Download - Mixsel
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
Vertical integration of ultrafast semiconductor lasers for wafer-scale mass production
Vertical integration of ultrafast semiconductor lasers for wafer-scale mass production
Prof. Bernd WitzigmannComputational Electronics and Photonics, University of Kassel (previously ETH Zurich)
Prof. Ursula Keller & Dr. Thomas Südmeyer Physics Department, ETH Zurich
Prof. Eli Kapon & Dr. Alexei SirbuInstitut de Photonique et d‘Electronique Quantiques, EPFL, Lausanne
Prof. Pierre ThomannInstitut de Physique, Université de Neuchâtel
Jan. 17, 2011
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
OutlineOutline
Motivation and research targets
VECSELs and SESAMs
MIXSEL concept
Highlights • 6.4 W modelocked OP-MIXSEL chip at 960 nm.
• 1 W femtosecond SESAM-modelocked OP-VECSEL at 960 nm.
• 2.62 W cw average power from a 1550 nm OP-VECSEL realized with wafer fusion. First Modelocking result at 1550 nm.
• 120 mW cw average power from an EP-VECSEL.
• Full stabilization of a frequency comb (CEO beat and laser repetition rate) using a SESAM modelocked diode-pumped Er:Yb:glass
Summary and outlook
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
Compact ultrafast lasers for “real world application”Compact ultrafast lasers for “real world application”Telecom & Datacom Interconnects Optical Clocking
Frequency comb
Multi-photon imaging
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
The first VECSELs conference at Photonics West
Jan. 24 - 25, 2011
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
OutlineOutline
Motivation and research targets
VECSELs and SESAMs
MIXSEL concept
Highlights• 6.4 W modelocked OP-MIXSEL chip at 960 nm.
• 1 W femtosecond SESAM-modelocked OP-VECSEL at 960 nm.
• 2.62 W cw average power from a 1550 nm OP-VECSEL realized with wafer fusion. First Modelocking result at 1550 nm.
• 120 mW cw average power from an EP-VECSEL.
• Full stabilization of a frequency comb (CEO beat and laser repetition rate) using a SESAM modelocked diode-pumped Er:Yb:glass
Summary and outlook
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
CW Optically-Pumped VECSELsCW Optically-Pumped VECSELs
OP-VECSEL = Optically Pumped Vertical-External-Cavity Surface-Emitting Semiconductor Laser
M. Kuznetsov et al., IEEE Photon. Technol. Lett. 9, 1063 (1997)
• Semiconductor gain structure with reduced thickness
IEEE JQE 38, 1268 (2002)• Pump: high power diode bar• External cavity
for diffraction-limited output
pump
laser
heat sink
gain structure
outputcoupler
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
VECSEL gain structureVECSEL gain structure
pump
laser
heat sink
gain structure
outputcoupler
gain structureheatsink
pump energy
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
Optically pumped semiconductor laser?Optically pumped semiconductor laser?
• 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
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
Semiconductor materials: bandgap engineeringSemiconductor materials: bandgap engineeringWavelength of interest 960 nm, 1.3 µm, and 1.5 µm
1.5 µm
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
VECSELs: cw spectral coverage (Jennifer Hastie)VECSELs: cw spectral coverage (Jennifer Hastie)
• 2‐2.8 μm – GaInAsSb / AlGaAsSb
• 1.5 μm – InGaAs / InGaAsP
• 1.2‐1.5 μm – AlGaInAs / InP (fused)
• 1.2‐1.3 μm – GaInNAs / GaAs
• 1‐1.3 μm – InAs QDs
• 0.9‐1.18 μm – InGaAs / GaAs
• 850‐870 nm – GaAs / AlGaAs
• 700‐750 nm – InP QDs
• 640‐690 nm – InGaP / AlGaInP
• Frequency‐doubled VECSELs have been reported throughout the visible and into the UV
Infrared review: N. Schulz et al., Laser & Photonics Reviews 2, 160 (2008)Visible and UV review: S. Calvez et al., Laser & Photonics Reviews 3, 407 (2009)
updated by Jennifer Hastie, University of Strathclyde, group of Prof. Martin Dawson
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
SESAMSemiconductorSaturableAbsorber Mirror
Ultrafast VECSELs: Modelocking with SESAMs Ultrafast VECSELs: Modelocking with SESAMs
pump
modelockedlaser
heat sink
gain structure
outputcoupler
SESAM
cwlaser
Review article for VECSELs: U. Keller and A. C. Tropper, Physics Reports, vol. 429, Nr. 2, pp. 67-120, 2006
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
OutlineOutline
Motivation and research targets
VECSELs and SESAMs
MIXSEL concept
Highlights• 6.4 W modelocked OP-MIXSEL chip at 960 nm.
• 1 W femtosecond SESAM-modelocked OP-VECSEL at 960 nm.
• 2.62 W cw average power from a 1550 nm OP-VECSEL realized with wafer fusion. First Modelocking result at 1550 nm.
• 120 mW cw average power from an EP-VECSEL.
• Full stabilization of a frequency comb (CEO beat and laser repetition rate) using a SESAM modelocked diode-pumped Er:Yb:glass
Summary and outlook
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
Motivation for semiconductor lasers: Wafer scale integrationMotivation for semiconductor lasers: Wafer scale integrationD. Lorenser et al., Appl. Phys. B 79, 927, 2004
MIXSELmodelocked integrated external-cavity surface emitting laser
SESAM
Passively modelocked VECSELvertical external cavity surface emitting laser
Review: Physics Reports 429, 67-120, 2006
D. J. H. C. Maas et al., Appl. Phys. B 88, 493, 2007
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
MIXSEL wafer scale integrationMIXSEL wafer scale integration
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 ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
Review article for VECSELs: U. Keller and A. C. Tropper, Physics Reports, vol. 429, Nr. 2, pp. 67-120, 2006
Comparison of Ultrafast GHz LasersComparison of Ultrafast GHz Lasers
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
OutlineOutline
Motivation and research targets
VECSELs and SESAMs
MIXSEL concept
Highlights• 6.4 W modelocked OP-MIXSEL chip at 960 nm.
• 1 W femtosecond SESAM-modelocked OP-VECSEL at 960 nm.
• 2.62 W cw average power from a 1550 nm OP-VECSEL realized with wafer fusion. First Modelocking result at 1550 nm.
• 120 mW cw average power from an EP-VECSEL.
• Full stabilization of a frequency comb (CEO beat and laser repetition rate) using a SESAM modelocked diode-pumped Er:Yb:glass
Summary and outlook
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
Optically pumped ultrafast VECSELs / MIXSELsOptically pumped ultrafast VECSELs / MIXSELs
B. Rudin, V. J. Wittwer, D. J. H. C. Maas, M. Hoffmann, O. D. Sieber, Y. Barbarin, M. Golling, T. Südmeyer, U. Keller,
Opt. Express 18, 27582, 2010
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
Resonant vs. antiresonant MIXSEL designResonant vs. antiresonant MIXSEL design
Initial MIXSEL demonstration had a resonant design:D. J. H. C. Maas et al., Appl. Phys. B 88, 493, 2007 • sensitive to growth errors
• high GDD - long pulses
• tolerant to growth errors
• low GDD - short pulses
Here: MIXSEL demonstration with antiresonant design
growth error simulation: layer thickness variations < 1%
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
MIXSEL: improved thermal managementMIXSEL: improved thermal management
Finite Element (FE) temperature simulations
• exchange the copper with CVD diamond
reasonable temperatures
• leads to highest output power from a ultrafast semiconductor laser
heat sink material
thermal conductivity (W m-1K-1)
estimated heating power (pump power)
pump/ laser mode radius
temp. rise(FE sim.)
heat sink temperature
output power
GaAs 45 1.5 W (1.7 W) 80 µm 149 K -15 °C 41.5 mW
copper 400 3.2 W (4.3 W) 80 µm 98 K +10 °C 660 mW
diamond 1800 26.6 W (36.7 W) 215 µm 100 K -15 °C 6400 mW
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
High power MIXSELHigh power MIXSEL
• Optical pumping 36.7 W at 808 nm
• Pump / laser spot radius: ~215 m
• Efficiency (opt-opt): 17.4 %
• Cavity length: 60.8 mm 2.47 GHz
• Output coupling: 0.7%
• TBP: 1.35 (4.2 times sech2)
B. Rudin, V. J. Wittwer, D. J. H. C. Maas, M. Hoffmann, O. D. Sieber, Y. Barbarin, M. Golling, T. Südmeyer, U. Keller, Opt. Express 18, 27582, 2010
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
OutlineOutline
Motivation and research targets
VECSELs and SESAMs
MIXSEL concept
Highlights • 6.4 W modelocked OP-MIXSEL chip at 960 nm.
• 1 W femtosecond SESAM-modelocked OP-VECSEL at 960 nm.
• 2.62 W cw average power from a 1550 nm OP-VECSEL realized with wafer fusion. First Modelocking result at 1550 nm.
• 120 mW cw average power from an EP-VECSEL.
• Full stabilization of a frequency comb (CEO beat and laser repetition rate) using a SESAM modelocked diode-pumped Er:Yb:glass
Summary and outlook
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
Optically pumped ultrafast VECSELs / MIXSELsOptically pumped ultrafast VECSELs / MIXSELs
M. Hoffmann, O. D. Sieber, V. J. Wittwer, I. L. Kestnikov, D. A. Livshits, T. Südmeyer, U. Keller,
Opt. Express 19, 8108, 2011
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
Femtosecond all Quantum Dot VECSELFemtosecond all Quantum Dot VECSELSeparate pump mirrorDBR separation tuning for maximum absorption
higher efficiencyActive regionchirped QD-layer positions
• each layer stack resonant for different laser wavelength
• according to absorption intensity broader gain
AR sectionhybrid semiconductor / fused silica
reduction of the GDD
pump
modelockedlaser
CVD-diamond QD-gainstructure
outputcoupler QD-SESAM
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
heat sink: thinned QD gain structure on CVD substrate
output coupler: 100 mm
output coupler transmission: 2.5%
laser mode radius on QD-VECSEL: 115 µm
laser mode radius on QD-SESAM: 115 µm
heat sink temperature: -20°C
Femtosecond QD-VECSELFemtosecond QD-VECSEL
pump
modelockedlaser
CVD-diamond QD-gainstructure
outputcoupler QD-SESAM
repetition rate: 5.4 GHzTBP: 1.3 sech2
peak power: 219 W
pulse duration: 784 fsoutput power: 1.05 Wcenter wavelength: 970 nm
M. Hoffmann, O. D. Sieber, V. J. Wittwer, I. L. Kestnikov, D. A. Livshits, T. Südmeyer, U. Keller, Opt. Express 19, 8108, 2011
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
OutlineOutline
Motivation and research targets
VECSELs and SESAMs
MIXSEL concept
Highlights• 6.4 W modelocked OP-MIXSEL chip at 960 nm.
• 1 W femtosecond SESAM-modelocked OP-VECSEL at 960 nm.
• 2.62 W cw average power from a 1550 nm OP-VECSEL realized with wafer fusion. First Modelocking result at 1550 nm.
• 120 mW cw average power from an EP-VECSEL.
• Full stabilization of a frequency comb (CEO beat and laser repetition rate) using a SESAM modelocked diode-pumped Er:Yb:glass
Summary and outlook
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
2.62 W wafer fused VECSEL at 1550 nm2.62 W wafer fused VECSEL at 1550 nm
Opt. Express 16, 21881-21886 (2008)
• Combine advantages of InP-based active medium with GaAs/AlGaAs reflector
• Intra-cavity diamond for good heat dissipation
2.62 W cw
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
First wafer-fused modelocked VECSEL at 1550 nmFirst wafer-fused modelocked VECSEL at 1550 nm• First wafer-fused passively modelocked VECSEL at 1550 nm!
• Combine advantages of InP-based active medium with GaAs/AlGaAs reflector
• Intracavity diamond for good heat dissipation
• Beam-spot diameters: 210 µm on gain chip; 50 µm on GaInNAs-based SESAM
• 600 mW in 16 ps pulses at 1.29 GHz with 10 W pump power
E. J. Saarinen, J. Puustinen, A. Sirbu, A. Mereuta, A. Caliman, E. Kapon, O. Okhotnikov, Optics Letters, 34, 3139 (2009)
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
OutlineOutline
Motivation and research targets
VECSELs and SESAMs
MIXSEL concept
Highlights• 6.4 W modelocked OP-MIXSEL chip at 960 nm.
• 1 W femtosecond SESAM-modelocked OP-VECSEL at 960 nm.
• 2.62 W cw average power from a 1550 nm OP-VECSEL realized with wafer fusion. First Modelocking result at 1550 nm.
• 120 mW cw average power from an EP-VECSEL.
• Full stabilization of a frequency comb (CEO beat and laser repetition rate) using a SESAM modelocked diode-pumped Er:Yb:glass
Summary and outlook
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
Bottom disk contact
DBR
Top ring contact
Electrical vs. optical pumpingElectrical vs. optical pumpingOutput coupler
Active region
Heat spreader
DBR
OP-VECSEL EP-VECSEL
~ 50 μm
Pump laser
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
ETH Zurich EP-VECSEL designETH Zurich EP-VECSEL design
Design guidelines: P. Kreuter, B. Witzigmann, D.J.H.C. Maas, Y. Barbarin, T. Südmeyer and U. Keller, Appl. Phys. B, 91, 257, 2008
Suitable for modelocking • Relatively low GDD: AR section• Confined current injection for good beam profile
• 6 µm current spreading layer• bottom p-doped, top n-doping• small bottom disk p-contact
Power scalability• Wafer removal• Large apertures possible
Trade off between electrical and optical losses• Optimized doping profile
• High doping → high free carrier absorption• Low doping → high resistivity
• Intermediate n-DBR for increased gain
top contact
bottom contact
CuW wafer
p-DBR
current spreading
layer
AR section
n-DBR
SiNx
SiNx
active region
SEM
14 µm
11
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
Growth, processing, and evaluation implemented 60 different EP-VECSEL lasing in cw Output power up to 120 mW (cw) achieved Good homogenous electroluminescence profiles measured for
devices up to 100 µm (excellent agreement with our simulations)
First EP-VECSEL resultsFirst EP-VECSEL results
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
EP-VECSEL cw resultsEP-VECSEL cw results40 EP-VECSELs with different bottom contact diameters
Power scaling considerations• Output power should scale with area (P α Ø2)
and current density (P α J )• Ideal power scaling, ∆T independent of device size
17
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
OutlineOutline
Motivation and research targets
VECSELs and SESAMs
MIXSEL concept
Highlights• 6.4 W modelocked OP-MIXSEL chip at 960 nm.
• 1 W femtosecond SESAM-modelocked OP-VECSEL at 960 nm.
• 2.62 W cw average power from a 1550 nm OP-VECSEL realized with wafer fusion. First Modelocking result at 1550 nm.
• 120 mW cw average power from an EP-VECSEL.
• Full stabilization of a frequency comb (CEO beat and laser repetition rate) using a SESAM modelocked diode-pumped Er:Yb:glass
Summary and outlook
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
A key application: optical frequency combsA key application: optical frequency combs
www.faszination-uhrwerk.de
- Phase stable link between optical (100s THz) and microwave frequencies (GHz)
- Counting of arbitrary optical frequencies practicable for the first time
offer
- Fundamental physics- Optical clocks- Satellite navigation- Large bandwidth telecommunication- Spectroscopy- Medical applications, noninvasive
diagnostics
impact
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
Femtosecond Er:Yb:glass laserFemtosecond Er:Yb:glass laser
Stumpf, Zeller, Schlatter, Südmeyer, Okuno, Keller, Opt. Express 16, 10572 (2008)
Telecom center wavelength (1.55 µm) Reliable telecom grade pump diode Low power consumption (< 1.5 W electrical) Clean soliton pulses Polarized output
Total resonator losses below 3 %
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
Moving of the laser from ETH to NeuchatelMoving of the laser from ETH to Neuchatel
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
Noise performance of DPSSLs and VECSELsNoise performance of DPSSLs and VECSELs
+ high-Q cavity, low nonlinearities⇒ extremely low intrinsic noise
+ convenient and robust
DPSSLs
Compare 75 MHz 1.5-µm Er:Yb glass DPSSL with commercial 1.5-µm Er-fiber laser
Example excellent noise performance of DPSSLs: Optical ultra-stable microwave oscillator
S.Schilt, M. C. Stumpf, L. Tombez, N. Bucalovic, V. Dolgovskiy, G. Di Domenico, D. Hofstetter, S. Pekarek, A. E. H. Oehler, T. Südmeyer, U. Keller, P. Thomann,“Phase noise characterization of a near-infrared solid-state laser optical frequency comb for ultra-stable microwave generation”,Optical Clock Workshop, Torino, Italy, December 1-3, 2010
Relative frequency stability of the CEO frequency measured with the same feedback loop
(right scale: relative frequency stability with respect to the optical carrier)
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
fCEO detected with a DPSSL without pulse compression or amplification
targeted VECSEL
VECSELs for Frequency Comb GenerationVECSELs for Frequency Comb Generationcrucial for frequency comb stabilization:
detection of the carrier envelope offset frequency (fCEO)
278 fs
74 mW
75 MHz
3.1 kW1550 nm
p
Pav
frep
Ppeak
λcenter
200 fs
1 W
1 GHz
4.4 kW960 nm
Femtosecond VECSEL: promising candidate for compact, low cost frequency comb generation
Stumpf, Pekarek, Oehler, Südmeyer, Dudley, Keller, Appl. Phys. B 99, 401 (2010)
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
OutlineOutline
Motivation and research targets
VECSELs and SESAMs
MIXSEL concept
Highlights• 6.4 W modelocked OP-MIXSEL chip at 960 nm.
• 1 W femtosecond SESAM-modelocked OP-VECSEL at 960 nm.
• 2.62 W cw average power from a 1550 nm OP-VECSEL realized with wafer fusion. First Modelocking result at 1550 nm.
• 120 mW cw average power from an EP-VECSEL.
• Full stabilization of a frequency comb (CEO beat and laser repetition rate) using a SESAM modelocked diode-pumped Er:Yb:glass
Summary and outlook
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
Optically pumped ultrafast VECSELs / MIXSELsOptically pumped ultrafast VECSELs / MIXSELs
ETH ZurichUltrafast Laser Physics
nano-tera.ch Annual Meeting 12. 5. 11
Gantt chartGantt chart
• Excellent result of 960 nm MIXSEL => 1550 nm SESAM and MIXSEL delayed (Tasks 1.1, 1.2 and 2.1)
• Femtosecond VECSEL demonstrated (Task 4.2) => high expectation for fs-MIXSEL (Task 4.3)
• First EP-VECSEL in a university,120 mW realized => 200 mW achievable in a next realization (Task 5.3)