Femtosecond Laser Damage Resistance of Optical Coating Materials. Laurent Gallais and Mireille Commandré

Transcription

1 Femtosecond Laser Damage Resistance of Optical Coating Materials Laurent Gallais and Mireille Commandré

2 Outline of the presentation Introduction Interaction of sub-ps pulses with optical coatings Energy deposition and damage mechanisms Dynamics of the damage process Resistance of optical coating materials An exhaustive comparison of coating materials Dependence on operating conditions Conclusion 2

3 Introduction Ultra-short pulse laser applications have opened a broad field of new investigation possibilities in many fields Material sciences, medical applications, fundamental research Progress in available laser systems: Peak power, pulse energy are increasing Available pulse duration is decreasing Specific and complex optical interference coatings are required Bandwidth, dispersion, dimensions, wavefront distorsion & laser damage resistance Fundamental and experimental research for a progressive optimization of laser optics with improved damage thresholds

4 Outline of the presentation Introduction Interaction of sub-ps pulses with optical coatings Energy deposition and damage mechanisms Dynamics of the damage process Resistance of optical coating materials An exhaustive comparison of coating materials Dependence on operating conditions Conclusion 4

5 Overview of damage process Basic process occur at different timescales: 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 phonons 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 fs ps ns µs time

6 Free electron generation in dielectrics Energy Conduction band E c E g E V Valence band Time

7 Free electron generation in dielectrics Energy Photoionization Conduction band E c E g E V MPI TI Valence band Time

8 Free electron generation in dielectrics Energy Photoionization Free carrierheating Conduction band E c E g E V MPI TI Valence band Time

9 Free electron generation in dielectrics Energy Photoionization Free carrierheating Impact ionization Conduction band E c E g E V MPI TI Valence band Time

10 Free electron generation in dielectrics Energy Photoionization Free carrierheating Impact ionization & avalanche Conduction band E c E g E V MPI TI Valence band Time

11 Free electron generation in dielectrics Energy Photoionization Free carrierheating Impact ionization & avalanche Conduction band Etc E c E g E V MPI TI Valence band Time

12 Free electron generation in dielectrics Energy Photoionization Free carrierheating Impact ionization & avalanche Relaxation, trapping Conduction band Etc E c E g ST DT Traps on native or Laserinduced defects E V MPI TI Valence band Time

13 Energy deposition in dielectric coatings Temporal evolution of free electron density Can be described in first approximation with the rate equation:

14 Energy deposition in dielectric coatings Evolution of free electron density Can be described in first approximation with the rate equation: Intensity (W/m²) 1x x x x x x x x x x x x x x x x x x x x x10 9 1x time (fs) Electron density (/cm3) HfO 2, 800nm, 100fs, 1J/cm²

15 Energy deposition in dielectric coatings Evolution of free electron density Can be described in first approximation with the rate equation: Initial Free electrons are created by Photo-ionization Intensity (W/m²) 1x x x x x x x x x x x x x x x x x x x x x10 9 1x time (fs) HfO2, 800nm, 100fs, 1J/cm² Electron density (/cm3) At sufficient density impact ionization is efficient and avalanche takes place

16 Energy deposition in dielectric coatings Evolution of free electron density Can be described in first approximation with the rate equation: Initial Free electrons are created by Photo-ionization Intensity (W/m²) 1x x x x x x x x x x x x x x x x x x x x x10 9 1x time (fs) HfO2, 800nm, 100fs, 1J/cm² Electron density (/cm3) Critical density: reached when plasma waves are resonant with the laser wavelength (~ cm -3 ) At sufficient density impact ionization is efficient and avalanche effect takes place

17 Energy deposition in dielectric coatings Case of multi-dielectric interference coatings Combination of different materials Interference effects leading to local E-field enhancement Free electrons modifies the optical response of the material

18 Energy deposition in dielectric coatings Spatio-temporal evolution of free electron density in optical interference coatings 1053nm, 500fs, S polarization HfO 2 HfO 2 SiO 2 SiO 2 SiO 2

19 Energy deposition in dielectric coatings Spatio-temporal evolution of free electron density in optical interference coatings 1,5 1E23 1E22 Intensity (W/m²) 1,0x ,0x Time (fs) E/E inc ² 1,0 0,5 1E21 1E20 1E19 1E18 1E17 Electronic density (cm -3 ) 1E16 *Gallais L., Mangote B., Comandré M., Melninkaitis A., Mirauskas J., Jeskevic M., Sirutkaitis V., 'Transient interference implications on the subpicosecond laser damage of multidielectrics', Applied Physics Letters, (2010)

20 Energy deposition in dielectric coatings Spatio-temporal evolution of free electron density in optical interference coatings 1,5 1E23 1E22 Intensity (W/m²) 1,0x ,0x Time (fs) E/E inc ² 1,0 0,5 1E21 1E20 1E19 1E18 1E17 Electronic density (cm -3 ) 1E16 *Gallais L., Mangote B., Comandré M., Melninkaitis A., Mirauskas J., Jeskevic M., Sirutkaitis V., 'Transient interference implications on the subpicosecond laser damage of multidielectrics', Applied Physics Letters, (2010)

21 Energy deposition in dielectric coatings Spatio-temporal evolution of free electron density in optical interference coatings 1,5 1E23 1E22 Intensity (W/m²) 1,0x ,0x Time (fs) E/E inc ² 1,0 0,5 1E21 1E20 1E19 1E18 1E17 Electronic density (cm -3 ) 1E16 *Gallais L., Mangote B., Comandré M., Melninkaitis A., Mirauskas J., Jeskevic M., Sirutkaitis V., 'Transient interference implications on the subpicosecond laser damage of multidielectrics', Applied Physics Letters, (2010)

22 Energy deposition in dielectric coatings Spatio-temporal evolution of free electron density in optical interference coatings 1,5 1E23 1E22 Intensity (W/m²) 1,0x ,0x Time (fs) E/E inc ² 1,0 0,5 1E21 1E20 1E19 1E18 1E17 Electronic density (cm -3 ) 1E16 *Gallais L., Mangote B., Comandré M., Melninkaitis A., Mirauskas J., Jeskevic M., Sirutkaitis V., 'Transient interference implications on the subpicosecond laser damage of multidielectrics', Applied Physics Letters, (2010)

23 Energy deposition in dielectric coatings Case of multi-dielectric interference coatings 1,5 1E23 1E22 Intensity (W/m²) 1,0x ,0x Time (fs) E/E inc ² 1,0 0,5 1E21 1E20 1E19 1E18 1E17 Electronic density (cm -3 ) 1E16 *Gallais L., Mangote B., Comandré M., Melninkaitis A., Mirauskas J., Jeskevic M., Sirutkaitis V., 'Transient interference implications on the subpicosecond laser damage of multidielectrics', Applied Physics Letters, (2010)

24 Energy deposition in dielectric coatings Case of multi-dielectric interference coatings 1,5 1E23 1E22 Intensity (W/m²) 1,0x ,0x Time (fs) E/E inc ² 1,0 0,5 1E21 1E20 1E19 1E18 1E17 Electronic density (cm -3 ) 1E16 *Gallais L., Mangote B., Comandré M., Melninkaitis A., Mirauskas J., Jeskevic M., Sirutkaitis V., 'Transient interference implications on the subpicosecond laser damage of multidielectrics', Applied Physics Letters, (2010)

25 Energy deposition in dielectric coatings Spatio-temporal evolution of free electron density in optical interference coatings 1,5 1E23 1E22 Intensity (W/m²) 1,0x ,0x Time (fs) E/E inc ² 1,0 0,5 1E21 1E20 1E19 1E18 1E17 Electronic density (cm -3 ) 1E16 *Gallais L., Mangote B., Comandré M., Melninkaitis A., Mirauskas J., Jeskevic M., Sirutkaitis V., 'Transient interference implications on the subpicosecond laser damage of multidielectrics', Applied Physics Letters, (2010)

26 Energy deposition in dielectric coatings Case of multi-dielectric interference coatings 1,5 1E23 1E22 Intensity (W/m²) 1,0x ,0x Time (fs) E/E inc ² 1,0 0,5 1E21 1E20 1E19 1E18 1E17 Electronic density (cm -3 ) 1E16 *Gallais L., Mangote B., Comandré M., Melninkaitis A., Mirauskas J., Jeskevic M., Sirutkaitis V., 'Transient interference implications on the subpicosecond laser damage of multidielectrics', Applied Physics Letters, (2010)

27 Energy deposition in dielectric coatings Case of multi-dielectric interference coatings 1,5 1E23 1E22 Intensity (W/m²) 1,0x ,0x Time (fs) E/E inc ² 1,0 0,5 1E21 1E20 1E19 1E18 1E17 Electronic density (cm -3 ) 1E16 *Gallais L., Mangote B., Comandré M., Melninkaitis A., Mirauskas J., Jeskevic M., Sirutkaitis V., 'Transient interference implications on the subpicosecond laser damage of multidielectrics', Applied Physics Letters, (2010)

28 Energy deposition in dielectric coatings Spatio-temporal evolution of free electron density in optical interference coatings 1,5 1E23 1E22 Intensity (W/m²) 1,0x ,0x Time (fs) E/E inc ² 1,0 0,5 1E21 1E20 1E19 1E18 1E17 Electronic density (cm -3 ) 1E16 *Gallais L., Mangote B., Comandré M., Melninkaitis A., Mirauskas J., Jeskevic M., Sirutkaitis V., 'Transient interference implications on the subpicosecond laser damage of multidielectrics', Applied Physics Letters, (2010)

29 Energy deposition in dielectric coatings Case of multi-dielectric interference coatings 1,5 1E23 1E22 Intensity (W/m²) 1,0x ,0x Time (fs) E/E inc ² 1,0 0,5 1E21 1E20 1E19 1E18 1E17 Electronic density (cm -3 ) 1E16 *Gallais L., Mangote B., Comandré M., Melninkaitis A., Mirauskas J., Jeskevic M., Sirutkaitis V., 'Transient interference implications on the subpicosecond laser damage of multidielectrics', Applied Physics Letters, (2010)

30 Energy deposition in dielectric coatings Case of multi-dielectric interference coatings 1,5 1E23 1E22 Intensity (W/m²) 1,0x ,0x Time (fs) E/E inc ² 1,0 0,5 1E21 1E20 1E19 1E18 1E17 Electronic density (cm -3 ) 1E16 *Gallais L., Mangote B., Comandré M., Melninkaitis A., Mirauskas J., Jeskevic M., Sirutkaitis V., 'Transient interference implications on the subpicosecond laser damage of multidielectrics', Applied Physics Letters, (2010)

31 Energy deposition in dielectric coatings Spatio-temporal evolution of free electron density in optical interference coatings 1,5 1E23 1E22 Intensity (W/m²) 1,0x ,0x Time (fs) E/E inc ² 1,0 0,5 1E21 1E20 1E19 1E18 1E17 Electronic density (cm -3 ) 1E16 *Gallais L., Mangote B., Comandré M., Melninkaitis A., Mirauskas J., Jeskevic M., Sirutkaitis V., 'Transient interference implications on the subpicosecond laser damage of multidielectrics', Applied Physics Letters, (2010)

32 Damage mechanisms following energy deposition, several damage processes can be observed depending on material properties and/or irradiation conditions: Thermal effects (phase change, thermal explosion) Mechanical effects (shock wave, relaxation of laser-induced stress) Ripples, surface plasmons Plasma scald Nb 2 O 5 HfO 2 HfO 2

33 *Mende M., Schrameyer S., Ehlers H., Ristau D., Gallais L., Laser damage resistance of ion-beam sputtered Sc2O3/SiO2 mixture optical coatings Applied Optics, (2013). Damage mechanisms Example: Thermal effects: phase changes, thermal explosion Example: Sc 2 O 3 /SiO 2 mixture (single layer)* LIDT 5.6J/cm² 6J/cm² 6.25J/cm² 6.4J/cm² 6.6J/cm² Fluence at 1030nm/500fs

34 Damage mechanisms Example Thermal effects: phase changes, thermal explosion Example: Sc2O3/SiO2 mixture (single layer)* 1,6x ,4x ,2x10 17 Incident Intensity Absorbed intensity in the film LIDT Intensity (W/m²) 1,0x ,0x10 Absorbed J/cm² 6J/cm² 6,0x J/cm² 6.4J/cm² energy 6.6J/cm² 4,0x ,0x10 16 Fluence at 1030nm/500fs time (fs)

35 Damage mechanisms Example Thermal effects: phase changes, thermal explosion Example: Sc2O3/SiO2 mixture (single layer)* Absorbed in the film 500fs) Sc 2 O 3 melting (C p Τ+Η m ) LIDT Specific energy (J/g) J/cm² 6J/cm² 6.25J/cm² 6.4J/cm² 6.6J/cm² Fluence at 1030nm/500fs ,0 5,2 5,4 5,6 5,8 6,0 6,2 6,4 Fluence (J/cm²)

36 Damage mechanisms Example: Mechanical effects Pt film (single layer)* Ag film (single layer)* 0.33J/cm² 0.41J/cm² Fluence at 1030nm/500fs 0.88J/cm² *Wang B., Gallais L., A theoretical investigation of the laser damage threshold of metal multi-dielectric mirrors for high power ultrashort applications, Optics Express 21, 14698, 2013

37 Damage mechanisms Example: Mechanical effects Pt film (single layer)* LatticeTemperature Ag film (single layer)* Film 0.33J/cm² Substrate 0.41J/cm² 0.88J/cm² *Wang B., Gallais L., A theoretical investigation of the laser damage threshold of metal multi-dielectric mirrors for high power ultrashort applications, Optics Express 21, 14698, 2013

38 Damage mechanisms Evolution with film properties HfO 2 /SiO 2 mixtures* (IBS) HfO2 Composition SiO2 Jupé M., Mende M., Ristau D., Mangote B., Gallais L., Measurement and calculation of tenare oxide mixtures for ultra short pulse laser Thin Film Optics, Laser-Induced Damage in Optical Materials, Proc. SPIE 2011

39 Damage mechanisms Evolution with E-field distribution Ta 2 O 5 films (DIBS)* Optical thickness λ/8 λ/4 λ/2 λ *Mangote B., Gallais L., Commandre M., Zerrad M., Natoli J.-Y., Lequime, M., Subpicosecond pulse laser damage behavior of dielectric thin films prepared by different techniques, Proc. SPIE Vol. 7504, Laser- Induced Damage in Optical Materials, 2009.

40 Outline of the presentation Introduction Interaction of sub-ps pulses with optical coatings Energy deposition and damage mechanisms Dynamics of the damage process Resistance of optical coating materials An exhaustive comparison of coating materials Dependence on operating conditions Conclusion 40

41 Dynamics of the damage process Recent results obtained with Time Resolved Digital Holography* Objectives: direct observation of film response to high intensity pulses with quantitative measurements of transmission and phase delay Description of the experiment: Yb:KGW 300fs, 1030nm NOPA 550nm, 25fs reference probe pump Obj. CCD Delay line lens *Šiaulys N., Melninkaitis A., Gallais L., Application of time-resolved digital holographic microscopy to study femtosecond damage process in thin films, Submitted

42 Dynamics of the damage process Recent results obtained with Time Resolved Digital Holography* Measurements on a Ta 2 O 5 single layer: Pump pulse T/Tinit -300fs -200fs -100fs 0fs 200fs 600fs 1.4ps 3ps 10ps 100ps 500ps 1ns Pump/probe delay rad *Šiaulys N., Melninkaitis A., Gallais L., Application of time-resolved digital holographic microscopy to study femtosecond damage process in thin films, Submitted

43 Dynamics of the damage process Recent results obtained with Time Resolved Digital Holography* Measurements on a Ta2O5 single layer: Pump pulse T/Tinit -300fs -200fs -100fs 0fs 200fs 600fs 1.4ps 3ps 10ps 100ps 500ps 1ns Pump/probe delay rad Kerr effect in the susbtrate *Šiaulys N., Melninkaitis A., Gallais L., Application of time-resolved digital holographic microscopy to study femtosecond damage process in thin films, Submitted

44 Dynamics of the damage process Recent results obtained with Time Resolved Digital Holography* Measurements on a Ta2O5 single layer: Pump pulse T/Tinit -300fs -200fs -100fs 0fs 200fs 600fs 1.4ps 3ps 10ps 100ps 500ps 1ns Pump/probe delay rad Kerr effect in the susbtrate Free electron gas *Šiaulys N., Melninkaitis A., Gallais L., Application of time-resolved digital holographic microscopy to study femtosecond damage process in thin films, Submitted

45 Dynamics of the damage process Recent results obtained with Time Resolved Digital Holography* Measurements on a Ta 2 O 5 single layer: Pump pulse T/Tinit -300fs -200fs -100fs 0fs 200fs 600fs 1.4ps 3ps 10ps 100ps 500ps 1ns Pump/probe delay rad Kerr effect in the susbtrate Free electron gas Material changes *Šiaulys N., Melninkaitis A., Gallais L., Application of time-resolved digital holographic microscopy to study femtosecond damage process in thin films, Submitted

46 Dynamics of the damage process Recent results obtained with Time Resolved Digital Holography* Comparison to simulations 1,0 1.8J/cm², 1030nm, P polar, 45 AOI, 300fs FWHM (I(t)=gaussian) Relative probe transmittance Transmission and phase shift of the probe are calculated (take into account spatial and temporal modifications of refractive index at 550nm due to the pump excitation) 0,8 0,6 0,4 0,2 1E-13 1E-12 1E-11 1E-10 1E-9 Time (s) H/2 H 2H 4H *Šiaulys N., Melninkaitis A., Gallais L., Application of time-resolved digital holographic microscopy to study femtosecond damage process in thin films, Submitted

47 Outline of the presentation Introduction Interaction of sub-ps pulses with optical coatings Energy deposition and damage mechanisms Dynamics of the damage process Resistance of optical coating materials An exhaustive comparison of coating materials Dependence on operating conditions Conclusion 47

48 Laser resistance of optical coating materials Metrology of damage effect: sub-ps damage testing system at IF 1030 / 515 / 343nm SHG THG Autocorrelator Yg:KGW 400fs-3ps 1mJ 1030nm 10Hz- 100kHz λ/2 Pol. Pyro. Calo. DIC microscope *Mangote B., Gallais L., Zerrad M., Lemarchand F., Gao L.H., Commandré M., Lequime M., A high accuracy femto-/picosecond laser damage test facility dedicated to the study of optical thin films, Review of Scientific Instruments, (2012)

49 Laser resistance of optical materials Case of simple materials for laser coatings 500fs, 1on1, 1030nm Threshold (J/cm²) 5,0 4,5 4,0 3,5 3,0 2,5 2,0 1,5 SiO2 Nb2O5 ZrO2 Ta2O5 Al2O3 HfO2 Sc2O3 AlF3 Y2O3 TiO2 Linear fit Data from * 1,0 0, Bandgap (ev)

50 Laser resistance of optical materials Case of simple materials for laser coatings 500fs, 1on1, 1030nm Threshold (J/cm²) 5,0 4,5 4,0 3,5 3,0 2,5 2,0 1,5 SiO2 Nb2O5 ZrO2 Ta2O5 Al2O3 HfO2 Sc2O3 AlF3 Y2O3 TiO2 Linear fit Data from * 1,0 0, Bandgap (ev)

51 Laser resistance of optical coating materials Case of simple materials for laser coatings 500fs, 1on1, 1030nm, internal LIDT Threshold (J/cm²) 5,0 4,5 4,0 3,5 3,0 2,5 2,0 1,5 1,0 0, Bandgap (ev) SiO2 Nb2O5 ZrO2 Ta2O5 Al2O3 HfO2 Sc2O3 AlF3 Y2O3 TiO2 Linear fit Data from * *Mero,M., Liu J., Rudolph W., Ristau D., Starke, K., Scaling laws of femtosecond laser pulse induced breakdown in oxide films, Physical Review B, 2005, 71,

52 Resistance of optical coating materials Comparison with simulations A quantitative description of experimental data can be obtained with the simple models described previously *Mangote B., Gallais L., Commandré M., Mende M., Jensen L., Ehlers H., Jupé M., Ristau D., Melninkaitis A., Mirauskas J., Sirutkaitis V., Kičas S., Tolenis T., Drazdys R., 'Femtosecond laser damage resistance of oxide and mixture oxide optical coatings', Optics Letters, 37 (2012)

53 Resistance of optical coating materials Comparison with bulk materials? 500fs, 1on1, 1030nm, internal LIDT 5 4 LIDT (J/cm²) 3 2 Dielectric films Bandgap (ev)

54 Resistance of optical coating materials Comparison with bulk materials Pt, Ag, 500fs, 1on1, 1030nm, internal LIDT 5 4 LIDT (J/cm²) Metal films Bandgap (ev)

55 Resistance of optical coating materials Comparison with bulk materials Pt, Ag, 500fs, 1on1, 1030nm, internal LIDT 5 Si, Ge, ZnS, ZnSe, 4 LIDT (J/cm²) 3 2 Semiconductors 1 Metal films Bandgap (ev)

56 Resistance of optical coating materials Comparison with bulk materials Pt, Ag, 500fs, 1on1, 1030nm, internal LIDT Si, Ge, ZnS, ZnSe, 5 4 Intermediate bandgap dielectrics NaCl, KBr, Al2O3, Infrasil, Suprasil, Quartz, LIDT (J/cm²) 3 2 Semiconductors 1 Metal films Bandgap (ev)

57 Resistance of optical coating materials Comparison with bulk materials Pt, Ag, 500fs, 1on1, 1030nm, internal LIDT Si, Ge, ZnS, ZnSe, 5 4 Intermediate bandgap dielectrics High bandgap dielectrics NaCl, KBr, Al2O3, Infrasil, Suprasil, Quartz, BaF2, CaF2, MgF2, LIDT (J/cm²) Metal films Semiconductors Bandgap (ev)

58 Resistance of optical coating materials Influence of deposition process? In case of good quality coatings, LIDT approaches that of bulk materials However optimization of deposition parameters is critical to reach highest available LIDT: 2,5 Ex: 11 different samples of HfO 2 made by different manufacturers: 2,0 LIDT (J/cm²) 1,5 1,0 0,5

59 Resistance of optical coating materials Influence of deposition process? In case of good quality coatings, LIDT approaches that of bulk materials However optimization of deposition parameters is critical to reach highest available LIDT: 2,5 Ex: 11 different samples of HfO 2 made by different manufacturers: 2,0 +/-7% LIDT (J/cm²) 1,5 1,0 0,5

60 Resistance of optical coating materials LIDT vs n Case of simple coating materials Threshold (J/cm²) 6 SiO2 Nb2O5 ZrO2 5 Ta2O5 Al2O3 HfO2 4 Sc2O3 AlF3 3 Y2O3 TiO ,4 1,6 1,8 2,0 2,2 2,4 refractive index

61 Resistance of optical coating materials LIDT vs n Case of mixtures (IBS*) 6 5 SiO2 Nb2O5/SiO2 Nb2O5 Threshold (J/cm²) ,4 1,6 1,8 2,0 2,2 2,4 refractive index *Melninkaitis A., Tolenis T., Mažulė L., Mirauskas J., Sirutkaitis V., Mangote B., Fu X., Zerrad M., Gallais L., Commandré M., Kičas S., Drazdys R., 'Characterization of zirconia and niobia silica mixture coatings produced by ion-beam sputtering', Applied Optics, 50 C (2011)

62 Resistance of optical coating materials LIDT vs n Case of mixtures (IBS*) 6 Threshold (J/cm²) SiO2 Nb2O5/SiO2 Nb2O5 ZrO2 ZrO2/SiO ,4 1,6 1,8 2,0 2,2 2,4 refractive index *Melninkaitis A., Tolenis T., Mažulė L., Mirauskas J., Sirutkaitis V., Mangote B., Fu X., Zerrad M., Gallais L., Commandré M., Kičas S., Drazdys R., 'Characterization of zirconia and niobia silica mixture coatings produced by ion-beam sputtering', Applied Optics, 50 C (2011)

63 Resistance of optical coating materials LIDT vs n Case of mixtures (IBS*) 6 Threshold (J/cm²) SiO2 Nb2O5/SiO2 Nb2O5 ZrO2 ZrO2/SiO2 Ta2O5 Ta2O5/SiO ,4 1,6 1,8 2,0 2,2 2,4 refractive index *Mangote B., Gallais L., Commandré M., Mende M., Jensen L., Ehlers H., Jupé M., Ristau D., Melninkaitis A., Mirauskas J., Sirutkaitis V., Kičas S., Tolenis T., Drazdys R., 'Femtosecond laser damage resistance of oxide and mixture oxide optical coatings', Optics Letters, 37 (2012)

64 Resistance of optical coating materials LIDT vs n Case of mixtures (IBS*) 6 Threshold (J/cm²) SiO2 Nb2O5/SiO2 Nb2O5 ZrO2 ZrO2/SiO2 Ta2O5 Ta2O5/SiO2 HfO2 HfO2/SiO ,4 1,6 1,8 2,0 2,2 2,4 refractive index *Mangote B., Gallais L., Commandré M., Mende M., Jensen L., Ehlers H., Jupé M., Ristau D., Melninkaitis A., Mirauskas J., Sirutkaitis V., Kičas S., Tolenis T., Drazdys R., 'Femtosecond laser damage resistance of oxide and mixture oxide optical coatings', Optics Letters, 37 (2012)

65 Resistance of optical coating materials LIDT vs n Case of mixtures (IBS*) 6 Threshold (J/cm²) SiO2 Nb2O5/SiO2 Nb2O5 ZrO2 ZrO2/SiO2 Ta2O5 Ta2O5/SiO2 HfO2 HfO2/SiO2 Al2O3 Al2O3/SiO ,4 1,6 1,8 2,0 2,2 2,4 refractive index *Mangote B., Gallais L., Commandré M., Mende M., Jensen L., Ehlers H., Jupé M., Ristau D., Melninkaitis A., Mirauskas J., Sirutkaitis V., Kičas S., Tolenis T., Drazdys R., 'Femtosecond laser damage resistance of oxide and mixture oxide optical coatings', Optics Letters, 37 (2012)

66 Resistance of optical coating materials LIDT vs n Case of mixtures (IBS*) 6 Threshold (J/cm²) SiO2 Nb2O5/SiO2 Nb2O5 ZrO2 ZrO2/SiO2 Ta2O5 Ta2O5/SiO2 HfO2 HfO2/SiO2 Al2O3 Al2O3/SiO2 Sc2O3 Sc2O3/SiO2 0 1,4 1,6 1,8 2,0 2,2 2,4 refractive index *Mende M., Schrameyer S., Ehlers H., Ristau D., Gallais L., Laser damage resistance of ion-beam sputtered Sc2O3/SiO2 mixture optical coatings, Applied Optics, (2013).

67 Resistance of optical coating materials LIDT vs n Case of mixtures (IBS*) Threshold (J/cm²) ,4 1,6 1,8 2,0 2,2 2,4 refractive index SiO2 Nb2O5/SiO2 Nb2O5 ZrO2 ZrO2/SiO2 Ta2O5 Ta2O5/SiO2 HfO2 HfO2/SiO2 Al2O3 Al2O3/SiO2 Sc2O3 Sc2O3/SiO2 Al2O3/AlF3 AlF3 *Mende M., Balasa I., Ehlers H., Ristau D., Douti D.B., Gallais L., Commandré M., Correlation of Optical Properties and Laser Damage Resistance for Ion Beam Sputtered Al2O3/AlF3 and Al2O3/SiO2 Mixture Coatings, OIC 2013 Poster FA.5

68 Resistance of optical coating materials LIDT vs n Overview of experimental results at 500fs / 1030nm 6 Threshold (J/cm²) ,4 1,6 1,8 2,0 2,2 2,4 refractive index SiO2 Nb2O5/SiO2 Nb2O5 ZrO2 ZrO2/SiO2 Ta2O5 Ta2O5/SiO2 HfO2 HfO2/SiO2 Al2O3 Al2O3/SiO2 Sc2O3 Sc2O3/SiO2 Al2O3/AlF3 AlF3 Y2O3 TiO2

69 Outline of the presentation Introduction Interaction of sub-ps pulses with optical coatings Energy deposition and damage mechanisms Dynamics of the damage process Resistance of optical coating materials An exhaustive comparison of coating materials Dependence on operating conditions Conclusion 69

70 Dependence on operating conditions For practical applications, scaling of LIDT values with irradiation parameters is of interest: Pulse duration t 0.3 dependence for t<1ps for dielectrics coatings*,** Multiple pulses: pulse number and repetition rate Wavelength Air/vacuum... *Stuart B.C., Feit M.D., Herman S., Rubenchik, A.M., Shore B. W., Perry M. D., Optical ablation by high-power short-pulse lasers, J. Opt. Soc. Am. B 13, 459, **Mero,M., Liu J., Rudolph W., Ristau D., Starke, K., Scaling laws of femtosecond laser pulse induced breakdown in oxide films, Physical Review B,71, , 2005

71 Normalized values LIDT (J/cm²) Dependence on operating conditions LIDT vs wavelength 4,0 3,5 3,0 2,5 2,0 1,5 1,0 0,5 Measurements with Ti:Sa + OPA system (100fs, 1on1)* Nb2O5 Ta2O5 HfO2 Sc2O3 Al2O3 SiO2 Max available Fluence ,0 Bandgap (ev) 2,5 2,0 1,5 1,0 0,5 Nb2O5 Ta2O5 HfO2 Sc2O3 Al2O3 SiO2 Max available Fluence Bandgap (ev) LIDT (J/cm²) LIDT (J/cm²) 2,5 2,0 1,5 1,0 0, Nb2O5 Bandgap (ev) Ta2O5 HfO2 Sc2O3 Al2O3 SiO2 *Measurements done at the Laser Research Center, Vilnius University. Laserlab project n VULRC ,5 1,0 0,5 Nb2O5 Ta2O5 HfO2 Sc2O3 Al2O3 SiO2 1240nm 1eV 800nm 1.5eV 650nm 1.9eV LIDT (J/cm²) Bandgap (ev) 2,5 2,0 1,5 1,0 0,5 Nb2O5 Ta2O5 HfO2 Sc2O3 Al2O3 SiO ,2 Nb2O5 Bandgap (ev) Ta2O5 1,0 HfO2 Sc2O3 Al2O3 Max available Fluence 0,8 SiO2 0,2 500nm 2.5eV 400nm 3eV 350nm 3.5eV LIDT (J/cm²) 0,6 0, Bandgap (ev)

72 Dependence on operating conditions LIDT vs wavelength Same simulation parameters LIDT (J/cm²) 4,0 3,5 3,0 2,5 2,0 1,5 Nb2O5 Ta2O5 HfO2 Sc2O3 Al2O3 SiO2 Bulk materials simulation 800nm, 100fs, 1on1 LIDT (J/cm²) 3,5 3,0 2,5 2,0 1,5 Nb2O5 Ta2O5 HfO2 Sc2O3 Al2O3 SiO2 Bulk materials Simulation 400nm, 100fs, 1on1 1,0 1,0 0,5 0, Bandgap (ev) Bandgap (ev)

73 Dependence on operating conditions Multiple pulses 1,1 Nb2O5 HfO2 Nb2O5 HfO2 SiO2 Bulk material 1,0 0,8 Normalized LIDT 1,0 0,9 0,8 0,7 0,6 0,5 300fs- 1030nm Number or pulses (at 10Hz) LIDT (J/cm²) 1 0,1 1 pulse 1000 pulses (50Hz) 1000 pulses (50kHz) Bandgap (ev) 300fs 515nm 0,6 0,4 0,2 Incubation coefficient

74 Conclusions Damage is linked to electronic properties of the film Deposition process can influence these properties Damage resistance is decreasing with applied number of pulses Simulation of the physical processes involved can provide valuable tools for scaling LIDT with laser parameters LIDT metrology is a critical point to develop high power laser coatings This talk was focused on intrinsic laser damage resistance but defects can be involved in the damage process:

75 Acknowledgments Contribution to these studies Institut Fresnel D.B. Douti, B. Mangote, F. Lemarchand, C. Hecquet, M. Lequime Laser Zentrum Hannover M. Mende, H. Ehlers, L. Jensen, M. Jupé, D. Ristau Laser Research Center of Vilnius University A. Melninkaitis, G. Batavičiūtė, E. Pupka, N. Šiaulys, V. Sirutkaitis Laboratoire d'optique Appliquée G. Chériaux REOSC company A. Hervy, D. Mouricaud 75

76 Thank you for your attention