TOPTICA S ROBUST SODIUM GUIDE STAR LASER

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Doris Greene
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TOPTICA S ROBUST SODIUM GUIDE STAR LASER Martin Enderlein 1, Axel Friedenauer 1, Robin Schwerdt 1, Paul Rehme 1, Daoping Wei 2, Vladimir Karpov 2, Bernhard Ernstberger 1, Patrick Leisching 1, Wallace

1 TOPTICA S ROBUST SODIUM GUIDE STAR LASER Martin Enderlein 1, Axel Friedenauer 1, Robin Schwerdt 1, Paul Rehme 1, Daoping Wei 2, Vladimir Karpov 2, Bernhard Ernstberger 1, Patrick Leisching 1, Wallace R. L. Clements 2, Thomas Niederreiter 1, Wilhelm G. Kaenders 1 1 TOPTICA Photonics AG, Lochhamer Schlag 19, D Gräfelfing, Germany 2 MPB Communications Inc., 147 Hymus Boulevard, Montreal, Quebec H9R 1E9, Canada Installation and system verification at ESO VLT in April 2015

TOPTICA: Key Figures Key Figures Employees:

Diode Laser Systems 191 2880 nm Ultrafast

2 TOPTICA: Key Figures Key Figures Employees: 200 Sales: 50 Mio USD Founded: 1998 (1995) Locations: Gräfelfing (Munich), Berlin Victor (NY/USA) San Jose (CA/USA) Technology Diode Laser Systems nm Ultrafast Fiber Lasers nm Terahertz Generation 0 10 THz

3 TOPTICA Latest Product Releases TeraFlash (THz) FemtoFiber smart Series FemtoFiber dichro Optical Frequency Combs Diode HeNe Replacement ichrome MLE TopMode pro Lasers & Digital Controller 589 nm (2 W) / 193 nm (400 µw) CTL widely tunable Guide Star Laser

4 Outline Introduction Laser Concept and Realization Laser Units Production and Testing Summary

5 Adaptive Optics Technology Courtesy: Claire Max

6 And it works!

7 Sodium Laser Guide Star Technology Enhanced return flux by resonance fluorescence

8 Relevance for Space Debris No natural guide star available/needed Higher resolution for laser tracking Higher photon density on target Smaller ground stations and reduced laser power of LIDAR or de-orbiting laser [1] Bennet et al., Adaptive Optics for Space Debris Tracking, SPIE 2014

Technical Challenge Engineering a laser system meeting the following requirements: Output

(subtract Rayleigh) D 2 b repumping sideband Operational environment: -10 to +20 C High

9 Technical Challenge Engineering a laser system meeting the following requirements: Output power > 20 W Narrow linewidth Precise wavelength stabilization Fast tuning / toggling (subtract Rayleigh) D 2 b repumping sideband Operational environment: -10 to +20 C High ozone concentration Gravity-invariant operation Earth-quake resistant Surface temperature within 1.5 K from ambient Small footprint (cooling, power, space) Reliable operation at high altitude (Cerro Paranal 2635 m, Mauna Kea 4200m) Restricted access for service Modularity

10 Outline Introduction Laser Concept and Realization Laser Units Production and Testing Summary

Laser Concept Seed diode laser @ 1178 nm ~1 MHz linewidth Sideband generation for D 2 b repumping [1]

$suppressed SBS 36 W @ 1178 nm Efficient SHG 22 W @ 589 nm ~5 MHz linewidth Diffraction-limited output$ stabilized HeNe reference laser All-fiber design Polarization-maintaining 100 W @ 1120 nm [1] R.

stabilized HeNe reference laser All-fiber design Polarization-maintaining 100 W @ 1120 nm [1] R.

11 Laser Concept Seed diode 1178 nm ~1 MHz linewidth Sideband generation for D 2 b repumping [1] via current modulation Tunability Raman fiber amplification (RFA) Linewidth-conserving Efficiently suppressed SBS nm Efficient SHG nm ~5 MHz linewidth Diffraction-limited output Doubly resonant cavity Solid state wavelength meter 10 MHz resolution Absolute calibration with stabilized HeNe reference laser All-fiber design Polarization-maintaining nm [1] R. Holzlöhner et al., Optimization of cw sodium laser guide star efficiency, Astron. & Astrophys. 510, A20 (2010).

12 System Integration Centerpiece integration possible Gravity-invariant operation No heat source: Surface temperature within 1.5 K from ambient Vibration-free liquid cooling: 5 l/min Suitable for mountain facilities Earthquake proof Suitable materials (ozone-resistant) Easy maintenance & safety Line-replaceable units (LRUs) PLC-based safety concept Additional flexibility for telescope integration Electronics Cabinet: main heat sources, < 600 W Laser head: < 100 W with integrated control electronics

13 SodiumStar Electronics Cabinet Proven gravity-invariant operation Dissipated heat < 700 W (entirely removed by 5 l/min liquid cooling) Line-replaceable Units (LRU) Earthquake proof cabinet Surface temperature within 1.5 K from ambient External connections on the bottom Connections to Laser Head on the top Size: 900 x 900 x 1730 mm 3 Weight: 600 kg

SodiumStar Laser Head Compact Laser Head Gravity-invariant operation Dissipated heat < 100 W (entirely removed by liquid cooling) Line-replaceable Unit Integration into Launch

14 SodiumStar Laser Head Compact Laser Head Gravity-invariant operation Dissipated heat < 100 W (entirely removed by liquid cooling) Line-replaceable Unit Integration into Launch Telescope maybe even behind M2? Surface temperature within 1.5 K from ambient Size: 700 x 500 x 285 mm 3 Weight: 70 kg With thermal insulation cover Size: 900 x 700 x 400 mm 3 Weight: 90 kg

15 Telescope Laser Heads integrated into Launch Telescope Systems Cabinets attached to the sides of center-piece The Heat Exchanger is mounted on the 4LGSF platform below Nasmyth

16 Telescope Remote pumping option allows spatial separation between Cabinet and Laser Head maximum interconnection cable length 27 m

Maintenance and Service Concept Mean time between failure > 1 year System Software fully automated control 100 parameter supervision for cause identification

17 Maintenance and Service Concept Mean time between failure > 1 year System Software fully automated control 100 parameter supervision for cause identification well below LRU level Service Software remote maintenance self-repair (health checks) intuitive GUI Last resort: LRU exchange < 4 hours Long-term Support Contract

18 Service Software Intuitive system overview and manual control Automated health check routines for in-depth system analysis and self-repair of wear/degradation effects Graphical tools, scope

19 Outline Introduction Laser Concept and Realization Laser Units Production and Testing Summary

20 Laser Output Wavefront measurement: Wavefront error 16 nm rms (measured over 2 times the beam diameter) ESO spec: < 70 nm rms, goal < 25 nm rms Emission linewidth: measured 4.4 MHz ESO spec: < 250 MHz, goal 5 MHz

21 Output Power Long-term output power mean value W ± 0.04 W (rms) or 2% peak-to-peak ESO spec: < 15% p-p Short-term output power mean value 22.0 W ± W or 0.05% rms ESO spec: < 6%, goal: < 3% rms Proprietary and Confidential Information 21

22 Emission Wavelength Emission wavelength: Peak-to-peak variation 42.8 MHz ESO Spec: ± 40 MHz Proprietary and Confidential Information 22

23 Optical Spectrum Optical sidebands at a frequency of GHz: to repump the electronic population from the other hyperfine ground state simultaneously generated in the doublyresonant cavity (patented design) direct current modulation technique allows generation of sidebands without any deteriorating effect on beam quality On-the-fly adjustable from 0 10 % Proprietary and Confidential Information 23

24 Environmental Testing Operation under varying gravity vector Shock tests Climate chamber tests 24

25 Specs

26 Consistency & Reproducibility Accumulated running hours during testing: more than hours at operational power level Test Beam quality Unit ESO Spec. PPU LU1 LU2 LU3 LU4 wavefront error ( rms ) [nm] < Polarization PER [db] > 20 > 24 > 24 > 23 > 22 > 24 Laser linewidth (measured with 1-GHz FPI) Power Consumption (@ BOL) FWHM [MHz] < 250 < 4.5 < 4 < 6 < 5 < 8 overall efficiency [%]

27 Live Presentation at SPIE AI in Montreal 2014

28 Summary First turn-key sodium guide star laser commercially available! Laser concept: efficient, stable, excellent beam quality System integration: robust, flexible, low footprint, easy to maintain Power scalability to 50W and µs pulsed format have been demonstrated Hoping for European initiative for optical satellite and space debris tracking infrastructure ground-based laser de-orbiting demonstrator (deep) space optical communications

SodiumStar 20/2 High Power cw Tunable Guide Star Laser

SodiumStar 20/2 High Power cw Tunable Guide Star Laser Laser Guide Star Adaptive Optics Facilities LIDAR Atmospheric Monitoring Laser Cooling SodiumStar 20/2 High Power cw Tunable Guide Star Laser Existing