1. Yb Fiber Laser System
Xiangyu Zhou
19. Feb. 2015

2. Properties of laser medium
Ti-doped
Nd-doped
Yb-doped
Type
Solid
Fiber&Solid
Energy-extraction Efficiency
0.5% 3%
Pump
Laser LD
Gain Spectrum
Broadband
Narrowband
Cost
High
Low
Maintenance
Often
Less
Best for RF-Gun
mJ, UV, ~40 ps, broadband laser source

3. Fiber Advantage High repetition rate High amplify efficiency
Simple configuration
Good stability
Low-cost
Outer Clad
Inner Clad
Core
Signal
Disadvantage
Pulse energy
Pump light
Yb-doped fiber
Higher amplify efficiency
Multimode pump core
Broadband gain spectrum
Pump 940nm, 976nm

4. Yb Fiber Oscillator 60 cm 30 cm Aluminium breadboardLD
Pump
WDM
coupler
Isolator
Yb-doped fiber
SMF
Collimator
Polarizing
l/4
Output
l/2
250mW
976 nm
40cm
600-grooves/mm
Grating pair
30 cm
Aluminium breadboard
A unidirectional ring cavity is employed in the passive mode- locked oscillator.
A PZT attached to the end mirror is used to control the cavity length to lock the 51.9 MHz (10.38*5 MHz) from KEKB with 2856 MHz, produce extremely low jitter of ~ps.

5. Measurement by streak camera
The pulse energy is 0.8 nJ.
The pulse energy is 0.2 nJ.

6. Improvement of OscillatorLD
Pump
WDM
coupler
Isolator
Yb-doped fiber
SMF
Collimator
Polarizing
l/4
Output
l/2
250mW
976 nm
1000-grooves/mm
Grating pair
PEZ
P.D.
Super-invar breadboard provides near zero coefficient of thermal expansion (Thermal stability)
Transmission gratings (Mode-lock stability)
Piezo mirror on lead block at an extra cavity (Reduce vibration)

7. Selection of Oscillator
λ/2
λ/2
E.O.
λ/2
λ/2
Gain area of Yb:YAG
Fiber Amplifier
Oscillator1: Narrow (Less ASE)
Oscillator2: Broadband (Stable)

8. Pre-amplifier after Oscillator 2
Gain area of Yb:YAG
Grating pair
Spatially dispersed
Yb-doped Fiber
4μm
WDM
coupler LD
Pump

9. Produce from Menlosystems
ORANGE-Comb-250 nm
> 10mW
1-4ps
114.24MHz&2,856MHz SYNCRONIZATION

10. Yb-doped Double cladding Fiber
Fiber Amplification
Low power amplifier
High power amplifier
Isolator
Yb-doped Double cladding Fiber PM LD
Pump
Collimator
Dichroic mirror nm nm
Ɵ=20°
Collimator
Yb-doped Fiber
4μm
75 W
WDM
coupler
750 mW LD
Pump
Low loss
Compact
High amplify efficiency

11. Fiber Type LIEKKI Yb1200-20/400 DC Yb1200-25/250 DC-PM CRYSTAL FIBRE
DC-200/40-PZ-Yb-03
Feature
Double clad
Polarization Maintain
PCF
Core diameter
20±2 mm
25±2 mm
40±2 mm
Cladding diameter
400±15 mm
250±15 mm
200±5 mm
Peak cladding absorption at 976nm
3.0 dB/m
10.8 dB/m
10 dB/m
Cost
￥32,000 /m
￥90,000 /m 
￥300, ,000
Gain area of Yb:YAG

12. The price of PCF

13. Consumable Accessories
700 nm Butterfly LD
￥160,000 ~￥200,000
CRYSTAL FIBRE
DC-200/40
Lapping Machine

14. Amplified spontaneous emission (ASE) Problem
ASE is produced when the lasing threshold is reached.
Signal: Weak
Pump: Strong
ASE Generated

15. Layout for 25 Hz

16. Pulse picker & Stretcher
4μm
l/2
Stretcher
WDM
coupler LD
Pump
SMF
NIR-MX-LN-10
51.98 MHz
10.38 MHz
1740 gooves/mm
Transmission grating

17. Stretcher and Yb Fiber AmplifierLD LD
40 μm Photonic crystal fiber
40 μm Photonic crystal fiber
976 nm
940 nm I
l/2 II
l/4
l/2
E.O.
l/2
III I II
III

18. A1 Electron gun room
Entrance
Laser room
Elevator
Entrance

19. Thin-disk Multi-pass Amplifier
RF GUN
Laser Room
Entrance
Tunnel
Fiber Oscillator 2
Fiber Oscillator 1
Synchronization
Table 1
Pre-Amp & Stretcher
Main-Amp
Main-Amp
Pulse picker
Table 2
Thin-disk Multi-pass Amplifier
SHG B1
Entrance

20. Problem Oscillator Fiber Amp Stability (< ps level)
ASE ( nm)
Amplification Efficiency (thermal control of LD)
Higher Output Energy

21. Conclusion Yb-doped fiber pre amplifier Yb-doped fiber pre amplifiernm
Yb-doped fiber pre amplifier
Yb-doped fiber oscillator with Transmission grating
Yb-doped fiber pre amplifier
Transmission grating pair stretcher
51.9 MHz
2, 5, 25, 50 Hz
Single or Double bunch nm
Synchronization system
Yb-doped fiber main amplifier
Yb-doped fiber main amplifier
Pulse picker
2856 MHz trigger
From Accelerator
Yb:YAG thin-disk regenerative amplifier
Yb:YAG thin-disk multipass amplifier
RF GUN
Spectral Range Adjustment
SHG
SHG