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Composite Materials for Ultrafast and Large Third-order Optical Nonlinearity and Photonic Applications. Qihuang Gong, Xiaoyong Hu, Jiaxiang Zhang, Hong Yang. Department of Physics, Peking University, Beijing, P. R. China. Email: [email protected] ; Fax: +86-10-62756567. Contents. Motivation

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slide1

Composite Materials for Ultrafast and Large Third-order Optical Nonlinearity and Photonic Applications

Qihuang Gong, Xiaoyong Hu, Jiaxiang Zhang, Hong Yang

Department of Physics, Peking University, Beijing, P. R. China

Email: [email protected]; Fax: +86-10-62756567

contents
Contents
  • Motivation
  • Enhanced ultrafast 3rd nonlinearity
  • using composite materials
  • Photonic crystal and PC optical switch
  • Conclusion
slide3

Motivation

  • 1980- Third-order Optical Nonlinear Materials

Photonics Applications

All optical device

Optical switching

Optical computing

Integrated photonic circuits

Fast and large 3rd NLO response

fs NLO response

large off-resonant c(3)

} fs measur.

  • conjugated organic molecules and polymers
  • Semiconductors
slide4

Measurement on ultrafast 3rd nonlinearity

  • l : 760 - 850nm
  • : ~100fs
  • I1:I2 = 10:1

Femtosecond OKE System

slide5

OKE – four wave mixing process

Es

E1

P

E1

Is

Es

E2

E2

450

I2

I1

c(3)

I

s=

Typical OKE signal of CS2

slide6

3rd optical nonlinearity of routine materials:

Liquid crystal 10-7 10-6

☆Large 3rd nonlinear susceptibility and ultrafast response

are difficult to achieve simultaneously

slide7

II Enhanced ultrafast 3rd nonlinearity using

composite materials

Composite I: Coumarine 153 doped Polystyrene

n2(c(3))~1/(w0 – w – iG)

* Near resonant enhancement

(enlarge the response time of excited state lifetime )

* Inter-molecular excited-state electron transfer

slide8

Coumarine 153 doped Polystyrene

Inter molecular electron transfer

~ 1ps

400nm near-resonant excitation

800nm probe

C153 molecule

Polystyrene

Polymer composite material: C153:Polystyrene

slide9

Composite Material II: Nano-Ag doped MEH-PPV

surface plasmonics enhanced 3rd optical nonlinearity

The effective third-order nonlinear optical susceptibility of the composite material can be written as

and are permittivity for host material and metal nanoparticles

and are third-order optical susceptibility of host material and metal nanoparticles

p is the volume fraction of Ag nanoparticles

a very large nonlinear coefficient

In the SPR peak

slide10

Nano-Ag doped MEH-PPV

Energy transfer ~ps

SPR resonant excitation

MEH-PPV

Ag nanoparticle

slide11

III. Photonic crystal and PC optical switch

★ Photonic crystal is a novel photonic material with a

periodic dielectric distribution

One-dimensional Photonic crystal

Two-dimensional photonic crystal

Three-dimensional photonic crystal

★Photonic crystal possesses photonic bandgap and

can control the propagation states of photons

slide12

Defect states

When a structure defect is introduced in the photonic crystal, the defect states will appear in the photonic bandgap

Frequency

Dielectric Defect

Air Defect

Air Band

Photonic

Bnadgap

Dielectric Band

Defect Radius

slide13

Photonic

Bandgap

Wavelength

Pump Light

Probe Light

Bandgap or Defect state shift

---------- change the refractive index

☆Third-order optical nonlinear photonic crystal

Pump Beam Intensity

Photonic Bandgap Shift

Defect State Shift

Transmittance

Photonic Bandgap

Transmittance

Defect State

Wavelength

Probe Light

Pump Light

Light beam controlled Shift

slide14

Concept for All-Optical Switching effect

Pump light

Probe light

Probe light

Using Photonic bandgap shift or defect state shift by Pump Beam

Photonic crystal optical switching

slide15

1) PC optical switch using pure polymer

Organic polymer: Polystyrene

n2=1×10-13cm2/W

Schematic Structure of Polystyrene Molecule

slide16

Two-dimensional Polystyrene Photonic Crystal Fabrication Process

Spin Coating + FIB etching

cylindrical air holes embodied in the polystyrene slab.

Film Thickness 300nm

Lattice Constant 320nm

Radius of Air Hole 130nm

Width of Line Defect 450nm

The patterned area is about 4 μm×100 μm

A line defect in the center of a two-dimensional photonic crystal to form photonic crystal filter

slide17

Photonic Crystal Devices:

Filter, Switch

line defect

transmission mode

Transmission spectra :

(a) Measured result

(b) Theoretical result of multiple

scattering method

* Central Wavelength 791nm, Quality Factor 500, Line width 1.6nm

slide18

X

Prism Mode

Z

Air Gap

Air Gap

Waveguide

Waveguide

Guided Mode

Substrate

Substrate

Evanescent Field Coupling System

probe beam

W

θp

Cross Section Structure

Electric-field Distribution

1) Energy of the incident light is coupled into optical waveguide

with the help of evanescent field

2)Coupling efficiency ~ 20%

slide19

Ti:sapphire Laser

Diode

Aperture

Lens

Prism

Micro Lens

Delay Line

Computer

PMT

Monochromator

Experimental Setup

800nm Pump beam

Ti:sapphire laser:

Pulse Duration 120fs

Pulse Repetition 76MHz

Wavelength 700nm-860nm

800nm

800nm

Waveguide

100 μm×2.5 mm

The patterned area is about 4 μm×100 μm

slide20

Switching Performance

800nm Pump beam

Conclusion:

An all-polymer tunable photonic crystal filter, switch with ultrafast time response is realized.

Time Response ( as fast as the time-resolution of measurement system )

Pump Intensity as high as GW/cm2

* Transmittance Contrast 60%

* Time Response~120fs

slide21

2) C153:Polystyrene PC optical switch

Polystyrene doped with 15% Coumarin 153

Absorption peak of Coumarin 153 is around 400nm

Film thichness: 300nm

Lattice constant: 320nm

Air hole radius: 120nm

Line defect width: 440nm

slide22

Electric field distribution of defect mode

Electric field was mainly confined in the defect structure

slide23

Tunability of the photonic bandgap microcavity

Measured result Simulated result

Transmittance spectra of the microcavity resonant mode as functions of the energy of the pump light

experimental setup

Ti:sapphire Laser

Aperture

Lens

BBO Crystal

Prism

Filter

Micro Lens

Delay Line

Computer

PMT

Fiber Spectrophotometer

Experimental setup

Near-resonant enhanced ----- 400nm Pump beam

800nm

☆ Near-resonant enhanced nonlinearity of polystyrene

400nm

slide25

All-optical switch effect

Switching efficiency: 80%

Response time: 1.2ps

Pump power: 110 KW/cm2

(reduced by 4 orders)

Chinese patent: 发明专利(ZL200710099383.2)“降低全光开关泵浦功率的方法、全光开关及其制备方法”

Nature Photonics 2 (2008) 185-189

slide26

Nature Photonics

‘Controlling photons with light’

A strongly nonlinear photonic crystal with a wavelength-tunable bandgap could provide the solution to realizing all-optical switches for signal processing‘

slide27

IOP optics.org:

‘ Photonic crystals speed up all-optical switching’

A polystyrene photonic crystal that acts as an all-optical switch boasts picosecond response time and low power requirements. The picosecond switching time is impressive.

一种光子晶体开关以具备皮秒时间响应和低泵浦功率而值得自豪,皮秒的超快开关时间令人印象深刻。

slide28

Nature Asia Materials:

Ultrafast Optical Switches:Now you see it, now you don’t

Researchers from Peking University, China, now demonstrate fast all-optical switching in a photonic crystal made from a composite material.

slide29

Nature China:

“Optical Switches: A New Low”

Qihuang Gong and co-workers at the Peking University in Beijing have devised a strategy for making ultrafast photonic-crystal-based optical switches that can operate under low-power pump light)。

slide30

3) Nano-Ag:MEH-PPV PC optical switch

SPP resonant-enhancement

Switching efficiency: 65%

Response time: 35ps

Pump power: 230 KW/cm2

Appl. Phys. Lett. 94, 031103 (2009)

slide31

PhysOrg.com:

‘ Nanocomposite material provides photonic switching’

The development of integrated photonic devices in tomorrow’s technology is taking place today at Peking University in Beijing, China, where a group of scientists has manufactured and tested nanocomposite material that could be used in integrated photonic devices

slide32

Nanomaterials World :

“Seeing the light”

Nanomaterials world 5 (2009,Mar. 17) 5

Photonic devices could aid developments in computing, following research in China.

The team from Peking University is working on a nanocomposite that could be integrated into photonic devices.

iv conclusion
IV. Conclusion

☆New composite materials are demonstrated to develop the 3rd optical nonlinearity

☆Large 3rd nonlinear susceptibility (4-orders enhanced ) and ultrafast response time ( of ps order ) were achieved

☆An ultrafast low-power photonic crystal all-optical

switch was realized by using the composite materials

slide34

V. Acknowledgement

Financial Supported by:

NNSFC, China

MOST, China

MOE, China,

Peking Uiversity

slide35

THE END

Thank You!

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