Nanolasers: Current Status of Trailblazer of Synergetics Cun-Zheng Ning cning@asu.edu, http://nanophotonics.asu.edu School of Electrical, Computer, and Energy Engineering Arizona State University Support: ARO, AFOSR, DARPA, NASA, SFAz cning@asu.edu, http://nanophotonics.asu.edu
Miniaturization of Semiconductor Lasers mm ~ cm scale (1962) 0.5 mm First laser diode (GaAs) Lincoln Lab 100 nm ~ µ m scale (2012) cning@asu.edu, http://nanophotonics.asu.edu
Radiative coupling between light and semiconductor Engineering Photon-Semiconductor Interaction ( ) ( ) • ρ r ∝ ρ ph ω E e cv Density of Photonic States Density of Electronic States 2 ω ( ) 3 ρ D ω = 0 3 Free space: * 0 1 2 ph 2 3 m π 2 c Cavity Size Reduction ( ) 3 ρ = − D E E E Bulk Size Quantization e 2 2 2 g π h 3D cavity: 1 1 κ * m ( ) ( ) ρ cav ω = 2 ρ = D E ( ) QW: ph 2 π V 2 ω − ω + κ e 2 π h c 0 Decreasing V c 2 * 1 m ( ) 1 ρ D = E QWR: e π − E E Purcell Enhancement h n ( ) 3 ρ cav ω λ 3 0 0 2 ( ) ρ D = δ E − = ph = E F Q QD: ( ) e n P 3 2 4 ρ D ω π V 0 ph c cning@asu.edu, http://nanophotonics.asu.edu
Engineering the Densities of States Density of Photonic States Density of Electronic States ( ) ρ cav ω 0 ph 2 ω ( ) 3 ρ D ω = 0 0 ph 2 3 π c Cavity Size Reduction Size Quantization More efficiently use of photons More efficiently use of electrons/holes More efficiently coupling photons and semiconductors cning@asu.edu, http://nanophotonics.asu.edu
Why Nanolasers? From Application Point of View • Optical and electronic integration, size compatibility with electronic devices • VLSI photonics: more functions in smaller volume • On-chip light sources (e.g., micro and nano-fluidic) • General trends in nanotechnology development: the smaller the better • Other new applications not envisioned yet, but will be enabled once smaller and smaller lasers are available cning@asu.edu, http://nanophotonics.asu.edu
Moore’s Law in Photonics M.K. Smit, Moore’s law in photonics cning@asu.edu, http://nanophotonics.asu.edu
Moore’s Law in Photonics Technology Breakup M.K. Smit, Moore’s law in photonics cning@asu.edu, http://nanophotonics.asu.edu
Moore’s Law for Microelectronics cning@asu.edu, http://nanophotonics.asu.edu
Challenges for Nanophotonics • Size, Size, and Size / 2 > λ n a) Passive devices (waveguides): , single mode fiber: 5 µ µ µ µ m; silicon wire or other semiconductor nanowire: 100-200 nm b) Active devices: (lasers): gain length required to achieve threshold: 1-100 µ µ µ µ m, large footprint, difficult for integrate • Complexity, diversity, and cost: diversity of devices and materials, small market share of each device, expensive manufacturing • Compatibility with silicon for integration with electronics light emitting materials: non-silicon (III-V, II-VI) such as GaAs, InP • No silicon light source (external to CMOS) • … cning@asu.edu, http://nanophotonics.asu.edu
Examples of Smallest Lasers…( before 2007) (what is in common: pure dielectric waveguide structures) nanowire substrate 55 nm-think ZnO nanocrystal layer is Erbium doped silica disk of 60 microns in diameter on a dispersed on a SiO 2 disk of 10 microns in silicon stem (Kippenberg, PRA 2006) (optically pumped) diameter, Liu et al, APL (2004) Park et al. Science 305 , 1444 InAs/AlGaAs single layer of QD, 60 nW output (2004). (Optically pumped, RT-CW, smallest, PC laser, (Painter group, Opt. Exp. 2006) Baba’s group, InGaAsP/InP, Opt. Exp.2007) cning@asu.edu, http://nanophotonics.asu.edu
Questions • Can lasers be made even smaller? • What is the ultimate size limit? • How about electrical injection, rather than optical? • Can you make a laser that is smaller than vacuum wavelength in all three dimensions (DARPA NACHOS program)? NACHOS (Nanoscale Architectures for Coherent Hyper-Optic Sources) Goals: Electrical injection, room temperature, subwavelength in all 3- dimensions cning@asu.edu, http://nanophotonics.asu.edu
How to Make Smaller Cavities? • Pure dielectric cavities are not adequate • Metallic, especially plasmonic structures offer potential hope Plasmonics, Spasers, Before 2007…. • Bergman and Stockman, PRL 2003 • Stockman and Bergman, Laser Phys, 2004 • Nezhad, Tedz, and Fainman, Opt. Exp. 2004 • Maier, Opt. Comm. 2006 • Miyazaki and Kurokawa, PRL 2006 cning@asu.edu, http://nanophotonics.asu.edu
Plasmon Photon Coupling Plasma/Plasmon: Longitudinal excitation of electron motion (in metals or doped semiconductors) Drude model: 1/2 2 ω 2 Ne ω = ε ω ( ) = − 1 p p ε 2 ω + γω m i 0 Surface Plasmon or Surface Plasmon Polariton: Coupled EM wave and plasmon excitation at the interface of a dielectric layer and a metallic layer. ε 1 ω ε ε = 1 2 k ε 2 z ε + ε c 1 2 cning@asu.edu, http://nanophotonics.asu.edu
Surface Plasmon Polariton (SPP) 2 π 540 λ SPP wave along the interface nm λ = 15 . 4 0 = = eff k ′ 35 λ nm eff z k ′ z Semiconductor Silver Silver 2 ( ′ ′ ′ ) + = i k i k z I I e k ′ ′ 0 z (eV) Near SPP Resonance: 1) Huge wave compression (35 nm) 2) Strong localization ( few nm) 3) Huge loss (3.6 million 1/cm) ~ nm cning@asu.edu, http://nanophotonics.asu.edu
Lasers, Spasers, and Photon-Plasmon Coupling k ω = k n c BPP SPP ω SP BP Plasmonicity ω ω p p SPASERS: Bergman and Stockman, 2 Phys. Rev. Lett. 90 , 027402 (2003) cning@asu.edu, http://nanophotonics.asu.edu
Light Coupling to SPP Mode: Dramatic Purcell Enhancement InGaN QW-Silver (8nm) by GaN thickness: (Neogi et al, PRB66, 153305(2002) Neogi et al, PRB, 2002 cning@asu.edu, http://nanophotonics.asu.edu
Feasibility of a Semiconductor-Core Metal-Shell (Jan 2007 SPIE Paper) Maslov-Ning , 2007 cning@asu.edu, http://nanophotonics.asu.edu
First Experimental Demonstration of the Semiconductor-Metal Core-Shell Laser M. Hill et al. Nat. Photonics, 1, (2007),589 cning@asu.edu, http://nanophotonics.asu.edu
A Zoo of Nanolaser Designs… after 2007 (What is in Common? Everyone Likes Metals) Chuang-Bimberg Group Hill , 2007 Hill -Ning 2009 Maslov-Ning , 2007 250 nm Ni/Au Aluminum 230 nm Alumina p-GaN PMMA MQW Ti/Au n-GaN (Wu Group, Berkeley) (Zhang Group, 2009 Sapphire Yang Group Fainman UCSD) Noginov/Shalaev, 2009) Painter Group 2009 (Lieber, Harvard, Park, Korea) cning@asu.edu, http://nanophotonics.asu.edu
Summary of Short History and Status • Design and theoretical study: Maslov and Ning, Proc. SPIE 6468, (2007)64680I • 1 st experimental demonstration: M. Hill et al. Nat. Photonics, 1, (2007),589 • Electrical injection sub-half-wavelength laser: Hill et al, Opt. Exp., 2009 • Metal encased in a doped shell: Noginov et al., 2009 • Wire on a metal surface: Oulton et al., 2009 • Metal-semiconductor disk laser, Parahia et al, APL, 95 (2009) 201114 • Optically pumped lasing at RT: Nezhad et al, Nat. Phontonics, 4, (2010),395 • Nano patch laser: Yu et al., Opt. Exp. , 18 (2010) 8790 • Nano pan laser: Kwon et al. (2010), Nano. Lett, 10, (2010),3679 • Metallic cavity VCSEL, RT operation, Lu et al, Appl. Phys. Lett, 96, 251101 (2010) • Goals: Sub-wavelength, CW RT operation, electrical injection cning@asu.edu, http://nanophotonics.asu.edu
Semiconductor-Metal Core-Shell Nanolaser n-contact 500 polyamide n-InP 300 nm Ag Si 3 N 4 500 InGaAs p-InP Ti/Pt/Au p-cntct InP Subs. Circular pillars: diameters ~280nm to 500nm � Rectangular pillars: 6 and 3 micron long; core width � ~80nm +/- 20nm to ~340nm Hill, Marell, Leong, Smalbrugge, Zhu, Sun, Veldhoven, Geluk, Karouta, Oei, Nötzel, Ning, Smit, Opt. Exp.,17, 11107 (2009) cning@asu.edu, http://nanophotonics.asu.edu
Lasing in a Silver-Coated 90+40 nm-Thick Pillar: (thickness below half-wavelength limit) Total light output vs current 4 Run6 row 1 dev #17, 10K, 130uA 5 7 x 10 x 10 Run 6 row 1 dev #18 10K 6 90nm Run6 row 1 dev #17, 10K 6 40 microamps 5 450 60 microamps 80 microamps 400 100 microamps 5 350 4 Intensity (counts) Intensity (counts) Intensity (counts) 300 4 250 200 3 150 3 100 50 2 2 0 1300 1350 1400 1450 1500 wavelength (nm) 1 1 0 0 1250 1300 1350 1400 1450 1500 1550 0 50 100 150 200 250 Wavelength (nm) current (microamps) / 2 670 = λ = Optical thickness = 3.1X90 + 2X20X2 + 2X10X2 = 400 nm < DL nm (Semicond.) (Dielectric) (Metal) The thinnest electrical injection laser ever demonstrated ! Hill, Marell, Leong, Smalbrugge, Zhu, Sun, Veldhoven, Geluk, Karouta, Oei, Nötzel, Ning, Smit, Opt. Exp.,17, 11107 (2009) cning@asu.edu, http://nanophotonics.asu.edu
More Recent Progress on Nanolasers with V < λ λ λ λ 3 2009, pulse, LT 2011, CW 260K 2012, CW, RT wide linewidth A 10 7 6 Integrated intensity (a.u.) 8 5 linewidth (nm) 6 4 3 4 2012, CW, RT 2 2 final goal! 1 0 0 0.0 0.5 1.0 1.5 2.0 Current (mA) cning@asu.edu, http://nanophotonics.asu.edu
cning@asu.edu, http://nanophotonics.asu.edu
cning@asu.edu, http://nanophotonics.asu.edu
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