them. But light is always moving, so how do we keep it in one place to take a picture of it?



The scientists in Lausanne shot a beam of ultraviolet light onto a nano-wire. The UV light increased the energy of the wire, and caused a stream of photons to travel in opposite directions, creating a standing wave. In order to capture an image of this standing wave, the scientists shot a beam of electrons to see the light particles interact with the electrons, which was recorded to produce the first picture of light as both a particle and a wave!

This imaging technology can prove to be revolutionary, for it would allow scientists to image and even record the quantum world and it's effects directly. It could provide breakthroughs in fields like quantum computing, as well as help bridge the gap between the macro-world of stellar astronomy, and the quantum world.

For more information about this, check out this video:

Citation:
http://www.spacedaily.com/reports/The_first_ever_photograph_of_light_as_a_particle_and_a_wave_999.html