Stabilizing the Carrier-Envelope Phase of the Kansas Light Source
-
Upload
claire-pittman -
Category
Documents
-
view
43 -
download
1
description
Transcript of Stabilizing the Carrier-Envelope Phase of the Kansas Light Source
Stabilizing the Stabilizing the Carrier-Envelope Carrier-Envelope Phase of the Kansas Phase of the Kansas Light SourceLight Source Eric Moon
Zuoliang Duan11-9-2005
Outline Theoretical Description of the CE phase Why do we care about the CE phase? Can we control it? Yes! Here’s how it’s done
for the KLS and why it works. Single-Shot CE Phase Measurement Setup Results Future Plans
Why do we care about controlling the change of the carrier-envelope phase? Important for experiments utilizing few-cycle
laser pulses, e.g. High Harmonic Generation Can use a stabilized frequency comb to
perform spectroscopy. Related to this year’s Nobel prize! More applications to come!
Results from Others
• Fortier et al1, have reported phase coherence times of 326 s.
• Witte et al2, have observed coherence times of 500 s.
• Our group has observed coherence times of 85 s.
• The main goal is to achieve long term, on the order of hours, for running experiments.
[1] Fortier et al, IEEE Journal Topics Quantum Electron, Vol. 9, 1002-1010, 2003
[2] Witte et al, App. Physics B, 78, 5-12, 2004
Theory1
)(ˆ tE
)](exp[)(ˆ)( CEctitEtE
CE
c
For a single laser pulse:
Carrier-frequency
Carrier-envelope phase
Envelope-function
Mode-locked lasers emit a regular train of pulses.
[1] Fortier et al, IEEE J. Select. Topics Quantum Electron., vol. 9, pp.1002-1010,2003.
Theory1Time-Domain Description of the Mode-Locked Pulse Train
[1] Fortier et al, IEEE J. Select. Topics Quantum Electron., vol. 9, pp.1002-1010,2003.
Theory1
0L
Due to material dispersion inside the laser cavity, the CE phase changes.
The laser cavity length:
ddnLCE 02)
1()( 0
0
cn
vLnn
cL
ggCE
[1] Fortier et al, IEEE J. Select. Topics Quantum Electron., vol. 9, pp.1002-1010,2003.
Theory1
)])((exp[)(ˆ)( 0 cCEc ntintEtE
m
CEc mEiE )2()(ˆ)exp()( 0
Mode-Locked Pulse Train in the Time Domain:
Mode-Locked Pulse Train in the Frequency Domain:
0 CECE n
20CErepf
f
0fmff repm
[1] Fortier et al, IEEE J. Select. Topics Quantum Electron., vol. 9, pp.1002-1010,2003.
Frequency Comb and Laser Spectrum1
[1] Fortier et al, IEEE J. Select. Topics Quantum Electron., vol. 9, pp.1002-1010,2003.
TheoryThe regular spacing of the frequency comb allows access to the change of the carrier-envelope phase.
How?
Can use a self-referencing technique!
Theory1
The self-referencing technique requires an octave-spanning spectrum of the laser.
Beating the second harmonic and fundamental frequency combs of the laser yields a frequency proportional to the change of the carrier-envelope phase.
)2()(22 0020 fnffnffff reprepnn
20CErepf
f
[1] Fortier et al, IEEE J. Select. Topics Quantum Electron., vol. 9, pp.1002-1010,2003.
Theory
The CE phase change can be controlled by locking the offset frequency, f0, to a known frequency.
In the case of the KLS, f0 is set equal to one-quarter of the repetition rate of the oscillator.
420repCErep ff
f
2
CE
Experiment
The KLS utilizes a Kerr-Lens Mode locked Ti:Sapphire Oscillator emitting a ~77 million pulses per second.
The pulses are roughly 12 fs at the output of the laser and carry nJ energy per pulse.
The oscillator is the starting point for the self-referencing technique.
Why not use the amplifier output?
600 700 800 900 10000.0
0.2
0.4
0.6
0.8
1.0
FWHM=35.8 nm
10-10-05
KLS Amplifier Output
Nor
mal
ized
Inte
nsity
(arb
. uni
ts)
Wavelength (nm)
One reason: Spectrum too narrow!
Ti:S
Pump
M0
A1Lens
M1
M2
M3
M4M4E
M5
M6M7
M8
CPOC
M9
M10UltrashortPulseOutput
ECDC-Module
KLS Oscillator Cavity
500 600 700 800 900 1000 1100 12000.0
0.2
0.4
0.6
0.8
1.0
9-7-2005
Spectrum of Ti:Sapphire Oscillator Beam Measured at input to PCF
Norm
alize
d In
tens
ity (a
rb. u
nits)
Wavelength (nm)
From fs Laser
half wave plate 800nmλ/2
IR mirror
out-couplingobjectivef=8.55mm
in-couplingobjectivef=7.5mm
Silvermirror
dichroic beam splitter HR 532nm,HT1064nm
HR532nm mirror
HR532nm mirror
HR1064nm mirror
λ/2half wave plate
532nm
λ/2 half wave plate 1064nm
filter RG715
focusing Lensf=30mm
collimating Lensf=30mm
BBO crystal
HR532nm mirror
polarizingbeam-splitter532nm
polarizingbeam-splitter532nm
λ/2half wave plate
532nm
grating900lines/mm
focusing Lensf=30mm
offset frequencyphotodiode
APD
Stabilization Experimental Setup
PCF
Chirped mirror
Chirped mirror
500 600 700 800 900 1000 1100 12000.0
0.2
0.4
0.6
0.8
1.0
9-7-2005
PCF Output Spectrum yielding Phase Lock2nd Order Spectrometer Diffractions Included
Norm
alize
d In
tens
ity (a
rb. u
nits)
Wavelength (nm)
1064 nm
532 nm
500 600 700 800 900 1000 1100 12000.0
0.2
0.4
0.6
0.8
1.0
9-7-2005
Infrared Spectrum of PCF Output yielding Phase Lock
Norm
alize
d In
tens
ity (a
rb. u
nits)
Wavelenth (nm)
~1064 nm, Doubled in BBO Crystal
Offset Frequency while Phase Locked
Observation of Beat Note and Frequency Comb
f0=19.375MHz frep-f0
CE Phase Stability After Pulse Amplification2
A second f-2f interferometer after the KLS amplifier provides a means for quantifying the CE phase stabilization stability.
10% of the KLS amplifier output is sent to the experimental setup.
White-light is generated in a sapphire plate and a BBO crystal provides second-harmonic generation.
[2] Baltuska et al.,IEEE J. Select. Topics Quantum Electron., vol. 9, pp. 972-989, 2003.
Theory2
Interference between the white light and second harmonic pulses:
))()(cos(*)()()1(2)()()1()( 0 wwwwIwIaawaIwIawS WLSHGSHGWLSHGWL
0)()( www WLSHGPhase of the Interference Signal:
The shot-to-shot change of this phase can be monitored by the second f-2f setup.
[2] Baltuska et al.,IEEE J. Select. Topics Quantum Electron., vol. 9, pp. 972-989, 2003.
Experiment
M2
BS50:50
Ti:S
Pump
M0
A1Lens
M1
M3
M4M4E
M5
M6M7
M8
CPOC
AO modulator
spectralbroadening
nonlinearinterferometer
lockingelectronics
HR IR mirror
HR
IR m
irror
HR IR mirror
BS 9:1stretcheramplifiercompressor
1kHz fs laser
Single-shot phase measurement
f-2f Interferometer after KLS Amplifier
half wave plate
VNA
silver mirrorf=70mm
half wave plate
sapphire d=2.3mm
BBO
f=75mm
spectrometer
1kHz fs laser
SHG
two silver mirrors
concave silver Mirrors: f=100mm
silver mirrorsFCWL: fundamental Continuum white light
FCWL
FCWL
SHG
polarizer
532nm HR mirror532nm HR mirror
VNA
∆T=0.265ps
Spectrum of the Second Harmonic generated in the BBO Crystal
Single-Shot: Not Locked
Line-Out of the Interference Pattern
1 pulse
Phase-Locked
Not Phase-Locked
Phase-Locked
Not Phase-Locked
51 pulses
Phase-Locked
Not Phase-Locked
101 pulses
Phase-Locked
Not Phase-Locked
200 pulses
1000 pulsesPhase-Locked
10000 pulsesphase-locked
103000 pulsesPhase-locked
Summary
The change of the carrier-envelope phase of the KLS has been stabilized.
A technique for observing the carrier-envelope phase change shot-to-shot has been utilized.
CE phase coherence times of up to 85 seconds have been observed.
Future
Send a slow CE phase drift signal from the second f-2f interferometer back to the locking electronics to achieve longer locking times.
Thanks!
Dr. Zenghu Chang Al Rankin KLS Members: Mahendra Shakya, Shambhu
Ghimire, Chris Nakamura, Chengquan Li, and Steve Gilbertson
Zuoliang Duan for being a great partner on this project.
Dr. Corwin and Dr. Washburn