Stabilized High Power Laser for Advanced Gravitational Wave Detectors

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• Stabilized High Power Laser for Advanced
  Gravitational Wave Detectors
• Amaldi6 , Okinawa June 2005

Benno Willke
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Overview

• Power generation
• Techniques used in 200W laser / achieved output
  power
• Concept 40W amplifier / achieved output power
• AdvLIGO stabilization concept
• Spatial profile and pointing
• Measurement breadboard
• Spatial Profile of 45W laser
• Pointing Requirements DC/AC and measurements
• Challenge is power stabilization
• Pointing RIN coupling
• Results 12W

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End Pumped Rods
NdYAG - GEO600 Laser (14W) NdYVO4 - Virgo
Laser (20W)
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Pump-Light Homogenization
? Homogeneous and uniform fluorescence
distribution ? Compensation of laser diode
degradation and failure
fluorescence w/o homogenization
fluorescence with homogenization
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Birefringence Compensation
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4 Head Ring Laser
output

• key elements
• undoped bonded end-caps
• birefringence compensation
• pumplight homogenization

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4 Head Ring Laser

mode aperture
? 243 W linearly polarized output power with M2 lt
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? 213 W linearly polarized output power with M2 lt
1.15
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4 Head Ring Laser

• 4 Head Ring Laser

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Single Frequency Operation
12W
0.8W
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Injection-Locked Single Frequency Power
P 195 W
? continuously single-frequency operation gt8h
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4 Rod NdYVO4 Amplifier
39W output power11W seed / 115W pump
2/8/2 mm NdYVO4 rod
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Output Power 4 Rod Amplifier
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Prestabilized Laser PSL

• frequency stability
• stabilize master laser to rigid or
  suspended-mirror cavity
• power stability
• feed-back to pump source of high power stage
• passive filtering at rf
• spatial profile
• passiver modecleaning
• active mode compesation

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PSL stabilization scheme
intensity stabilizationouter loop
injection locking
intensity stabilizationinner loop
PMC loop
frequency stabilizationinner loop
frequency stabilizationouter loop
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CCD Camera Measurement
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M2 Measurement Device
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AutoAlignment
PZT M2
Laser
PZT
PD
QPD2
PZT M1
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AutoAlignment
PZT M2
Laser
PZT
PD
QPD2
PZT M1
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PMC Transmission - NPRO
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Fit Non-Linear PZT Response
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Automated Peak Search
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9. spatial profile scanning cavity
Master Laser 3,2 (1,3) 12W Slave Laser
11,4 (8,9)
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PMC Scan 3Head Rod Amplifier
35W Laser 10.5 (7.9)
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Beam Profile
90 Gauss
10 garbage
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AutoAlignment
PZT M2
Laser
PZT
PD
QPD2
PZT M1
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Pointing of the 35W Laser
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Free Running Power Noise
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Power Stabilization 12W Laser
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Photodiode Non-Uniformity
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9. pointing Miser