10W Injection-Locked CW Nd:YAG laser
David Hosken, Damien Mudge, Peter Veitch, Jesper Munch
Department of PhysicsThe University of Adelaide
Adelaide SA 5005Australia
LSC – LLO March 2004 LIGO-G040069-00-Z
LSC – LLO March 2004 LIGO-G040069-00-Z
Talk Outline
• Overall motivation• ACIGA HPTF • Laser design• Laser performance• Conclusions
LSC – LLO March 2004 LIGO-G040069-00-Z
• Gravitational wave interferometers require high power CW lasers that produce a single frequency TEM00 mode
Overall Motivation
LSC – LLO March 2004 LIGO-G040069-00-Z
Overall Motivation
• Gravitational wave interferometers require high power CW lasers that produce a single frequency TEM00 mode
• Our strategy: injection-locked chain
- injection-locking of 5W prototype previously demonstrated
NPRO0.5W
10W 100W
LSC – LLO March 2004 LIGO-G040069-00-Z
Overall Motivation
• Gravitational wave interferometers require high power CW lasers that produce a single frequency TEM00 mode
• Our strategy: injection-locked chain
- injection-locking of 5W prototype previously demonstratedSpecific project objectives:• Field deployable 10W TEM00 CW Nd:YAG travelling-wave slave
laser• Characterise injection-lock• Meet or exceed the frequency and intensity noise requirements
of ACIGA / TAMA 300
NPRO0.5W
10W 100W
LSC – LLO March 2004 LIGO-G040069-00-Z
ACIGA HPTF
• The lasers we are developing will be delivered to the Australian Consortium for Interferometric Gravitational Astronomy (ACIGA) high power test facility (HPTF) at Gingin, Western Australia.
• We will also provide a laser upgrade for the TAMA300 gravitational wave interferometer in Japan.
The Australian International Gravitational Observatory (AIGO)
LSC – LLO March 2004 LIGO-G040069-00-Z
Gain Medium for 10W Slave Laser
• Coplanar folded zigzag slab (CPFS) *
• Side pumped using fast-axis collimated diode bars*J. Richards and A. McInnes, Opt. Lett. 20, (1995), 371.
(Diode power derated for increased lifetime)
D iode Laser(20W )
D iode Laser(20W )
P um p ligh t re flecto r M ax R
80%
LSC – LLO March 2004 LIGO-G040069-00-Z
• Top and bottom cooled
• Mounted on a single air-cooled base
Compact laser with increased portability and reliability
Gain Medium for 10W Slave Laser
H eats ink
H eats inkN d:YA G S lab
H eats ink
P um p reflector
D ouble d iode bar package
LSC – LLO March 2004 LIGO-G040069-00-Z
Standing-Wave Results
D iode Laser(20W )
D iode Laser(20W )
P um p ligh t re flecto r M ax R
80%
LSC – LLO March 2004 LIGO-G040069-00-Z
With ~20mm mirror to slab arm lengths we achieved:• Multimode power = 15.9W (40W pump power)• Multimode slope efficiency = 45%
Standing-Wave Results
D iode Laser(20W )
D iode Laser(20W )
P um p ligh t re flecto r M ax R
80%
LSC – LLO March 2004 LIGO-G040069-00-Z
Travelling-Wave Resonator
D iode Laser(20W )
M ax R (60 inc idence)0
In jected beam
O utput
P ZT
P ZT
D iode Laser(20W )
P um p ligh t re flecto r
O utput coupler (10 incidence)0
LSC – LLO March 2004 LIGO-G040069-00-Z
Travelling-Wave Resonator
Injection locking servo control system:Low bandwidth, high dynamic range PZT plus high bandwidth, low dynamic range PZT together provide sufficient bandwidth and dynamic range.
D iode Laser(20W )
M ax R (60 inc idence)0
In jected beam
O utput
P ZT
P ZT
D iode Laser(20W )
P um p ligh t re flecto r
O utput coupler (10 incidence)0
LSC – LLO March 2004 LIGO-G040069-00-Z
10W Slave Laser
LSC – LLO March 2004 LIGO-G040069-00-Z
ACIGA HPTF and TAMA Lasers
LSC – LLO March 2004 LIGO-G040069-00-Z
Control and Confinement of Mode
• Astigmatic thermal lensing in the pumped slab: fvertical ~ 6-8cm fhorizontal ~ 2-3m
• Vertical (cooling) plane- mode confinement provided primarily by strong thermal lensing- mode control achieved by matching the laser mode to the
pumped region
• Horizontal plane - mode confinement by residual curvature of the slab sides, very
weak thermal lens and mirror curvature- higher order mode rejection by apertures formed by Brewster
entrance/exit windows
Careful adjustment of cavity length and pump power achieves anexcellent fundamental mode, in both horizontal and vertical planes.
LSC – LLO March 2004 LIGO-G040069-00-Z
Travelling-Wave Results
Using 90% reflective, 5.00mconcave output coupler
• M2horizontal < 1.1
• M2vertical < 1.1
• Output power = 9.2 W (31W pump power)
Measured using Spiricon M2
Beam Analyser
LSC – LLO March 2004 LIGO-G040069-00-Z
Injection-Locking SetupN P R O
H W P
E O M
F araday iso la to r
H W P
10W S lave
M ode m a tch ing
P ow er m e ter
LSC – LLO March 2004 LIGO-G040069-00-Z
Injection-Locking SetupN P R O
H W P
E O M
F araday iso la to r
H W P
10W S lave
M ode m a tch ing
P ow er m e ter
LSC – LLO March 2004 LIGO-G040069-00-Z
Injection-Locking SetupN P R O
H W P
E O M
F araday iso la to r
H W P
10W S lave
M ode m a tch ing
P ow er m e ter~5W
LSC – LLO March 2004 LIGO-G040069-00-Z
Injection-Locking SetupN P R O
H W P
E O M
F araday iso la to r
H W P
10W S lave
M ode m a tch ing
P ow er m e ter~10W
LSC – LLO March 2004 LIGO-G040069-00-Z
Multi- longitudinal mode operation of free-running slave laser (left), and single frequency operation (right) when locked using a stable master laser.• Currently developing and testing a PDH servo control circuit, and have achieved prolonged suppression of reverse-wave with closed servo loop
(Traces measured using a scanning Fabry-Perot cavity (10GHz FSR))
3 ) Ref A : 2 Vo lt 2 .5 m s 4 ) Ref B : 5 0 0 m Vo lt 2 .5 m s
3 ) Re f A : 2 0 0 m Vo lt 2 .5 m s 4 ) Re f B: 5 0 0 m Vo lt 2 .5 m s Passive injection-locking
LSC – LLO March 2004 LIGO-G040069-00-Z
Conclusions
Progress to date:• Efficient robust compact design• Robust thermal control system• M2
x,y < 1.1 with 9.2W output in travelling-wave• Short term injection-locking achieved
Future plans:• Increase output power to over 10W• Long-term injection-locking• Characterisation of noise
Delivery of injection-locked laser to AIGO in May 2004.
