Goddard Space Flight Center 9th LISA Symposium, 23 May 2012Kenji Numata
Laser Development for Gravitational-Wave Interferometry in Space
Kenji Numata1,2, Jordan Camp2
1Department of Astronomy, University of Maryland, College Park, Maryland, 20742, USA
2NASA Goddard Space Flight Center, Greenbelt, Maryland, 20771, USA
Goddard Space Flight Center 9th LISA Symposium, 23 May 2012Kenji Numata
Outline
o 1. Introduction– GSFC’s space laser history and recent trends
o 2. Master oscillator– Planar waveguide external cavity diode laser (PW-ECL)
o 3. Pre-amplifier– Low-risk component
o 4. Power amplifier– Noise and qualification tests
o 5. Summary
Goddard Space Flight Center 9th LISA Symposium, 23 May 2012Kenji Numata
1. Introduction
o NASA/GSFC space laser history– Nd:YAG laser altimeters
o Recent activities and trends– Advanced laser altimeter (ICESat2, LIST, etc.)
• Yb fiber + Waveguide amp.
– Gas sensing lidar (ASCENDS, etc.)• Er fiber + Waveguide amp., stabilized seed laser• Parametric amplification
– Laser communication (LCRD, etc.)• Er fiber amp., telecom fiber components
– Interferometry (NGO/SGO, OpTIIX, etc.)
• Fiber & waveguide technologies wherever possible
MESSENGER/MLA - Mercury(2004-2012)Nd:YAG laser, >0.5B shots to date
LRO/LOLA - moon(2008-2012)Nd:YAG laser, 1+ Billion shots to date
ICESat/GLAS – Earth(2003-2010)Nd:YAG laser, 1.98 billion shots
MGS/MOLA - Mars(1996 -2000)Nd:YAG laser, 670 million shots
Goddard Space Flight Center 9th LISA Symposium, 23 May 2012Kenji Numata
Space laser for interferometry
o Master oscillator/fiber amplifier (MOFA) configuration– Both 1.0 µm and 1.5 µm
o Fiber/waveguide advantages– High robustness, high efficiency, small mass & size, easy cooling– Reliability data available (Telcordia) for many components– Reliable pump source at 97x ~ 980 nm for amplifier– New technologies become available
* Modulator, isolator, redundant LDs are not shown.
OpTIIX, GRACE-FO (1.54µm) NGO/SGO (1.06µm) MO+Preamplifier package
MO + Pre-amplifier Power amplifier
Master Oscillator
Pump LD(MM)
Gain fiber
Pump LD(SM)
Gain fiberWDM TFB~10mW ~100mW~2W
Goddard Space Flight Center 9th LISA Symposium, 23 May 2012Kenji Numata
2. Master Oscillator
o Looking into various possibilities– Non-planar ring oscillator (NPRO)
• Best high-freq. noise performance. Legacy device.
– Fiber laser• Ring design (GSFC), DBR design (NP photonics)• Large relaxation oscillation
– Planar-waveguide external cavity laser (PW-ECL)• Semiconductor laser• Simplest, smallest, and most cost-effective• Best noise performance at low frequency
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ise
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rtH
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Frequency [Hz]
Reference (master) laser
Stabilized Freerun
NGO requirement
K. Numata, 10.7452/lapl.201210034
DBR FL under thermal cycle test
Ring FL and its frequency noise performance NPRO and PW-ECL package comparison
Goddard Space Flight Center 9th LISA Symposium, 23 May 2012Kenji Numata
PW-ECL features & status
o Features– Semiconductor gain chip + Planar lightwave circuit (PLC)
• Design details open to NASA
– C-band (~1550nm), ~10mW output– Conversion to 1064nm underway
• Gain chip material change• Awarded SBIR contract to RIO for $750K (3/2012 ~ 9/2013)• NGO/SGO and other lidar applications
o Passed all space qualification tests– No performance degradation by
• Gamma, low/high energy proton, vacuum thermal cycling, pyro shock
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B]
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Dose [kRad]
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ower
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]
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Number of cycles
40C -10C
Example result of high energy proton irradiation Example result vacuum thermal cycling
PLC
Goddard Space Flight Center 9th LISA Symposium, 23 May 2012Kenji Numata
PW-ECL noise performance
o Relative intensity noise (RIN)– Smallest level among any lasers
• No relaxation oscillation peak around MHz range• Shot noise limited above ~100kHz
o Frequency noise– Phase lockable by injection current (100kHz UGF)– Frequency lockable to high finesse cavity and/or hyperfine molecular line
• NGO requirement level demonstrated by 13C2H2 molecule at 1542nm
• Cavity stabilization facility under construction at UT Brownsville (V. Quetschke)
– GSFC funded 1/f noise reduction activity
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Frequency [Hz]
Shot noise
PW-ECL
NPRO
DBR fiber laser
Littman ECL
DFB LD
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oise
[Hz/
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z]0.0001 0.001 0.01 0.1 1 10 100 1000
Frequency [Hz]
Freerun Simplified setup Full setup NGO requirement
C. Clivati10.1109/TUFFC.2011.2121
Freerun RIN of various lasers
Freerun freq. noise of various lasers PW-ECL cavity locking PW-ECL molecular line locking
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Frequency [Hz]
PW-ECL
NPRO
DFB LD
DBR fiber laser
Littman ECL
Goddard Space Flight Center 9th LISA Symposium, 23 May 2012Kenji Numata
3.Pre-amplifier
o Design– Single-clad Er- or Yb-doped fiber– Core pump by PM 97x-nm diode– Redundancy addition by polarization combiner
o Noise performance– No significant noise addition– Controllable after amplifier (demonstrated)
o Low risk component– Gamma radiation tests done on 1µm components– Simulation tools, many different vendors available
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ise
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Frequency [Hz]
PW-ECL + EDFA After preamp Before preamp
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Hz]
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Frequency [Hz]
PW-ECL + EDFA After preamp Before preamp
Frequency noise before/after pre-amplifier RIN before/after pre-amplifier
Goddard Space Flight Center 9th LISA Symposium, 23 May 2012Kenji Numata
Metrology interferometer for OpTIIX
o PW-ECL + preamp to be flown with OpTIIX – Optical Testbed and Integration on ISS eXperiment
• Technology demonstrator of ATLAST (~16m space telescope)
– Spaceflight of PW-ECL + acetylene cell• Planned launch: ~2015
– Metrology system: heterodyne interferometer (S. Rao)
– <1nm measurement error over hours• Requirement achieved by simplified saturation setup• No external modulator, single pass
Simplified C2H2 locking setup with PW-ECL
Laser truss system concept
Goddard Space Flight Center 9th LISA Symposium, 23 May 2012Kenji Numata
4.Power Amplifier
o Design– All fiber coupled (tapered fiber bundle)– Large mode area, double-clad Yb fiber– Forward pump to avoid risk and noise sources
• Catastrophic failure can occur with improper implementations
o Noise performance– No additional frequency noise– NGO requirement level
• Differential phase noise (@2GHz)• Stabilized low frequency RIN
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Frequency [Hz]
Differential phase noise (1.4W output, Liekki fiber) NGO requirement
MM Pump LD Yb LMA DC fiber
TFB>1.4W
Redundant LD
Isolator Input mon. Output mon.90/10
coupler99/1
coupler
From seed>40mW
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Frequency [Hz]
After amplifier (stabilized) After amplifier (free-run) NPRO (seed) only Shot noise
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After amplifier (stabilized) After amplfiier (freerun) Requirement (LISA)
Differential phase noise RIN and its stabilization (low/high frequency ends)
Goddard Space Flight Center 9th LISA Symposium, 23 May 2012Kenji Numata
Qualification tests on power amp.
o Packaging optimization for TFB– Screening by thermal imager– Proper packaging reduces temperature gradient
o Gamma irradiation on gain fiber– 200 Rads(Si)/min to a total dose of 60 kRads(Si)– Certain brand shows unrecoverable damage
• Probably due to dopants in the core
– Sensitive but no showstopper
o Vacuum thermal cycling– Marginal power/PER degradation at ~1.5W level
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0Tem
pera
ture
[C] /
PER
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Time [hours]
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er [W]
Temperature (left axis) PER (left axis) Power (right axis)
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tpu
t p
ow
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[W]
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Pump power [W]
Nufern fiber Before gamma irradiation After gamma irradiation
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Pump power [W]
Liekki fiber Before gamma irradiation After gamma irradiation
Vacuum thermal cycling test Gamma on two different Yb fibers
Goddard Space Flight Center 9th LISA Symposium, 23 May 2012Kenji Numata
Summary
o NASA/GSFC has been involved in space-borne laser since 90’s– Actively seeking innovative solutions to meet future science missions’ goals
• Fiber/waveguide technologies to space
– In-house capability to build & test space lasers– Common requirements for all laser instruments
• Lifetime, reliability, and efficiency
o GSFC invested ~$1.2 M over 3 years on LISA laser development– Amplifier development and noise measurements– PW-ECL noise and reliability studies
o Expected to finish qualification of LISA laser by the end of FY13
– System test with 1064nm PW-ECL + pre-amp. + power amp. to be done– 1542nm PW-ECL + Er pre-amplifier to be flown to ISS– No showstopper found