
52-1
52.1 Introduction
A laser is a device that emits an optical beam. A laser beam carries a certain amount of optical power.
Lasers emit beams in two dierent ways: continuous wave (CW) or pulsed. A CW laser emits a steady
po
wer
as sh
own
in Fi
gure
52.1. CW la
ser
po
wer
is me
asured
in te
rms
of wa
tts
. e po
wer
of co
mmonly
us
ed
CW la
sers
ra
nges
fr
om
a fr
action
of mi
lliwatts
fo
r
a sm
all
he
lium–neon
(H
e–Ne)
la
ser
to te
ns
of
ki
lowatts
fo
r
a ca
rbon
di
oxide
(C
O
2
) laser. A pulsed laser emits a pulsed power as shown in Figure 52.2.
e pulse can be repeated. e pulse duration and repetition rate vary for lasers of dierent types and
ar
e
ad
justable
fo ...