10.1 outline of the course - kit - lti · outline of the course 1. introduction 2. optoelectronic...

Universität Karlsruhe (TH)Research University � founded 1825

Universität Karlsruhe (TH)

Lichttechnisches Institut

Uli Lemmer

10.1

Outline of the course

1. Introduction

2. Optoelectronic properties of organic semiconductors

3. Organic light emitting diodes (OLEDs)

4. Device and display production

5. Organic FETs

6. Organic photodetectors and solar cells

7. Lasers and integrated optics

7.1 Organic laser basics

7.2 Organic semiconductor laser

7.3 Distributed feedback laser

7.4 Lab-on-chip-systems

7.4.1 Waveguide coupled lasers

7.3.2 Fast photodetectors




Uli Lemmer

10.2

What means LASER ?

LightAmplification by

StimulatedEmission ofRadiation




Uli Lemmer

10.3

Laser History

1958: Theoretical prediction (Schawlow, Townes et al., Bell-Labs)

1960: First experimental realization: Ruby laser (Al2O3 mit Cr)(Maiman et al., Hughes Research)

1961: First continuous wave laser (HeNe)

1962: First semiconductor diode laser (GaAs)

1966: First organic dye laser

1996: First organic semiconductor laser

2000: First organic laser diode (Bell-Labs) „The Schön-Scandal“




Uli Lemmer

10.4

| 1>

| 2>Laser beam

Laser principle: Optical amplification and positive feedback

Mirror Mirror

Pump

Active material

LASING




Uli Lemmer

10.5

Some basics ... Optical amplification

| 1>

| 2>

ActiveMedium Absorption (|1> →|2>) ~N1Wn

Stim. Emission (|2> →|1>) ~N2Wn

Spon. Emission (|2> →|1>) ~N2W

Lower state population: N1

Upper state population: N2

Photon number: nTransition rate: W




Uli Lemmer

10.6

Why lasing with organic materials ?

Abs.Emiss.

highly allowed absorption and emission (high W)

spectral separation of absorption and emission ⇒ 4 level-system( N1≈0, ⇒ low laser threshold, highly tunable)




Uli Lemmer

10.7

Organic dye lasers

History:

1966: Sorokin and Lankard (IBM Yorktown Heights)chloro-aluminum-phthalcyanine-dyeIBM J. Res. Develop. 10, 162 (1966)

1966 F. Schäfer et al. (University of Marburg)various cyanine dyes

Appl. Phys. Lett. 9, 306 (1966)




Uli Lemmer

10.8


1. Introduction




5. Organic FETs












Uli Lemmer

10.9

Towards organic solid state lasers: dyes in a polymer matrix

•0.8% rhodamine 6G in polyurethane,

•thickness 800 nm on a glass rod




Uli Lemmer

10.10

Towards organic solid state lasers: molecular crystals

1972: Optically pumped anthracene laserN. Karl, Phys. Stat. Sol. (a) 13, 651(1972)




Uli Lemmer

10.11

fs pump-probe to test optical gain

Simultaneous detection of ∆T/T and emisson

pump-pulse

white lightprobe-pulse

detection

∆t

Spectrograph




Uli Lemmer

10.12

a)

A

bs.(

a.u

)

PL

(a. u

.)b)

350 400 450 500 550 600

0

2000 c)

Wavelength (nm)

Ga

in (

cm

-1)

Optical spectra of m-LPPP: Abs., PL, Gain(0 ps)

t = 0 psS0

S1

Ab

sorp

tio

n

T. Pauck, U. L. et al., CPL 244, 171 (1995). A. Haugeneder, U. L. et al., JAP 85, 1124 (1999).

R

R

R'

R' nx

x




Uli Lemmer

10.13

The first conjugated polymer laser

Tessler et al. Nature 382, 695 (1996)

Threshold pulse energy: ≈ µJ




Uli Lemmer

10.14


1. Introduction




5. Organic FETs












Uli Lemmer

10.15

a) b)

c)

d) e) f)

Organic semiconductor laser resonators

U. Lemmer et al., Phys. Bl. 56, 25 (2000)




Uli Lemmer

10.16

Organic DFB laser

substrate

organic material

Λ⋅⋅= effBragg nm

2λ

2nd ordersubstrate

organicmaterial

Λ

m: order

neff: effective refractive index

Λ: periodicity

1st order

Λ

Advantages

• monochromatic light source• wide spectral range and tunability• low pumping thresholds• wide range of fabrication processes on

different substrates




Uli Lemmer

10.17

425 450 475 500 525 550

FWHM < 0.3 nm

EP = 2,0 nJ

Inte

nsit

y(a

rb. U

nit

s)

Wavelength (nm)

EP = 1,3 nJ

EP= 1,1 nJ

0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,50

100

200

300

1D-DFB

2D-photonic crystal laser

Excitation Energy (nJ / pulse)

Ou

tpu

t P

ow

er (n

orm

alized)

– Lower laser threshold

– Increased efficiency

S. Riechel, U.L. et al., APL 77, 2311 (2000)

2D Photonic Crystal Laser




Uli Lemmer

10.18

Variation of the grating periodicity

130 nm tuning range

Alq3:DCM

600 625 650 675 700 7250.00

0.25

0.50

0.75

1.00

0.0

2.5

5.0

7.5

10.0

12.5

Norm

aliz

ed

In

tensity

Wavelength / nm

Thre

shold

/ µ

J/c

m²

360 380 400 420 440 460

600

620

640

660

680

700

720

740

Wa

ve

len

gth

/ n

mGrating period / nm




Uli Lemmer

10.19

Variation of the active material

300 350 400 450 500 550 600 6500,0

0,2

0,4

0,6

0,8

1,0

norm

iert

e I

nte

nsität

Wellenlänge in nm

Pump-

laser

300 350 400 450 500 550 600 6500,0

0,2

0,4

0,6

0,8

1,0

no

mie

rte

Em

issio

n/A

bso

rptio

n

Wellenlänge in nm

Ab

so

rpti

on

Spiro-6-φdotiert mit

DPVABdotiert mit

DCM

Pump wavelength: 355 nm

Laser wavelength: 420 nm - 650 nm

⇒∆λ = 230 nm

Wavelength / nm

rela

tive f

loure

scence

inte

nsity

/ arb

. u.

Wavelength / nm

M. Stroisch et al.




Uli Lemmer

10.20

Resonators

C. Karnutsch, U.L. et al., Appl. Phys. Lett. 89, 201108 (2006) C. Karnutsch, U.L. et al., Appl. Phys. Lett. 90, 131104 (2007)




Uli Lemmer

10.21

Laser diode pumping

400 450 500 550 600 650 700

0.0

0.2

0.4

0.6

0.8

1.0

Inte

nsity /

arb

.u.

Wavelength /nm

Single low-cost GaN laser diode for pumping lasers

Parameters

λPump = 406 nm

τPump = 20 nsfRep = 16 Hz

C. Karnutsch, M. Punke et al., IEEE Photon. Technol. Lett., 19, 741 (2007)




Uli Lemmer

10.22

J. H. Schön, C. Kloc, A. Dodabalapur, B. Batlogg, Science 289, 5999 (2000).

Ith= 500 A/cm2

λ=575 nmcw op. up to 77 Kpulsed @ 300 K

t

The first organic laser diode (unfortunately not) or “The Jan Hendrik Schön scandal”




Uli Lemmer

10.23

Optical model Electronic model

Design rules for an organic laser diode

Active layer

Cladding

CladdingEL

ETL

HTL

Critical:

- Waveguide losses

Critical:

- Annihilation processes

- Polaronabsorption

C. Pflumm, U. L. et al., IEEE JQE. 41, 316 (2005)C. Gärtner, C. Karnutsch, C. Pflumm, U. Lemmer,Journ. of Appl. Phys. 101, 023107 (2007).

Why is an organic laser diode so difficult ?




Uli Lemmer

10.24


1. Introduction




5. Organic FETs












Uli Lemmer

10.25Motivation: Lab-on-a-chip systems

Organic DFB

lasers

GaN laser diode

Waveguides Microfluidic

system

Organic

photodiode




Uli Lemmer

10.26

Si master electro-plating Ni stamp

imprinting imprinted substrate vapor deposition

Thermal and UV- Nanoimprint




Uli Lemmer

10.27

DUV modification of PMMA

resonator structure DUV modification

Parameter

power / wavelength: 5 J @ 240 nm

refractive index change: 0.008

(1.4797 � 1.4847 @ 633 nm)

waveguide depth: ~ 5 µm

waveguide width: 3-50 µm

D. Rabus et al., IEEE Photon. Technol. Lett. 7, 591, (2005)




Uli Lemmer

10.28

Integration: Laser and waveguides

DUV modificationimprint thin-film deposition waveguide-coupled

laser

completed sample




Uli Lemmer

10.29

Optical characterization

M. Punke, U.L. et al. IEEE Phot. Tech. Lett. 19, 61 (2007)




Uli Lemmer

10.30

Waveguide-coupled lasing

laser + waveguide

600 610 620 630 640 650 660

FWHM = 0.4 nm

Inte

nsity / a

rb.u

.

Wavelength / nm

Pump parameter

excitation wavelength: 355 nm

pulse length: 1.65 ns

pump spot size: ~ 150x150 µm

Laser / waveguide parameter

laser wavelength: 643 nm

waveguide width: 50 µm

coupled peak power: ~ 3.2 µW




Uli Lemmer

10.31Direct two-photon laser writing




Uli Lemmer

10.32Direct two-photon laser writing




Uli Lemmer

10.33Direct two-photon laser writing in SU 8

d=220 nm (600 nm in z-direction)d=320 nm (1,6 µm in z-direction)




Uli Lemmer

10.34Waveguide AND DFB resonator by Direct TP-laser Writing

Direct laser writing works for nano- AND microstructures




Uli Lemmer

10.35DFB-resonators by Direct TP-laser Writing

Alq3:DCM

50 0 550 600 650 700 750E

mis

sio

n In

ten

sity / a

rb. u

.E m iss ion W ave leng th / nm




Uli Lemmer

10.36Motivation: Lab-on-a-chip systems

Organic DFB

lasers

GaN laser diode

Waveguides Microfluidic

system

Organic

photodiode




Uli Lemmer

10.37


1. Introduction




5. Organic FETs












Uli Lemmer

10.38

Getting faster: Layout for reduced C

• Active area is defined by photolithographic proceduresusing SU-8 as insulator

• Capacitor is formed (with SU-8 as dielectric) �SU-8-layer has to be as thick as possible

Contact pin Contact pin

Al cathode

Active material

Hole transport layer

SU-8

ITO anode

Glass substrate

Activearea

Structure

ITO Anode (125 nm)

P3HT:PCBM (300 nm)

Al Kathode (100 nm)

Pedot:PSS (40 nm)

Substrat

M. Punke, U.L. et al., Appl. Phys. Lett. 91, 071118 (2007)




Uli Lemmer

10.39

Results: Carrier sweep out in OPDs

Photoresponse vs. Bias voltage

�FWHM < 15ns

�Rise times < 2ns

�Fall times < 10 ns

(at -5V bias voltage)

-assuming the fall time is sweep out limited the mobility is estimated to 1⋅10-3cm2/Vs-the buildup of space charges has to be taken into accout

M. Punke, U.L. et al., Appl. Phys. Lett. 91, 071118 (2007).




Uli Lemmer

10.40

Optical interconnects




Uli Lemmer

10.41

Optical interconnect: results

Alq3-High Frequency-OLED

Eyediagram of an all-organicdata transmission (S/PDIF)

�Data rate: 2.8 Mbit/s

�Min. pulse length: 165 ns P3HT/PCBM-High Frequency-OPD

M. Punke, U. L. et al., Journ. of Lightw. Tech. 26, 816 (2008)




Uli Lemmer

10.42Laser direct writing of an SU8 Ridge Waveguide

Ridge waveguide

5µm x 5µm

TIR mirror at end facet

10.1 outline of the course - kit - lti · outline of the course 1. introduction 2. optoelectronic...

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