status of high-power laser development at stanford todd s. rutherford*, shailendhar saraf, karel...
TRANSCRIPT
Status of High-Power Laser Development at Stanford
Todd S. Rutherford* , Shailendhar Saraf, Karel Urbanek, Justin Mansell, Eric K. Gustafson, and Robert L. Byer
E. L. Ginzton Laboratory, Stanford University
LIGO Science Collaboration Meeting
Hanford Site, August 15-17 2000
Outline
• Review
• Progress since last LSC– Preliminary results on wavefront distortion– Installation of new diodes
• (Near) Future Work
Configuration
• Two zig-zag slab amplifiers– Brewster ends– 3:1 aspect ratio (width/thickness)
• About 900 W total pump power
• Use Lightwave 10 W as master oscillator
• Goal: 100 W, low M2
The Single -Triple Pass Amplifier
0
5
10
15
20
25
0 20 40 60 80 100
300 mW
1W
8.5 W
Out
put P
ower
% Pump
1.25 W
4.03 W
22.2 W
0
0.5
1
1.5
0 20 40 60 80 100
300 mW (goL)
8.5 W (gL)
Gai
n-L
engt
h P
rodu
ct, g
L
% Pump
G=4.17
G = 2.6
Pin = 8.5 W
Pout = 22.2 WM2=1.1
M2=1.3
The Double-Triple Pass Amplifier
50 cm ROC
0
1
2
3
4
5
6
7
8
0 20 40 60 80 100
300 mW
1W
Out
put P
ower
(W
)
% Pump Power (26 LD's)
7.4 W
3.7 W
0
0.5
1
1.5
2
2.5
3
0 20 40 60 80 100
300 mW (goL)
1W (gL)
Gai
n-L
engt
h P
rodu
ct ,
gL
% Pump Power (26 LD's)
G = 12.3
G = 7.5
Unsaturated Amplifier
0
0.5
1
1.5
2
2.5
3
3.5
4
0 20 40 60 80 100
1 x 3 Pass
2 x 3 Pass
Out
put P
ower
(W
)
% Pump Power
Unsaturated Amplifier Pin = 300 mW
0
0.5
1
1.5
2
2.5
3
0 20 40 60 80 100
1x3 Pass
2x3 Pass
Uns
atur
ated
Gai
n, g
oL
% Pump Power
8 m
Slab Wavefront
• Measured with Shack-Hartmann wavefront sensor
• Dominant distortion is tilt
• More detailed analysis in progress
2.25 m
Tilt Removed
Laser diode upgrade
Laser diodes• Manufacturer:
Coherent
• 30 W each
• 808 nm
• Fiber coupled– 400 m core
– 0.2 NA
• 24 units
• 720 W total
Power Supplies• Manufacturer:
Newport
• 100 A, 14 V– Drive 6 bars in series
• Temperature Control– PID controllers
– TEC drivers
• GPIB/RS-232
• Fault protection
Installation Complete
-Labview control of diode: -Current -Voltage -Temperature-Interlocks
Power Scaling Challenges
• Beam Quality– Difficult to model
• Distortions depend critically on slab boundary conditions
• RF Intensity noise– High circulating power in PMC(s)
– Requirements eased with DC readout
• Parasitic Oscillations• Depolarization
– Near edges only
• Temperature detuning
Depolarization
• Stress near edge of slab is not completely aligned with polarization
• Sensitive to fiber position and distribution
• 300 W pump ~ 15 % stress fracture limit0
0.01
0.02
0.03
0.04
0.05
50 100 150 200 250 300
Edge
Center
Dep
olar
izat
ion
Los
s
Pump power (W)
Future Work
• Calibrate Diodes (1 week)– Temperature for optimum absorption
– Power vs Current curves
• Assemble second amplifier head (2 days)– Machining finished
• Mount fiber clamp to second head (1 week)• Power tests of second head (2 weeks)• Begin amplification experiments