Worshop : LasINOF, June 14th 2010

Aurélien Delestre, E. Fargin, M. Lahaye (ICMCB, Bordeaux, France)

V. Rodriguez, F. Adamietz, M. Dussauze (ISM, Bordeaux, France)

M.Bellec, A. Royon, L.Canioni (CPMOH, Bordeaux, France)

PATTERNED SECOND HARMONIC GENERATION ON OXIDE GLASSES SURFACE BY THERMAL

POLING

Outline

I / Thermal poling and Second Harmonic Generation (SHG)

II / Silver injection by thermal poling and SHG

- Samples elaboration and preparation for silver injection

- poling voltage and SHG efficiency

- Results and interpretation

III / Efficient structuring of SHG

- Laser ablation, poling

- µSHG patterning measurements

- Results and interpretation

02 /15

T°

Time

High Voltage

T°

Time

High Voltage

Thermal poling for Internal field engraving

03 / 15

AnodeCathode

A

i ~ 0.5 mA

U = 1kV

230°C

G

Negatively charged depletion zone

Na+ cations depletion zone creation (L=3-15 µm)

Mobile cations can migrate from anode to cathode

- ---------

----

-Eint

X

YZ

- - - -- - -Eint

Eint

Embedded internal field induces Second Harmonic Generation in Glasses

int)3()2( .3 Eeff

Glasses are centro-symmetric materials (2)=0

Composition : sodium and niobium borophosphate glasses (BPN42)

(1-x)[0,95NaPO3+0,05Na2B4O7]+xNb2O5 x = 0,42

Silver injection by poling :

Silver layer deposition on the glass surface

Glass samples elaboration + silver injection

04 / 15

Metallic silver film

GlassE

SHG modified ?

Why silver ? Na+ and Ag+ : Comparable diffusion coefficients in oxide glasses

Structuration of silver electrode SHG structuration

~ 5 mm

Poled surface after poling

Zone outside the anode

Zone under the anode

*Référence : M. Dussauze Optics Express, Vol. 13, Issue 11, pp. 4064-4069

Thermal Poling induces - departure of sodium ions

- injection of silver ions

Observation : Efficient poling leads to (2) comparable to the reference

Efficient poling Non efficient Efficient poling

Sample Reference no Ag Ag Ag Ag Ag Ag

Silver thin film thickness (nm)e ±10 nm 0 200 220 170 240 300

2) (pm/V) ± 10-2 1.06 0 0 1.20 1.00 0.96

Nonlinear zone thickness (µm)

L ± 0.1 µm3.0 - - 2.9 3.8 3.0

(2) values deduced from Maker Fringes simulations

05 / 15

Why poling is efficient?

Why poling can be inefficient?

Thermal poling

230 °C, t = 1 h, U ~ 1 kV, i0 = 0.5 mA (sample thickness 1 mm)

0 5 10 15 20 250

2

4

6

8

10

12

14

16

18

20

a

Ato

mic

perc

en

tag

e

Penetration depth under the anode surface (m)

Nb Na P

Sodium depletion zone: 3 µm thickness

Space charge zone identical to SHG efficient zone

*Reference : M. Dussauze Optics Express, Vol. 13, Issue 11, pp. 4064-4069

Reference Without AgNa, Nb, P atomic concentration profiles

Cathode

Anode

Poled zone Poled zone

Quantitative X-ray analysis on the reference

06 / 15

Cations migrations :

- Na+ ions depletion (6 µm)

- Ag+ ions penetration (6 µm)

Quantitative X-ray analysis

07 / 15

Sample efficient poling With Ag

Ag thickness(nm) ±10 nm 170

(2) (pm/V) ± 10-2 1.20

Nonlinear zone thickness (µm) ± 10

-1 2.9

SHG profile correlated to total cations depletion

- between 2.9 µm and 6 µm Ag substitutes to Na

Efficient poling with Ag

- the nonlinear zone producing SHG is located between 0 to 2.9 µm under the surface

efficient SHG zone

Na depletion zone

Ag injection zone

2.90 2 4 6 8 10 12 14 160

2

4

6

8

10

12

14

16

18

20

% A

tom

ic

Depth under the anode surface (µm)

Na Ag P Nb

Atomic concentration profiles under the anode

Cations migration :

- Na+ depletion ( 2 µm)- Ag+ injection ( 2 µm)

*reference : E. Fargin Advanced Materials Research Vols. 39-40 (2008) pp 237-242

déplétion

zone

Quantitative X-ray analysis

08 / 15

Inefficient poling with Ag

Ag+ injection compensatesNa+ depletion

No SHG

0 2 4 6 8 10 120

2

4

6

8

10

12

14

16

% A

tom

ic

Depth under the anode surface (µm)

Na Ag P Nb

Atomic concentration profiles

No space charge zone creation

Poling voltage ~1 kV is the minimum to develop efficient poling

Influence of voltage on poling efficiency

First polings mistake : special attention on the current

Now big care on the voltage !!!Thermal poling

230 °C, t = 1 h, U = different voltage, i0 < 0.6 mA (sample thickness 500µm)

SHG efficiency is linked with poling tension

09 / 15

SHG architecture

Surface profile image of ablated lines

BPN42 + Ag thin film deposition

Laser Ablation of silver lines

(Length = 3 mm, width = 2 µm)

Thermal poling

230 °C, t = 1 h, U = 1 kV, i0 < 0.6 mA

laser Yb :

Wavelength = 1030 nm

pulse duration= 470 fs

Repetition rate = 10 MHz

Mean power = 6 WLa

ser

fs IR

AOM

Lase

r fs

IR

AOM

Lase

r fs

IR

AOM

Lase

r

fs IR

AOM

Lase

r fs

IR

AOM

Lase

r fs

IR

AOM

Ag thin film

Ablated line

100µm

10 / 15

X

YZ

Image of ablated lines (optical microscopy)

Y

X

µSHG Analysis

40

5 µm

-30

-20

-10

0

10

20

30

Length Y (µm)

-40 -20 0 20 40

Length X (µm)

-30

-20

-10

0

10

20

30

-40 -20 200Y (µm)

X (

µm

) Ag Ablated

Poled lines

Ag Non ablated

poled zone

)2(ijk i

kj 2ω (polarization of reflected SHG field)

ω (polarization of incident beam field)

µGSH allows different fields orientations

Different components in )2(

Exemple : YXX )2(

yxx

Ablated lines

X

YZ

11/ 15

zxyzxzzyzzzzzyyzxx

yxyyxzyyzyzzyyyyxx

xxyxxzxyzxzzxyyxxx)2(

Y

X

XXX polarization

SHG signal analysis on the surface

SHG signal is very intense on the lines

non ablated zone

Inte

nsité

(u.

a.)

Nombre d’onde (cm-1)

Ablated zone :600

500

400

300

200

100

0

-500 0 500 1000

Analysis Incident

Surface 3 µm under

the surface

Z=0 Z=1 Z=2 Z=3 Z=4

3D mapping:

12 / 15

zxyzxzzyzzzzzyyzxx

yxyyxzyyzyzzyyyyxx

xxyxxzxyzxzzxyyxxx)2(

0)2( xxx

Z

Wavenumber (cm-1)

Inte

nsité

(u.

a.)

14

12

10

8

6

4

2

0

-500 0 500 1000

Nombre d’onde (cm-1)

Flight intensity

xxx(2) 0

SHG signal for different pump and probe polarizations

New Symmetry induced by poling

13 / 15

Usual symmetry obtained by poling

C∞v

- ---------

----

-Eint

X

YZ

00

0000

00)2(

zzxzzzzyyzxx

yyxyyz

xxzxzzxyyxxx

Cs (symmetry plane: xz)

X

YZ

*reference : A. Delestre, Applied Physics Letters, volume 96, Issue 9, id. 091908(2010)

Quantitative analysis of elements under anode

Silver concentration mapping

14 / 15

Lifted lines

Silver concentration variation through ablated lines

Ablated lines Silver layer

Silver injection

[Ag+] [Ag+][Ag+]

DCXE

X

YZ

DCZE

z

x

Ionic profile in the non ablated area

Ionic profile in the ablated area

Conclusion and perspectives

15 / 15

+ Silver ions introduction by thermal poling :

Silver injection is compatible with SHG

Control the applied voltage (threshold for efficiency)

+ Surface SHG architecture obtained by structured silver deposited electrode:

- creation of new symmetry in nonlinear poled surface

Objective :

Laser ps

532 nm

/2

PrismGlan

Taylor

Laser ps 1064 nm

Power

regulation

µSHG Setup

11 / 23

M1

Platine XYZ

CCD

polarization

Pine hole

/4

M2

M3 M4

M5

M6

M7NIR Objective

Filter 2

Filter Notch1064 ou 532nm

Advantages :

- Mapping (platine XYZ + CCD)

- Résolution ~ 1 µm (Objective NIR 100X, ON = 0,5)

- Simultaneous µRaman spectroscopy

Sample

Présence de signal GSH dans la zone polée

Pas de variation de signal GSH dans la zone ablatée

Y

X

Polarisation YXX

40

-30

-20

-10

0

10

20

30

-40 -20 200

Y (µm)

X (

µm

)

Analyse Incident

1 µm

-5

0

5

10

X (µm)

-4 -2 0 2 4Y (µm)

1.5

1.0

0.5

0.0

Pas de contraste de signal GSH

Signal GSH dans/hors des lignes ablatées

24 / 30

zxyzxzzyzzzzzyyzxx

yxyyxzyyzyzzyyyyxx

xxyxxzxyzxzzxyyxxx)2( 0)2( yxx

6

5

4

3

2

1

0

Intensity (a.u.)

-500 0 500 1000

Wavenumber (cm-1)

Inte

nsité

(u.

a.)

Nombre d’onde (cm-1)

5 µm

-30

-20

-10

0

10

20

30

Y (µm)

-40 -20 0 20 40X (µm)

Echantillon tourné de 90°

Analyse Incident

X

Y

Y (

µm

)X (µm)

Polarisation YYY

Signal GSH homogène

Pas de contraste de signal GSH

50

40

30

20

10

0

Intensité (a.u.)

-500 0 500 1000

Nombre d’onde (cm-1)

Zone ablatée XYY

Signal GSH dans/hors des lignes ablatées

25 / 30

zxyzxzzyzzzzzyyzxx

yxyyxzyyzyzzyyyyxx

xxyxxzxyzxzzxyyxxx)2(

1 µm

-5

0

5

10

Y (µm)

-5 0X (µm)

4

3

2

1

05

Polarisation XYY

Variation de signal GSH

5

4

3

2

1

0

Intensité (u.a.)

-500 0 500 1000

Nombre d’onde (cm-1)

Zone non ablatée XYY

0)2( yyy

0)2( xyy

500

400

300

200

100

0

Intensité (u.a.)

520 530 540 550 560Longueur d’onde (nm)

Les échantillons sont coupés au travers des lignes d’ablation

Polarisation ZZZ

Lignes ablatées

Zone non linéaire

Surface d’analyse

Signal GSH sur la tranche de l’échantillon

100

80

60

40

20

0

Intensité (u.a.)

520 530 540 550 560Longueur d’onde (nm)

Zone non ablatée XZZ

Zone ablatée XZZ 5 µm

-30

-20

-10

0

10

20

30

Z (µm)

-40 -20 0 20 40X (µm)

Y

Z

Analyse Incident

X

YZ

2 µm

-4

-2

0

2

4

6

Z (µm)

-10 -5 0 5 10 15X (µm)

2000

1500

1000

500

0

2 µm

-6

-4

-2

0

2

4

6

Z (µm)

-10 -5 0 5 10 15X (µm)

150

100

50

0

Polarisation XZZ

ONL perpendiculaire aux lignes d’ablation

26 / 30

zxyzxzzyzzzzzyyzxx

yxyyxzyyzyzzyyyyxx

xxyxxzxyzxzzxyyxxx)2(

?)2( zzz

0)2( xzz

µSHG on cross section with a 90° sample rotation

XY

Z

Polarisation XXX Polarisation ZXX

1 µm

-10

0

10

20

X (µm)

-5 0 5 10Z (µm)

200

150

100

50

01 µm

-10

0

10

20

X (µm)

-5 0 5 10Z (µm)

100

80

60

40

20

0

Hypothèse

L’augmentation de GSH dans les lignes ablatées viendrait d’un champ interne perpendiculaire à

ces lignes

DCZE

GSH par polarisation thermique + ablation

Variation de la concentration d’argent au travers des lignes

ablatées

Lignes ablatées

Couche d’argent

Pénétration d’argent

[Ag+

][Ag+

][Ag+

]

Champ interne additionnel perpendiculaire aux lignes

ablatées

Z=0

Polarisation YYY

X

Y

Polarisation YXX

Résultats de µGSH

2 µm

-6

-4

-2

0

2

4

6

Z (µm)

-10 -5 0 5 10 15X (µm)

150

100

50

0

Polarisation d’analyse lignes d’ablation

Variations GSH dans la zone d’ablation

Polarisation XZZdéplétion

Migration des cations depuis l’anode

Création d’une zone de déplétion (L=3-15µm)

anode

Création d’un champ interne

GSH par polarisation thermique

cathode

28 / 30

DCXE

DCZE

X

YZ

0 5 10 15 200

2

4

6

8

10

12

14

16

18

Ato

mic

%

Depth (µm)

lifted unlifted

Sodium + Silver ionic migration profile