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					                               Real Genius - Laser Power

Title / year:
Real Genius / 1985

Scientific subject and topic:
Physics / Laser

Movie producer:
Delphi III, Tristar Pictures

Martha Coolidge

Val Kilmer, Gabriel Jarret, Michelle Meyrink, Willam Atherton

Websites of movie:
Filmography links and data courtesy of The Internet Movie Database

Description of movie:
A pair of young geniuses is commissioned by a college professor to build a powerful
laser. Unbeknownst to Chris Knight (Val Kilmer) and Mitch Taylor (Gabriel Jarret),
their professor intends to hand the laser over to the military to be used for strategic
assassinations. When Chris and Mitch find out, they hatch a plan to foil the plot
without ruining their chances of graduating.

Link to Trailer Site:
Filmography links and data courtesy of The Internet Movie Database

Buy DVD:
DVD: Real Genius (U.K.)

Buy DVD:
DVD: Real Genius” (U.S.A.)

Title of scene:
Laser Power

Video clip or still:
DVD cover scan from the movie Real Genius, claimed as fair use

Time interval:
01:11:28-1:13:50 in Chapter 20

Graham H. Konecki []

Heinz Oberhummer []

Scientific keywords:
Laser, Coherence, Electromagnetic Spectrum

Description of scene:
This scene shows Chris and Mitch powering up their laser with a new fuel source that
Chris has just discovered. The laser is only on for a short period of time, but it is
powerful enough to burn through a steel plate target, the brick target behind it, through
the lab wall, and a statue on the university campus grounds beyond that.
Author:         Graham H. Konecki

Movie:          Real Genius
Movie Clip:     1:11:28-1:13:50 in Chapter 20
Director:       Martha Coolidge
Film Studio:    Delphi III, Tristar Pictures

Basic description

This clip shows Chris and Mitch firing their project laser. Their laser, as is clearly
shown, is a very fascinating and powerful device. It burns right through steel, brick,
and laboratory wall in a matter of seconds. What exactly is a laser though? The word
laser is actually an acronym, or a word made from the abbreviations of a series of
words. The letters L.A.S.E.R. stand for Light Amplification by Stimulated Emission of
Radiation. The initial light or energy source is getting amplified (increased) as it is
used to excite and energize atoms within the laser material. Each time these excited
atoms “de-energize” or lose that extra energy, the energy is re-emitted (radiated)
outward as more energy, and the process is constantly being repeated. It is like
having a ball bouncing back and forth between two walls though each time it hits a
wall the ball leaves going faster. In this case, the light is bouncing back and forth
between two mirrors. Each time it passes through the laser material, more light is
emitted. It is important to note that this light and energy have to keep being fed into
the laser for this process to continue; otherwise the initial light would just be emitted
and then eventually get absorbed. This emitted light is very special for two reasons: it
is both monochromatic (all one colour) and coherent (all moving in the same direction,
at the same time, in the same way.) Coherence makes the light “stronger” in a sense.
It produces an effect like synchronized waves in a bathtub. The waves get bigger and
bigger until they can slosh out of the bathtub. In the laser's case, the light becomes
more intense until it comes out of the laser as a beam.

The function of the laser can be tailored to different situations. The different qualities
of mirrors can be used to alter the qualities of the beam as it emerges. Different laser
materials can produce different types of beams at different parts of the
electromagnetic spectrum. In other words, the laser does not have to produce a beam
in the visible spectrum, or the range our eyes can see. The functions that these
different lasers can have are diverse. One type of laser might be used in eye surgery.
Another might be used for surveying a building sight and making sure structures are
flat and level. Still another might be for cutting materials such as metal (as is seen in
this film clip) into very specific shapes. There have even been discussions of using
lasers for weapons or as part of missile defence systems, where a laser might shoot
down an incoming missile before it reaches its target.
Author:         Graham H. Konecki

Movie:          Real Genius
Movie Clip:     1:11:28-1:13:50 in Chapter 20
Director:       Martha Coolidge
Film Studio:    Delphi III, Tristar Pictures

Advanced description

The word “laser” is an acronym standing for Light Amplification by Stimulated
Emission of Radiation. A light or power source is used to excite and stimulate a
particular medium which is enclosed in a cavity between two mirrors, which then
reemits light in a certain form. There are two basic types of lasers: the laser that
focuses on the excitations at the atomic level and the diode laser. Both types follow
the same three steps in creating a beam: priming, emission, and lasing. The priming
stage essentially gets the laser materials ready for lasing. Light or some other form of
energy source specifically tailored for the material is used to excite a large number of
atoms into higher energy levels. These excited states, in an ideal situation, quickly
decay into a partially stable (meta-stable) energy level. These meta-stable states exist
longer than the higher level excited states (they can last for microseconds) and they
have not released all the energy they absorbed yet. When more atoms exist in this
higher energy level than in the unexcited state (a situation called population inversion)
the material is ready for emission to occur.

In the emission process, a single photon at the right energy can interact with one of
the meta-stable electrons forcing it to emit its energy. Both the original photon and the
new photon can then move on to interact with other meta-stable electrons. The first
electron can literally trigger a photon avalanche that cascades through the entire
system. When the emitted photons reach one of the two mirrors, at either end of the
laser’s cavity, they bounce off of it and, on the return trip through the system, interact
with the re-excited meta-stable electrons again causing more emissions. The photons
continue to bounce back and forth between the two mirrors, exciting more and more
electrons as they travel. The system is now ready for lasing.

When enough photons have been emitted, they begin making it through the “weaker”
of the mirrors in the lasing cavity (rather than bouncing off of it) producing a tightly
collimated beam. This beam is made of photons all at exactly the same wavelength
and in phase with each other. One may picture this scenario as a kind of resonance
system where the beam is the product of the resonating particles in the laser cavity.

The diode laser, though more complicated in terms of physics principles, still operates
in the same basic way. Electrons from a conduction band of a metal “fall” into to slots
or “holes” in a particular kind of material. When the electrons fall they emit photons.
There are several advantages to these diode lasers. They can be built incredibly small
(sizes comparable to a grain of salt). They are also more energy efficient than the
normal laser. They convert up to 20% of their power directly into the laser as opposed
to the 0.1% converted with some normal lasers. Also, the diode lasers can be run off
of normal batteries (which make them ideal for devices such as CD players and laser
pointers) as opposed to normal lasers that require substantially more power to
operate. Finally, they are easily controllable and adjustable.
Author:          Graham H. Konecki                                                              5

Movie:           Real Genius
Movie Clip:      1:11:28-1:13:50 in Chapter 20
Director:        Martha Coolidge
Film Studio:     Delphi III, Tristar Pictures

Scientific description

The scene shows the test firing of the high power laser. The laser quickly burns
through steel plate, brick, and laboratory wall. We know that lasers are plausible, but
are this one realistic? To a certain extent it is. However, one must certainly note that
there is a fair amount of Hollywood over-dramatization here. For example, Chris says
that they will have photons at 600 nano-meters. 600 nano-meters correspond to a
yellow-orange color and not the pinkish-red colour visible in the clip. Also, it is
important to note that the laser beam would not be visible the way it is in this film clip.
Lasers are generally visible only when something is interrupting its path (little flashes
in the beam line are usually dust particles being briefly illuminated). It is possible to get
a glow due to diffraction and Rayleigh scattering, but that generally occurs with lasers
in the blue region of the visible spectrum. And while it is possible to produce lasers
with power outputs exceeding 5 mega Watts, these are generally large lasers used in
fusion experiments (i.e., much larger than the small and compact design visible on the
laboratory table in the clip).

Some other laser terminology is tossed about in this scene. Excimers, for example,
are compounds that are stable only in their excited states. Therefore, it is much easier
to keep such lasers primed and ready. Also, this laser is intended as an orbital
weapon (in the film). Such a weapon would be highly impractical. Though the laser’s
photons come out almost perfectly parallel, they are not exactly parallel and over time,
the beam will spread. The spreading effect will be accelerated by the medium the
beam is travelling through (in this case, the atmosphere). So, in effect, the beam
would have diverged from the nice narrow beam that it started as in space to some
sort of “cone-shaped” pattern reminiscent of a flashlight by the time it hit the ground.
Firing the beam from space would also make it difficult to hit targets with accuracy on
the ground because the beam would be deflected by dust, moisture, and pollution in
the air on its way down. So yes, the movie is correct in the idea that they are able to
make a powerful laser with a very intense beam that could be “hotter” than the sun,
but there were many scientific inconsistencies and assumptions made that made the
laser in this scene a bit implausible.

Websites about laser, coherence and electromagnetic spectrum: