Y. Messaddeq IQ-UNESP, Araraquara-Brasil

Transcription

1 Photosensitive Glasses for Optical Storage Y. Messaddeq IQ-UNESP, Araraquara-Brasil

2 Younés Messaddeq Sidney J.L.Ribeiro 02 Researchers, 04 post-docs 10 PhD, 04 MSc, 12 undergraduated Main research projects (basic and applied science) -New glass compositions for photonics -Planar waveguides -Optical fibers (chalcogenide, tellurites, mixed glasses) -Transparent glass-ceramics -Photoinduced Phenomenon in glasses -Sol-gel materials (organic-inorganic hybrids) - Nanomaterials -Bio-medical Materials - Polymeric Materials Support FAPESP, FINEP, CNPq ERICSSON, VERILLON BIONEXT- KOTA SAINT-GOBAIN

3 Nanobiotecnologia Celulose bacteriana Acetobacter xylinum Celulose 100% pura

4 OUTLINE 1. INTRODUCTION 2. OBJECTIVE 3. GLASS SYSTEM STUDIES TUNGSTATE ANTIMONATE CHALCOGENIDE 4. CONCLUSION

5 ħħ ħħ ħħ STRUCTURAL Change on density MECHANICAL Rheological Properties OPTICAL PD (Eg PB ( Eg ω) ω) CHEMICAL photodissolution prata GeS 2 produto da reação E g As2S3 =2.4 ev ω =2 ev H. Hisakuni Appl. Phys. Lett. 65(1994)2925 Optical fiber As 2 S 3 (He-Ne) 5 hours η NIL > poise η IL = poise K. Tanaka Science 1995 Film As 2 S 3 (He-Ne) 17 hours D. Neufville JNCS 13(1971)1023 GeS 2 glass U.V. A.V. Kolobov Adv. Phys.40(1991)625

6 APPLICATIONS Phase-change optical memories e.g., DVDs As 2 S 3 photonic crystal A. Feigel,Thin Solid Film 488 (2005) Nanowheels in As 2 S 3 M. Vlček, H. Jain, A. Simmens, M. Dubey, C.M. Waits, Lehigh Materials &Nanotechnology Forum 2005 Fresnel lens with a diameter of 4 µm N.P. Eisenberg, JNCS 352(2006)1632

7 OBJECTIVE Explore new materials based on heavy oxide and Chalcogenide Explain the origin of the Photoinduced effects. Explore potential applications

8 WO 3 based Glasses

9 Optical properties of the most WO 3 concentrated samples Composition : 40 NaPO 3 10 BaF 2 50 WO 3 5mn melting 30mn melting min melting min melting Tranmittance min melting mn melting 60mn melting 5 min melting Wavelength (nm) Rapid cooling (~ K/min) 90 Slow cooling 80 Medium cooling 70 Medium cooling (~100 K/min) Transmittance Rapid cooling Slow cooling (~1 K/min) Wavelength (nm)

10 Annealing temperature Composition : 40 NaPO 3 10 BaF 2 50 WO 3 Tg = 475 C Annealing for 2 hours at : 400 C 420 C 2,5 2,0 Annealing at 400 C Annealing at 420 C Absorbance 1,5 1,0 0,5 0, Wavelength (nm)

11 Glass prepared on the System NaPO 3 - WO 3 Colour Dark blue Deep Blue Blue Transparent Yellow Orange Purple Synthesis Melting for 5 min in air atmosphere Melting for 15 min in air atmosphere Melting for 30 min in air atmosphere Melting for 60 min in air atmosphere Oxidized by the Sb 2 O 3 /NaNO 3 couple Oxidized by CeO 2 Annealing above 410 C

12 XANES study at the tungsten L 1 edge (12100 ev) a) A Na 2 WO 4 WO 3 b ) A NBW60 N a 2 W O 4 Intensity (a.u) NBW40 NBW30 NBW10 Intensity (a.u) N B W 1 0 N B W 3 0 N B W 4 0 N B W 6 0 W O Energy (ev) E n e r g y (e V ) The tungsten is only present in a distorted octahedral configuration WO 6 in the vitreous samples

13 Determination of the 2 photons absorption coefficient Transmitted intensity (MW/cm 2 ) NBW30 NBW40 NBW Incident intensity (MW/cm 2 ) Light attenuation for a 2 photons absorption : di = -(α 0 I+ α 2 I 2 ) dz Integration between z=0 and z=l gives : I 0 (1-R) 2 exp(-α 0 L) I = 1+(α 2 /α 0 )I 0 (1-R)[1-exp(-α 0 L)] Samples n 1 α 1 (cm -1 ) α 2 (cm/gw) NBW NBW NBW Ge 10 As 10 Se G. Poirier, C.B. Araújo, M. Poulain, Y. Messaddeq, S.J.L Ribeiro, J.Appl.Phys., 91 (12) (2002)

14 Photochromic properties Photochromic phosphate tungstate glass Transmitância (%) nm 488nm 514nm 850nm Continuous UV laser Continuous visible laser Pulsed infrared laser (femtosecond) Comprimento de onda (nm) Patent, Fapesp (2005)

15 Absorption mechanisms Exposure to continuous UV (350nm) or visible (488nm, 514nm) laser beam Exposure to femtosecond infrared (850nm) laser beam Conduction Band Conduction Band 350nm 488nm 514nm 850nm 850nm Valence Band Valence Band One Photon absorption Two Photons absorption

16 15 min 60 min Absorbance min 30 min 15 min 5 min Non irradiated Wavelength (nm) 5 min 30 min 4 WO 3 As-quenched glass Irradiated glass hν + W 5+ (A) + W 6+ (B) W 5+ (B) + W 6+ (A) Absorbance (a.u) hν + W 5+ (A) + W 4+ (B) W 5+ (B) + W 4+ (A) Energy (ev)

17 Raman scattering XANES at the W-L 1 edge (a) (b) Irradiated glass As-quenched glass 3000 Intensidade (u.a) NBW50SN NBW50SN(1,2W-2h) NBW50Ce Absorbância (u.a) WO 3 Na 2 WO NBW50Ce(1,2W-2h) Comprimento de onda (cm -1 ) Energy (ev) Apparently, the photosensitive effect is not related to a structural change

18 Thin films prepared from these tungstate glasses Electron Beam Heat Treatment 350 C 1h Glasses Blue Thin films (W 5+ ) Transparent Thin films (W 6+ ) Intensisty (a.u;) θ (degree) Amorphous thin films Regular thickness ~ 5µm

19 Optical properties 1,0 Absorbance 0,5 As-prepared film Treated film Intensity (a.u.) modo substrato 0,0 n D = Wavelength (nm) Incident angle θ ( 0 ) These thin films are useful for : - optical waveguides - non linear optics

20 Chalcogenide Glasses

21 UV ABSORPTION Ge x S 1-x glasses compositions with 11<x<45 absorption coefficient /α/ (cm -1 ) S Ge 40 S 60 Ge 38 S 62 Ge 33 S 63 Ge 31 S 69 Ge 25 S 75 Ge 11 S 89 S 1,8 1,9 2,0 2,1 2,2 2,3 2,4 2,5 2,6 2,7 2,8 photon energy (ev)

22 he characteristics temperatures obtained by DSC glass T g ( o C) T x ( o C) T x -T g ( o C) T c ( o C) Ge 25 S ±2 502±2 164±2 Ga 2 Ge 23 S ±2 495±2 145±4 510±1 Ga 5 Ge 25 S ±2 457±2 76±4 472±1 Ga 10 Ge 25 S ±2 486±2 73±4 503±1 Ga 15 Ge 20 S ±2 490±2 75±4 509±1 Ga stability

23 UV ABSORPTION absorption coefficient /α/ (cm -1 ) Ga 2 GeS (b) (a) 2,50 2,55 2,60 2,65 2, Ga 5 GeS (b) (a) 2,50 2,55 2,60 2,65 2,70 absorption coefficient /α/ (cm -1 ) Ga 10 GeS (a) (b) 2,50 2,55 2,60 2,65 2,70 photon energy (ev) Ga 15 GeS (a) (b) 2,50 2,55 2,60 2,65 2,70 photon energy (ev)

24 Chalcogenide Film for Holographic Recording 2,10 absorption coefficient (cm -1 ) UV VIS 2,4 2,6 2,8 3,0 3,2 3,4 photon energy (ev) Photobleaching Refraction Index 2,05 2,00 1,95 1,90 1,85 1,80 1,75 non-exposed exposed UV 1, wavelenght (nm) Photorefraction

25 3D representation of profile measurement of GaGeS thin film showing the effect of the photoexpansion on the surface at 351 nm

26 PHOTOLUMINESCENCE PL in chalcogenide glasses is due to the under and over coordinated centers. These defects are denoted D+ and D- charged dangling bonds 2D 0 D + +D - D+ CB Ge-S Antibonding states Ga 10 Ge 25 S 75 D 0 D- S lone pair states VB Ge 25 S wavelenght (nm) Ge-S bonding states

27 Since four electrons per atoms are needed to fill the valence band completely, this doping creates electron deficiency in this band. The missing electrons - called holes - behave as positively charged particle which are mobile, and carry current. Ge +4 Ge +4 Ga +3 Ge +4 HOLE Ge +4 A semiconductor where the electric current is carried by holes is called p-type This gallium defect implies in compensation by the formation of edge linkages between (Ge/Ga)-O units

28 Lloyd Interferometer setup Showing the diffraction orders 45 o view of two dimensional photonic crystal structures (poles) of 1µm period

29 Sb 2 O 3 based glasses

30 Antimony based glasses Vitreous Systems: Observed Effects: Applications: Sb 2 O 3 based glasses SbPO 4 based glasses Sb 2 S 3 based glasses High refractive index (near 2.0) High non-linear refractive index Ultrafast Kerr effect Photosensitivity Optical Limiters Optical Switching Bragg Grating 2D/3D Optical Storage Holographic Data Storage

31 Glass Synthesis Powder Mixture Melting in Platinum Tubes at C Quenching Annealing Around Tg Polishing WO 3 -SbPO 4 WO SbPO 4 Content (Mol%)

32 ABSORPTION COEFFICIENT MODULATION nm % Transmitance nm wsbp4 wsbp nm Wavelength (nm) 0,07 0, nm 488 nm 514 nm wsbp4 0,14 0, nm 488 nm 514 nm wsbp5 0,05 0,10 α (mm -1 ) 0,04 0,03 α (mm -1 ) 0,08 0,06 0,02 0,04 0,01 0,02 0,00 0, Time (s) Time (s) 40% WO 3 50% WO 3 α wsbp5 = 2 α wsbp4

33 ABSORBANCE MEASUREMENTS 1,0 Wavelength Dependence λ = 514 nm 1,0 λ = 488 nm 50% WO 3 P = 200 mw Absorbance 0,8 0,6 0,4 wsbp6-4h wsbp6-3h wsbp6-2h wsbp6-1h wsbp6-ni 0,8 0,6 0,4 wsbp6-4h wsbp6-3h wsbp6-2h wsbp6-1h wsbp6-ni 0,2 0,2 0,0 0,

34 Proposed Model for Sb-W Based Glasses The photochromic effect is due to the formation of W +V species In Thin Films: Formation of bronzes W + VI + + V + VI O ( 3 + xe + X HW x x W1 xo3 X = H, Li, Na) WO 2h WO h e + hν WO + H + xh 2 O 2H + + xe heat * 3 + e + + O + h HW x + + VI 1 x W + V x O IN Sb-W BASED GLASSES 3 W + VI O 3 hν + III + V + VI + Sb Wx W1 xo3 + Sb + V

35 Photonic Crystal

36 Scanning Electronic Microscopy Glass evaporation Selective corrosion Template Template + Film 2D Photonic Crystal

37 THEORETICAL PREDICTIONS 1,2 1,0 0,8 a/λ 0,6 0,4 0,2 0,0 Κ Γ Μ Κ Μ' Γ Κ' Μ' Ligth intensity simulation obtained from superposition of two fringes detuned from 60º between each exposition giving an hexagonal pattern Theoretical Band diagram obtained for TE polarization, for an hexagonal arrangement and n = 1.9 (film composition 50Sb 2 O 3-50Sb 2 S 3 )

38 EXPERIMENTAL RESULTS UV-Vis - Spectroscopy 60 o 140 Experimental setup Transmitância (a.u.) o Brillouin zone Comprimento de Onda (nm)

39 EXPERIMENAL X THEORIC 1,2 TE n=1,9 1,0 0,8 a/λ 0,6 0,4 0,2 0,0 Lines: theoretic Scatter: measured Γ M'

40 Conclusions WO 3 show a high non linear optical absorption probably due to the presence of WO6 clusters. Photochromic properties under UV, visible and infrared laser exposure witch may be related to WO 6 clusters. In the GeS glass system addition of Ga induced PE Microlens and 2D photonic crystal have been produced using PE Increasing WO 3 content increasing α Increasing power increasing α The photochromic effect is reversible by heat treatment No degradation of the glass is observed after ht

41 Acknowledgments I. SKRIPACHEV S. H. MESSADDEQ M.NALIN G. POIRIER