JED - November 2015 - 81

E W101
A third developmental chemical laser system was the Tactical High Energy Laser (THEL) which used Deuterium Fluoride
(DF) fuel. This was very successful in destroying a large number of in-flight rockets, artillery and mortar rounds during its
testing, but it was very large. It was mounted in five large
shipping containers on a 10,000-square-foot pad.
Ongoing efforts are working to improve the efficiency of
chemical lasers and reduce their size, weight, and logistical
requirements.

SOLID STATE LASERS

LASER RESONATOR
Low
Pressure
Reaction
Chamber

Vacuum
Pump

BULK LASERS
The first high energy SSLs were bulk lasers which demonstrated over 100 kilowatt output power, up to 19 percent efficiency and long run times. The efficiency (sometimes called
the "wall-plug efficiency,") is the ratio of laser output power
to the electrical power from the prime power supply. One such
developmental system is the High Energy Liquid Laser Air Defense System (HELLADS). The HELLADS program intends to develop lasers which weigh less than 5 kilograms per kilowatt of
output power and a volume of 3 cubic meters. Such lasers could
be mounted on tactical aircraft.
Multiple bulk lasers can be combined to
increase the delivered output power, thus increasing their operational range.

Beam
Steering
Mirrors

Chemical
Fuel
Supply

FIBER LASERS

Target

Figure 1: A chemical laser requires a low pressure reaction chamber and uses corrosive/
toxic fuel that must be replaced after few operations.

FIBER

PARTIALLY
REFLECTIVE
MIRROR

MIRROR

LASER
DIODES

FOCUSING
OPTICS

Figure 1: A chemical Laser requires a low pressure reaction chamber and uses
corrosive/toxic fuel that must be replaced after few operations.

LASER BEAM

Figure 2: The fiber laser uses a strand of lasing fiber and mirrors to form the laser beam.
Multiple fiber outputs can be summed to increase the laser power.

PROTECTIVE COVER

Figure 2: The fiber laser uses a strand of lasing fiber and mirrors to form the laser
OUTER CORE
beam. Multiple fiber outputs can
be summed to increase the laser power.

INNER CORE

As shown in Figure 2, a fiber laser uses a
long optical fiber to generate the laser output.
The fibers are very thin, and much longer than
shown in this figure. They can be formed into
compact coils, which allow a much smaller system size than would be required for a comparable bulk laser. Multiple laser diodes can be
combined to increase the input power to the fiber. The partially reflective mirror in the figure
is a Bragg grating which reflects the laser wavelength but allows other wavelengths to pass.
The structure of the fiber is shown in
Figure 3. The inner core of the fiber is glass
which is doped with heavy metals. The outer
core confines the input laser beam and bounces it back and forth through the inner core to
intensify the output laser beam. Individual fiber lasers can output a few kilowatts, and the
outputs of several can be combined coherently
to produce much larger laser output power.
An advantage of the long fiber laser is that
the fiber has a large surface area to volume
ratio, allowing the quick and efficient radiation of heat. Also, the fiber laser can achieve
electrical to optical energy conversion ratios
greater than 30%, reducing the amount of heat
generated as compared to bulk lasers.

WHAT'S NEXT

Figure 3: The laser fiber has an outer core which carries the light from laser diodes, and
an inner core in which the laser light is converted into an intense laser beam as the laser
input bounces through the inner core.

Figure 3: The laser fiber has an outer core which carries the light from laser
diodes, and an inner core in which the laser light is converted into an intense laser

Next month, we will continue our discussion of types of lasers used in high energy weapons. For your comments and
suggestions, Dave Adamy can be reached at
dave@lynxpub.com. a

The Journal of Electronic Defense | November 2015

Solid State Lasers (SSL) were invented in 1960, and milliwatt class SSLs are now used in many commercial applications. Watt class SSLs are used in many military applications.
Examples are: target range finders, laser radars (LADARs), laser
imagers, target designators, and a large family of laser-based
jammers. These laser-based jammers were discussed in their

role of defeating heat seeking missiles in the August and September 2013 EW 101 columns.
SSLs use ceramic or glass, doped with various chemicals, as
their lasing media. These lasers do not use chemical fuel, and
require moderate amounts of electrical power. Three types of
SSLs are: bulk lasers, fiber lasers, and thin disk lasers.

81



JED - November 2015

Table of Contents for the Digital Edition of JED - November 2015

The View From Here
Conferences Calendar
Courses Calendar
From the President
The Monitor
World Report
Airborne Electronic Attack for A2AD
52nd Annual AOC International Symposium and Convention Guide
2016 EW/SIGINT Resource Guide
EW 101
AOC News
Index of Advertisers
JED Quick Look
JED - November 2015 - cover1
JED - November 2015 - cover2
JED - November 2015 - 3
JED - November 2015 - 4
JED - November 2015 - 5
JED - November 2015 - The View From Here
JED - November 2015 - 7
JED - November 2015 - Conferences Calendar
JED - November 2015 - 9
JED - November 2015 - Courses Calendar
JED - November 2015 - 11
JED - November 2015 - From the President
JED - November 2015 - 13
JED - November 2015 - 14
JED - November 2015 - The Monitor
JED - November 2015 - 16
JED - November 2015 - 17
JED - November 2015 - 18
JED - November 2015 - 19
JED - November 2015 - 20
JED - November 2015 - 21
JED - November 2015 - 22
JED - November 2015 - 23
JED - November 2015 - World Report
JED - November 2015 - 25
JED - November 2015 - Airborne Electronic Attack for A2AD
JED - November 2015 - 27
JED - November 2015 - 28
JED - November 2015 - 29
JED - November 2015 - 30
JED - November 2015 - 31
JED - November 2015 - 32
JED - November 2015 - 33
JED - November 2015 - 34
JED - November 2015 - 35
JED - November 2015 - 36
JED - November 2015 - 37
JED - November 2015 - 38
JED - November 2015 - 39
JED - November 2015 - 40
JED - November 2015 - 52nd Annual AOC International Symposium and Convention Guide
JED - November 2015 - 42
JED - November 2015 - 43
JED - November 2015 - 44
JED - November 2015 - 45
JED - November 2015 - 46
JED - November 2015 - 47
JED - November 2015 - 48
JED - November 2015 - 49
JED - November 2015 - 50
JED - November 2015 - 51
JED - November 2015 - 52
JED - November 2015 - 53
JED - November 2015 - 54
JED - November 2015 - 55
JED - November 2015 - 56
JED - November 2015 - 57
JED - November 2015 - 58
JED - November 2015 - 59
JED - November 2015 - 2016 EW/SIGINT Resource Guide
JED - November 2015 - 61
JED - November 2015 - 62
JED - November 2015 - 63
JED - November 2015 - 64
JED - November 2015 - 65
JED - November 2015 - 66
JED - November 2015 - 67
JED - November 2015 - 68
JED - November 2015 - 69
JED - November 2015 - 70
JED - November 2015 - 71
JED - November 2015 - 72
JED - November 2015 - 73
JED - November 2015 - 74
JED - November 2015 - 75
JED - November 2015 - 76
JED - November 2015 - 77
JED - November 2015 - 78
JED - November 2015 - 79
JED - November 2015 - EW 101
JED - November 2015 - 81
JED - November 2015 - AOC News
JED - November 2015 - 83
JED - November 2015 - Index of Advertisers
JED - November 2015 - 85
JED - November 2015 - JED Quick Look
JED - November 2015 - cover3
JED - November 2015 - cover4
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