Installation, Commissioning and Operation of the Master Laser Oscillator at FLASH

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Patrick Geßler DESY

II Timing & Synchronization Workshop, ICTP, Trieste 09.03.2009

and Operation of the Master

Laser Oscillator at FLASH

V. Arsov, B. Bayer, M. K. Bock, M. Felber, K. Hacker, F. Loehl, B. Lorbeer,

F. Ludwig,

K-H. Matthiesen, H. Schlarb, B. Schmidt, A. Winter, J. Zemella

(Deutsches Elektronen-Synchrotron)

S. Schulz, L. Wissmann

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2 Agenda



_{Overview of the Synchronization System at FLASH}



_{Requirements for the Master Laser Oscillator (MLO)}



_{3 Generations of MLOs}



_{RF Lock to Master Oscillator}



_Measurements



_Pitfalls

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3 Overview of the Synchronization System

Narrow

Band.

Direct/

Interferometer

EOMs/

Seeding

End-station

Laser

MLO

MO-RF

Laser pulse

Arrival beam/laser

DWC/Kly

A &

φ

cavity

Desired point-to-point stability ~ 10 fs

<5fs

Direct

Distribution

LO-RF

Optical link

<5fs

Optical link

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4 Overview of the Synchronization System

MLO2

MLO1

Fiber link

stabilization

units

(max 14)

Free space opt.

distribution

-Switching unit

-Invar base plate

-Vibration isolated

-16 outputs

Distr. With EDFA

for each link

-Special passive

thermal stabilization

-One output for

MLO lock based

on Sagnac loop

at 1.3GHz

Final implementation design

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5 BC3

SASE-Undulators

BC2

RF gun

ACC 23

Diag.

ACC 456

ACC 1

CDR

LOLA

THz

Laser

ISR

TEO

MO

• Backbone: beam based stabilization of arrival time

• Conjunction with high precision synchronization of lasers

• Synchronization of all timing critical devices ( ~ 14 incl. FLASHII)

• Point-to-point synchronization ~ 10 fs rms (e- < 30 fs rms)

• Permanent operation and long term stability /availability investigation

Laser building

EO, HHG

and ORS

BPM

BAM

L2L

BAM

BPM

_BAM

PP-laser

MLO

BAM

L2RF

DWC

L2L

Seed

Beam arrival monitor

Laser to laser synchronization

Direct laser seeding

High precision down converter

Laser to RF conversion

ORS

Overview of the Synchronization System

ISR

L2L

L2RF

DWC

L2L

BAM

L2RF

DWC

Seed

Experiment

sFLASH

Opt-Cross..

12 FLASH

2 FLASH II

D

is

tr

ib

ut

io

n

HHG

Photo-cathode

Laser

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6 Requirements for the Master Laser Oscillator



_{Mode-Locked Erbium Doped Fiber Laser}



_{Pulse Duration <100fs (FWHM)}



_{Repetition Rate 216.66MHz}



_{Output Power >120mW}



_{Integrated Timing Jitter <10fs [10Hz – 40MHz]}



_{Amplitude Noise <2 x 10}

-4

_{[10Hz – 1MHz]}

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7 1st Generation MLO (Breadboard Version)

Original design:

J. Chen et. al., Opt. Lett.

32 ,

1566-1568 (2007)

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8 2nd Generation MLO

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9 2nd Generation MLO



_{Temp. Stabilization}



Controller included



Variable Set point



_{Stable Ground Plate}



_{Distribution included}



_{RF Electronic included}



_{Motorized Wave Plates}

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10 3nd Generation MLO

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11 3rd Generation MLO



_Compact



_{Modular Parts}



_{Lower Costs}



_{Online Spectrometer}

A. Winter

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12 MLO Included Features Overview



Modular Parts



Electrical Monitor Output



Optical Monitor Output



Motorized Translation Stage



RF Lock Electronic



Online Spectrometer



Motorized Wave Plates



Temperature Stabilization



Piezo

3rd Generation

2nd Generation

1st Generation

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13 RF Lock to Master Oscillator

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14 Measurements – Noise and Jitter

Integrated timing jitter:

< 6 fs

[10kHz – 40 MHz]

relative intensity noise:

0.016 % [10 Hz – 1MHz]

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15 Measurements – Spectrum and Pulse Shape (I)



_{For different Pump Laser Power Level}



_{Wave Plates optimized for maximum Output Power}



_{Similar Spectra / Shapes are Achievable}

F. Löhl

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16 Measurements – Spectrum and Shape (II)



_{For different Wave Plate Settings}



_{Constant Pump Laser Power of around 890mW}

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17 Measurements – Autocorrelation



_{Different Wave Plate Settings}



_{Constant Pump Laser Power}



_{Pulse Width: 60 – 90 fs [FWHM]}

(depending on Configuration)



_{Different Output Power}

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18 Measurements – Amplitude Stabilization

Without Feedback

With Feedback

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19 Pitfalls



_{Piezo bends due to weight / torque}

_

_Alignment



_{Make every Parts removable from the top}



_{Have enough degrees of Freedom}



_{Make the Ground Plate thick / stable enough}



_{A Modular Design could cause alignment problems}

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20 Conclusion



_{The MLO has a strong influence on the complete system}



_{Wave plate and pump power settings influence the optical}

spectrum



_{A high precision diagnostic is needed to investigate the}

impacts



_{In contrast to stretched pulse lasers, to achieve}

mode-locking wave plate settings have to be changed



_{Different wave plate settings for minimum phase noise and}

maximum output power



_{Questionable whether two identical MLOs could be set up}

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