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 790-784, Korea odkwon@postech.ac.kr http://www.postech.ac.kr/ee/light

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]

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

Micro Whispering Gallery Mode(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 SiO2 WGM Bessel (Jm) field profile Helical wave

(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

PQR hole (3D WCM) PQR (concave) & PQR hole (convex) CMP-Metal-WireBond-Packaging P-metal N-metal PQR hole OPTO Paper # 6897-29 :Mega-pixel PQR hole chip : PC eff. isolations Ion implantation for hole isolation H+-Ion Implantation Hole etching, passivation Metal contact

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).

PQR Threshold Ith ( ) # of wires I. QW assumption II. QWR assumption Ahn et al., PRL, 82, 536 (1999). Kwon et al., APL, 89, 11108 (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).

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

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).

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 intensity @5psec Carrier distribution@5psec Stripe of WRayleigh ~ 5 [#] 10psec time Carrier distribution

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).

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 : +135o (a): without polarizer (b): polarizer (c): polarizer (d): +45o polarizer (e): +135o polarizer =15 μm, I=150 A (10kHz)

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) 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.

Blue PQR laser at 480nm

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

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

Multimode PQR Lasing PQR LED

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. 319. pp. 445 Ith=6.9 A (67 kA/cm2)pulse (GaN)–PhC-SEL ; latt. cn. 100 - 200 nm GaN-hybrid VCSEL InGaN/GaN 10QW @77K APL Lu et al, 92, 141102 (4/2008) AlN/GaN DBR –Cracks/Leaks /p-doping & Ta2O5/SiO2 dielectric DBR

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

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

[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