YAG, CO2 and Excimer Lasers Compared (as Industrial Lasers)
YAG is an acronym for Yttrium
Aluminum
Garnet, a crystal doped with
the rare earth element, Neodymium, abbreviated as Nd:YAG
or simply "YAG." Nd does the lasing, YAG is the host for
the Nd. The crystal, called a laser rod, is mostly YAG, only
a few percent Nd. A nice characteristic of solid
state lasers like YAG is safety. There
are no
compressed or lethal gasses. Another crystal, vanadate, is used.
Loosely speaking, we call it YAG for convenience.
Solid state lasers were the first to be invented
(1960), CO2 in 1964 and excimer in 1970. YAG, a
solid state laser, has the most experience.
Laserod has years of experience in all the major YAG
types: lamp, fiber and diode.
Both CO2 and excimers are mixtures of various gases.
CO2 is a source of far infrared (IR) radiation only.
Excimers are ultraviolet (UV) sources only whereas YAG
is multi-wavelength from near IR to UV. YAG is therefore
more versatile.
Both carbon dioxide (CO2) and excimer are gas lasers.
Solids are denser than gases. YAG is more
compact than either of the large and bulky gas
lasers. However, Laserod's principle holds a patent on a
compact excimer whose laser head is only a few feet
long. And Synrad, a CO2 supplier, offers low power
compact CO2 sources. Each laser type has it's unique applications. For
example excimers are used in semiconductor wafer
lithography and are famous for eye surgery. But the vast
majority of lasers in the world are solid types:
computer hard drives and DVDs. But the majority of
industrial lasers are CO2.
YAG vs CO2 and Excimer:
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There are more than 500 laser job shops in
the United States. Most specialize in CO2
lasers. Our specialty is YAG. Excimer houses are
even more rare. CO2 and YAG are expensive, but
excimers tend to be more expensive. The most
expensive laser to operate is excimer with UV
diode pumped type coming in as a close second.
High power industrial excimers are jokingly said
to require PhDs for maintenance; UV YAGs require
no maintenance, just diode replacement.
The big difference between YAG compared to CO2
lasers is the narrow kerf of less than 0.001 inch
(25 microns). Therefore, YAG permits
precision machining. Because of the
10:1 wavelength difference, CO2 lasers, as a
rule of thumb, have a kerf ten times greater
than YAG for the same beam delivery optics. Two
examples of optics are fixed beam with moving
part and galvanometer (galvo) moving beam. It's
possible to combine a galvo and an X/Y stage or
a galvo and a moving web to both move the beam
and the part. Both CO2 and YAG lasers integrate
well into these devices. More YAG versus CO2
differences are:
- wavelength: YAG's fundamental wavelength
is 10
times smaller and produces relatively slag free cuts.
YAG can be frequency multiplied (wavelength
divided), CO2 cannot. When frequency tripled
to the UV, YAG produces a kerf 30 times smaller.
Doubled to the green, it's 20X smaller.
-
peak power: YAG has many orders of
magnitude
higher peak power (by Q-switching) producing cleaner and
smoother cuts due to higher vaporization
temperatures. Yet in spite of the higher
focused beam temperature, thermal effects are
usually negligible. CO2 is not normally
Q-switched. Laser peak power is pulse energy
divided by how long the laser pulse lasts --
femtoseconds to milliseconds.
- average power:
Both are available at multi-kilowatt average
powers - which is laser energy delivered per
second. By comparison, peak power is energy
delivered per pulse.
- efficiency: CO2 is
easily an order of magnitude more efficient
than YAG but this is mainly important to
scientists, not us machine tool makers.
YAG vs Excimer and CO2:
- frequency multiplication of YAG
from IR to green (1064 to 532nm) and to UV
at 355nm allow YAG lasers to compete with
excimers.
- pulse rate of excimer
is typically 100 pulses per second (Hz)
compared to up to 400,000 for one of our
YAGs.
- pulse energy of excimer
can be joules. YAG is millijoules. These
orders of magnitude differences in energy
and speed make for vastly different
applications.
- applications: low power
CO2 is good for thick plastics, high power
for thick metal cutting. YAG is good for
thin metal cutting and UV YAG for thin
plastics. But YAG cuts are cleaner. Q-switched
YAG lasers excel in
high precision line ablation compared to
excimers as area ablators. Consider plated
surfaces - a metallized coating of gold,
copper, or ITO for
example - are easily ablated or patterned by
either YAG or excimer.
YAG excels as a line scriber, excimer for
ablation of small pattern areas. YAG can
pattern a thin coating up to 1.6m x 1.6m
whereas excimer is an order of magnitude
smaller. CO2 lasers cannot ablate copper or gold.
Feature size of excimer can be submicron
whereas YAG is 10um.
The choice of which laser to use is
application specific. It comes down to what
works best for a given job. Our job is to prove
what works for you.
You may call us, fax us or
e-mail your requirements. Typically, send us a
sketch or dxf via e-mail. In most cases
you supply the material. We will quote on a
turnkey basis. Prototypes are welcome! We
sell systems as well as offering a laser
processing service.
We look forward to working with
you.
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