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

Présentation au sujet: "Aurélien Delestre, E. Fargin, M. Lahaye (ICMCB, Bordeaux, France)"— Transcription de la présentation:

1 Aurélien Delestre, E. Fargin, M. Lahaye (ICMCB, Bordeaux, France)
PATTERNED SECOND HARMONIC GENERATION ON OXIDE GLASSES SURFACE BY THERMAL POLING 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) Worshop : LasINOF, June 14th 2010

2 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 02 /15

3 Thermal poling for Internal field engraving
Glasses are centro-symmetric materials (2)=0 - Eint Mobile cations can migrate from anode to cathode Anode Cathode A i ~ 0.5 mA U = 1kV 230°C G - Eint Na+ cations depletion zone creation (L=3-15 µm) Negatively charged depletion zone Eint Embedded internal field induces Second Harmonic Generation in Glasses 03 / 15

4 SHG modified ? Glass samples elaboration + silver injection
Composition : sodium and niobium borophosphate glasses (BPN42) (1-x)[0,95NaPO3+0,05Na2B4O7]+xNb2O x = 0,42 Silver layer deposition on the glass surface Silver injection by poling : - departure of sodium ions - injection of silver ions Thermal Poling induces ~ 5 mm Zone outside the anode Metallic silver film Glass Zone under the anode SHG modified ? Poled surface after poling Na+ and Ag+ : Comparable diffusion coefficients in oxide glasses Structuration of silver electrode SHG structuration Why silver ? *Référence : M. Dussauze Optics Express, Vol. 13, Issue 11, pp 04 / 15

5 Why poling is efficient? Why poling can be inefficient?
c(2) values deduced from Maker Fringes simulations Thermal poling 230 °C, t = 1 h, U ~ 1 kV, i0 = 0.5 mA (sample thickness 1 mm) Efficient poling Non efficient Sample Reference no Ag Ag Silver thin film thickness (nm) e ±10 nm 200 220 170 240 300 2) (pm/V) ± 10-2 1.06 1.20 1.00 0.96 Nonlinear zone thickness (µm) L ± 0.1 µm 3.0 - 2.9 3.8 Observation : Efficient poling leads to (2) comparable to the reference Why poling is efficient? Why poling can be inefficient? 05 / 15

6 Quantitative X-ray analysis on the reference
Reference Without Ag Na, Nb, P atomic concentration profiles Cathode Anode Poled zone Poled zone Sodium depletion zone: 3 µm thickness Space charge zone identical to SHG efficient zone *Reference : M. Dussauze Optics Express, Vol. 13, Issue 11, pp 06 / 15

7 Quantitative X-ray analysis
Efficient poling with Ag efficient SHG zone Na depletion zone Ag injection zone 2.9 2 4 6 8 10 12 14 16 18 20 % Atomic Depth under the anode surface (µm) Na Ag P Nb Atomic concentration profiles under the anode Cations migrations : - Na+ ions depletion (6 µm) - Ag+ ions penetration (6 µm) Sample efficient poling With Ag Ag thickness(nm) ±10 nm 170 c(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 - the nonlinear zone producing SHG is located between 0 to 2.9 µm under the surface 07 / 15

8 Inefficient poling with Ag Ag+ injection compensates
Quantitative X-ray analysis Inefficient poling with Ag Atomic concentration profiles 16 Cations migration : 14 déplétion zone Na+ depletion ( 2 µm) Ag+ injection ( 2 µm) 12 10 % Atomic 8 Ag+ injection compensates Na+ depletion 6 Na Ag 4 P Nb 2 2 4 6 8 10 12 Depth under the anode surface (µm) No space charge zone creation No SHG Poling voltage ~1 kV is the minimum to develop efficient poling *reference : E. Fargin Advanced Materials Research Vols (2008) pp 08 / 15

9 First polings mistake : special attention on the current
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

10 SHG architecture BPN42 + Ag thin film deposition
Laser fs IR AOM BPN42 + Ag thin film deposition Laser fs IR AOM Laser fs IR AOM Laser fs IR AOM Laser fs IR AOM Laser fs IR AOM 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 Ablated line Ag thin film 100µm laser Yb : Wavelength = 1030 nm pulse duration= 470 fs Repetition rate = 10 MHz Mean power = 6 W Image of ablated lines (optical microscopy) Surface profile image of ablated lines 10 / 15

11 µGSH allows different fields orientations
µSHG Analysis 40 -30 -20 -10 10 20 30 -40 Y (µm) X (µm) Ablated lines Ag Ablated Poled lines Ag Non ablated poled zone µGSH allows different fields orientations Different components in 2ω (polarization of reflected SHG field) ω (polarization of incident beam field) Exemple : YXX 11/ 15

12 xxx(2)  0 SHG signal analysis on the surface Analysis Incident
Wavenumber (cm-1) Intensité (u.a.) 14 12 10 8 6 4 2 -500 500 1000 Nombre d’onde (cm-1) Flight intensity xxx(2)  0 non ablated zone Analysis Incident XXX polarization Surface 3 µm under the surface Z=0 Z=1 Z=2 Z=3 Z=4 3D mapping: Intensité (u.a.) Nombre d’onde (cm-1) Ablated zone : 600 500 400 300 200 100 -500 1000 SHG signal is very intense on the lines 12 / 15

13 Eint New Symmetry induced by poling Usual symmetry obtained by poling
SHG signal for different pump and probe polarizations Usual symmetry obtained by poling C∞v - Eint Cs (symmetry plane: xz) é xxx xyy xzz xxz ù ê ú c ( 2 ) = yyz yyx ê ú ê ë zxx zyy zzz zzx ú û *reference : A. Delestre, Applied Physics Letters, volume 96, Issue 9, id (2010) 13 / 15

14 Lifted lines Quantitative analysis of elements under anode
Silver concentration mapping Ionic profile in the non ablated area Lifted lines z x Ablated lines Silver layer Ionic profile in the ablated area Silver injection [Ag+] [Ag+] [Ag+] Silver concentration variation through ablated lines 14 / 15

15 Conclusion and perspectives
+ 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 : 15 / 15

16 µSHG Setup Advantages : - Mapping (platine XYZ + CCD)
Prism Glan Taylor Laser ps 1064 nm Power regulation Filter 2 l/4 M3 M4 Pine hole polarization Laser ps 532 nm Filter Notch 1064 ou 532nm M5 M6 M1 M2 M7 CCD NIR Objective Sample Platine XYZ Advantages : - Mapping (platine XYZ + CCD) - Résolution ~ 1 µm (Objective NIR 100X, ON = 0,5) - Simultaneous µRaman spectroscopy 11 / 23

17 Pas de contraste de signal GSH
Signal GSH dans/hors des lignes ablatées Analyse Incident Polarisation YXX Intensité (u.a.) Nombre d’onde (cm-1) 1 µm -5 5 10 X (µm) -4 -2 2 4 Y (µm) 1.5 1.0 0.5 0.0 40 -30 -20 -10 10 20 30 -40 Y (µm) X (µm) Pas de contraste de signal GSH Présence de signal GSH dans la zone polée Pas de variation de signal GSH dans la zone ablatée 24 / 30

18 Pas de contraste de signal GSH
Analyse Incident Signal GSH dans/hors des lignes ablatées Echantillon tourné de 90° Y (µm) X (µm) Polarisation YYY Signal GSH homogène Pas de contraste de signal GSH 5 µm -30 -20 -10 10 20 30 Y (µm) -40 40 X (µm) 50 40 30 20 10 Intensité (a.u.) -500 500 1000 Nombre d’onde (cm-1) Zone ablatée XYY 1 µm -5 5 10 Y (µm) X (µm) 4 3 2 1 Polarisation XYY Variation de signal GSH Intensité (u.a.) -500 500 1000 Nombre d’onde (cm-1) Zone non ablatée XYY 25 / 30

19 Signal GSH sur la tranche de l’échantillon
Analyse Incident Les échantillons sont coupés au travers des lignes d’ablation Polarisation ZZZ 2 µm -4 -2 2 4 6 Z (µm) -10 -5 5 10 15 X (µm) 2000 1500 1000 500 Lignes ablatées Zone non linéaire Surface d’analyse 5 µm -30 -20 -10 10 20 30 Z (µm) -40 40 X (µm) Zone non ablatée XZZ Zone ablatée XZZ 100 80 60 40 20 Intensité (u.a.) 520 530 540 550 560 Longueur d’onde (nm) 500 400 300 200 100 Intensité (u.a.) 520 530 540 550 560 Longueur d’onde (nm) Polarisation XZZ 2 µm -6 -4 -2 2 4 6 Z (µm) -10 -5 5 10 15 X (µm) 150 100 50 ONL perpendiculaire aux lignes d’ablation 26 / 30

20 µSHG on cross section with a 90° sample rotation
Polarisation XXX Polarisation ZXX 1 µm -10 10 20 X (µm) -5 5 Z (µm) 200 150 100 50 100 -10 80 60 X (µm) 10 40 20 20 1 µm -5 5 10 Z (µm)

21 Hypothèse Résultats de µGSH GSH par polarisation thermique + ablation
Z=0 Polarisation YYY Polarisation YXX Résultats de µGSH 2 µm -6 -4 -2 2 4 6 Z (µm) -10 -5 5 10 15 X (µm) 150 100 50 Polarisation d’analyse lignes d’ablation Variations GSH dans la zone d’ablation Polarisation XZZ GSH par polarisation thermique + ablation déplétion 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 Lignes ablatées Couche d’argent Pénétration d’argent [Ag+] Variation de la concentration d’argent au travers des lignes ablatées Champ interne additionnel perpendiculaire aux lignes ablatées L’augmentation de GSH dans les lignes ablatées viendrait d’un champ interne perpendiculaire à ces lignes 28 / 30

22

23