O’Dae KwonDepartment of Electrical Engineering

Pohang University of Science and Technology Pohang 790-784, Korea

odkwon@postech.ac.kr 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