1 GHz Erbium-doped fiber laser and home-made EDFAL Amp g z dz I I L g L 0 ( , ) (0 ) ( ) (O, ) 10 log O O O 980nm Input signal EDF WDM_out 1550 Output signal 980 980 1550 WDM_in Source:

KIT – University of the State of Baden-Wuerttemberg and

National Research Center of the Helmholtz Association www.ipq.kit.edu

Fanny Yang

1 GHz Erbium-doped fiber laser and home-made EDFA

Institute of Photonics and Quantum Electronics (IPQ), KIT (Karlsruhe), Germany

Optics and Quantum Electronics Group, MIT (Cambridge), USA

2 15.12.2012 Karlsruhe Institute of Technology (KIT)

Introduction – Ultrafast Optics

UFO Broad spectrum OCT

Source: RWTH Aachen

High peak power Material processing Surgery

Source: Direct Industry

Frequency combs Frequency metrology

Source: RP Photonics

High repetition rate High-precision spectroscopy Time keeping Optical communication

Source: www.c4scientific.com


Outline

Ultrafast Pulses

Theory Modelocking techniques Historical development

1 GHz Fiber Laser

Design Measured characteristics

Erbium-doped fiber amplifier (EDFA)

Parameter optimization Observations



Ultrafast Pulses – Theory

Stark levels

980 nm 1530 nm

W1

W2

W3

f1 f2



Source: Fibercore



Source: E. Desurvire, Erbium-doped fiber amplifiers

Lower population

inversion


Ultrafast Pulses – Mode-locking



NOLM: Nonlinear Optical Loop Mirror P-APM: Polarization Additive Pulse Modelocking KLM: Kerr Lens Modelocking

Passive Modelocking

Active Modelocking

Real Saturable Absorber

SBR/SESAM

CNT

Artificial Saturable Absorber

NOLM

P-APM

KLM

SBR: Saturable Bragg Reflector SESAM: Semiconductor Saturable Absorber Mirror CNT: Carbon Nanotubes



1

3

2


Ultrafast Pulses – History

Source: U.Keller in Nature, 2003

KLM: Kerr lens modelocking ML: Mode-locked CEO: Carrier envelope offset


1 GHz Fiber Laser – Design goals

Compact and cheap Fiber laser

Center Wavelength at 1550 nm Erbium doped fiber

Mode-locking

Short time duration High repetition rate Self-starting Long-term stability

SBR


1 GHz Fiber Laser – Design

Gain medium

Tra

nsm

issiv

e M

irro

r

Pumping

Output

Laser beam

OC 10%

Ferrule FC/PC connector

Adaptor

EDF + SMF

(93mm + 7mm)

WDM

980nm SBR with

pump-reflective

coating

Lossy

medium



OC 10%


Adaptor

EDF + SMF

(93mm + 7mm)

WDM

980nm SBR with

pump-reflective

coating

*Source: M. Sander, CLEO 2010 CTull1

*



OC 10%


Adaptor

EDF + SMF

(93mm + 7mm)

WDM

980nm SBR with

pump-reflective

coating

prevent

thermal

damage

*Source: M. Sander, CLEO 2010 CTull1

*


1 GHz Fiber Laser – Measurement

PD ESA COL

OSA

PM

WDM

10%

90%

EDF + SMF

(93mm + 7mm)

980nm

50%

50%

50/50

90/10

WDM loss: 1.8 dB OC loss: 10.7 dB

Coupler loss: 3 dB

Coupler loss: 0.88 dB

P intracavity

P out

P measured

PD: Photo detector

ESA: RF spectrum analyzer

OSA: Optical spectrum analyzer

PM: Power meter

Polarization beam splitter





1st state:

Pin = 526 mW

Pout = 14 mW

Dl = 8 nm / tFWHM = 315 fs

@ 1557 nm

2nd state:

Pin = 513 mW

Pout = 26 mW

Dl = 17 nm / tFWHM = 156 fs

@ 1571 nm


1 GHz Fiber Laser – Overnight test


EDFA - Principle

L

Amp dzzgI

LILg

0

),()0(

)(log10),( ll

l

l

980nm

Input signal

EDF WDM_out

1550

Output signal

980 980

1550

WDM_in



EDFA - Principle

L = 44 m; Ipump = 0-1100 mA


EDFA - Parameter space

Gain

SNR

Fiber type Fiber length Pump power Seed wavelength Seed power

f

a b c d e


EDFA - Measurement

TLS

PM2

WDM_out OSA

PM3

PM 1

EDF WDM_in

90/10

90/10

980nm

P seed P out

for fibertype = Liekki Er110 or Fibercore M-12 for LEDF = LEDF - DL for lseed = 1475 - 1600 nm, Dl = 5 nm for Ipump = 0 - 1150 mA, DI = 50 mA Take OSA spectrum Record powers end end end end

Fiber type Fiber length Pump power Seed wavelength Seed power

P pump


Optimal for

lseed = 1560 nm:

EDFA – Results

M-12

Length = 16.2 m

Gain = 26 dB

SNR = 32 dB

Er110

Length = 85 cm

Gain = 21 dB

SNR = 37 dB

Input

Ppump = 513 mW, Pseed = 0.1 mW

M12 M12

Er110 Er110


EDFA – M12 – Gain (length)

Observation: Gain maximum shifts to longer lengths! Explanation: Population inversion for zero-crossing curve is different is lower ( gain fiber longer) for longer wavelength


z1 z2 <


EDFA – M12 – SNR (length)

Observation: Gain drops but SNR rises for lseed>1560 nm

SNR Gain



Observation: Gain drops but SNR rises for lseed>1560 nm

SNR Gain



Observation: Gain drops but SNR rises for lseed>1560 nm Explanation: ASE at 1530-1560 nm absorbs more than at 1560 nm Observation: But it drops again!

SNR Gain



Observation: Gain drops but SNR rises for lseed>1560 nm Explanation: ASE at 1530-1560 nm more absorbed than 1560 nm Observation: But it drops again!

SNR Gain



Observation: Gain drops but SNR rises for lseed>1560 nm Explanation: ASE at 1530-1560 nm more absorbed than 1560 nm Observation: But it drops again! Explanation: You need high absorption which increases with length. For some the threshold might never be reached so continue to rise

SNR Gain


Conclusion

1 GHz Fiber laser tFWHM = 156 fs Pout = 26 mW Self-starting Heat problems solved

Amplifier at 1560 nm

Gain = 26 dB SNR = 32 dB

ASE source

Pout = 6 mW Bandwidth = 11 nm Center wavelength = 1558 nm

Picture taken by: Frederike Ahr

…

Documents

1 GHz Erbium-doped fiber laser and home-made EDFAL Amp g z dz I I L g L 0 ( , ) (0 ) ( ) (O, ) 10 log O O O 980nm Input signal EDF WDM_out 1550 Output signal 980 980 1550 WDM_in Source: