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C. Reynolds, H. Suedhoff,
M. DeAr=
mond,
J. Suelzer
and M.F.
Masters
![](3D"slide0023_image003.jpg")
Department
of Physics,
Indiana
University Purdue University Fort Wayne (IPFW),
Fort
Wayne IN 46805
=
Investigation of lasing from dye doped plastics using flash lamp and Nd:YAG excitation.
=
=
Abstract
=
We present an investigation of organic dye doped
plastics as a lasing mediu=
m. The
host materials examined are poly(methyl)methacrylate
[acrylic], epoxy, polyester and polyurethane.
Various solvents are used to improve dye dispersion within the material. Two forms of optic=
al excitation (flash lamp and frequency doubled Nd:YA=
G) are
used. For the Nd:YAG pumped dye
lasers, a disk of dye doped
plastic is mounted in a housing to provide random orbital motion. The disk is within a Littmann
configuration cavity=
. Each
dye disk is tested for threshold, durability, power output, bandwidth, and tuning range. An end =
pumped cylinder is also explored. For the flash la=
mp pumped dye lasers two configurations are used: a <=
/span>traditional dye cylinder within an elliptical refl=
ector
and a hollow cylinder w=
ith
the flash lamp within the hollow. A monolithic
cavity for the flash lamp pumped system is =
investigated.
<=
span
style=3D'font-size:75%;visibility:hidden'>•
Purpose
lasing characteristics, two
methods where used.
•Thin plastic disks, doped with Rhodamine 590,
were pumped with a Nd:YAG laser.
•Small diameter rods, also doped with Rhodamine
590, were pumped with flash lamps.
Motivat=
ion
=
in dye lasers because of several desirable =
features.
• The size of the system is greatly reduc=
ed
over conventional liqui=
d dye
lasers; no pumps or tubes.&=
#13;
•Changing of the =
lasing
medium is much easier and
quicker
•Hazardo=
us
waste handling is simplified.
Plastic
Fabrication
•Three plastics w=
ere
examined: Polyester, Polyurethane=
, Poly
Methyl Methacrylate (PMMA)
=
;
•Molding was done=
with
high density polyethylene and glass, which
produced parallel, unpolished faces.
The unpolished faces
contributed to instabilities of the dye laser output.
<=
/div>
•The dye, Rhodami=
ne
590, was pre-dissolved in ethanol before being added and mixed into the uncured polyester a=
nd polyurethane.
This method greatly reduces undissolved dye within the cured plastic which cause scattering.
• For the acrylic no solvent was used.
Plastic
Fabrication 2
• Each
of the three plastics have advantages and disadvantages with <=
span
style=3D'font-size:63%'>respect to the fabrication of the disks.
Polyester
advantages:
easy to make, easy to polish, very hard when cured, maintains shape with temperature
change.
disadvantages: strong odor, shrinks during curing
=
;
Polyurethane
advantages:
easy to make, gives most consistent results,
disadvantages: difficult to polish, deforms with heat=
PMMA
advantages:
very easy to polish, very hard when cured.
disadvantages: difficult and time consuming to produc=
e,
cannot <=
span
style=3D'position:absolute;top:92.25%;left:8.98%;width:86.7%;height:4.5%'>=
support high concentrations of dye.=
Disk Me=
thod
•To investigat=
e the
lasing properties of the different plastics =
doped with Rhodamine 590, we developed a random orbital mechanism to prevent the rapid exhaustion =
of the
dye by the Nd:YAG pump laser.&=
#13;
The disks were placed inside a Littman mount desig=
n for tuning
The output from the dye laser was then examined fo=
r several characteristics such as power, tuning rang=
e, and
threshold.
Pump Laser
•A pulsed frequency doubled Nd:YAG laser =
was
used for longitudinal pumping of the plastic disks.
<=
span
class=3DBB style=3D'position:absolute;left:-4.43%'>•25 mW average
power
<=
span
style=3D'font-size:94%'>•10 Hz pulse rate, 5 ns pulse, gaussian beam
<=
span
class=3DBB style=3D'position:absolute;left:-4.43%'>•532 nm waveleng=
th
=
Oscillator
=
Amplifier
Diffraction Grating
Focusing
Lens
Beam Splitter
HR
Tuning Mirror
Dye Laser Schematic
![](3D"slide0012_image004.gif")
Nd:YAG=
![](3D"slide0012_image005.gif")
![](3D"slide0018_image006.gif")
Motor
Dye Disk
Cam
Base mounted on slide bearing
![](3D"slide0018_image007.gif")
![](3D"slide0018_image008.gif")
Drive shaft
Simplified Top View of
Random Orbital Drive Mechanism
![](3D"slide0018_image010.gif")
![](3D"slide0018_image011.gif")
![](3D"slide0021_image012.gif")
Lasing
characteristics
>50=
,000
pulses
>36=
,000
pulses
> 36,000 pulses
Durabil=
ity
15.8 =
mJ/cm2&=
#13;
12.5 =
mJ/cm2<=
/span>
15.8 =
mJ/cm2<=
/span>
Thresh=
old
579-5=
87 nm
548-6=
00 nm
573- =
605 nm
Tuning
Range
Osc: .9
mW
Conc: =
1x10-4=
M
Osc: .9 mW
Conc:8=
x10-4=
M
Osc: 1 mW
Conc: =
1x10-3=
M
Power&#=
13;
PMMA
Polyu=
rethane
Polyester
Flash Lamp Method
•=
To investigate the viability of flash lamp pumped =
doped plastic rods
•=
The experiment tests the lasing characteristics =
of different types of plastic with different dye <=
/span>=
concentrations
•=
The apparatus consist of a flash lamp cavity and <=
/span>=
an external cavity with a high reflecting mirror <=
/span>and an output coupler
•=
A monolithic cavity is also tested, the faces of <=
/span>=
the rod are machined so that one face is the high reflector and the other is the output coupler=
![](3D"slide0001_image015.gif")
End
View
Top
View
Flash Lamp
Dye Doped Plastic Rod
6.4 cm
Flash Lamp Cavity
![3D"Text](3D"slide0001_image016.gif")
=
4.1 cm
![3D"Text](3D"slide0001_image017.gif")
=
1.8 cm
4 mm Dia.
8 mm Dia.
![](3D"slide0002_image019.gif")
![](3D"slide0002_image020.gif")
![](3D"slide0002_image021.gif")
![](3D"slide0002_image022.gif")
![](3D"slide0002_image023.gif")
![](3D"slide0002_image024.gif")
![](3D"slide0002_image025.gif")
![](3D"slide0002_image026.gif")
![](3D"slide0002_image027.gif")
100MW
100kW
H.V. in
![](3D"slide0002_image028.gif")
![](3D"slide0002_image029.gif")
![](3D"slide0002_image030.gif")
![](3D"slide0002_image031.gif")
Xe
Flash
Lamp
1
Triggered Spark Gap
40 nF
![](3D"slide0002_image032.gif")
![](3D"slide0002_image033.gif")
![](3D"slide0002_image034.gif")
![](3D"slide0002_image035.gif")
![](3D"slide0002_image036.gif")
Assembly
Side View
Assembly
Top View
Triggered Spark
Gap
Flash Lamp Cavity
40 nF Mica Low <=
span
style=3D'position:absolute;top:52.5%;left:84.26%;width:13.1%;height:2.75%'=
>Inductance Capacitor
H.V. Line In
Circuit
Diagram
Circuit Diagram and Pump Assembly
Xe
Flash
Lamp
2
Chart 1: =
The
above chart shows the behavior of the flash lamp as a function of time. The circuit is slightly under damped, this responsible=
for
the oscillation in the lamp intensity
Chart 2: =
Spectra
of three Rhodamine 590 doped plastic rods at different concentrations and =
two
different plastic types. The polyurethane has a peak value more=
to
the blue side of the spectrum where the polyester has a peak more to the red side of the
spectrum.
Chart 3: =
Spectral
narrowing due to an increasing energy.
The plastic used above was polyurethane with a dye concentration of 4.12x10-5=
M. The en=
ergy was
increased by increasing the capacitance of the storage capacitor.
Note that the three spectra have been scaled to the same intensity =
to
better show the narrowing
Chart 4: =
One
spectrum has an external cavity, one has a monolithic cavity and one is a
reference with no ex=
ternal
cavity. The plastic used above was
polyester with 6X10-5M dye
concentration. The peaks <=
/span>of these spectra are to the more red side of the
spectrum than in chart3.
![](3D"slide0003_image045.gif")
Scatter=
ing
Through Plastic Rods
=
37%
2.03mW=
Polyure=
thane
2.12x10=
-4=
M
22%
2.52mW=
Polyure=
thane
4.28x10=
-5=
M
3.22mW=
Test
Laser
% Loss
Power<=
/span>
•=
Scattering causes a significant reduction in the =
gain
through the lasing mediu=
m
•<=
/span>The cause of the scattering is undissolved dye wi=
thin
the plastic. Note:
solvents were not used when this data was taken
•=
The test laser used was a HeNe laser
•=
Scattering is proportional to the <=
span
style=3D'position:absolute;top:77.5%;left:4.49%;width:48.87%;height:5.25%'=
>amount of dye added to the plastic
Continuing Investigations
•Expanded investigation of a wider range of dye =
concentrations for both flash lamp and disk
methods.
•A new drive mechanism needs to be developed to =
minimize any mechanical instabilities in the rando=
m orbit.
•Other lasing characteristics need to be measured, =
including: bandwidth, temporal behavior, beam
quality.
<=
span
style=3D'font-size:78%'>•Reduction of scattering from undissolved dye.
=
;
<=
span
style=3D'font-size:78%'>•Shortened duration of flash lamp pulse.
•Expanded Investigation of rod shapes, including =
monolithic cavities.References
•A.Costela,
I.Garcia-Moreno, C.Gomez, O.Garcia, R.Sastre: Applied Physics B 78 629=
-634 (2004)
•
•F.J.Duarte: Optics Communicati=
ons 117 (1=
995)
480-484
•
•J.A.Russell,
D.P.Pacheco, W.H.Russell, H.R.Aldag, A.A.Manenkov: SPIE Proc. Solid =
State Lasers XI, 4630 (2002)
•
•A.J.Finlayson, N.Peters,
P.V.Kolinsky, M.R.W.Venner: Physi=
cs
Letters 72-17 (1998)
•
•Y.Yang, G.Qian, Z.Wang,
M.Wang: Optics Communications 204<=
/b> (2002)
•
•A.L.Dawar,
J.C.Joshi, S.K.Kapoor, N.K.Bishambhu, K.N.Tripathi: Applied Optics 2553 <=
/span>=
(1991)
•
•S.Singh,
V.R.Kanetkar, G.Sridhar, V.Muthuswamy, K.Raja:
Journal of Luminescence 101 (2003)
•
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