Yb:YAG Regenerative Amplifier for A1 Ground Laser Hut Rui Zhang ACCL Division V, RF-Gun Group Nov...

Yb:YAG Regenerative Amplifier for A1 Ground Laser Hut

Rui　 ZhangACCL Division V, RF-Gun Group

Nov 20, 2015

SuperKEKB Injector Laser RF Gun Review

Outline

Yb:YAG regenerative amplifier 2 of 11

• Back ground and introduction –Feasibility analysis and corporation–Current Yb laser system of A1 ground laser hut

• Yb:YAG regenerative amplifier–Cavity design –Experimental setup introduction

• Next step work–Ring cavity –Cryogenic experiment

• Summary

Feasibility analysis and corporation


• Feasibility analysis– In the picosecond or femtosecond domain, the regenerative amplifier is very powerful– Strong amplification factor can help relieve stress of multi-pass amplifier stages and

reduce thermal effect

• Corporation with HiLASE– Beamline B of HiLASE gets excellent laser amplification by use of Yb:YAG thin disk

regenerative amplifier1 – The parameters of HiLASE beamline B are very similar with our experiment

1. M. Chyla, et. al “Composite Yb:YAG/SiC-prism thin disk laser,” Optimization of beam quality and optical-to-optical efficiency of Yb:YAG thin-disk regenerative amplifier by pulsed pumping

Parameters of thin disk beamline B

MethodRegenerative amplifier with one thin

disk laser head

Seed repetition rate 50 MHz

Seed pulse width 500 ps

Seed output power 2 W @ 1030 nm

Pump power 1 kW @ 969 nm

Repetition rage of pump 1 kHz

Achieved energy 45 mJ

Next milestone energy 100 mJ

Under developmentAdd second thin disk laser head into

regenerative amplifier

Schematic of the current status of HiLASE beam line B

Menlo1030nm oscillator

Grating stretcher(Transmission)

SOApulse picker

Yb single mode fiber amp

Yb-doped double clad fiber amp

Repetition frequency114.24MHz

Wavelength selection1030nm & 1064nm

Repetition frequency 10MHz

Nd:YAG regenerative amplifier

EO modulepulse picker

Repetition frequency 10Hz

Yb:YAG Thin diskregenerative amplifier

1030nm oscillator(ANDi type)

1064nm oscillator(ANDi type)

Output@1030nmOutput@1064nm

ASE rejection grating pair

1030nm1064nm

1064nm

Fiber part

Current laser system of A1 ground laser hut


YAG crystal part

Yb:YAG regenerative amplifier: Cavity design


• Timing and cavity length

Seed laser repetition rate: 10 MHz 100 ns Pockels cell rise time: 10-15ns Length>3 m As to linear cavity: cavity length > 1.5 m Regenerative amplifier cavity length is 1.6 m

• Match of pump size and laser spot size

Pump size: 6 x 6 mm For getting higher gain, laser spot size should be bigger on the surface of Yb:YAG disk



Cavity design case I:

End mirror

DM

QWPPC PBS

Heatsink

Yb:YAG disk

f=300 f=1000

LD Stack

• Low threshold cavity oscillation and high output power

• Output laser beam pattern is excellent

• Bad tolerance for thermal lens effect

• Strange beam focus occurred and the dichroic mirror was damaged



Cavity design case II:

• Low threshold cavity oscillation and high output power

• Big output laser beam spot

• Very excellent tolerance for thermal lens effect

• Suitable to seed laser injection

Yb:YAG regenerative amplifier: Experimental setup


Yb:YAG disk soldering laser head• Old design

− Strong residual stress− Adhesion between soldering composite and heatsink decreased the heat removal

• New design

− Weak residual stress− More efficient thermal management can be realized− Suitable for Peltier cooler in vacuum chamber

Yb:YAG regenerative amplifier: Experimental setup


End mirror

DM

QWPPC PBS

Heatsink

Yb:YAG disk

PBS Faraday rotatorHWP Telescope

Seed from fiber part

Next step work


• Ring cavity (design is completed)– Long cavity length and laser beam size inside cavity– Cycle amplification and one-way transmission, lower ASE intensity

(IASE~1/L), excellent contrast ratio– Compare with linear cavity, more gain can be achieved under the same

saturation flux– Lower losses associate with thermally induced aberrations– More stored energy can be obtained because of absence of spacing hole

burning

• Cryogenic experiment– Peltier cooler can be adopted to current disk laser head– All the experiment equipment are available

Summary


• Different cavities (linear and ring) are designed and built for purchasing high gain and more stable operation in A1 ground laser hut

• High quality Yb:YAG disk laser head has been achieved

• Yb:YAG regenerative amplifier cavity is completed and amplification is going to be carried out

• Ring cavity regenerative amplifier and cryogenic experiment are carrying out at the same time

THANK YOU!

Yb:YAG Regenerative Amplifier for A1 Ground Laser Hut Rui Zhang ACCL Division V, RF-Gun Group Nov...

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