Quantum Dot Lasers and New Device Concepts for High-Brightness Applications · 2017-11-23 ·...
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Quantum Dot Lasers and New Device Concepts for High-Brightness Applications High Brightness Diode Laser Sources High Brightness Diode Laser Sources D. Bimberg and N.N. Ledentsov Technische Universität Berlin, Institut für Festkörperphysik, PN5-2 Hardenbergstr. 36, 10623 Berlin, Germany
Transcript of Quantum Dot Lasers and New Device Concepts for High-Brightness Applications · 2017-11-23 ·...
Quantum Dot Lasers and New Device Concepts
for High-Brightness Applications
High Brightness Diode Laser SourcesHigh Brightness Diode Laser Sources
D. Bimberg and N.N. LedentsovTechnische Universität Berlin, Institut für Festkörperphysik, PN5-2Hardenbergstr. 36, 10623 Berlin, Germany
Cooperation
M.V. Maximov, Yu.M. Shernyakov, I.I. Novikov, S.M.Kuznetsov, L.Ya. Karachinsky, N.Yu. Gordeev,
I.P.Soshnikov, Yu.G.Musikhin, N.V.Kryzhanovskaya, and V.A.Shchukin
A.F.Ioffe Physico-Technical Institute, St.Petersburg, Russia
N.N. Ledentsov, T.Kettler, K.Posilovic, and D.BimbergTechnische Universität Berlin, Institut für Festkörperphysik,
Berlin, Germany
R. Duboc, U.Ben-Ami, Dafna Bortman-Arbiv,and A.Sharon
PBC Lasers Ltd., Menlo Park, CA, USA and Kibbutz Einat, Israel
Problems of Laser Diodes and Motivation
Quantum Dot Lasers
Photonic Band Crystal (PBC) lasers
1D PBC lasers
2D and 3D PBC Lasers
Conclusion
Content
Infrared image of the top of a broad-area gain region illustrating the effect of filamentation.
Problems of Laser Diodes Limiting Their Market
Beams from broad stripes and bars are not focusable
Beam filamentation
Filaments cause facet degradation
Small aperture and divergent beams in the vertical direction
Dificult to manipulate and couple the lightHigh power density and facet degradation
Problems of Laser Diodes and Motivation
Quantum Dot Lasers
Photonic Band Crystal (PBC) lasers
1D PBC lasers
2D and 3D PBC Lasers
Conclusion
Content
QWs and QWWs: R. Dingle and H. Henry, 1975
Impact of the Reduced Number of Degrees of Freedom on Laser Performance
Strong modification of the density of states by quantum-size effect
bulk
quantum well
quantum wire
Advantage of QDs: Y.Arakawa Sakaki 82 and H. , 19
16W CW Operation of as-cleaved QD Lasers
No facet degradation up to ultrahigh power
Burn-in test at 1 A current for 3mm-long narrow-stripe (4 µm) lasers with uncoated facets. (a) stability of output power, (b) stability of the emission wavelength, (c) Light-current characteristics before/after
burn-in tests.
Total cw power limited by thermal roll-over is ~520 mW
Far field stability:
as function of heating time and
as function of the drive current in
the whole range
High-Power Operation of 1.25 – 1.3 µm QD Lasers
500
400
300
200
100Tota
l Pow
er (m
W)
W = 4 µm
High-Power Operation and Degradation Robustness of 1.25 – 1.3 µm QD Lasers
The Arrhenius activation energy EA of 0.79 eV was extracted
Assuming the temperature of normal operation being 40oC, the median lifetime of QD lasers to be 1.2x106 h
Lifetime > 106 h
40 mW80 mW
Facet passivation Lumics, Berlin
Degradation test HHI, Berlin
Problems of Laser Diodes and Motivation
Quantum Dot Lasers
Photonic Band Crystal (PBC) lasers
1D PBC lasers
2D and 3D PBC Lasers
Conclusion
Content
Anticipated PBC Laser Capabilities(demonstrated: 4 deg. divergence, >1 W single mode, coherently coupled beams)
Single mode coupled PBC stripe emitters (anticipate up to 20 W CW)
Large vertical waveguide extension may enable efficient coupling of beams to enable Kwatt single mode beams
Single mode single stripe PBC emitters (anticipate >3 W CW)
Vertical PBC
Filtering of high-order modes by vertical photonic crystal
Lateral PBC
Filtering of high-order modes by lateral photonic crystal
Courtesy of PBC Lasers
Problems of Laser Diodes and Motivation
Quantum Dot Lasers
Photonic Band Crystal (PBC) lasers
1D PBC lasers
2D and 3D PBC Lasers
Conclusion
Content
Photonic Bandgap Crystal (PBC) lasers concept
1D Edge-Emitting PBC Laser with an optical defect
Fundamental optical mode is localized by the optical defectand decays away from it
High–order modes are extended over the entire PBCstructure
High-order modes may leak into the substrate
Courtesy of PBC Lasers
Engineering leakage for high order modes
Leakage loss may be engineered.It may be order (or orders) of magnitude higher for the excited modes than for the fundamental mode
Engineering Robustness
Decrease in the thickness of the optical defect from ~50 to 30 nm.
Some narrowing of the beam
No dramatic reduction in the optical confinement factor for the fundamental mode
No dramatic increase in losses for the fundamental mode
While the change (50 nm to 30 nm) is dramatic !
ROBUST ! Analogue of PC Fiber
Comparison of Generic and PBC Lasers (Pulsed)
0 2 4 6 8 10 12 14 16 180
5
10
15
20 Conventional PBC laser
655 nm
W = 100 μm L = 1500 μm Pulsed
Tota
l Out
put P
ower
(W)
Current (A)
646 nm
COMD
-10 0 10
Nor
mal
ized
Inte
nsity
(arb
. uni
ts)
Conventional PBC
FWHM ~ 17oL = 2mmW = 100 μmPulsed
Vertical Angle (deg.)
FWHM ~ 8o
Pmax of conventional lasers is < 8 W and limited by COMD
Pmax of as-cleaved PBC lasers is ~ 20 W
FWHM of the vertical far field pattern is 7-8° for PBC laser and 17° for conventional laser
IQE growth: 1 to 1 comparison with generic
4 μm Single Mode 650 nm CW PBC (~8ox7o) lasers
0.0 0.1 0.2 0.30
20406080
100120
0.83 W/A
W = 4 μm L=1500 μmHR/ARCW, 200C
Opt
ical
Pow
er, m
W
Current, mA
Single mode operation up to the highest currents applied.
Maximum CW output optical power is ~ 120 mW and limited by COMD
Low Aspect ratio ~ 1.2 – 1.4
-20 -10 0 10 20
EL
Inte
nsity
, arb
. uni
ts
Lateral Angle, degrees
150mA 200mA 250mA 300mA
θ1/2 ~ 6.5°
No kinks
No passivation/coating of the facets !
0 1 2 3 4 5 6 7 80
1
2
3
4
5
6
7
Ith = 0.47 AηD = 51%
2718W=50 μmL=1000 μm (N15)SolderedPulse (400 ns, 2kHz)18oC
Tota
l Pow
er, W
Current, A
1 W/A940 A/cm2
636 nm
0.0 0.2 0.4 0.6 0.8 1.0 1.20
100
200
300
400
500
0.00.51.01.52.02.53.03.54.04.55.0
0
2
4
6
8
10
12
14
16
2718W=50μ L=1mm170C
To
tal o
utpu
t pow
er, m
W
Current,A
Volta
ge,V
Con
vers
ion
effic
ienc
y (%
)
50 μm single mode 636 nm PBC (~12o) lasers
Total CW power >500 mW without facet passivation/coating
pulsed CW
CW 980 nm PBC (~8o) lasers at High Power
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
00 20 40 60 80 100
Temperature
LN(S
E)
323
T1
T (oC)
7-9 W CW at non-optimized heat sinking
W=100 μm
L=2000 μm
15oC CW
T heat sink =
85oC CW15oC CW
Pow
er (m
W)
CW 980 nm PBC (~8o) lasers at High Temperature
L=2000 μm
W=100 μm
Good CW high-temperature performance
T heat sink =
980 nm PBC Lasers: Reliability
50oC, 6Aclammed to heat sink
Passivated and coated ~100% yieldZero infant mortality
Problems of Laser Diodes and Motivation
Quantum Dot Lasers
Photonic Band Crystal (PBC) lasers
1D PBC lasers
2D and 3D PBC Lasers
Conclusion
Content
Broad Stripe and Coupled Cavities
Stripe
Conventional
PBC:- single mode to broader stripes- multistripe processing keepingstrongly coupled field
- wavelength stabilization is easy
Courtesy of PBC Lasers
Thick PBC waveguide
Courtesy of PBC Lasers
Courtesy of PBC Lasers
Multistripe PBC Laser: Experiment
17 stripes with a ridge width and a pitch of 7 μmand 12 μm, respectively. 200 μm total width
-20 -10 0 10 200
1 #2770L=1000 μmWtot=200 μm
Pulsed, 17oC
FWHM ~ 4.8o
Nor
mal
ized
inte
nsity
(arb
.un.
)
Vertical angle (deg)-20 -10 0 10 20
0
1
Δ~4.6o
#2770L=1000 μmWtot=200 μm
Pulsed, 17oC
FWHM~0.6o
Nor
mal
ized
inte
nsity
(arb
. un.
)
Parallel angle (deg)
0 5 10 15 200
5
10
15
20
Ith=1.4 A2ηD=84%
#2770L=1000 μmWtot=200 Pulsed (300 ns, 1 kHz)17oC
Tota
l Pow
er, W
Current, A
Coherent filament-free beam over 200 µm. 980 nm
Multistripe 7o PBC Laser: CW Experiment
0 1 2 3 4 50
1
2
3
Current, A
Tota
l Pow
er, W
L=1 mm
0
1
2CW, 17oCW= 200 μm
Vol
tage
, V
0
10
20
30
40
50
Con
vers
ion
effic
ienc
y (%
)
Potential for high-performance CW operation
Vertical angle (deg.)Lateral angle (deg.)
FWHM ~7 degFWHM ~0.6 deg
#2768
4 μm x 23Total width 202 μmL= 1mmI = 1A
Multistripe 7o PBC Laser: 2D Far Field (W=202 μm)
gain chip
non-linearcrystal
holder
Potential PBC Performance Advantage
Laser Intra-Cavity Power density
Conversion efficiency• = 40-1000 X power increase
PBC RGB Module
Potential PBC Cost Advantage• Lower optical parts count• Required power from minimal # of
emitters and non-linear crystals• <1/5 wafer space; <1/4 crystal
volume• Simpler assembly (lower tolerances)
mirror/filter
non-linearcrystalholder
gain chip
VCSEL
substrate
Thermal lensing significantly limits power & efficiency
PBC optical pump power: potential of 10-20W SM in extended cavity
Surface Emitter with a Large Aperture
Potential of Frequency Conversion Using PBC Laser
Courtesy of PBC Lasers
PBC Laser: Publications
20W pulsed at 640 nm, W=100 µm
120 mW single mode CW at 658 nm, W=4 µm
250 mW single mode CW at 840 nm, W=4 µm
Review:
Problems of Laser Diodes and Motivation
Quantum Dot Lasers
Photonic Band Crystal (PBC) lasers
1D PBC lasers
2D and 3D PBC Lasers
Conclusion
Content
Filamentation problem can be eliminated or reducedby using Quantum Dot active media:
- ultalong expected lifetime >106h, 50 mW SM 40oC- >16W CW without COMD without facet
passivation or coating
Photonic Band Crystal (PBC) lasers:- single mode to broader stripes
(higher brightness)- ultrahigh brightness by lateral field engineering- reliable
Combining the advantages (QD+PBC) may be important
Conclusion
