1. Photonic Quantum Ring Laser & Mega-Pixel Laser Chip for Display
IEEE-LEOS 2008
Nov. 11, 2008
(GaN)
Photonic Quantum Ring Laser &
Mega-Pixel Laser Chip for Display
[Whispering Cave Mode]
O’Dae Kwon
Department of Electrical Engineering
Pohang University of Science and Technology
Pohang , Korea

2. 2-D Whispering Gallery vs. 3-D Whispering Cave
toroidal cavity 3D TIR  3D WCM prop. of PQR
PQR from carrier-photon couple
Single Mode
Red PQR Laser
Blue PQR Laser
Laser TV [model]

3. St. Paul cathedral : Lord Rayleigh
concave Whispering Gallery – Bessel function
2D TIR (Total Intn’l. Reflec’n) - 2D symmetry

4. Micro Whispering Gallery Mode(WGM)
1910 Lord Rayleigh. WGM from concave surface
Philosophical magazine, xx (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
SiO2 WGM
Bessel (Jm)
field profile
Helical wave

5. (3D WCM) PQR fabrication & structure
Vertical mesa using CAIBE
Ar: Cl2: BCl3
Silicon nitride
coating
SiNx
P-DBR
Active layer
N-DBR
substrate
Epi structure
Planarization using polyimide
Polymide
CF4
SiNx etching by RIE for metal contact

6. PQR hole (3D WCM) PQR (concave) & PQR hole (convex)
CMP-Metal-WireBond-Packaging
P-metal
N-metal
PQR hole
OPTO Paper # :Mega-pixel PQR hole chip : PC eff. isolations
Ion implantation for hole isolation
H+-Ion Implantation
Hole etching, passivation Metal contact

7. Photonic Quantum Ring Low threshold current (ϕ=15 μm)
Ahn et al., PRL, 82, 536 (1999).
12㎂, near the
PQR threshold
11.5㎃, below
VCSEL threshold
12.2 ㎃, above
Low threshold current (ϕ=15 μm) z
P-DBRs
N-DBRs ρ
P-metal
MQW
Bessel (Jm)
field profile
Helical wave
Temperature stability (T1/2 dependent)
A. Yariv. APL, 53, 12 (1988).

8. PQR Threshold Ith ( ) # of wires I. QW assumption II. QWR assumption
Ahn et al., PRL, 82, 536 (1999).
Kwon et al., APL, 89, (2006).
PQR Threshold Ith
A. Yariv. APL, 53, 12 (1988).
I. QW assumption
( )
Chin-Chu-Ho,
JAP 75,3302(1994)
PQR mesa: ● (threshold) ○ (transparency)
PQR hole: ▪ (threshold) ▫(transparency)
II. QWR assumption
WRayleigh 10
0.314
3 (2.4) 20
0.629
5 (4.85) 30
0.943
7.2
# of wires
λ/2
Park et al., APL, 79, 1593 (2001).

9. Spectral PQR Analy. of 3D WCM theoy Opt. Lett. Vol. 28, 1861 (2003)

10. PQR: carrier-photon dynamic model
Dynamic filamentation and beam quality of quantum-dot lasers
E. Gehrig and O. Hess, APL, 84, 1650 (2004).
Park et al., APL, 79, 1593 (2001).
Bessel (Jm)
field profile
Helical wave
evanescent region
Toroidal cavity z x
z=L
x=W
Stripe of WRayleigh
E. Gehrig et al., APL, 84, 1650 (2004).

11. WRayleigh~1 µm, ϕ = 30 µm [MEJ,2008]
Field intensity 10
0.314
2.4 20
0.629
4.8 30
0.943
7.2
Stripe of WRayleigh x
Field
Carrier
Stripe of WRayleigh
~ 5 [#]
10psec
time
Carrier distribution

12. Local density of states in 2DEG
Electron standing waves in a 2DEGs
Coherent branched electron flow in a 2DEGs
Room temp
1.7K
Au(111) surface
Period:15Å
P. Avouris, Physics Today, 11, 17 (1993).
M. F. Crommie, et al. Nature, 363, 524 (1993).
Quantum corral of electrons
M.A. Topinka, R.M. Westervelt, E.J. Heller,
“Imaging Electron Flow", Physics Today 56, 12 (2003).

13. Polarization Vectors // PQR
Kim et al., JAP, 102(5), xx (2007).
Strong Carrier-Photon Coupling
fiber ② ③ ①
① : linear polarizer
② : linear polarizer
③ : o
(a): without polarizer
(b): polarizer
(c): polarizer
(d): o polarizer
(e): o polarizer
=15 μm, I=150 A (10kHz)

14. Single mode PQR Laser
JAP (2008) to appear
500 nA
1 uA
3 uA
5 uA

15. Red PQR Laser Array
PQR emission
LED emission
256 array ( = 7 m)
Spacing = 68 m
256 array ( = 10 m)
I = 2 mA (7.8 A/cell )
Emission image of the 16x16 mesa type red PQR laser array; reveals two different regions at an injection current of 24uA. The PQR lasing occurs in the periphery of the active disk called the Rayleigh band and the LED emission occurs in the middle part of the disk. It shows that the PQR region is emitting first and much brighter than the LED emission region, which means very high emission efficiency of the PQR laser.
- The PQR lasing region is brighter than the LED emission region, which means very high emission efficiency of the PQR laser.

16. Blue PQR laser at 480nm

17. PQR array ( , spacing)
CW/ room temp /at 60mA :
without & with an attenuation filter

18. Blue PQR Laser
LLO & dielDBR Structure
20um
Ti/Al
SiNx

19. Multimode PQR Lasing
PQR
LED

20. GaN Surface-Emitting Laser at Blue Wavelengths H. M. , S
GaN Surface-Emitting Laser at Blue Wavelengths H. M., S. Yoshimoto, et al., & S. Noda Science 25 Jan. 2008: Vol pp. 445
Ith=6.9 A (67 kA/cm2)pulse
(GaN)–PhC-SEL ; latt. cn nm
GaN-hybrid VCSEL InGaN/GaN
APL Lu et al,
92, (4/2008)
AlN/GaN DBR –Cracks/Leaks /p-doping & Ta2O5/SiO2 dielectric DBR

21. Structure of PQR Laser image chip TV Color recombination system
Projection system
이 그림은 PQR laser image chip TV의 구조도입니다.
Image chip은 R,G,B PQR array 및 FPGA controller로 구성됩니다.
각 RGB 영상을 합성하기 위해 다이크로익 프리즘을 통과 시킨 후,
프로젝션 시스템에 의해 확대 투사하게 됩니다. 이 사진은 글자 ‘ST’-RED PQR array를 140배 확대한 image입니다.
(메사 수 870)
장차 구현하게 될 Image chip TV에서는 이 mesa하나가 one 픽셀이 될 것입니다.
이제 PQR image chip TV 구현을 위한 기초적인 실험 결과에 대해 말씀 드리겠습니다.
실험은 크게 두 부분으로 나뉘어져 있습니다. Image chip의 메사 수 및 size등을 얻기 위한 기초적인 최적화 과정과, Projection system의 설계를 위한 기초적인 Lens 실험입니다.
Color recombination system

23. Matrix addressable scheme 1. First etching
Matrix addressable PQR array
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

24. [Matrix addressable] PQR laser chip TV
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
Matrix addressable scheme
Addressed through a row and column connection
Minimizing the chip size
Lowering the number of connections
for the array :
High count arrays
[Matrix addressable] PQR laser chip TV