odae kwon department of electrical engineering pohang university of science and technology pohang...
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O’Dae KwonDepartment of Electrical Engineering
Pohang University of Science and Technology Pohang 790-784, Korea
[email protected] http://www.postech.ac.kr/ee/light
IEEE-LEOS 2008Nov. 11, 2008
(GaN) Photonic Quantum Ring
Laser & Mega-Pixel Laser Chip for
Display[Whispering Cave Mode]
2-D Whispering Gallery vs. 3-D Whispering Cave
toroidal cavity 3D TIR 3D WCM prop. of PQR
PQR from carrier-photon coupleSingle ModeRed PQR LaserBlue PQR Laser• Laser TV [model]
St. Paul cathedral : Lord Rayleigh
concave Whispering Gallery – Bessel function
2D TIR (Total Intn’l. Reflec’n) - 2D symmetry
Micro Whispering Gallery Mode(WGM)
SiO2 WGM
1910 Lord Rayleigh. WGM from concave surface Philosophical magazine, xx. 1001 (1910). 2D TIR 1992 A.F.J. Levi, R.E. Slusher et al. 2D WGM microdisk lasers (thumb-tack), Appl. Phys. Lett. 60, 289 (1992). 2D TIR 1998 J.C. Ahn, et al., O’Dae Kwon. 3D WGM lasers by using naturally produced toroidal cavity in cylinders 3D TIR (whispering cave mode:WCM) Phys. Rev. Lett. 82, 536 (1999); SPIE (1998)
2003 D.K. Armani et al & K.J. Vahala. WGM by using laser-baked toroid-shaped cavity Nature. 421, 926 (2003). 3D TIR possible WCM
Bessel (Jm) field profile
Helical wave
Epi structure
N-DBR
P-DBRActive layer
Silicon nitride coating
SiNx
substrate
Planarization using polyimide
Polymide
Vertical mesa using CAIBE
Ar: Cl2: BCl3
(3D WCM) PQR fabrication & structure
CF4
SiNx etching by RIE for metal contact
CMP-Metal-WireBond-Packaging
P-metal
N-metal
(3D WCM) PQR (concave) & PQR hole (convex)
Ion implantation for hole isolation
H+-Ion Implantation
Hole etching, passivation Metal contact
PQR hole
OPTO Paper # 6897-29 :Mega-pixel PQR hole chip : PC eff. isolations
Photonic Quantum Ring
z
P-DBRs
N-DBRs
ρ
P-metal
MQW
0 10 20 30 40 50 60
Temperature, C
794
794.5
795
795.5
796
796.5
797
797.5
798
798.5
799
Pea
k W
avel
eng
th, n
m
VCSEL modePQR mode0.418567*SQRT(T-17.83553)+794.29160.0749T+794.282
Temperature stability (T1/2 dependent)
A. Yariv. APL, 53, 12 (1988).
Bessel (Jm) field profile
Helical wave
12 ㎂ , near thePQR threshold
11.5 ㎃ , belowVCSEL threshold
12.2 ㎃ , aboveVCSEL threshold
Low threshold current (ϕ=15 μm)
Ahn et al., PRL, 82, 536 (1999).
PQR Threshold Ith
PQR PQR PQRth tr iI I I
1
2
RayleighPQR Dtr tr
PQR
eff
W eI N
n
QW QW QWth tr iI I I
( ) , 12
effRayleigh
nwW w
n
I. QW assumption
II. QWR assumption
WRayleigh
λ/2
# of wires
A. Yariv. APL, 53, 12 (1988).
ητ
eπ
2
wNI 2D
trQWtr
10 0.314 3 (2.4)
20 0.629 5 (4.85)
30 0.943 7.2
][ m ][ mWRayleigh
Park et al., APL, 79, 1593 (2001).
Ahn et al., PRL, 82, 536 (1999).Kwon et al., APL, 89, 11108
(2006).
Chin-Chu-Ho,
JAP 75,3302(1994)PQR mesa: ● (threshold) ○
(transparency)
PQR hole: ▪ (threshold)
▫(transparency)
Emission pattern
Fiber Probe
Tip (core) diameter = 3μm
Polyimide
n+-GaAs Substraten-electrode
p-DBR
n-DBR
p-DBR Active Layer
p-electrode
Emission pattern
Fiber Probe
Tip (core) diameter = 3μm
Polyimide
n+-GaAs Substraten-electrode
p-DBR
n-DBR
p-DBR Active Layer
p-electrode
845 846 847 848 849 850
m15
m13
m11m9
m7
m5
m3
m1
m0
= 10o
= 15o
Spec
tral
Inte
nsity
(a.u
)
= 20mI =2.5 mA
T = 18oC
Wavelength (nm)
Spectral PQR Analy. of 3D WCM theoy Opt. Lett. Vol. 28, 1861 (2003)
2
12
0
0
0
01
21
2sin
Rn
m
n
n
R
m mm
0 30 60 90 120 150 180 210 240
0.06
0.09
0.12
0.15
0.18
0.21
0.24
15 m
12 m
10 m
9 m845 846 847 848 849 850
FWHM = 0.055 nmI = 800 AD = 10 m
Wavelength (nm)
FWHM
,
1/2
(nm
)
Current Level (I/Ith)
7 m
PQR: carrier-photon dynamic model
FaNiNgxFxix
FiD
z
F
t
FP ])()[()(
2
2
BaNiNgxBxix
BiD
z
B
t
BP ])()[()(
2
2
))(()()(22
2
2
BFNgxNxJx
ND
t
Nf
timeionrecombinatvenonradiati
injectioncarrierJ
tcoefficiendiffusionD
tcoefficiengaina
factortenhancemenlinewidth
functiongaing
factortconfinemen
factorgwaveguidinpassivetransverse
tcoefficiennDiffractioD
densitycarrierN
fieldelectricbackwardB
fieldelectricforwardF
f
P
:)/1(
:
:
:
:
:
:
:
:
:
:
:
)()( 0NNaNg
evanescent region
Toroidal cavity
z
x0
z=L
x=W
Bessel (Jm) field profile
Helical wave
Park et al., APL, 79, 1593 (2001).
E. Gehrig et al., APL, 84, 1650 (2004).
t
BE
t
DJH
PED 0
HB 0
EJ )exp(),,(
)exp(),,(
tiikztzxB
tiikztzxFE
ENP )(0
Dynamic filamentation and beam quality of quantum-dot lasersE. Gehrig and O. Hess, APL, 84, 1650 (2004).
Stripe
of WRayleigh
0 20 40 60 80 1000
5 1017
1 1018
1.5 1018
1.055 1018
4.669 1015
I_total ii 1
N_cii 1 2 1014
1000 ii
Field intensity
Carrier distribution
Carrier distribution@5psec
Field intensity @5psec
~ 5 [#]
WRayleigh~1 µm, ϕ = 30 µm [MEJ,2008]
[sec]2.2222
pico
n
vr
n
vL
pico8.2
][47.0 m
sec]/[1068.1sec]/[168.08.2
47.0 7 cmpicom
10 0.314 2.4
20 0.629 4.8
30 0.943 7.2
][ m ][ mWRayleigh
10psec
x
time
Stripe
of WRayleigh
Stripe
of WRayleigh
P. Avouris, Physics Today, 11, 17 (1993).M. F. Crommie, et al. Nature, 363, 524 (1993).
Quantum corral of electrons
Electron standing waves in a 2DEGs Coherent branched electron flow in a 2DEGs
Period:15Å
Room temp 1.7K
Au(111) surface
M.A. Topinka, R.M. Westervelt, E.J. Heller, “Imaging Electron Flow", Physics Today 56, 12 (2003).
Local density of states in 2DEG
Polarization Vectors // PQR
x
y
z
①
②
③
① : linear polarizer ② : linear polarizer ③ : +135o
fiber
(a): without polarizer(b): polarizer(c): polarizer(d): +45o polarizer(e): +135o polarizer
Kim et al., JAP, 102(5), xx (2007).
=15 μm, I=150 A (10kHz)
Strong Carrier-Photon Coupling
837 838 839 840 841 842 843-1.0x10-9
0.0
1.0x10-9
2.0x10-9
3.0x10-9
4.0x10-9
5.0x10-9
6.0x10-9
7.0x10-9
8.0x10-9
9.0x10-9
0.6 mA0.7 mA0.8 mA0.9 mA1.0 mA1.1 mA1.2 mA1.3 mA1.4 mA1.5 mA1.6 mA1.7 mA1.8 mA
2.0 mA1.9 mA
Inte
ns
ity
(a
.u.)
Wavelength (nm)
= 900 nm, NormalSingle mode
Single mode PQR Laser
JAP (2008) to appear
500 nA 1 uA
3 uA 5 uA
Red PQR Laser Array
PQR emission
LED emission 256 array ( = 7 m) Spacing = 68 m
256 array ( = 10 m)Spacing = 68 m
I = 2 mA (7.8 A/cell )
- The PQR lasing region is brighter than the LED emission region, which means very high emission efficiency of the PQR laser.
Blue PQR laser at 480nm
PQR array ( , spacing)CW/ room temp /at 60mA : without & with an attenuation filter
]20[ m m35
Blue PQR Laser LLO & dielDBR Structure
20um
SiNxTi/Al
-2 0 2 4 6 8 10
0
5
10
15
20
Cu
rren
t (m
A)
Voltage (V)
I-V curve
Multimode PQR Lasing
420 440 460 480 500 520 540 560 580
400
600
800
1000
1200
1400
1600
1800
2000
Inte
nsity
(cou
nt)
Wavelength (nm)
3mA 5mA 10mA 15mA 20mA 25mA 30mA 35mA 40mA 45mA 50mA 55mA 60mA 65mA 70mA 75mA 80mA
420 440 460 480 500 520 540 560 580350
400
450
500
550
600
650
700
750
Inte
nsity
(cou
nt)
Wavelength (nm)
15mA 20mA 80mA
PQR
LED
GaN Surface-Emitting Laser at Blue Wavelengths
H. M., S. Yoshimoto, et al., & S. Noda Science 25 Jan. 2008: Vol. 319. pp. 445
(GaN)–PhC-SEL ; latt. cn. 100 - 200 nm
GaN-hybrid VCSEL InGaN/GaN 10QW @77K
AlN/GaN DBR –Cracks/Leaks /p-doping & Ta2O5/SiO2 dielectric DBR
Ith=6.9 A (67 kA/cm2)pulse
APL Lu et al,92, 141102 (4/2008)
Projection system
Structure of PQR Laser image chip TV
Color recombination system
Image chip
Matrix addressable scheme 1. First etching
2. N-metal evaporation 3. Second etching Perfect isolation )
4. PI planarization & P-metal evaporation 5. Fully addressable PQR array
(
Matrix addressable PQR array
PQR (Photonic Quantum Ring) laser Ultra-low threshold current ( )
dependent temperature stability
High speed modulation : ~100MHz to GHz
Speckle Free : 3-dim WCM (Whispering Cave Mode)
Low power consumption PQR array
nAA ~
T
Matrix addressable scheme
Minimizing the chip size
Lowering the number of connections
Addressed through a row and column connection
2Nfor the array : NN N2
High count arrays
[Matrix addressable] PQR laser chip TV