Nonlinear Optical Properties of

woundcallousΗμιαγωγοί

1 Νοε 2013 (πριν από 3 χρόνια και 9 μήνες)

62 εμφανίσεις

Ultrafast THz Spectroscopy and
Nonlinear Optical Properties of
Semiconductor Nanostructures

Zhen
-
Yu ZHAO


17 July 2008



Laboratoire Pierre Aigrain
-

Ecole Normale Supérieure, Paris


State Laboratory of Precise Spectroscopy
-

East China Normal University, Shanghai

1

Outline


Section 2:


Nonlinear Optical Properties of AgCl Nanocrystals doped Tellurite
Glasses


Fabrication


Characterization


Nonlinear Optical Measurement


Section 1:


Development

of
THz

Time Domain
Spectroscopy

(
THz
-
TDS)



Optical Rectification


Micro
-
Photoconductive

Emitter



Application of
THz

-

TDS


Gain
Measurement

of Quantum Cascade Laser (QCL)

2


Section 1

Development & Application of
THz Time Domain Spectroscopy

3

THz

Radiation


Section 1

1THz↔300
μ
m↔1picosecond↔4.1meV↔10K

Application THz spectroscopy : Semiconductor nanostructures

http://www.thznetwork.org

4

THz Time domain Spectroscopy


Section 1

Ti

: sapphire laser

τ

BS

M2

M5

M1

M3

M4

Emitter

Electro
-
Optic Sampling

S

ZnTe

λ/4

WP

Balanced
photodiodes

Probe beam

Pump
beam

Free
Space

Electro
-
Optic

Sampling

THz

emitter
:


Optical Rectification


Photoconductive

antenna

5

Δτ

Optical Rectification

Laser pulse,

Δτ

:100fs,
λ

:800nm

ZnTe
crystals

THz radiation

Z

Lens

SHG & Transmitted
beam


Section 1

6

FFT

Optical Rectification


Section 1

7

Bolometer

PMT

Photodiode

Z

Z

Z

Teflon

Filter

Picarin

Lens

Lens

Lens

8

Optical Rectification


Section 1

1. Optical Rectification

2. Second
Harmonic

Generation

3.
Two

Photon Absorption

4. Free Carrier Absorption

ħ
ω


ω

ħ
ω

ħ
ω

Nonlinear Crystals

Nonlinear Crystals

high state

low state

Conduction band

Valence band


ω

β
: TPA coefficient

Nonlinear

Optical
Processes

9

Optical Rectification


Section 1

θ

[001]

Laser
polarization

ZnTe

X.
-
C. Zhang et al.
J. Opt. Soc. Am. B
18
: 823 (2001)


D.C. Hutchings and B.S. Wherrett,
J. Opt. Mod.

41
: 1141 (1994)

Optical Rectification

Lens :f=4cm

ZnTe

Rotation

Laser beam

THz

radiation

15mm

BBO

Two

Color

Experiments


Section 1

10

Interdigitated photoconductive antenna



Section 1

11

Laser pulse,

Δτ

:100fs,
λ

:800nm

Hemisphere Si lens

+



Conventional
Photoconductive
antenna

12

Interdigitated photoconductive antenna


+

-

Electrods

Opaques

A. Dreyhaupt et al.
Appl. Phys. Lett.
86

:121114 (2005)

A. Dreyhaupt et al.
Opt
.
Lett
.
31

:1546

(2006)

Nathan Jukam, UCSB

stripline gap1.5µm

500µm

Interdigitated photoconductive emitter


Section 1

Bias dependence

13

Interdigitated

photoconductive

emitter


Section 1

Γ→
L Intervalley scattering

C. Ludwig and J.
Kuhl
,
Appl
. Phys.
Lett
.
69

(9), 1194
(1996)

J.
-
H. Son, T. B. Norris, and J. F. Whitaker,
J. Opt. Soc. Am. B
11
, 2519 (1994)

14

Interdigitated

photoconductive

emitter

Optimization by change the exciting intensity


Section 1

15

Interdigitated

photoconductive

emitter

Space Charge Screenings Effect


Bias Field

Coulomb Field


Section 1

16

-

-

High Optical Flux

Low Optical Flux

+

+





Interdigitated

photoconductive

emitter

Temperature Dependence of THz emitter


Section 1

17

J. S.Blakemore,
J. Appl. Phys.

53
: R123
-
R181 (1982)


Section 1

Comparison

of 2
THz

emitters

ZnTe Crystals

Interdigitated Photoconductive antenna

THz Amplitude

10V/cm

100V/cm

Central Frequency

2THz

1THz~~1.4THz

Bandwidth

0.5~~2.7THz

0~~3.5THz

S/N

500~1000

5000~~10000

18

THz

Quantum Cascade Laser

Concept

ħ
ω

Interband

transition

Inter
-
subband

transition

Semiconductor

Laser

Quantum Cascade Laser


Section 1

1970

First
Idea

1980

1990

2000

First QCL @ Bell
Labs

THz

QCL

Years

1994

2002

Milestone

2.9
THz

QCL 77k

2004

19

2006

1.9
THz

QCL 95k

1971

THz

Quantum Cascade Laser


Section 1

Bound to Continuum Active
-
injection Region of 2.9THz QCL

20

21

THz Quantum Cascade Laser


Section 1

Surface Plasmon Waveguide of 2.9 THz QCL

Active

Region

Metal 220µm

SI Substrate

12µm

(a)

Bottom

n+ layer

Metal

Contact

220µm

MPQ
-
Paris VII

THz

Quantum Cascade Laser


Section 1

V

QCL

Pyroelectric

Detector

A

THz

Collimation

THz

Characterization of 2.9 THz QCL

22

THz

Gain
Measurement

Ti

: sapphire laser

τ

BS

M2

M5

M1

M3

M4

E
THz

FSEOS

S

A

B

C

D

Probe beam

Pump
beam


Section 1

23

THz

Gain
Measurement

Amplified THz transmission by gain of quantum cascade laser

2.9THz


Section 1

24

THz Gain at different injection current


THz Gain at different temperature


THz

Gain
Measurement


Section 1

Gain Clamping

25

26


Section 1

Summary

1


Development of THz
-
TDS



THz performance of
ZnTe

crystal.


THz output of
interdigitated

photoconductive antenna



Application of THz
-
TDS



First measurement of Gain of 2.9 THz Quantum Cascade Laser


Section 2

Nonlinear Optical Properties of
AgCl NCs doped Tellurite Glasses

27

Introduction


Section 2

28

Glass

Χ
(3)

~ 10
14
esu

SiO
2

2.4

46PbO

42Bi
2
O
3

12Ga
2
O
3

42

20Nb
2
O
5

80TeO
2

72

------
J. Lin et al.
J. Non
-
Cryst. Solids

336

: 189

194 (2004)


Photonic Glasses

------
Y.Q. LI et al.
J. Rare Earth

25

: 412


415 (2007)


Er
+

Doped TeO
2
-
Nb
2
O
5
-
ZnO Glass

Optical Switching

Optical limiting

Nanocrystals doped Tellurite Glasses

Tellurite Glasses

Fabrication


Melting:


80TeO
2
:20Nb
2
O
5

& 1%wt AgCl powder


800
°
C / 15minutes.


Quenching:


Annealed at 300
°
C



Thermal treatment:


At 360
°
C


30min, 60min, 90min, 120min




Section 2

29

Characterization

(a) 30min thermal treated

(b) 60min thermal treated


Section 2

30

Nanocrystals FESEM Image vs Termal treatment time

Characterization

(c) 90min thermal treated

(d) 120min thermal treated


Section 2

31

Nanocrystals FESEM Image vs Termal treatment time


Characterization

12nm / 30 min


Section 2

32

Size distribution function vs thermal treatment time


26nm / 90 min

17nm / 60 min

35nm / 120 min

Characterization

Cl
-

Ag
+

Jahn
-
Teller effect : Lattice deformation

Cl
-

colour center

Reaction: 2Cl
-

→Cl
2

+ 2e
-

& 2Ag
+
+2e
-
→2Ag



Section 2

33

H. Vogelsang, Phys. Rev. B

61
: 1847
-
1852 (2000)


Characterization

E
g

Urbach law:

Samples

E
g

(eV)

undoped

3.1

0 min

2.9

30 min

2.9

60 min

2.3

90 min

1.9

120 min

1.7

Bandgap of glass
matrix

Bandgap redshift of
treated glass

E
g

Trapped
state


Section 2

34

35

Nonlinear Optical Properties


Section 2

50% BS

lens

lens

Sample

Attenutation

Powermeter

Powermeter

Nonlinear

Optical
Properties

Lock
-
In

PC

Ti

:sapphire

Laser

M
1

M
2

L

L

L

S

D

Z

Open Aperture Z
-
scan


Section 2

β
: 1GW/cm ~~ 1.8 GW/cm

36

Nonlinear

Optical
Properties


Section 2

Lock
-
In

M1

M2

M3

M4

M5

BS

Δτ

PC

L

S

K
1

K
2

2K
2
-
K
1

2K
1
-
K
2

D

Ti

:sap
phire

Laser

Samples

E
g

(eV)

n
0

χ
(3)

(10
-
13
esu)

n
2

(10
-
11
esu)

undoped

3.1

2.0

7.2

1.2

0 min

2.9

2.1

7.3

1.3

30 min

2.6

2.2

7.8

1.4

60 min

2.3

2.2

14

2.3

90 min

1.9

2.2

11

1.9

120 min

1.7

2.2

9.5

1.6

DFWM
experiment

37

38


Section 2

Summary 2



Nonlinear optical properties of
AgCl

NCs doped
tellurite

glass



Samples were Prepared by Melt
-
Quenching and Thermal Treatment Methods



Characterization with Microscopic and Spectroscopic Methods



Nonlinear Optical Properties were Measured by Z
-
scan, Optical Limiting and
DFWM


Conclusion

39


Section 2:


Nonlinear Optical Properties of
AgCl

Nanocrystals

doped
Tellurite

Glasses


Fabrication


Optical limiting performance and Two
-
photon absorption


Enhancement of χ(3)


Section 1:


Development

of
THz

Time Domain
Spectroscopy

(
THz
-
TDS)



Competition

OR TPA FCA,
Azimuthal

dependence


Intervally

scattering
,
Space

charging

screening, Electron
mobility


Application of
THz



TDS


Gain
Measurement

of 2.9THz QCL

Acknowledgement



THz

group (LPA
-
ENS)

Advisor
:


Jérôme
Tignon

Staff
members
:

Sophie Hameau,
Sukhdeep

Dhillon et al.

Postdoc
:


Nathan
Jukam
;

Ph.D

student
:

Dimitri
Oustinov
;

Master
student
:

Julien
Amijo
,
Geog

Dürr
;

Techniciens:

Pascal
Morfin
,
Phillipe

Pace et al.

Collaborators
:

Carlo
Sirtori

et al.



Sun’s

Group (East China Normal
University
)

Co
-
Advisor
:

Zhenrong

Sun,

Staff
members
:

Tianqing

Jia
,
Xiaohua

Yang et al.

Collaborators
:

Jian

Lin, et al.