Solid State UV Lasers

From: Ross Gates (Select Manufacturing  Services,     .), Terry Wohlers (Wohlers Associates), Allan Lightman (University of Dayton)
To: RP-ML
Date: Friday, October 13, 1995
Subject: Solid State UV Lasers
     I have heard that the EOS StereoLithography machines in Europe may be running
a solid state UV laser system. These are supposed to last 50,000 hours and
will maintain their power output throughout the life of the laser.
     Since we are subjected to expensive short lived lasers for our systems, this
would be a real interest to me and other SLA owners. 
     Can anyone in Europe enlighten us on this laser, if it can be imported in the
US and what it might take to retrofit them on a 3D SLA?
Ross Gates
Select Mfg. Services

Date: 17 Oct 95 19:13:44 EDT
     Stereolithography developers and laser experts -- please correct me if I'm
wrong ...
     The EOS STEREOS MAX 600 machine uses a frequency-tripled YAG laser which is
50-60 times more energy efficient then an Argon-ion laser, according to one
source.  Also, it doesn't require water cooling.  The YAG laser that EOS is
using puts out about 300 milliwatts (mW) of energy; about 250mW at the resin
surface, yet it requires only 300W of power, which is about the same as needed
to run a small appliance.  3D Systems' newest and most powerful machine, the
SLA-500-30H, delivers 132mW of power at the vat for 2,000 hours.  The STEREOS
MAX 600 can use the same resins used in Argon-ion systems.  EOS presently uses
the Exactomer resins from Allied-Signal and DuPont's new 6100 epoxy resin. 
     Additions or corrections are welcomed.
Terry Wohlers

95 10 30:
     The UV solid state lasers that are of interest for RP are frequency-tripled 
diode pumped Nd, usually in YAG, lasing at 355 nm.  Both Spectra-Physics and 
ADLAS have pulsed systems that are operational.  The diodes couple with the 
Nd very efficiently and may give as much as 2% wall plug conversion in the 
fundamental (1.06 microns in the IR).  Conversion to green (frequency 
doubling) can be 50% efficient for pulsed systems and then conversion to UV 
may be 10-20% leading to the 0.1% given by Terry Wohlers (300mW out for 300W 
in).  EOS mentions that their system operates at about 40kHz, which may be 
needed for the high writing speed of the STEREOS 600.  Tests at high pulse 
rates have indicated difficulties realizing high rep-rate operation and 
10kHz is mentioned by many as the upper limit in their systems (which may 
lead to a perforation style of exposure at high scan speeds).  A cw system 
would be preferable but it is difficult to efficiently convert the cw 
operation.  This may be overcome in the near future.  I have seen very 
compact systems (laser head of about 15 cm on a side) providing 12 W IR and 
6 W green for about 600W at the plug.  The manufacturer estimated the life 
at 10,000 HRS and expected that this would be considerably extended at lower 
powers.  Tests are underway.  They are investigating tripling - even 
inefficient conversion may yield significant UV when they start with 6 W.
Allan Lightman
University of Dayton Research Institute