Lase r damage res i s t ance o f op t i ca l componen ts : l im i t a t i ons and improvemen t o f damage t h resho ld
Laurent Gal la is Inst i tut Fresnel (Aix-Marsei l le Universi té, CNRS, Ecole Centrale Marsei l le) , Domaine Universi ta i re de St Jérôme, Marsei l le , FRANCE
laurent .ga l la is@fresnel . f r
Out l i ne
• Introduct ion • Some resul ts and discussions on l imi tat ions and
improvements for : • Intrinsic damage threshold of optical materials • Defect-induced damage • Damage growth
• Conclusions, perspect ives
I ns t i t u t F resne l
• Research f ie lds: • Photonics, Electromagnetism, Image processing
• Topics: • Biophotonics, image processing, laser material interactions,
medical applications, nanophotonics, numerical simulations, optical coatings, optical instrumentation,…
• People: • 10 groups • Permanent staff: 83 • PhD students: 54 • Post-docs and fixed term contracts : 31
UMR 7249
H I L A S E / H E P Te c h , 5 m a r c h 2 0 1 5
I LM g roup
• Topics: • Experimental and theoretical work to study the physics of laser
material interactions (fs to CW) • Laser damage of optical components for high power
applications • Laser processing
• People: • 5 permanent staff • 1 Engineer • 6 PhD students
Interact ion Laser Mat ière / Laser Mater ia l Interact ions
H I L A S E / H E P Te c h , 5 m a r c h 2 0 1 5
I LM g roup
L . E s c o u b a s – 1 9 9 7 : l o c a l i z e d a b s o r p t i o n a n d l a s e r d a m a g e P. Vo l t o – 1 9 9 8 : l a s e r d a m a g e i n o p t i c a l t h i n f i l m s A . G a t t o – 1 9 9 9 : E v o l u t i o n o f a b s o r b i n g d e f e c t s u n d e r i r r a d i a t i o n L . G a l l a i s – 2 0 0 2 : l a s e r d a m a g e m e t r o l o g y a n d s t a t i s t i c a l m o d e l s A . D u r i n g – 2 0 0 2 : p h o t o t h e r m a l m i c r o s c o p y O . T h o m a s – 2 0 0 4 : n s n o n - l i n e a r e f f e c t s F. B i l l a r d – 2 0 0 5 : f s / p s n o n - l i n e a r e f f e c t s B . B e r t u s s i – 2 0 0 5 : K D P c r y s t a l s H . K r o l – 2 0 0 6 : t h i n f i l m s f o r M i d I R J . C a p o u l a d e – 2 0 0 8 : D a m a g e s t a t i s t i c s i n K D P a n d t h i n f i l m s H . H i l d e n b r a n d – 2 0 0 8 : N o n - l i n e a r c r y s t a l s ( R T P, B B O , . . . ) A . C i a p p o n i – 2 0 0 9 : l u m i n e s c e n c e f o r l a s e r d a m a g e s t u d i e s B . B u s s i è r e – 2 0 0 9 : T i : S a p h i r e c r y s t a l s S . R e y n é – 2 0 11 : m u l t i - w a v e l e n g t h e f f e c t s i n K D P c r y s t a l s B . M a n g o t e – 2 0 11 : s u b - p s l a s e r d a m a g e o f o p t i c a l t h i n f i l m s X . F u – 2 0 1 2 : n s l a s e r d a m a g e r e s i s t a n c e o f b i n a r y o x i d e f i l m s a n d D O E C . G o u l d i e f f – 2 0 1 3 : F a t i g u e e f f e c t s u n d e r n s U V i r r a d i a t i o n M . C h a m b o n n e a u – 2 0 1 4 : m u l t i - w a v e l e n g t h e f f e c t s i n s i l i c a A . H e r v y – e x p 2 0 1 5 : o p t i c a l i n t e r f e r e n c e c o a t i n g s f o r i n t e n s e u l t r a s h o r t p u l s e s D . B . D o u t i – e x p 2 0 1 5 : p h y s i c s o f f s l a s e r d a m a g e i n t h i n f i l m s T. D o u a l l e – e x p 2 0 1 6 : d a m a g e m i t i g a t i o n p r o c e s s e s f o r s i l i c a o p t i c s R . D i a z – e x p 2 0 1 6 : n s d a m a g e p r o c e s s i n t h i c k s i l i c a w i n d o w s M . S o z e t – e x p 2 0 1 7 : m e t r o l o g y a n d i m p r o v e m e n t o f L I D T f o r P W o p t i c s A . B a u d i e r – e x p 2 0 1 7 : F a t i g u e e f f e c t s u n d e r n s D U V i r r a d i a t i o n
Laser damage PhD student topics
I LM g roup
Academics: Agencies: Industry:
Col laborat ions on Laser Damage issues (past and present)
Lase r damage Context
« Laser damage » in title, Web of Science database (medical applications excluded, conferences excluded)
1960 1970 1980 1990 2000 20100
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20
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40
50
60
70
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100
Cou
nt
Year
Peer Reviewed Articles
*M. Hercher, “Laser-induced damage in transparent media”, JOSA 54 563 (1964). **C. Giuliano, “Laser-induced damage to transparent dielectric materials”, JOSA 54 1400 (1964).
• Laser damage: • I r revers ib le modi f icat ion of a
mater ia l submi t ted to laser i r rad ia t ion
• Resul t o f the coupl ing of laser l ight wi th mater ia l
• Subject is s tudied s ince the advent of lasers*,**
• Large database and sc ient i f ic work on the subject
• Sti l l a main l imi tat ion • Growing interest wi th the
development of intense lasers
Lase r damage o f op t i ca l componen ts Consequences in h igh power laser chains
High power laser
Very expensive optic
Lase r damage o f op t i ca l componen ts Consequences in h igh power laser chains
High power laser
Damage Initiation
Lase r damage o f op t i ca l componen ts Consequences in h igh power laser chains
High power laser
Damage Initiation
Local reduction of damage resistance
Lase r damage o f op t i ca l componen ts Consequences in h igh power laser chains
High power laser
Damage Initiation
Local reduction of damage resistance
Damage growth
Lase r damage o f op t i ca l componen ts Consequences in h igh power laser chains
High power laser
Damage Initiation
Local reduction of damage resistance
Damage growth
contamination
Lase r damage o f op t i ca l componen ts Consequences in h igh power laser chains
High power laser
Damage Initiation
Local reduction of damage resistance
Damage growth
contamination
Integrety of the optical component
Lase r damage o f op t i ca l componen ts Consequences in h igh power laser chains
High power laser
Damage Initiation
Local reduction of damage resistance
Damage growth
contamination
Integrety of the optical component
Beam obscuration
Lase r damage o f op t i ca l componen ts Consequences in h igh power laser chains
High power laser
Damage Initiation
Local reduction of damage resistance
Damage growth
contamination
Integrety of the optical component
Beam obscuration
Scattering Losses
Lase r damage o f op t i ca l componen ts Consequences in h igh power laser chains
High power laser
Damage Initiation
Local reduction of damage resistance
Damage growth
contamination
Integrety of the optical component
Beam obscuration
Scattering Losses
Wavefront modulations
Degradation of beam quality
Lase r damage o f op t i ca l componen ts Consequences in h igh power laser chains
High power laser
Damage Initiation
Local reduction of damage resistance
Damage growth
contamination
Integrety of the optical component
Beam obscuration
Scattering Losses
Wavefront modulations
Degradation of beam quality
Damage propagation
Other expensive optic
Out l i ne
• Introduct ion • Some resul ts and discussions on l imi tat ions and
improvements for : • Intrinsic damage threshold of optical materials • Defect-induced damage • Damage growth
• Conclusions, perspect ives
L im i t a t i ons
Basic processes occur at d i fferent t imescales: – Excitation
• Absorption by free electrons in the material – Initial free electrons in metals – Free electrons created by non-linear ionisation in dielectrics
– Energy transfer • From electrons to lattice • Heat diffusion in the material
– Response of the material • Phase change • Hydrodynamic motion, shock waves • Thermo-mechanical stress
– Material removal • Thermal or mechanical effects depending on the deposited energy,
material properties and irradiation conditions
Physics of laser damage under intense i r radiat ion
time
fs
ps
ns
µs
L im i t a t i ons Physics of laser damage
time
fs
ps
ns
µs
fs pulse ns pulse
Laser / plasma
interaction will drive energy
deposition and
damage process
Energy deposition
and damage
processes are
separated in time
Main property: related to defects that can iniate a
plasma
Main property: related to intrinsic
properties of the material
L im i t a t i ons Intr insic exci tat ion processes in d ie lectr ic mater ia ls
Conduction band
Energy
Time
EV
Ec
Eg
PhotoionizationFree carrier-heating
Impact ionization& avalanche
Relaxation, trapping
MPI TI
Valence band
Etc…
Trapson native or Laser-induceddefects
ST
DT
L im i t a t i ons Intr insic damage resistance of opt ical mater ia ls - fs
Improvement of damage resistance?
1 2 3 40.0
0.5
1.0
1.5
2.0
LIDT
(J/c
m²)
Photon energy (eV)
Nb2O5 Simulation Ta2O5 Simulation HfO2 Simulation Sc2O3 Al2O3 Simulation
L. Gallais et al., Submitted.
L. Gallais et al., Appl. Opt. 53 (2014)
1 10 100 1000 10000 1000000.0
0.2
0.4
0.6
0.8
LID
T (J
/cm
²)
Number of pulses
1030nm 515nm 343nm MS IAD
D.B. Douti, Opt. Eng. 53 (2014)
LIDT vs Bandgap LIDT vs photon energy LIDT vs Number of pulses
1on1, 800nm, 100fs 1on1, 310-1200nm, 100fs Nb2O5 film, Son1, 1030/515/343nm, 500fs
1 2 3 4 5 6 7 8 9 10 110.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
Si Simulation Ge Nb2O5
Ta2O5
HfO2
Sc2O3
Al2O3
SiO2 (film) SiO2 (bulk) CaF2
LIDT
(J/c
m²)
Bandgap (eV)
Imp rovemen t mater ia ls
1,4 1,6 1,8 2,0 2,2 2,40
1
2
3
4
5
6
SiO2 Nb2O5/SiO2 Nb2O5 ZrO2 ZrO2/SiO2 Ta2O5 Ta2O5/SiO2 HfO2 HfO2/SiO2 Al2O3 Al2O3/SiO2 Sc2O3 Sc2O3/SiO2 Al2O3/AlF3 AlF3 Y2O3 TiO2
Thre
shol
d (J
/cm
²)
refractive index
A. Melninkaitis et al., Appl. Opt. 50 (2011). Mangote et al., Opt. Lett. 37(2012).
M. Mende et al., Appl. Opt. 52 (2013).
Mixture materials: • With an adapted design, the use of mixture materials can lead to subsequent enhancement of the LIDT of multilayer systems compared to the use of pure material systems
Imp rovemen t
The design can be opt imized to improved the damage threshold:
• Reduce E- f ie ld in the ‘weak ’ layer (non-quar ter wave s tacks)
• Remove in ter faces (Rugate f i l ters) • Inser t grad ients • Combine mater ia l wi th d i f ferent
proper t ies (d ie lec t r ics , meta ls) • Reduce s t ress • Protect ion, adhes ion layers • Manage thermal issues • …
Case of opt ical Inter ference coat ings: Designs
To be discuss by A. Hervy…
0,0
0,5
1,0
1,5
|E/E
inc|²
Imp rovemen t Case of fs regime
• Comparat ive study R-max (99,5%) at 800nm, tes ted at 200 fs :
C.J. Stolz et al., « Thin Film Femtosecond Laser Damage Competition », Laser Damage Symposium, 2010
Imp rovemen t Case of ns regime
• Comparat ive study R-max (99,5%) à 1064nm tested at 5ns :
C.J. Stolz et al., « Thin Film nanosecond Laser Damage Competition », Laser Damage Symposium, 2009
Out l i ne
• Introduct ion • Some resul ts and discussions on l imi tat ions and
improvements for : • Intrinsic damage threshold of optical materials • Defect-induced damage • Damage growth
• Conclusions, perspect ives
L im i t a t i on : de fec t i n i t i a t ed damage
Main mechanism=absorpt ion delocal isat ion: • Defect= seed for the damage process • Af ter reaching a cr i t ica l temperature, severa l processes
can lead to the extens ion of an absorpt ion f ront
Physics of ns defect in i t ia ted damage
e- hν T>Tcrit.
Grua et al., Phys. Rev B,2003 Danileiko et al., Sov. J. Quant. Elec., 1978 Saito et al., Phys. Rev B,2000 Bude et al., Laser damage symposium 2007
A nanometric defect can lead to significant absorption of laser energy
L im i t a t i on : de fec t i n i t i a t ed damage Physics of ns defect in i t ia ted damage
A nanometric defect can lead to a macroscopic damage
Simulations of energy deposition, shock wave and fracture propagation with hydrodynamic codes. Defect is a gold inclusion in a silica martix. 6J/cm², 355nm, 3ns
F. Bonneau et al., Appl. Phys. B,2004
surface
volume
L im i t a t i on : de fec t i n i t i a t ed damage Examples of defects
J. Fournier et al, Opt. Express 18 (2010).
J. Bude et al, Opt. Express 22 (2014).
S. Demos et al, Opt. Lett .26 (2001).
Surface contamination
Fractures Clusters of electronic
defects
Many others!
160µm
Imp rovemen t : de fec t m i t i ga t i on Local mel t ing/anneal ing
P. Cormont et al, Opt. Express 21 (2013). P. Cormont et al, Advanced Engineering materials (2014).
Application on an optic representative of LMJ production:
Polishing scratch
CO2 Laser•CO2laser is an interesting tool to remove scratches because it can melt efficiently the silica in a rapid and localized way, without generating debris •Can be applied between polishing and finishing
3ns, 355nm
Imp rovemen t : de fec t m i t i ga t i on Anneal ing
15 16 17 18 19 20 21 22 23
0
20
40
60
80
100
Sample 1 Initial Annealed
Sample2 Initial Annealed
Dam
age
prob
abili
ty (%
)
Fluence (J/cm²)N. Shen et al. et al., Opt. Eng. 51 (2012)
T. Doualle et al. et al., Submitted
One widely applied method of removing point defects in silica is to isothermally anneal the material in a furnace.
Application on polished fused silica substrates (3ns, 355nm):
Imp rovemen t : de fec t m i t i ga t i on Laser condi t ioning
M. Commandré et al., Eur. Phys. J. 153 (2008)
Annihilation and/or passivation of defects can be observed, depending on fluence and exposure time => conditioning process
Absorption evolution of an isolated defect (250nm gold particle in a silica matrix) under successive ns exposures at 1064nm (no surface modification)
Out l i ne
• Introduct ion • Some resul ts and discussions on l imi tat ions and
improvements for : • Intrinsic damage threshold of optical materials • Defect-induced damage • Damage growth
• Conclusions, perspect ives
L im i t a t i on : Lase r damage g row th Analyse of damage s i tes
18 µm 50 µm
9,5 µm Crack zone
Damage zone
M.A Norton et al. Proc SPIE 6403 (2006) J. Wong et al. J. Non Cryst. Sol. 352 (2006)
B. Bertussi et al. Opt. Express 17 (2009)
UV, ns, rear face, damage site on silica surface
L im i t a t i on : Lase r damage g row th Growth laws
L. Lamaignère et al., Appl. Phys. B 114 (2014)
k depends on: -mean fluence -size of the damage sites -pulse duration
Growth of damage site area versus shot number under laser irradiation at 351 nm— 3 ns.
An+1=Anexp(k)
R. Courchinoux et al., Proc. SPIE 5273 (2004)
Imp rovemen t : l ase r damage m i t i ga t i on Methods
Remove / Anneal / Transform…any potential initiating defect to recover initial material properties
Ideas:
CO2 CW10,6µmHF
CF4
fs
micropolishing Plasma torch Acid etching Laser thermal processing
Laser micromaching
Imp rovemen t : l ase r damage m i t i ga t i on Examples from l i t terature
S. Yang et al., Appl. Opt. 49 (2010)
J. Wolfe et al., Appl. Opt. 50 (2011)
CO2 Laser Galvo-scanner
AOM
fs LaserGalvo-
scanner
4.6µm CO2 Laser I. Bass et al., Proc. SPIE (2010)
Imp rovemen t : Lase r damage m i t i ga t i on Development of mit igat ion process for LMJ opt ics
Modeling surface defects for laser wave propagation
A. Bourgeade et al., JOSA B (2015)
Thermo-mechanics simulations
T. Doualle et al., submitted
Develop process to treat mm size damage Optimize LIDT of treated sites
P. Cormont et al., Opt. Express 18(2010)
Conc lus ions
Laser damage is a complex physical process wi th many potent ia l causes.
- improvement o f damage threshold requi res deta i led knowledge of these causes
-wi l l cont inue to be the subject o f extens ive research « Damage densi t ies / f luence » is more sui table than
« damage threshold » to def ine the damage resistance of an opt ical component
- improvement requi res reduct ion of damage dens i t ies , ie in i t ia t ing defect reduct ion
Damage growth is the main l imi tat ion for appl icat ion - can be mi t igated to recyle opt ics in some cases
Thank you f o r you r a t t en t i on !