Parallel mirrors Detector Actual image
12 Industrial Laser Solutions NOVEMBER/DECEMBER 2016 www.industrial-lasers.com
of a thermopile with
the response speed
of a semiconductor
photodiode [ 2].
This unique set
of characteristics is
in this application.
Unlike a photodi-
ode, which saturates
at very low light lev-
els, the detector
measures high laser
power directly in tens
This minimizes the
need for attenuating
optics in the beam
path, which can be
a source of absolute measurement
error. Also, in contrast to a photodi-
ode, the response of
this detector is highly
linear, and the entire
ment system (detec-
tor/electronics/soft-ware) is calibrated
Therefore, it delivers highly accurate,
of laser power. This
is critical to know
in order to optimize
process parameters, or for analyz-
ing the precise laser/
in the development
of new alloys.
The high response
speed of the detec-
tor also enables it to
directly observe pulse shape, rather than
simply report average power. This is useful because deposition quality (e.g., grain
size, tensile strength, etc.) is dependent
upon peak power, rise time, and other
pulse parameters. And, even when work-
ing with CW lasers, it’s important to know
how fast the laser reaches full power
when powered on.
In conclusion, LAM represents a rev-
olutionary step forward in metal fabrica-
tion technology. But for this technique to
achieve its maximum impact, improve-
ments are necessary in process cost,
speed, and resultant part quality. High-
speed, compact, and cost-effective beam
diagnostic tools that deliver beam waist
location, beam size, and power density
information in <1s will be a key element in
achieving these ends. ✺
The author wishes to thank Dr. Rich
Martukanitz, Director of the Center
for Innovative Materials Processing
through Direct Digital Deposition at the
Pennsylvania State University, and Michael
Scaggs and Gilbert Haas of Haas Laser
Technologies, for their invaluable help in
the preparation of this article.
BWA-CAM is a registered trademark of
Haas Laser Technologies.
[ 1] T. Rockstroh, D. Abbott, K. Hix, and J. Mook, “Additive
manufacturing at GE Aviation,” Industrial Laser Solutions, 28,
6, 4–6 (Nov/Dec. 2013).
[ 2] S. Bergman, “Laser power measurement: Time is money,”
Industrial Laser Solutions online (Aug. 2015); see http://bit.
SEAN BERGMAN ( firstname.lastname@example.org) is
product manager for laser measurement instrumentation at Coherent (Santa Clara, CA); www.coherent.com.
FIGURE 4. A simplified schematic of the optical arrangement used
in the BWA-CAM to simultaneously image a beam at multiple
locations along the optical axis.
FIGURE 3. The compact BWA-CAM ( 2. 4 × 2. 4 × 3.3in.), which provides near-instantaneous beam shape, size, focus,
and power measurement, easily fits in the build platform of most PBF systems. (Photo courtesy of the Applied
Research Laboratory, Pennsylvania State University)