Our world today is constantly dreaming up new ways to connect people to one another.  We have social media, cell phones, instant messaging, and video conferencing, just to name a few.  What is the next step?  If you have watched any science fiction in your lifetime, the answer of “holograms” may have entered your mind.  And if it did, you’re not alone.  Scientists all over the world are working on producing and perfecting holographic images to increase the quality of long distance communication.

Holograms will obviously open up a whole new world of possibilities in all different sectors of life, but before we touch on that, let us look at the physics behind the hologram.

We must first understand a couple of things about light.  White light, like what shines down from the Sun or most ceiling lights, is a combination of all different colors (or wavelengths) of light.  When you combine all the colors of the rainbow – red, orange, yellow, green, blue, and violet – white light is produced.  This light travels in all different directions and is relatively unorganized, or incoherent.   Monochromatic light, like what is produced by a laser, has one single color or wavelength.  This light is highly organized and is referred to as coherent.  Coherent light is the type of light that is necessary to produce a hologram.

The basic setup for a reflection hologram is shown below.  Monochromatic light from a laser is shined through a device that uses mirrors (off which light reflects*) and prisms (through which light diffracts*) that splits the one beam of light into two separate beams.  These split beams are transmitted through holographic film, which is sandwiched between two glass plates, as shown below.  This film is much like photographic film except that holographic film has to be much more sensitive.  The additional sensitivity of holographic film is needed to recognize and record very small changes in light that occur over very small distances.


Image from: http://hyperphysics.phy-astr.gsu.edu/hbase/optmod/holog3.html

The process of producing a reflection hologram is basically a more sensitive version of the process of producing a photograph.  Both capture and record incoming light.  There are many other and more advanced types of holograms, including transmission holograms or hybrids, such as multichannel or computer-generated holograms.  You may have seen an example of a computer-generated hologram if you saw Tupac’s historical post-mortem performance at Coachella.  

(http://music.yahoo.com/blogs/live/coachella-2012-sunday-hologram-tupac-flesh-blood-rihanna-103530317.html Warning: Explicit Lyrics)

Other examples of holograms in recent history:

CNN: http://www.youtube.com/watch?v=thOxW19vsTg

Hatsune Miku (Japan’s Hologram Pop Star): http://www.youtube.com/watch?v=DTXO7KGHtjI

Just imagine the possibilities of this technology becoming mainstream.  As online students, your physics instructor could teach a lecture in your living room (don’t be too scared, we’re not there yet).  Skype would become obsolete!  Outside of pure communication, advancements in hologram technology will be powerful tools for science, education, entertainment, advertisement, and security. 



*Diffraction: The bending and spreading of a light wave around an object.

*Reflection: The return of light rays from a surface in such a way that the angle at which a given ray is returned is equal to the angle at which it strikes the surface.