goddard space flight center 9 th lisa symposium, 23 may 2012 kenji numata laser development for...

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


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


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


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


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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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


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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Example result of high energy proton irradiation Example result vacuum thermal cycling

PLC


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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PW-ECL

NPRO

DBR fiber laser

Littman ECL

DFB LD

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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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PW-ECL

NPRO

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DBR fiber laser

Littman ECL


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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PW-ECL + EDFA After preamp Before preamp

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PW-ECL + EDFA After preamp Before preamp

Frequency noise before/after pre-amplifier RIN before/after pre-amplifier


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


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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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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After amplifier (stabilized) After amplfiier (freerun) Requirement (LISA)

Differential phase noise RIN and its stabilization (low/high frequency ends)


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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Nufern fiber Before gamma irradiation After gamma irradiation

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Liekki fiber Before gamma irradiation After gamma irradiation

Vacuum thermal cycling test Gamma on two different Yb fibers


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

goddard space flight center 9 th lisa symposium, 23 may 2012 kenji numata laser development for...

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