Nanolasers: Current Status of Trailblazer of Synergetics Cun-Zheng - - PowerPoint PPT Presentation

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Nanolasers: Current Status of Trailblazer of Synergetics Cun-Zheng - - PowerPoint PPT Presentation

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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

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cning@asu.edu, http://nanophotonics.asu.edu

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

Nanolasers:

Current Status of Trailblazer of Synergetics

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cning@asu.edu, http://nanophotonics.asu.edu First laser diode (GaAs) Lincoln Lab 0.5 mm

Miniaturization of Semiconductor Lasers

mm ~ cm scale (1962) 100 nm ~ µm scale (2012)

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cning@asu.edu, http://nanophotonics.asu.edu

Engineering Photon-Semiconductor Interaction

Radiative coupling between light and semiconductor

( )

E

e

ρ

  • ( )

ω ρ ph

cv

r ∝

( )

g D e

E E m E −         =

2 3 2 * 2 3

2 2 1 h π ρ

( )

n D e

E E m E − = 1 2

* 1

h π ρ

( )

2 * 2

h π ρ m E

D e

=

) ( 2

n D e

E E − = δ ρ

Bulk QW: QWR: QD:

Density of Electronic States Density of Photonic States

( ) ( )

Q V F

c D ph cav ph P

        = =

3 2 3

4 3 λ π ω ρ ω ρ

Purcell Enhancement

Size Quantization

( )

3 2 2 3

c

D ph

π ω ω ρ = ( )

( )

2 2

1 1 κ ω ω κ π ω ρ + − =

c cav ph

V

Decreasing Vc

Cavity Size Reduction

Free space: 3D cavity:

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cning@asu.edu, http://nanophotonics.asu.edu

Size Quantization

Density of Electronic States

Engineering the Densities of States

More efficiently use of photons More efficiently use of electrons/holes More efficiently coupling photons and semiconductors

( )

3 2 2 3

c

D ph

π ω ω ρ =

( )

ω ρ cav

ph

Cavity Size Reduction

Density of Photonic States

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cning@asu.edu, http://nanophotonics.asu.edu

Why Nanolasers? From Application Point of View

  • Optical and electronic integration, size compatibility with

electronic devices

  • On-chip light sources (e.g., micro and nano-fluidic)
  • VLSI photonics: more functions in smaller volume
  • 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

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cning@asu.edu, http://nanophotonics.asu.edu

Moore’s Law in Photonics

M.K. Smit, Moore’s law in photonics

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cning@asu.edu, http://nanophotonics.asu.edu

Moore’s Law in Photonics Technology Breakup

M.K. Smit, Moore’s law in photonics

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cning@asu.edu, http://nanophotonics.asu.edu

Moore’s Law for Microelectronics

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cning@asu.edu, http://nanophotonics.asu.edu

Challenges for Nanophotonics

  • Size, Size, and Size

a) Passive devices (waveguides): , single mode fiber: 5 µ µ µ µm; silicon wire or other semiconductor nanowire: 100-200 nm b) Active devices: (lasers): gain length required to achieve threshold: 1-100 µ µ µ µm, 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)
  • …

n 2 / λ >

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cning@asu.edu, http://nanophotonics.asu.edu

Examples of Smallest Lasers…( before 2007)

(what is in common: pure dielectric waveguide structures)

55 nm-think ZnO nanocrystal layer is dispersed on a SiO2 disk of 10 microns in diameter, Liu et al, APL (2004) Erbium doped silica disk of 60 microns in diameter on a silicon stem (Kippenberg, PRA 2006) (optically pumped) InAs/AlGaAs single layer of QD, 60 nW output (Painter group, Opt. Exp. 2006)

substrate nanowire

Park et al. Science 305, 1444 (2004). (Optically pumped, RT-CW, smallest, PC laser, Baba’s group, InGaAsP/InP, Opt. Exp.2007)

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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

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cning@asu.edu, http://nanophotonics.asu.edu

  • 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

How to Make Smaller Cavities?

  • Pure dielectric cavities are not adequate
  • Metallic, especially plasmonic structures offer

potential hope Plasmonics, Spasers, Before 2007….

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cning@asu.edu, http://nanophotonics.asu.edu

Plasmon Photon Coupling

Plasma/Plasmon: Longitudinal excitation of electron motion (in metals or doped semiconductors) Drude model: Surface Plasmon or Surface Plasmon Polariton: Coupled EM wave and plasmon excitation at the interface of a dielectric layer and a metallic layer.

2 2

( ) 1

p

i ω ε ω ω γω = − +

1/2 2 p

Ne m ω ε   =    

1 2 1 2 z

k c ε ε ω ε ε = +

ε1 ε2

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cning@asu.edu, http://nanophotonics.asu.edu

Surface Plasmon Polariton (SPP)

Near SPP Resonance: 1) Huge wave compression (35 nm) 2) Strong localization ( few nm) 3) Huge loss (3.6 million 1/cm)

Silver Silver Semiconductor

SPP wave along the interface

(eV)

z k i k i

e I I

) ( 2 ′ ′ + ′

=

z

k ′ ′

z

k′

4 . 15 35 540 = = nm nm

eff

λ λ

z eff

k′ = π λ 2

~ nm

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cning@asu.edu, http://nanophotonics.asu.edu

BPP SPP

Lasers, Spasers, and Photon-Plasmon Coupling

SPASERS: Bergman and Stockman,

  • Phys. Rev. Lett. 90, 027402 (2003)

ω

k

2

p

ω p

ω

n c k ω =

SP BP

Plasmonicity

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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

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cning@asu.edu, http://nanophotonics.asu.edu

Feasibility of a Semiconductor-Core Metal-Shell (Jan 2007 SPIE Paper)

Maslov-Ning , 2007

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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
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cning@asu.edu, http://nanophotonics.asu.edu Noginov/Shalaev, 2009) 250 nm 230 nm (Wu Group, Berkeley)

(Lieber, Harvard, Park, Korea)

Fainman UCSD)

A Zoo of Nanolaser Designs… after 2007

(What is in Common? Everyone Likes Metals)

Hill , 2007 Chuang-Bimberg Group

Ti/Au Ni/Au Sapphire Alumina Aluminum MQW p-GaN n-GaN PMMA Yang Group

Maslov-Ning , 2007 (Zhang Group, 2009 Hill -Ning 2009 Painter Group 2009

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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
  • 1st 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
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cning@asu.edu, http://nanophotonics.asu.edu

Semiconductor-Metal Core-Shell Nanolaser

InP Subs. p-InP InGaAs Ag Si3N4 n-InP Ti/Pt/Au p-cntct polyamide n-contact 500 300 500 nm

  • 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)

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cning@asu.edu, http://nanophotonics.asu.edu

The thinnest electrical injection laser ever demonstrated !

1250 1300 1350 1400 1450 1500 1550 1 2 3 4 5 6 7 x 10

4

Wavelength (nm) Intensity (counts) Run6 row 1 dev #17, 10K, 130uA

50 100 150 200 250 1 2 3 4 5 6 x 10

5

Total light output vs current Run 6 row 1 dev #18 10K current (microamps) Intensity (counts)

Lasing in a Silver-Coated 90+40 nm-Thick Pillar: (thickness below half-wavelength limit)

90nm

1300 1350 1400 1450 1500 50 100 150 200 250 300 350 400 450 wavelength (nm) Intensity (counts) Run6 row 1 dev #17, 10K 40 microamps 60 microamps 80 microamps 100 microamps

Optical thickness = 3.1X90 + 2X20X2 + 2X10X2 = 400 nm < DL nm 670 2 / = = λ

Hill, Marell, Leong, Smalbrugge, Zhu, Sun, Veldhoven, Geluk, Karouta, Oei, Nötzel, Ning, Smit, Opt. Exp.,17, 11107 (2009)

(Semicond.) (Dielectric) (Metal)

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cning@asu.edu, http://nanophotonics.asu.edu

More Recent Progress on Nanolasers with

2009, pulse, LT

V < λ λ λ λ3

2012, CW, RT final goal!

0.0 0.5 1.0 1.5 2.0 2 4 6 8 10

Current (mA) Integrated intensity (a.u.)

1 2 3 4 5 6 7

linewidth (nm)

A

2011, CW 260K 2012, CW, RT wide linewidth

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cning@asu.edu, http://nanophotonics.asu.edu

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cning@asu.edu, http://nanophotonics.asu.edu

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cning@asu.edu, http://nanophotonics.asu.edu

Disappearance of Threshold in Nanolasers

0.0000 0.0004 0.0008 0.0012 0.00E+000 5.00E+014 1.00E+015 photon density current (uA) 1e-4 1e-3 1e-2 0.1 0.2 0.4 0.6 0.8 1.0

I L ∝ I L ∝

18

I L ∝

1E-7 1E-6 1E-5 1E-4 1E9 1E10 1E11 1E12 1E13 1E14 1E15 Intensity Current (A)

1e-3 1e-2 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

β =

Thresholdless? Yes.

But approaching zero (lasers)? or infinity (LED)?

V ∝ β 1

Similar to disappearance of phase transitions in finite or lower dimensional systems, threshold becomes increasingly soft and disappears eventually in nanolasers as size decreases

β β β β= = = =

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cning@asu.edu, http://nanophotonics.asu.edu

Photon Statistics Near Threshold

Gies et al, PRA ,75, 013803,2007

2 ) 2 (

) ( ) ( ) ( ) ( t I t I t I g τ τ + =

thermal light

2 ) (

) 2 (

= g

laser light

1 ) (

) 2 (

= g

Threshold infinity?

There seems to be a more fundamental limitation (beyond gain requirement and cavity mode etc) to how small laser can be made: When size becomes too small, we cannot make a laser with the coherent state emission

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cning@asu.edu, http://nanophotonics.asu.edu

Further on Nanolasers…

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cning@asu.edu, http://nanophotonics.asu.edu

Summary

  • Nanolsaer research is driven both by the engineering
  • f photonic and electronic densities of states and by

future applications in nanophotonic integrated systems

  • Plasmonic structures provide an interesting means

for the cavity miniaturization to reach nanoscale

  • There seems to be a fundamental limit in terms of

how small a laser cavity can be: when the cavity is so small that spontaneous emission coupling to the lasing mode is approaching 100%, the threshold becomes increasingly high!

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cning@asu.edu, http://nanophotonics.asu.edu

Thank You!