begins at the atomic level, and more specifically with the electron.
an electron becomes energized, it jumps to a higher level within the
structure. In a normal atom, all of the electrons fill the lowest
possible, and thus want to drop from an energized state to a base
an electron drops from a higher, energized state, it emits a photon as
Lasers themselves are large groups of photons focused into a beam, but
from a randomly moving photon generated from an electron to a nice beam
easy task. From here, stimulated emission comes in.
An example of stimulated emission.
emission works like an amplifier. If we take a system
with a large amount of atoms that have electrons in high energy states,
electrons will want to come down from those states into a lower one.
emits a photon of a certain wavelength, depending on which energy state
electron began in and which state it dropped to. In order to get an
drop from a high state to a low one, we can make it interact with an
electromagnetic wave, or another photon! Under the hood is a quantum
that allows us to essentially put in one photon and get two out of the
same wavelength. This is our "stimulation" portion of Einstein's
theory. When another photon interacts with the electron with a high
atom, the electron will drop and emit two photons. This is our
The entire process gives us an amplification of photons that can be
Diagram illustrating how photons are "aligned" and allowed
how do we get our electrons to get energized in the first place? The
answer: Flash Tubes. These tubes act as a "pump" to start driving the
atoms in our lasing medium. They emit extremely intense bursts of light
short amounts of time, and this full spectrum light energizes the laser
As stated before, now that we have energized electrons, we can get
the laser medium begins emitting photons, they need to be focused and
in order to establish our beam. To do this, we look to the physical
of our laser.
A flash tube wrapped around a laser medium
lasers have the same basic structure; the inside of a laser consists of
a cylindrical tube of some medium that can be energized (such as a gas
helium or neon in a gas laser, or a crystal like ruby). This tube is
by a flash tube, and has a 100% reflectivity mirror at one end to keep
photons inside the tube. The other end of the tube, the end that is
emitting our beam, is capped with a semi-reflective mirror. This mirror
photons to travel through it if they are moving in the right direction,
reflects the photons if they aren't. In some cases, a photon may travel
forth billions of times before it leaves the medium.
- F05 - 2011