Transcript High Power Laser System for Advanced Virgo

High Power Laser System
for Advanced Virgo
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C.N.Man
Design goals
Present technology
Other activities in the world
Virgo+ and Laser System - possible planning
Advanced Virgo HP laser
HP related photonics (fibers as MC, modulators,…)
All-fibered laser system
Conclusion
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Design goals
• Laser power: 200W
• Wavelength : 1 mm to 1.6 mm, linked to
SiO2 or Si, laser material, optical technology,…
• Input Beam propagation: free space, fibre ?
• Beam cleaning: resonant MC or fibre MC?
• Modulation:
– Bulk, or fibre components ? Which frequency(ies) ?
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Present technology : laser designs
High power  cooling problem (birefringence induced by thermal
loading, …)
 large surface/volume ratio and material conductivity
 high efficiency
Solutions :
new crystals, or ceramics
disk amplifiers or fibres
Today, kW single mode lasers are available
with both disks and fibre amplifiers
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Other activites in the world
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Laser systems (< kW)
- GW groups activities: mainly Germany and Australia
-Very high power lasers ( up to MW CW)
-Disk lasers for military and industry : Boeing, …
-Fibre lasers for welding, cutting (kW`s)
-Scientific and telecom lasers (> 100 W)
-Disks and fibre lasers, many European small companies
Yb and Er doped Fiber lasers: 1,06 and 1,3 mm
-Nb: telecom lasers  MTBF > 100 000 h
 Fibre integrated isolators, modulators, etc
 1.3- 1.5 mm wavelength
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Virgo + : First Step in the Studies
Virgo+: as master laser, Fiber laser or SSL
HP Solid State laser/amplifier (LZH)
To start :
1 - investigations on the FL as a potential new Master laser
2 - development of a 50 W laser/amplifier in SS technology
Deliverables in 07-08:
A Single-Frequency Fiber laser of 2W
A laser amplifier to scale up the 20W to 50W
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Laser System for Virgo +
20W laser
injection locking
Fiber
laser
Master
Laser
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50W Amplifier
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Fiber Master Laser for Virgo +
100 mW Oscillator amplified to 2 W at 1.06 mm
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Virgo + : Nd:YVO4 50WAmplifier (LZH)
Four-stage end-pumped Nd:YVO4
Each stage pumped by 45 W laser
diode
Each diode indiv temp controlled
Each 2diodes connected in series to 1
current driver
Diodes current controlled
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Possible Planning for Virgo + Laser System
2005
Tasks and Deliverables
Q4
2006
Q1
Q2
Q3
2007
Q4
Q1
Q2
Q3
2008
Q4
Q1
Q2
Q3
Task #1 Master fiber laser
#1.1 Purchase a commercial fib er
laser (Nice)
#1.2 T est of the free-running fiber
laser (Nice)
#1.3 Design and realization of
servo-loops (Nice)
#1.4 Charact. of the frequency
stability (Nice)
#1.5 Injection locking of the slave
laser (Nice)
Tasks #2 50W las er ampl ifi er
#2.1 Definition of specifications
(Nice)
#2.2 Realization of laser amplifier
(LZH)
#2.3 T est and characterization of
amplifier (EGO & Nice)
#2.4 Design fo r slaveĞamplifier
integration (EGO)
#2.5 Integration slaveĞamplifier
(EGO & Nice)
#2.6 Virgo+ laser characterization
(Nice & EGO)
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Adv. Virgo: HP single-mode fiber lasers
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HP related photonics
Beam propagation: free space or through fibre ?
Fiber laser : no MC needed
SSL: resonant cavity MC or fibre MC?
Modulation:
Bulk, or fibre modulators ? (Which frequency(ies) ?)
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Requirements for mode cleaning
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Spatial filtering of modes
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Resonant mode close to a gaussian beam
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Output beam independent of input beam or ouput phase
noise independent of input beam jitter
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No addition of any extra noise
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Power standing required
Why using a fiber:
simplicity of the system, its control and its maintenance
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PCF as Input Mode Cleaner
Use of monomode fibers not realistic up to now, due to power
handling capabilities
Photonic Crystal Fiber offers this possibility of power handling
What is a PCF ?
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High Index Guiding Fiber
Light is guided in the core by total internal
reflection: the airholes in the cladding make
its effective index lower than that of the core
NA = 0.8
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Low Index Guiding Fiber:
Photonic bandgap fiber
Light is guided in the core by Bragg reflection caused by the
spatial periodicity of the holes in the cladding
B
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Fabrication of PCF
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PCF R&D financed by EGO
Started in 11/04 - Goals: test of a commercial PCF hollow-core
fiber in terms of :
** Handling, Coupling efficiency, loss measurements
* Output Beam analysis, comparison with numerical modeling
(coll with IRCOM-Limoges, Blaze Photonics)
** Measurement of phase noise introduced by the fiber in a
normal environment
*** Power standing of 20W, Induced amplitude noise, Polarisation
noise (this fiber is not polar.maintaining fiber now),
dependency of input/output noise
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Results on hollow-core HC-1060-02
Quasi-gaussian monomode >90%
HC-1060-02 Blaze Photonics
Core 10 mm, pitch 2.75 mm,
holey region diam 50 mm
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Attenuation < 0.1 dB/m
Mode field diameter 6.5 mm
Fresnel reflection at end faces <10-4
No bend loss at 3 mm radius
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Experimental results (2005)
Coupling and handling like standard fibers; Attenuation loss measured 0.05 dB/m
coupling of 90% obtained: further improvements with a phase plate or an adaptive
mirror
Transmission : output/input of 45%
loss of 4.5% with a bending of 0.8 cm
Residual coupling between core and cladding modes due to imperfections
Input face of the PCF
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Measured near-field intensity
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Extra Noise measurement
The ouput of the PCF is
sent into a high finesse
Fabry-Perot as discriminant
=> no evidence of extra
frequency noise
No fast polarization &
amplitude noises
Power handling of 20W
To be done: Choice between hollow core PCF and large silica core PCF (30 µm)
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Available fiber components (for power <1W)
Faraday isolators (> 55 dB isolation)
35 mm
55 mm
Phase and amplitude modulators (GHz
bandwidth, low voltage drive)
Polarization controllers (20 kHz bandwidth)
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All-fibered Laser System
Oscillator
(Nd-YAG
or fibre
Amplifier
100 mW
Faraday
isolator
Monomode
fibre (PM?)
Frequency control
Vacuum
Amplitude control
Polarization control
Beam
monitoring
100W
to interferometer
Vacuum (optional)
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Conclusion: Proposed main steps
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2006 Acquisition and test 1-2 W fibre laser (Yb @ 1064 nm)
- Evaluation and control in Nice
- 2007 Test as a master laser in Cascina
Acquisition of a high power Yb-doped fiber amplifier
- 2009 ? Test of a HP Yb-doped fiber amplifier
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2006-2008 Development and tests of a fibre mode-cleaner
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After the choice of advanced mirrors material:
- Definition and acquisition of the advanced laser system prototype
( 3 years ahead of installation)
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