AAWSAP DIRD, State of the Art and Evolution of High-Energy Lasers, March 2010

Text

This text came with the file. It may have mistakes. When the text and the image disagree, the image is right.

UNCLASSIFIED/fFOA OFFl&I.t.k YSE &P•tv
High Power Laser
High Power Optics Pointer I Tracker I
Atmospheric
Target
Device
and Beam Shaping Target Designator
Propagation
EXHAUST
TRACKER
Atmospheric,
absorption,
ENERGY SOURCE
scattering,
and turbulence
Figure 2, Elements of an HEL Weapon System
Laser Devices
LASER FUNDAMENTALS
The term "Laser" is an acronym for Light Amplification by Stimulated Emission of
Radiation. It is a unique device that employs the quantum states of matter to store
and convert energy into electromagnetic radiation. The resulting radiation is referred to
as "coherent," meaning it is single wavelength or "monochromatic" and highly focusable
due to its well controlled phase. In its simplest form, any laser device can be viewed as
an "energy-conversion" box with one input and two outputs. The input is energy, which
can take a variety of forms (electricity, light, or a chemical reaction) depending on the
specific laser, while the two outputs are a coherent beam and heat (Figure 3). Since
the overall energy-conversion lasing process is considerably less than 100 percent
efficient, significant waste heat is generated which must be removed from the laser.
Inside the laser is a "gain-medium" which stores a fraction of the input energy in its
atoms or molecules and then releases the energy at the laser's selected wavelength.
The laser also contains "resonator" mirrors which repeatedly relay the beam back and
forth through the gain medium to increase its energy level. The laser device functions
as the optical equivalent of an electrical oscillator with the resonator optics providing
the feedback. Different lasers, which use various materials as their gain medium, emit
radiation at wavelengths ranging from the infrared through the visible spectrum and
into the ultraviolet.
UNCLASSIFIED/fFOA OFFI&I.t.k YSE 8,.L\f
3