ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
Vertical integration of ultrafast semiconductor lasers for wafer-scale mass production
Prof. Ursula Keller (PI) Physics Department, ETH Zurich
Prof. Eli Kapon, Dr. Alexei Sirbu Institut de Photonique et d‘Electronique Quantiques, EPFL, Lausanne
Prof. Thomas Südmeyer Institut de Physique, Université de Neuchâtel
Prof. Bernd Witzigmann Computational Electronics and Photonics, University of Kassel (previously ETH Zurich)
nano-tera.ch
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
Ultrafast lasers
… generate coherent light pulses with pico- or femtosecond duration
observe and use fast dynamics • understand chemical reaction dynamics • fast communication • …
interconnects optical clocking
access ultrashort time scales
1
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
Ultrafast lasers
… generate coherent light pulses with pico- or femtosecond duration
observe and use fast dynamics • understand chemical reaction dynamics • fast communication • …
concentrate in time and space achieve extremely high intensities • material processing • multi-photon biomedical imaging • …
access ultrashort time scales
R. Aviles-Espinosa, G. Filippidis, C. Hamilton, G. Malcolm, K. J. Weingarten, T. Südmeyer, Y. Barbarin, U. Keller, S. I. C. O Santos, D. Artigas and P. Loza-Alvarez, “Compact ultrafast semiconductor disk laser: targeting GFP based nonlinear applications in living organisms”, Biomedical Optics Express, vol. 2, No. 4, pp. 739-747, 2011
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
Ultrafast lasers
… generate coherent light pulses with pico- or femtosecond duration
observe and use fast dynamics • understand chemical reaction dynamics • fast communication • …
achieve extremely high intensities • material processing • multi-photon biomedical imaging • …
broad optical spectrum generate ultrastable frequency combs • high precision spectroscopy • optical clocks • …
concentrate in time and space
access ultrashort time scales
1
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
Ultrafast semiconductor lasers
1
• Currently, typical ultrafast lasers are bulky and complex
• Our approach: semiconductor laser with vertical integration
Modelocked Integrated External-Cavity Surface Emitting Laser
MIXSEL VECSEL Vertical External Cavity Surface Emitting Laser
Semiconductor Saturable Absorber Mirror
SESAM
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
Outline
Motivation and research targets
Introduction to VECSELs, SESAMs, and MIXSELs
Research targets
Highlights
- CW & modelocked VECSELs with wafer fusion (granted patent)
- 1-W femtosecond OP-VECSEL
- First QW-absorber based MIXSEL
- First modelocked VECSEL with multi-pass (new patent application)
- Generation of ultra-low-noise microwave for precision metrology
Summary and outlook
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
OP-VECSEL = Optically Pumped Vertical-External-Cavity Surface-Emitting Semiconductor Laser
M. Kuznetsov et al., IEEE Photon. Technol. Lett. 9, 1063 (1997)
Maybe a bad idea coming from semiconductor diode lasers?
But for sure a good idea coming from diode-pumped solid-state lasers:
• more flexibility in operation wavelengths
• broad tunability
• efficient mode conversion from low-beam-quality high-power diode lasers
• modelocking possible with SESAMs
• waferscale integration: cheaper ultrafast lasers in the GHz pulse repetition rate regime
pump
laser
heat sink
gain structure
output coupler
CW optically-pumped VECSELs
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
Bandgap engineering
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
SESAM for pulse formation
pump
laser
heat sink
gain structure
output coupler
cw-laser modelocked laser
pump
laser
gain structure
SESAM
heat sink
output coupler
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
MIXSEL
MIXSEL Modelocked Integrated External-Cavity Surface Emitting Laser
VECSEL Vertical External Cavity Surface Emitting Laser
SESAM Semiconductor Saturable Absorber Mirror
abso
rber
in
tegr
atio
n
A. R. Bellancourt et al., “Modelocked integrated external-cavity surface emitting laser” IET Optoelectronics, vol. 3, Iss. 2, pp. 61-72, 2009 (invited paper)
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
OP-VECSEL: potential for cost-efficient mass-production
Green laser: optically-pumped VECSEL (OSRAM)
Ulrich Steegmueller et al., “Progress in ultra-compact green frequency doubled optically pumped surface emitting lasers”, High-Power Diode Laser Technology and Applications VII, Proc. of SPIE Vol. 7198 719807, 2009
H. Lindberg et al., “Recent advances in VECSELs for laser projection applications”, Vertical External Cavity Surface Emitting Lasers (VECSELs), Proc. of SPIE Vol. 7919 79190D, 2011
less than 0.4cm3 >70 mW green
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
Outline
Motivation and research targets
Introduction to VECSELs, SESAMs, and MIXSELs
Research targets
Highlights
- CW & modelocked VECSELs with wafer fusion (granted patent)
- 1-W femtosecond OP-VECSEL
- First QW-absorber based MIXSEL
- First modelocked VECSEL with multi-pass (new patent application)
- Generation of ultra-low-noise microwave for precision metrology
Summary and outlook
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
Research tasks Targets Better optically-pumped MIXSELs: higher power, shorter duration, new wavelengths
Better understanding and optimization of saturable absorbers
First electrically-pumped MIXSELs
Application studies: frequency combs and high precision metrology
Simulations of ultrafast VECSELs and MIXSELs
Optical testing
Semiconductor structures and characterization
Frequency comb generation and stabilization
Prof. Ursula Keller (PI) Physics Department, ETH Zurich
Prof. Eli Kapon, Dr. Alexei Sirbu Institut de Photonique et d‘Electronique Quantiques, EPFL, Lausanne
Prof. Thomas Südmeyer Institut de Physique, Université de Neuchâtel
Prof. Bernd Witzigmann Computational Electronics and Photonics, University of Kassel (previously ETH Zurich)
Partners
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
Outline
Motivation and research targets
Introduction to VECSELs, SESAMs, and MIXSELs
Research targets
Highlights
- CW & modelocked VECSELs with wafer fusion (granted patent)
- 1-W femtosecond OP-VECSEL
- First QW-absorber based MIXSEL
- First modelocked VECSEL with multi-pass (new patent application)
- Generation of ultra-low-noise microwave for precision metrology
Summary and outlook
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
Novel wafer-fusion technology: patent granted
3 4 5 6 7 8 9 100
20
40
60
80
100
120
Out
put p
ower
(mW
)Input pump power (W)
5
10
15
20
25
30
Pul
se w
idth
(ps)
First wafer fused SESAM fabricated according to the new invention demonstrates average output power in excess of 100 mW and pulsewidth as low as 6 ps:J. Rautiainen, J. Lyytikäinen, L. Toikkanen, J.Nikkinen, A. Sirbu, A. Mereuta, A. Caliman, E. Kapon,
and O. Okhotnikov, IEEE Photon. Technol. Lett., v.22, pp. 748-750, 2010
A novel wafer-fusion process allowing to considerably reduce the defect formation in the active region: A. Sirbu, A. Mereuta, A.Caliman,
VERTICAL CAVITY SURFACE EMITTING DEVICES INCORPORATING WAFER FUSED REFLECTORS,
International Publication Number WO 2011/000568 A1
CL image of a wafer-fused structure with no dark-line defects in the active region
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
Outline
Motivation and research targets
Introduction to VECSELs, SESAMs, and MIXSELs
Research targets
Highlights
- CW & modelocked VECSELs with wafer fusion (granted patent)
- 1-W femtosecond OP-VECSEL
- First QW-absorber based MIXSEL
- First modelocked VECSEL with multi-pass (new patent application)
- Generation of ultra-low-noise microwave for precision metrology
Summary and outlook
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
First Watt-level femtosecond VECSEL
pulse duration: 784 fs
output power: 1.05 W
repetition rate: 5.4 GHz
center wavelength: 970 nm
pump
modelocked laser
CVD-diamond QD-gain structure
output coupler QD-SESAM
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
Outline
Motivation and research targets
Introduction to VECSELs, SESAMs, and MIXSELs
Research targets
Highlights
- CW & modelocked VECSELs with wafer fusion (granted patent)
- 1-W femtosecond OP-VECSEL
- First QW-absorber based MIXSEL
- First modelocked VECSEL with multi-pass (new patent application)
- Generation of ultra-low-noise microwave for precision metrology
Summary and outlook
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
Pulse duration of MIXSELs
• slow recombination of the of the QD-absorber in the previous MIXSEL
• compared to the QD-SESAM used in the 1 W femtosecond VECSEL
• novel QW absorber with fast recombination and low Fsat
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
shorter pulses higher repetition rates: 20 GHz
novel fast QW absorber with a low Fsat more than 3 times shorter pulses
First MIXSEL with QW-absorber
25
Next step: optimize dispersion & demonstrate fs-MIXSEL with >1 W
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
Outline
Motivation and research targets
Introduction to VECSELs, SESAMs, and MIXSELs
Research targets
Highlights
- CW & modelocked VECSELs with wafer fusion (granted patent)
- 1-W femtosecond OP-VECSEL
- First QW-absorber based MIXSEL
- First modelocked VECSEL with multi-pass (new patent application)
- Generation of ultra-low-noise microwave for precision metrology
Summary and outlook
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
Biomedical imaging
Yb- hi rep
2-photon imaging FOM map of laser sources
Average power 0.1 mW 1 mW 10 mW 100 mW 1 W 10 W 100 W
100 kW
10 kW
1 kW
100 W
10 W
1 W
0.1 W
Ti:S, Er-fiber (at sample plane)
Peak
pow
er
Nanosurgery
Photodamage Er-fiber (full power)
Yb-fiber (full power)
Ti:S 2G
Ti:S (full power)
Melting/
Burning?
TargetZone
Cr:F 500M
Double rep rate, double average power, keep peak power constant
Er-SCG
shorten pulsewidth
Note: microscope systems have loss of 3-10X typical from input
to sample plane VECSEL 500M
at sample
in collaboration with Dr. Kurt Weingarten
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
Multi-pass for increased peak power (patent application)
Semiconductor gain: short gain lifetime (~1 ns)
⇒ limit in low-repetition rate operation, challenge for highest peak powers
Solution multipass-cavity: gain is passed every ns
⇒ 250 MHz operation achieved
⇒ new patent application
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
Outline
Motivation and research targets
Introduction to VECSELs, SESAMs, and MIXSELs
Research targets
Highlights
- CW & modelocked VECSELs with wafer fusion (granted patent)
- 1-W femtosecond OP-VECSEL
- First QW-absorber based MIXSEL
- First modelocked VECSEL with multi-pass (new patent application)
- Generation of ultra-low-noise microwave for precision metrology
Summary and outlook
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
Low-noise frequency comb
• Coherent stabilized CEO peak with only 5 kHz feedback bandwidth
• One of the lowest residual integrated phase noise (0.72 rad rms in 0-100 kHz) for a 1.5-µm comb
Diode-pumped solid-state laser (DPSSL) frequency comb with excellent noise performance
• 10-8 relative instability (at 1 s integration time) on the 20-MHz CEO contributes only 10-15 to the optical carrier frequency instability
• 20-fold improvement compared to a commercial self-referenced fiber comb
S. Schilt, N. Bucalovic, V. Dolgovskiy, C. Schori, M. C. Stumpf, G. Di Domenico, S. Pekarek, A. E. H. Oehler, T. Südmeyer, U. Keller, P. Thomann, “Fully stabilized optical frequency comb with sub-radian CEO phase noise from a SESAM-modelocked 1.5-µm solid-state laser”, Optics Express, 2012
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
Generation of ultra-low-noise microwave
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
Generation of ultra-low-noise microwave
fCEO detected with a DPSSL without pulse compression or amplification
targeted VECSEL
crucial for frequency comb stabilization: detection of the carrier envelope offset frequency (fCEO)
278 fs
74 mW
75 MHz
3.1 kW 1550 nm
p Pav
frep
Ppeak
λcenter
200 fs
1 W
1 GHz
4.4 kW 960 nm
Femtosecond VECSEL: promising candidate for compact, low cost frequency comb generation
goals consistent with biomedical applications (two photon imaging FOM) – similar peak, but lower rep-rate (with lower average power)
Stumpf, Pekarek, Oehler, Südmeyer, Dudley, Keller, Appl. Phys. B 99, 401 (2010)
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
Outline
Motivation and research targets
Introduction to VECSELs, SESAMs, and MIXSELs
Research targets
Highlights
- CW & modelocked VECSELs with wafer fusion (granted patent)
- 1-W femtosecond OP-VECSEL
- First QW-absorber based MIXSEL
- First modelocked VECSEL with multi-pass (new patent application)
- Generation of ultra-low-noise microwave for precision metrology
Summary and outlook
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
Prospects for year 4 • Demonstration of frequency comb with femtosecond OP-VECSELs and OP-MIXSELs
• Power scaling EP-VECSEL with modified designs (Simulations helped to identify key power limiting issues: heating, optical losses, electrical resistance in P-DBR ...)
• SESAM modelocked EP-VECSEL • First demonstration of wafer-fused SESAM modelocked femtosecond VECSELs at 1550 nm • Explore new collaborations: - several new industrial collaborations - inter nano-tera-project collaborations - international collaborations
ETH Zurich Ultrafast Laser Physics
nano-tera.ch annual 2012
Further information: poster session
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